Fix maxwait metric (#183 )

Max wait was being reported as 0 after #159 This PR fixes that and adds test
Replace a few types with more developer-friendly names (#182 )
2026-03-23 09:26:30 +00:00 · 2022-10-05 21:41:09 -05:00 · 2022-10-01 10:25:59 -07:00 · 2022-09-28 08:50:14 -05:00 · 2022-09-24 09:09:15 -07:00 · 2022-09-23 12:24:30 -07:00
38 changed files with 3644 additions and 1370 deletions
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -15,14 +15,34 @@ jobs:
          RUSTFLAGS: "-C instrument-coverage"
          LLVM_PROFILE_FILE: "pgcat-%m.profraw"
      - image: postgres:14
-        # auth:
-        #   username: mydockerhub-user
-        #   password: $DOCKERHUB_PASSWORD
+        command: ["postgres", "-p", "5432", "-c", "shared_preload_libraries=pg_stat_statements"]
        environment:
          POSTGRES_USER: postgres
          POSTGRES_DB: postgres
          POSTGRES_PASSWORD: postgres
          POSTGRES_HOST_AUTH_METHOD: scram-sha-256
+      - image: postgres:14
+        command: ["postgres", "-p", "7432", "-c", "shared_preload_libraries=pg_stat_statements"]
+        environment:
+          POSTGRES_USER: postgres
+          POSTGRES_DB: postgres
+          POSTGRES_PASSWORD: postgres
+          POSTGRES_HOST_AUTH_METHOD: scram-sha-256
+      - image: postgres:14
+        command: ["postgres", "-p", "8432", "-c", "shared_preload_libraries=pg_stat_statements"]
+        environment:
+          POSTGRES_USER: postgres
+          POSTGRES_DB: postgres
+          POSTGRES_PASSWORD: postgres
+          POSTGRES_HOST_AUTH_METHOD: scram-sha-256
+      - image: postgres:14
+        command: ["postgres", "-p", "9432", "-c", "shared_preload_libraries=pg_stat_statements"]
+        environment:
+          POSTGRES_USER: postgres
+          POSTGRES_DB: postgres
+          POSTGRES_PASSWORD: postgres
+          POSTGRES_HOST_AUTH_METHOD: scram-sha-256
+
    # Add steps to the job
    # See: https://circleci.com/docs/2.0/configuration-reference/#steps
    steps:
--- a/.circleci/pgcat.toml
+++ b/.circleci/pgcat.toml
@@ -11,9 +11,12 @@ host = "0.0.0.0"
 # Port to run on, same as PgBouncer used in this example.
 port = 6432

-# enable prometheus exporter on port 9930
+# Whether to enable prometheus exporter or not.
 enable_prometheus_exporter = true

+# Port at which prometheus exporter listens on.
+prometheus_exporter_port = 9930
+
 # How long to wait before aborting a server connection (ms).
 connect_timeout = 100

@@ -88,11 +91,13 @@ password = "sharding_user"
 # The maximum number of connection from a single Pgcat process to any database in the cluster
 # is the sum of pool_size across all users.
 pool_size = 9
+statement_timeout = 0

 [pools.sharded_db.users.1]
 username = "other_user"
 password = "other_user"
 pool_size = 21
+statement_timeout = 30000

 # Shard 0
 [pools.sharded_db.shards.0]
@@ -130,6 +135,7 @@ sharding_function = "pg_bigint_hash"
 username = "simple_user"
 password = "simple_user"
 pool_size = 5
+statement_timeout = 30000

 [pools.simple_db.shards.0]
 servers = [
--- a/.circleci/run_tests.sh
+++ b/.circleci/run_tests.sh
@@ -3,6 +3,9 @@
 set -e
 set -o xtrace

+# non-zero exit code if we provide bad configs
+(! ./target/debug/pgcat "fake_configs"  2>/dev/null)
+
 # Start PgCat with a particular log level
 # for inspection.
 function start_pgcat() {
@@ -13,17 +16,20 @@ function start_pgcat() {

 # Setup the database with shards and user
 PGPASSWORD=postgres psql -e -h 127.0.0.1 -p 5432 -U postgres -f tests/sharding/query_routing_setup.sql
+PGPASSWORD=postgres psql -e -h 127.0.0.1 -p 7432 -U postgres -f tests/sharding/query_routing_setup.sql
+PGPASSWORD=postgres psql -e -h 127.0.0.1 -p 8432 -U postgres -f tests/sharding/query_routing_setup.sql
+PGPASSWORD=postgres psql -e -h 127.0.0.1 -p 9432 -U postgres -f tests/sharding/query_routing_setup.sql

 PGPASSWORD=sharding_user pgbench -h 127.0.0.1 -U sharding_user shard0 -i
 PGPASSWORD=sharding_user pgbench -h 127.0.0.1 -U sharding_user shard1 -i
 PGPASSWORD=sharding_user pgbench -h 127.0.0.1 -U sharding_user shard2 -i

 # Install Toxiproxy to simulate a downed/slow database
-wget -O toxiproxy-2.1.4.deb https://github.com/Shopify/toxiproxy/releases/download/v2.1.4/toxiproxy_2.1.4_amd64.deb
-sudo dpkg -i toxiproxy-2.1.4.deb
+wget -O toxiproxy-2.4.0.deb https://github.com/Shopify/toxiproxy/releases/download/v2.4.0/toxiproxy_2.4.0_linux_$(dpkg --print-architecture).deb
+sudo dpkg -i toxiproxy-2.4.0.deb

 # Start Toxiproxy
-toxiproxy-server &
+LOG_LEVEL=error toxiproxy-server &
 sleep 1

 # Create a database at port 5433, forward it to Postgres
@@ -66,13 +72,26 @@ psql -U sharding_user -e -h 127.0.0.1 -p 6432 -f tests/sharding/query_routing_te
 # Replica/primary selection & more sharding tests
 psql -U sharding_user -e -h 127.0.0.1 -p 6432 -f tests/sharding/query_routing_test_primary_replica.sql > /dev/null

+# Statement timeout tests
+sed -i 's/statement_timeout = 0/statement_timeout = 100/' .circleci/pgcat.toml
+kill -SIGHUP $(pgrep pgcat) # Reload config
+sleep 0.2
+
+# This should timeout
+(! psql -U sharding_user -e -h 127.0.0.1 -p 6432 -c 'select pg_sleep(0.5)')
+
+# Disable statement timeout
+sed -i 's/statement_timeout = 100/statement_timeout = 0/' .circleci/pgcat.toml
+kill -SIGHUP $(pgrep pgcat) # Reload config again
+
 #
 # ActiveRecord tests
 #
 cd tests/ruby
 sudo gem install bundler
 bundle install
-ruby tests.rb
+bundle exec ruby tests.rb || exit 1
+bundle exec rspec *_spec.rb || exit 1
 cd ../..

 #
@@ -80,7 +99,7 @@ cd ../..
 # These tests will start and stop the pgcat server so it will need to be restarted after the tests
 #
 pip3 install -r tests/python/requirements.txt
-python3 tests/python/tests.py
+python3 tests/python/tests.py || exit 1

 start_pgcat "info"

@@ -90,9 +109,9 @@ psql -U admin_user -e -h 127.0.0.1 -p 6432 -d pgbouncer -c 'SHOW STATS' > /dev/n
 psql -U admin_user -h 127.0.0.1 -p 6432 -d pgbouncer -c 'RELOAD' > /dev/null
 psql -U admin_user -h 127.0.0.1 -p 6432 -d pgbouncer -c 'SHOW CONFIG' > /dev/null
 psql -U admin_user -h 127.0.0.1 -p 6432 -d pgbouncer -c 'SHOW DATABASES' > /dev/null
-psql -U admin_user -h 127.0.0.1 -p 6432 -d pgbouncer -c 'SHOW LISTS' > /dev/null
-psql -U admin_user -h 127.0.0.1 -p 6432 -d pgbouncer -c 'SHOW POOLS' > /dev/null
-psql -U admin_user -h 127.0.0.1 -p 6432 -d pgbouncer -c 'SHOW VERSION' > /dev/null
+psql -U admin_user -h 127.0.0.1 -p 6432 -d pgcat -c 'SHOW LISTS' > /dev/null
+psql -U admin_user -h 127.0.0.1 -p 6432 -d pgcat -c 'SHOW POOLS' > /dev/null
+psql -U admin_user -h 127.0.0.1 -p 6432 -d pgcat -c 'SHOW VERSION' > /dev/null
 psql -U admin_user -h 127.0.0.1 -p 6432 -d pgbouncer -c "SET client_encoding TO 'utf8'" > /dev/null # will ignore
 (! psql -U admin_user -e -h 127.0.0.1 -p 6432 -d random_db -c 'SHOW STATS' > /dev/null)
 export PGPASSWORD=sharding_user
@@ -117,11 +136,14 @@ toxiproxy-cli toxic remove --toxicName latency_downstream postgres_replica
 start_pgcat "info"

 # Test session mode (and config reload)
-sed -i 's/pool_mode = "transaction"/pool_mode = "session"/' .circleci/pgcat.toml
+sed -i '0,/simple_db/s/pool_mode = "transaction"/pool_mode = "session"/' .circleci/pgcat.toml

 # Reload config test
 kill -SIGHUP $(pgrep pgcat)

+# Revert settings after reload. Makes test runs idempotent
+sed -i '0,/simple_db/s/pool_mode = "session"/pool_mode = "transaction"/' .circleci/pgcat.toml
+
 sleep 1

 # Prepared statements that will only work in session mode
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -53,14 +53,14 @@ checksum = "904dfeac50f3cdaba28fc6f57fdcddb75f49ed61346676a78c4ffe55877802fd"

 [[package]]
 name = "bb8"
-version = "0.7.1"
+version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2e9f4fa9768efd269499d8fba693260cfc670891cf6de3adc935588447a77cc8"
+checksum = "1627eccf3aa91405435ba240be23513eeca466b5dc33866422672264de061582"
 dependencies = [
 "async-trait",
 "futures-channel",
 "futures-util",
- "parking_lot",
+ "parking_lot 0.12.1",
 "tokio",
 ]

@@ -159,6 +159,12 @@ dependencies = [
 "termcolor",
 ]

+[[package]]
+name = "exitcode"
+version = "1.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "de853764b47027c2e862a995c34978ffa63c1501f2e15f987ba11bd4f9bba193"
+
 [[package]]
 name = "fnv"
 version = "1.0.7"
@@ -487,7 +493,17 @@ checksum = "7d17b78036a60663b797adeaee46f5c9dfebb86948d1255007a1d6be0271ff99"
 dependencies = [
 "instant",
 "lock_api",
- "parking_lot_core",
+ "parking_lot_core 0.8.5",
+]
+
+[[package]]
+name = "parking_lot"
+version = "0.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3742b2c103b9f06bc9fff0a37ff4912935851bee6d36f3c02bcc755bcfec228f"
+dependencies = [
+ "lock_api",
+ "parking_lot_core 0.9.3",
 ]

 [[package]]
@@ -504,6 +520,19 @@ dependencies = [
 "winapi",
 ]

+[[package]]
+name = "parking_lot_core"
+version = "0.9.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "09a279cbf25cb0757810394fbc1e359949b59e348145c643a939a525692e6929"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "redox_syscall",
+ "smallvec",
+ "windows-sys",
+]
+
 [[package]]
 name = "pgcat"
 version = "0.6.0-alpha1"
@@ -515,13 +544,14 @@ dependencies = [
 "bytes",
 "chrono",
 "env_logger",
+ "exitcode",
 "hmac",
 "hyper",
 "log",
 "md-5",
 "num_cpus",
 "once_cell",
- "parking_lot",
+ "parking_lot 0.12.1",
 "phf",
 "rand",
 "regex",
@@ -539,20 +569,19 @@ dependencies = [

 [[package]]
 name = "phf"
-version = "0.10.1"
+version = "0.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fabbf1ead8a5bcbc20f5f8b939ee3f5b0f6f281b6ad3468b84656b658b455259"
+checksum = "928c6535de93548188ef63bb7c4036bd415cd8f36ad25af44b9789b2ee72a48c"
 dependencies = [
 "phf_macros",
 "phf_shared",
- "proc-macro-hack",
 ]

 [[package]]
 name = "phf_generator"
-version = "0.10.0"
+version = "0.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5d5285893bb5eb82e6aaf5d59ee909a06a16737a8970984dd7746ba9283498d6"
+checksum = "b1181c94580fa345f50f19d738aaa39c0ed30a600d95cb2d3e23f94266f14fbf"
 dependencies = [
 "phf_shared",
 "rand",
@@ -560,13 +589,12 @@ dependencies = [

 [[package]]
 name = "phf_macros"
-version = "0.10.0"
+version = "0.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "58fdf3184dd560f160dd73922bea2d5cd6e8f064bf4b13110abd81b03697b4e0"
+checksum = "92aacdc5f16768709a569e913f7451034034178b05bdc8acda226659a3dccc66"
 dependencies = [
 "phf_generator",
 "phf_shared",
- "proc-macro-hack",
 "proc-macro2",
 "quote",
 "syn",
@@ -574,9 +602,9 @@ dependencies = [

 [[package]]
 name = "phf_shared"
-version = "0.10.0"
+version = "0.11.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b6796ad771acdc0123d2a88dc428b5e38ef24456743ddb1744ed628f9815c096"
+checksum = "e1fb5f6f826b772a8d4c0394209441e7d37cbbb967ae9c7e0e8134365c9ee676"
 dependencies = [
 "siphasher",
 ]
@@ -599,12 +627,6 @@ version = "0.2.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "eb9f9e6e233e5c4a35559a617bf40a4ec447db2e84c20b55a6f83167b7e57872"

-[[package]]
-name = "proc-macro-hack"
-version = "0.5.19"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dbf0c48bc1d91375ae5c3cd81e3722dff1abcf81a30960240640d223f59fe0e5"
-
 [[package]]
 name = "proc-macro2"
 version = "1.0.36"
@@ -825,9 +847,9 @@ checksum = "6e63cff320ae2c57904679ba7cb63280a3dc4613885beafb148ee7bf9aa9042d"

 [[package]]
 name = "sqlparser"
-version = "0.14.0"
+version = "0.23.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b8f192f29f4aa49e57bebd0aa05858e0a1f32dd270af36efe49edb82cbfffab6"
+checksum = "0beb13adabbdda01b63d595f38c8bfd19a361e697fd94ce0098a634077bc5b25"
 dependencies = [
 "log",
 ]
@@ -906,7 +928,7 @@ dependencies = [
 "mio",
 "num_cpus",
 "once_cell",
- "parking_lot",
+ "parking_lot 0.11.2",
 "pin-project-lite",
 "signal-hook-registry",
 "tokio-macros",
@@ -1161,3 +1183,46 @@ name = "winapi-x86_64-pc-windows-gnu"
 version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
+
+[[package]]
+name = "windows-sys"
+version = "0.36.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ea04155a16a59f9eab786fe12a4a450e75cdb175f9e0d80da1e17db09f55b8d2"
+dependencies = [
+ "windows_aarch64_msvc",
+ "windows_i686_gnu",
+ "windows_i686_msvc",
+ "windows_x86_64_gnu",
+ "windows_x86_64_msvc",
+]
+
+[[package]]
+name = "windows_aarch64_msvc"
+version = "0.36.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9bb8c3fd39ade2d67e9874ac4f3db21f0d710bee00fe7cab16949ec184eeaa47"
+
+[[package]]
+name = "windows_i686_gnu"
+version = "0.36.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "180e6ccf01daf4c426b846dfc66db1fc518f074baa793aa7d9b9aaeffad6a3b6"
+
+[[package]]
+name = "windows_i686_msvc"
+version = "0.36.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2e7917148b2812d1eeafaeb22a97e4813dfa60a3f8f78ebe204bcc88f12f024"
+
+[[package]]
+name = "windows_x86_64_gnu"
+version = "0.36.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4dcd171b8776c41b97521e5da127a2d86ad280114807d0b2ab1e462bc764d9e1"
+
+[[package]]
+name = "windows_x86_64_msvc"
+version = "0.36.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c811ca4a8c853ef420abd8592ba53ddbbac90410fab6903b3e79972a631f7680"
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -9,7 +9,7 @@ edition = "2021"
 tokio = { version = "1", features = ["full"] }
 bytes = "1"
 md-5 = "0.10"
-bb8 = "0.7"
+bb8 = "0.8.0"
 async-trait = "0.1"
 rand = "0.8"
 chrono = "0.4"
@@ -20,11 +20,11 @@ serde_derive = "1"
 regex = "1"
 num_cpus = "1"
 once_cell = "1"
-sqlparser = "0.14"
+sqlparser = "0.23.0"
 log = "0.4"
 arc-swap = "1"
 env_logger = "0.9"
-parking_lot = "0.11"
+parking_lot = "0.12.1"
 hmac = "0.12"
 sha2 = "0.10"
 base64 = "0.13"
@@ -32,4 +32,5 @@ stringprep = "0.1"
 tokio-rustls = "0.23"
 rustls-pemfile = "1"
 hyper = { version = "0.14", features = ["full"] }
-phf = { version = "0.10", features = ["macros"] }
+phf = { version = "0.11.1", features = ["macros"] }
+exitcode = "1.1.2"
--- a/README.md
+++ b/README.md
@@ -1,8 +1,11 @@
-# PgCat
+![PgCat](./pgcat3.png)
+
+##### PgCat: PostgreSQL at petabyte scale

 [![CircleCI](https://circleci.com/gh/levkk/pgcat/tree/main.svg?style=svg)](https://circleci.com/gh/levkk/pgcat/tree/main)
-
-![PgCat](./pgcat3.png)
+<a href="https://discord.gg/DmyJP3qJ7U" target="_blank">
+    <img src="https://img.shields.io/discord/1013868243036930099" alt="Join our Discord!" />
+</a>

 PostgreSQL pooler (like PgBouncer) with sharding, load balancing and failover support.

@@ -15,7 +18,7 @@ PostgreSQL pooler (like PgBouncer) with sharding, load balancing and failover su
 | Session pooling                | :white_check_mark:          | Identical to PgBouncer.                                                                                                                               |
 | `COPY` support                 | :white_check_mark:          | Both `COPY TO` and `COPY FROM` are supported.                                                                                                         |
 | Query cancellation             | :white_check_mark:          | Supported both in transaction and session pooling modes.                                                                                              |
-| Load balancing of read queries | :white_check_mark:          | Using round-robin between replicas. Primary is included when `primary_reads_enabled` is enabled (default).                                            |
+| Load balancing of read queries | :white_check_mark:          | Using random between replicas. Primary is included when `primary_reads_enabled` is enabled (default).                                            |
 | Sharding                       | :white_check_mark:          | Transactions are sharded using `SET SHARD TO` and `SET SHARDING KEY TO` syntax extensions; see examples below.                                        |
 | Failover                       | :white_check_mark:          | Replicas are tested with a health check. If a health check fails, remaining replicas are attempted; see below for algorithm description and examples. |
 | Statistics                     | :white_check_mark:          | Statistics available in the admin database (`pgcat` and `pgbouncer`) with `SHOW STATS`, `SHOW POOLS` and others.                                      |
@@ -38,30 +41,35 @@ psql -h 127.0.0.1 -p 6432 -c 'SELECT 1'

 ### Config

-| **Name**                | **Description**                                                                                                                            | **Examples**                     |
-|-------------------------|--------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------|
-| **`general`**           |                                                                                                                                            |                                  |
-| `host`                  | The pooler will run on this host, 0.0.0.0 means accessible from everywhere.                                                                | `0.0.0.0`                        |
-| `port`                  | The pooler will run on this port.                                                                                                          | `6432`                           |
-| `pool_size`             | Maximum allowed server connections per pool. Pools are separated for each user/shard/server role. The connections are allocated as needed. | `15`                             |
-| `pool_mode`             | The pool mode to use, i.e. `session` or `transaction`.                                                                                     | `transaction`                    |
-| `connect_timeout`       | Maximum time to establish a connection to a server (milliseconds). If reached, the server is banned and the next target is attempted.      | `5000`                           |
-| `healthcheck_timeout`   | Maximum time to pass a health check (`SELECT 1`, milliseconds). If reached, the server is banned and the next target is attempted.         | `1000`                           |
-| `shutdown_timeout`   | Maximum time to give clients during shutdown before forcibly killing client connections (ms).      | `60000`                           |
-| `healthcheck_delay`   | How long to keep connection available for immediate re-use, without running a healthcheck query on it       | `30000`                           |
-| `ban_time`              | Ban time for a server (seconds). It won't be allowed to serve transactions until the ban expires; failover targets will be used instead.   | `60`                             |
-|                         |                                                                                                                                            |                                  |
-| **`user`**              |                                                                                                                                            |                                  |
-| `name`                  | The user name.                                                                                                                             | `sharding_user`                  |
-| `password`              | The user password in plaintext.                                                                                                            | `hunter2`                        |
-|                         |                                                                                                                                            |                                  |
-| **`shards`**            | Shards are numerically numbered starting from 0; the order in the config is preserved by the pooler to route queries accordingly.          | `[shards.0]`                     |
-| `servers`               | List of servers to connect to and their roles. A server is: `[host, port, role]`, where `role` is either `primary` or `replica`.           | `["127.0.0.1", 5432, "primary"]` |
-| `database`              | The name of the database to connect to. This is the same on all servers that are part of one shard.                                        |                                  |
-| **`query_router`**      |                                                                                                                                            |                                  |
-| `default_role`          | Traffic is routed to this role by default (round-robin), unless the client specifies otherwise. Default is `any`, for any role available.  | `any`, `primary`, `replica`      |
-| `query_parser_enabled`  | Enable the query parser which will inspect incoming queries and route them to a primary or replicas.                                       | `false`                          |
-| `primary_reads_enabled` | Enable this to allow read queries on the primary; otherwise read queries are routed to the replicas.                                       | `true`                           |
+| **Name**                     | **Description**                                                                                                                            | **Examples**                     |
+|------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------|
+| **`general`**                |                                                                                                                                            |                                  |
+| `host`                       | The pooler will run on this host, 0.0.0.0 means accessible from everywhere.                                                                | `0.0.0.0`                        |
+| `port`                       | The pooler will run on this port.                                                                                                          | `6432`                           |
+| `enable_prometheus_exporter` | Enable prometheus exporter which will export metrics in prometheus exposition format.                                                      | `true`                           |
+| `prometheus_exporter_port`   | Port at which prometheus exporter listens on.                                                                                              | `9930`                           |
+| `pool_size`                  | Maximum allowed server connections per pool. Pools are separated for each user/shard/server role. The connections are allocated as needed. | `15`                             |
+| `pool_mode`                  | The pool mode to use, i.e. `session` or `transaction`.                                                                                     | `transaction`                    |
+| `connect_timeout`            | Maximum time to establish a connection to a server (milliseconds). If reached, the server is banned and the next target is attempted.      | `5000`                           |
+| `healthcheck_timeout`        | Maximum time to pass a health check (`SELECT 1`, milliseconds). If reached, the server is banned and the next target is attempted.         | `1000`                           |
+| `shutdown_timeout`           | Maximum time to give clients during shutdown before forcibly killing client connections (ms).                                              | `60000`                          |
+| `healthcheck_delay`          | How long to keep connection available for immediate re-use, without running a healthcheck query on it                                      | `30000`                          |
+| `ban_time`                   | Ban time for a server (seconds). It won't be allowed to serve transactions until the ban expires; failover targets will be used instead.   | `60`                             |
+| `autoreload`                 | Enable auto-reload of config after fixed time-interval.                                                                                    | `false`                          |
+|                              |                                                                                                                                            |                                  |
+| **`user`**                   |                                                                                                                                            |                                  |
+| `name`                       | The user name.                                                                                                                             | `sharding_user`                  |
+| `password`                   | The user password in plaintext.                                                                                                            | `hunter2`                        |
+| `statement_timeout` | Timeout in milliseconds for how long a query takes to execute | `0 (disabled)`
+|                              |                                                                                                                                            |                                  |
+| **`shards`**                 | Shards are numerically numbered starting from 0; the order in the config is preserved by the pooler to route queries accordingly.          | `[shards.0]`                     |
+| `servers`                    | List of servers to connect to and their roles. A server is: `[host, port, role]`, where `role` is either `primary` or `replica`.           | `["127.0.0.1", 5432, "primary"]` |
+| `database`                   | The name of the database to connect to. This is the same on all servers that are part of one shard.                                        |                                  |
+|                              |                                                                                                                                            |                                  |
+| **`query_router`**           |                                                                                                                                            |                                  |
+| `default_role`               | Traffic is routed to this role by default (random), unless the client specifies otherwise. Default is `any`, for any role available.  | `any`, `primary`, `replica`      |
+| `query_parser_enabled`       | Enable the query parser which will inspect incoming queries and route them to a primary or replicas.                                       | `false`                          |
+| `primary_reads_enabled`      | Enable this to allow read queries on the primary; otherwise read queries are routed to the replicas.                                       | `true`                           |

 ## Local development

@@ -83,6 +91,14 @@ pgbench -t 1000 -p 6432 -h 127.0.0.1 --protocol extended

 See [sharding README](./tests/sharding/README.md) for sharding logic testing.

+Run `cargo test` to run Rust tests.
+
+Run the following commands to run Integration tests locally.
+```
+cd tests/docker/
+docker compose up --exit-code-from main # This will also produce coverage report under ./cov/
+```
+
 | **Feature**           | **Tested in CI**   | **Tested manually** | **Comments**                                                                                                             |
 |-----------------------|--------------------|---------------------|--------------------------------------------------------------------------------------------------------------------------|
 | Transaction pooling   | :white_check_mark: | :white_check_mark:  | Used by default for all tests.                                                                                           |
@@ -108,7 +124,7 @@ In transaction mode, a client talks to one server for the duration of a single t
 This mode is enabled by default.

 ### Load balancing of read queries
-All queries are load balanced against the configured servers using the round-robin algorithm. The most straight forward configuration example would be to put this pooler in front of several replicas and let it load balance all queries.
+All queries are load balanced against the configured servers using the random algorithm. The most straight forward configuration example would be to put this pooler in front of several replicas and let it load balance all queries.

 If the configuration includes a primary and replicas, the queries can be separated with the built-in query parser. The query parser will interpret the query and route all `SELECT` queries to a replica, while all other queries including explicit transactions will be routed to the primary.

@@ -147,18 +163,18 @@ Failover behavior can get pretty interesting (read complex) when multiple config

 | **Query**                 | **`SET SERVER ROLE TO`** | **`query_parser_enabled`** | **`primary_reads_enabled`** | **Target state** | **Outcome**                                                                                                                                                          |
 |---------------------------|--------------------------|----------------------------|-----------------------------|------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------|
-| Read query, i.e. `SELECT` | unset (any)              | false                      | false                       | up               | Query is routed to the first instance in the round-robin loop.                                                                                                       |
-| Read query                | unset (any)              | true                       | false                       | up               | Query is routed to the first replica instance in the round-robin loop.                                                                                               |
-| Read query                | unset (any)              | true                       | true                        | up               | Query is routed to the first instance in the round-robin loop.                                                                                                       |
-| Read query                | replica                  | false                      | false                       | up               | Query is routed to the first replica instance in the round-robin loop.                                                                                               |
+| Read query, i.e. `SELECT` | unset (any)              | false                      | false                       | up               | Query is routed to the first instance in the random loop.                                                                                                       |
+| Read query                | unset (any)              | true                       | false                       | up               | Query is routed to the first replica instance in the random loop.                                                                                               |
+| Read query                | unset (any)              | true                       | true                        | up               | Query is routed to the first instance in the random loop.                                                                                                       |
+| Read query                | replica                  | false                      | false                       | up               | Query is routed to the first replica instance in the random loop.                                                                                               |
 | Read query                | primary                  | false                      | false                       | up               | Query is routed to the primary.                                                                                                                                      |
-| Read query                | unset (any)              | false                      | false                       | down             | First instance is banned for reads. Next target in the round-robin loop is attempted.                                                                                |
-| Read query                | unset (any)              | true                       | false                       | down             | First replica instance is banned. Next replica instance is attempted in the round-robin loop.                                                                        |
-| Read query                | unset (any)              | true                       | true                        | down             | First instance (even if primary) is banned for reads. Next instance is attempted in the round-robin loop.                                                            |
-| Read query                | replica                  | false                      | false                       | down             | First replica instance is banned. Next replica instance is attempted in the round-robin loop.                                                                        |
+| Read query                | unset (any)              | false                      | false                       | down             | First instance is banned for reads. Next target in the random loop is attempted.                                                                                |
+| Read query                | unset (any)              | true                       | false                       | down             | First replica instance is banned. Next replica instance is attempted in the random loop.                                                                        |
+| Read query                | unset (any)              | true                       | true                        | down             | First instance (even if primary) is banned for reads. Next instance is attempted in the random loop.                                                            |
+| Read query                | replica                  | false                      | false                       | down             | First replica instance is banned. Next replica instance is attempted in the random loop.                                                                        |
 | Read query                | primary                  | false                      | false                       | down             | The query is attempted against the primary and fails. The client receives an error.                                                                                  |
 |                           |                          |                            |                             |                  |                                                                                                                                                                      |
-| Write query e.g. `INSERT` | unset (any)              | false                      | false                       | up               | The query is attempted against the first available instance in the round-robin loop. If the instance is a replica, the query fails and the client receives an error. |
+| Write query e.g. `INSERT` | unset (any)              | false                      | false                       | up               | The query is attempted against the first available instance in the random loop. If the instance is a replica, the query fails and the client receives an error. |
 | Write query               | unset (any)              | true                       | false                       | up               | The query is routed to the primary.                                                                                                                                  |
 | Write query               | unset (any)              | true                       | true                        | up               | The query is routed to the primary.                                                                                                                                  |
 | Write query               | primary                  | false                      | false                       | up               | The query is routed to the primary.                                                                                                                                  |
@@ -443,7 +459,7 @@ Always good to have a base line.

 ```
 $ pgbench -t 1000 -c 16 -j 2 -p 5432 -h 127.0.0.1 -S --protocol extended shard0
-Password: 
+Password:
 starting vacuum...end.
 transaction type: <builtin: select only>
 scaling factor: 1
@@ -457,7 +473,7 @@ tps = 139443.955722 (including connections establishing)
 tps = 142314.859075 (excluding connections establishing)

 $ pgbench -t 1000 -c 32 -j 2 -p 5432 -h 127.0.0.1 -S --protocol extended shard0
-Password: 
+Password:
 starting vacuum...end.
 transaction type: <builtin: select only>
 scaling factor: 1
@@ -471,7 +487,7 @@ tps = 150644.840891 (including connections establishing)
 tps = 152218.499430 (excluding connections establishing)

 $ pgbench -t 1000 -c 64 -j 2 -p 5432 -h 127.0.0.1 -S --protocol extended shard0
-Password: 
+Password:
 starting vacuum...end.
 transaction type: <builtin: select only>
 scaling factor: 1
@@ -485,7 +501,7 @@ tps = 152517.663404 (including connections establishing)
 tps = 153319.188482 (excluding connections establishing)

 $ pgbench -t 1000 -c 128 -j 2 -p 5432 -h 127.0.0.1 -S --protocol extended shard0
-Password: 
+Password:
 starting vacuum...end.
 transaction type: <builtin: select only>
 scaling factor: 1
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -1,7 +1,7 @@
 version: "3"
 services:
  postgres:
-    image: postgres:13
+    image: postgres:14
    environment:
      POSTGRES_PASSWORD: postgres
      POSTGRES_HOST_AUTH_METHOD: md5
--- a/examples/docker/pgcat.toml
+++ b/examples/docker/pgcat.toml
@@ -11,9 +11,12 @@ host = "0.0.0.0"
 # Port to run on, same as PgBouncer used in this example.
 port = 6432

-# enable prometheus exporter on port 9930
+# Whether to enable prometheus exporter or not.
 enable_prometheus_exporter = true

+# Port at which prometheus exporter listens on.
+prometheus_exporter_port = 9930
+
 # How long to wait before aborting a server connection (ms).
 connect_timeout = 5000

@@ -89,10 +92,14 @@ password = "postgres"
 # is the sum of pool_size across all users.
 pool_size = 9

+# Maximum query duration. Dangerous, but protects against DBs that died in a non-obvious way.
+statement_timeout = 0
+
 [pools.sharded.users.1]
 username = "postgres"
 password = "postgres"
 pool_size = 21
+statement_timeout = 15000

 # Shard 0
 [pools.sharded.shards.0]
@@ -130,6 +137,7 @@ sharding_function = "pg_bigint_hash"
 username = "postgres"
 password = "postgres"
 pool_size = 5
+statement_timeout = 0

 [pools.simple_db.shards.0]
 servers = [
--- a/pgcat.toml
+++ b/pgcat.toml
@@ -11,9 +11,12 @@ host = "0.0.0.0"
 # Port to run on, same as PgBouncer used in this example.
 port = 6432

-# enable prometheus exporter on port 9930
+# Whether to enable prometheus exporter or not.
 enable_prometheus_exporter = true

+# Port at which prometheus exporter listens on.
+prometheus_exporter_port = 9930
+
 # How long to wait before aborting a server connection (ms).
 connect_timeout = 5000

@@ -89,10 +92,14 @@ password = "sharding_user"
 # is the sum of pool_size across all users.
 pool_size = 9

+# Maximum query duration. Dangerous, but protects against DBs that died in a non-obvious way.
+statement_timeout = 0
+
 [pools.sharded_db.users.1]
 username = "other_user"
 password = "other_user"
 pool_size = 21
+statement_timeout = 15000

 # Shard 0
 [pools.sharded_db.shards.0]
@@ -130,6 +137,7 @@ sharding_function = "pg_bigint_hash"
 username = "simple_user"
 password = "simple_user"
 pool_size = 5
+statement_timeout = 0

 [pools.simple_db.shards.0]
 servers = [
--- a/src/admin.rs
+++ b/src/admin.rs
@@ -2,22 +2,25 @@
 use bytes::{Buf, BufMut, BytesMut};
 use log::{info, trace};
 use std::collections::HashMap;
+use tokio::time::Instant;

 use crate::config::{get_config, reload_config, VERSION};
 use crate::errors::Error;
 use crate::messages::*;
 use crate::pool::get_all_pools;
-use crate::stats::get_stats;
+use crate::stats::{
+    get_address_stats, get_client_stats, get_pool_stats, get_server_stats, ClientState, ServerState,
+};
 use crate::ClientServerMap;

 pub fn generate_server_info_for_admin() -> BytesMut {
    let mut server_info = BytesMut::new();

-    server_info.put(server_paramater_message("application_name", ""));
-    server_info.put(server_paramater_message("client_encoding", "UTF8"));
-    server_info.put(server_paramater_message("server_encoding", "UTF8"));
-    server_info.put(server_paramater_message("server_version", VERSION));
-    server_info.put(server_paramater_message("DateStyle", "ISO, MDY"));
+    server_info.put(server_parameter_message("application_name", ""));
+    server_info.put(server_parameter_message("client_encoding", "UTF8"));
+    server_info.put(server_parameter_message("server_encoding", "UTF8"));
+    server_info.put(server_parameter_message("server_version", VERSION));
+    server_info.put(server_parameter_message("DateStyle", "ISO, MDY"));

    return server_info;
 }
@@ -44,32 +47,53 @@ where

    trace!("Admin query: {}", query);

-    if query.starts_with("SHOW STATS") {
-        trace!("SHOW STATS");
-        show_stats(stream).await
-    } else if query.starts_with("RELOAD") {
-        trace!("RELOAD");
-        reload(stream, client_server_map).await
-    } else if query.starts_with("SHOW CONFIG") {
-        trace!("SHOW CONFIG");
-        show_config(stream).await
-    } else if query.starts_with("SHOW DATABASES") {
-        trace!("SHOW DATABASES");
-        show_databases(stream).await
-    } else if query.starts_with("SHOW POOLS") {
-        trace!("SHOW POOLS");
-        show_pools(stream).await
-    } else if query.starts_with("SHOW LISTS") {
-        trace!("SHOW LISTS");
-        show_lists(stream).await
-    } else if query.starts_with("SHOW VERSION") {
-        trace!("SHOW VERSION");
-        show_version(stream).await
-    } else if query.starts_with("SET ") {
-        trace!("SET");
-        ignore_set(stream).await
-    } else {
-        error_response(stream, "Unsupported query against the admin database").await
+    let query_parts: Vec<&str> = query.trim_end_matches(';').split_whitespace().collect();
+
+    match query_parts[0] {
+        "RELOAD" => {
+            trace!("RELOAD");
+            reload(stream, client_server_map).await
+        }
+        "SET" => {
+            trace!("SET");
+            ignore_set(stream).await
+        }
+        "SHOW" => match query_parts[1] {
+            "CONFIG" => {
+                trace!("SHOW CONFIG");
+                show_config(stream).await
+            }
+            "DATABASES" => {
+                trace!("SHOW DATABASES");
+                show_databases(stream).await
+            }
+            "LISTS" => {
+                trace!("SHOW LISTS");
+                show_lists(stream).await
+            }
+            "POOLS" => {
+                trace!("SHOW POOLS");
+                show_pools(stream).await
+            }
+            "CLIENTS" => {
+                trace!("SHOW CLIENTS");
+                show_clients(stream).await
+            }
+            "SERVERS" => {
+                trace!("SHOW SERVERS");
+                show_servers(stream).await
+            }
+            "STATS" => {
+                trace!("SHOW STATS");
+                show_stats(stream).await
+            }
+            "VERSION" => {
+                trace!("SHOW VERSION");
+                show_version(stream).await
+            }
+            _ => error_response(stream, "Unsupported SHOW query against the admin database").await,
+        },
+        _ => error_response(stream, "Unsupported query against the admin database").await,
    }
 }

@@ -78,7 +102,8 @@ async fn show_lists<T>(stream: &mut T) -> Result<(), Error>
 where
    T: tokio::io::AsyncWrite + std::marker::Unpin,
 {
-    let stats = get_stats();
+    let client_stats = get_client_stats();
+    let server_stats = get_server_stats();

    let columns = vec![("list", DataType::Text), ("items", DataType::Int4)];

@@ -98,18 +123,18 @@ where
    res.put(data_row(&vec!["pools".to_string(), databases.to_string()]));
    res.put(data_row(&vec![
        "free_clients".to_string(),
-        stats
+        client_stats
            .keys()
-            .map(|address_id| stats[&address_id]["cl_idle"])
-            .sum::<i64>()
+            .filter(|client_id| client_stats.get(client_id).unwrap().state == ClientState::Idle)
+            .count()
            .to_string(),
    ]));
    res.put(data_row(&vec![
        "used_clients".to_string(),
-        stats
+        client_stats
            .keys()
-            .map(|address_id| stats[&address_id]["cl_active"])
-            .sum::<i64>()
+            .filter(|client_id| client_stats.get(client_id).unwrap().state == ClientState::Active)
+            .count()
            .to_string(),
    ]));
    res.put(data_row(&vec![
@@ -118,18 +143,18 @@ where
    ]));
    res.put(data_row(&vec![
        "free_servers".to_string(),
-        stats
+        server_stats
            .keys()
-            .map(|address_id| stats[&address_id]["sv_idle"])
-            .sum::<i64>()
+            .filter(|server_id| server_stats.get(server_id).unwrap().state == ServerState::Idle)
+            .count()
            .to_string(),
    ]));
    res.put(data_row(&vec![
        "used_servers".to_string(),
-        stats
+        server_stats
            .keys()
-            .map(|address_id| stats[&address_id]["sv_active"])
-            .sum::<i64>()
+            .filter(|server_id| server_stats.get(server_id).unwrap().state == ServerState::Active)
+            .count()
            .to_string(),
    ]));
    res.put(data_row(&vec!["dns_names".to_string(), "0".to_string()]));
@@ -169,11 +194,13 @@ async fn show_pools<T>(stream: &mut T) -> Result<(), Error>
 where
    T: tokio::io::AsyncWrite + std::marker::Unpin,
 {
-    let stats = get_stats();
+    let all_pool_stats = get_pool_stats();

    let columns = vec![
        ("database", DataType::Text),
        ("user", DataType::Text),
+        ("pool_mode", DataType::Text),
+        ("cl_idle", DataType::Numeric),
        ("cl_active", DataType::Numeric),
        ("cl_waiting", DataType::Numeric),
        ("cl_cancel_req", DataType::Numeric),
@@ -184,32 +211,33 @@ where
        ("sv_login", DataType::Numeric),
        ("maxwait", DataType::Numeric),
        ("maxwait_us", DataType::Numeric),
-        ("pool_mode", DataType::Text),
    ];

    let mut res = BytesMut::new();
    res.put(row_description(&columns));
-    for (_, pool) in get_all_pools() {
+    for (user_pool, pool) in get_all_pools() {
+        let def = HashMap::default();
+        let pool_stats = all_pool_stats
+            .get(&(user_pool.db.clone(), user_pool.user.clone()))
+            .unwrap_or(&def);
+
        let pool_config = &pool.settings;
-        for shard in 0..pool.shards() {
-            for server in 0..pool.servers(shard) {
-                let address = pool.address(shard, server);
-                let stats = match stats.get(&address.id) {
-                    Some(stats) => stats.clone(),
-                    None => HashMap::new(),
-                };
-
-                let mut row = vec![address.name(), pool_config.user.username.clone()];
-
-                for column in &columns[2..columns.len() - 1] {
-                    let value = stats.get(column.0).unwrap_or(&0).to_string();
-                    row.push(value);
+        let mut row = vec![
+            user_pool.db.clone(),
+            user_pool.user.clone(),
+            pool_config.pool_mode.to_string(),
+        ];
+        for column in &columns[3..columns.len()] {
+            let value = match column.0 {
+                "maxwait" => (pool_stats.get("maxwait_us").unwrap_or(&0) / 1_000_000).to_string(),
+                "maxwait_us" => {
+                    (pool_stats.get("maxwait_us").unwrap_or(&0) % 1_000_000).to_string()
                }
-
-                row.push(pool_config.pool_mode.to_string());
-                res.put(data_row(&row));
-            }
+                _other_values => pool_stats.get(column.0).unwrap_or(&0).to_string(),
+            };
+            row.push(value);
        }
+        res.put(data_row(&row));
    }

    res.put(command_complete("SHOW"));
@@ -251,11 +279,11 @@ where
    for (_, pool) in get_all_pools() {
        let pool_config = pool.settings.clone();
        for shard in 0..pool.shards() {
-            let database_name = &pool_config.shards[&shard.to_string()].database;
+            let database_name = &pool.address(shard, 0).database;
            for server in 0..pool.servers(shard) {
                let address = pool.address(shard, server);
                let pool_state = pool.pool_state(shard, server);
-                let banned = pool.is_banned(address, shard, Some(address.role));
+                let banned = pool.is_banned(address, Some(address.role));

                res.put(data_row(&vec![
                    address.name(),                         // name
@@ -373,6 +401,7 @@ where
    T: tokio::io::AsyncWrite + std::marker::Unpin,
 {
    let columns = vec![
+        ("instance", DataType::Text),
        ("database", DataType::Text),
        ("user", DataType::Text),
        ("total_xact_count", DataType::Numeric),
@@ -382,32 +411,32 @@ where
        ("total_xact_time", DataType::Numeric),
        ("total_query_time", DataType::Numeric),
        ("total_wait_time", DataType::Numeric),
+        ("total_errors", DataType::Numeric),
        ("avg_xact_count", DataType::Numeric),
        ("avg_query_count", DataType::Numeric),
        ("avg_recv", DataType::Numeric),
        ("avg_sent", DataType::Numeric),
+        ("avg_errors", DataType::Numeric),
        ("avg_xact_time", DataType::Numeric),
        ("avg_query_time", DataType::Numeric),
        ("avg_wait_time", DataType::Numeric),
    ];

-    let stats = get_stats();
+    let all_stats = get_address_stats();
    let mut res = BytesMut::new();
    res.put(row_description(&columns));

-    for ((_db_name, username), pool) in get_all_pools() {
+    for (user_pool, pool) in get_all_pools() {
        for shard in 0..pool.shards() {
            for server in 0..pool.servers(shard) {
                let address = pool.address(shard, server);
-                let stats = match stats.get(&address.id) {
+                let stats = match all_stats.get(&address.id) {
                    Some(stats) => stats.clone(),
                    None => HashMap::new(),
                };

-                let mut row = vec![address.name()];
-                row.push(username.clone());
-
-                for column in &columns[2..] {
+                let mut row = vec![address.name(), user_pool.db.clone(), user_pool.user.clone()];
+                for column in &columns[3..] {
                    row.push(stats.get(column.0).unwrap_or(&0).to_string());
                }

@@ -425,3 +454,107 @@ where

    write_all_half(stream, res).await
 }
+
+/// Show currently connected clients
+async fn show_clients<T>(stream: &mut T) -> Result<(), Error>
+where
+    T: tokio::io::AsyncWrite + std::marker::Unpin,
+{
+    let columns = vec![
+        ("client_id", DataType::Text),
+        ("database", DataType::Text),
+        ("user", DataType::Text),
+        ("application_name", DataType::Text),
+        ("state", DataType::Text),
+        ("transaction_count", DataType::Numeric),
+        ("query_count", DataType::Numeric),
+        ("error_count", DataType::Numeric),
+        ("age_seconds", DataType::Numeric),
+    ];
+
+    let new_map = get_client_stats();
+    let mut res = BytesMut::new();
+    res.put(row_description(&columns));
+
+    for (_, client) in new_map {
+        let row = vec![
+            format!("{:#010X}", client.client_id),
+            client.pool_name,
+            client.username,
+            client.application_name.clone(),
+            client.state.to_string(),
+            client.transaction_count.to_string(),
+            client.query_count.to_string(),
+            client.error_count.to_string(),
+            Instant::now()
+                .duration_since(client.connect_time)
+                .as_secs()
+                .to_string(),
+        ];
+
+        res.put(data_row(&row));
+    }
+
+    res.put(command_complete("SHOW"));
+
+    // ReadyForQuery
+    res.put_u8(b'Z');
+    res.put_i32(5);
+    res.put_u8(b'I');
+
+    write_all_half(stream, res).await
+}
+
+/// Show currently connected servers
+async fn show_servers<T>(stream: &mut T) -> Result<(), Error>
+where
+    T: tokio::io::AsyncWrite + std::marker::Unpin,
+{
+    let columns = vec![
+        ("server_id", DataType::Text),
+        ("database_name", DataType::Text),
+        ("user", DataType::Text),
+        ("address_id", DataType::Text),
+        ("application_name", DataType::Text),
+        ("state", DataType::Text),
+        ("transaction_count", DataType::Numeric),
+        ("query_count", DataType::Numeric),
+        ("bytes_sent", DataType::Numeric),
+        ("bytes_received", DataType::Numeric),
+        ("age_seconds", DataType::Numeric),
+    ];
+
+    let new_map = get_server_stats();
+    let mut res = BytesMut::new();
+    res.put(row_description(&columns));
+
+    for (_, server) in new_map {
+        let row = vec![
+            format!("{:#010X}", server.server_id),
+            server.pool_name,
+            server.username,
+            server.address_name,
+            server.application_name,
+            server.state.to_string(),
+            server.transaction_count.to_string(),
+            server.query_count.to_string(),
+            server.bytes_sent.to_string(),
+            server.bytes_received.to_string(),
+            Instant::now()
+                .duration_since(server.connect_time)
+                .as_secs()
+                .to_string(),
+        ];
+
+        res.put(data_row(&row));
+    }
+
+    res.put(command_complete("SHOW"));
+
+    // ReadyForQuery
+    res.put_u8(b'Z');
+    res.put_i32(5);
+    res.put_u8(b'I');
+
+    write_all_half(stream, res).await
+}
--- a/src/client.rs
+++ b/src/client.rs
@@ -1,13 +1,15 @@
 /// Handle clients by pretending to be a PostgreSQL server.
 use bytes::{Buf, BufMut, BytesMut};
-use log::{debug, error, info, trace};
+use log::{debug, error, info, trace, warn};
 use std::collections::HashMap;
+use std::time::Instant;
 use tokio::io::{split, AsyncReadExt, BufReader, ReadHalf, WriteHalf};
 use tokio::net::TcpStream;
 use tokio::sync::broadcast::Receiver;
+use tokio::sync::mpsc::Sender;

 use crate::admin::{generate_server_info_for_admin, handle_admin};
-use crate::config::{get_config, Address};
+use crate::config::{get_config, Address, PoolMode};
 use crate::constants::*;
 use crate::errors::Error;
 use crate::messages::*;
@@ -73,21 +75,29 @@ pub struct Client<S, T> {
    /// Last server process id we talked to.
    last_server_id: Option<i32>,

+    /// Connected to server
+    connected_to_server: bool,
+
    /// Name of the server pool for this client (This comes from the database name in the connection string)
-    target_pool_name: String,
+    pool_name: String,

    /// Postgres user for this client (This comes from the user in the connection string)
-    target_user_name: String,
+    username: String,
+
+    /// Application name for this client (defaults to pgcat)
+    application_name: String,

    /// Used to notify clients about an impending shutdown
-    shutdown_event_receiver: Receiver<()>,
+    shutdown: Receiver<()>,
 }

 /// Client entrypoint.
 pub async fn client_entrypoint(
    mut stream: TcpStream,
    client_server_map: ClientServerMap,
-    shutdown_event_receiver: Receiver<()>,
+    shutdown: Receiver<()>,
+    drain: Sender<i32>,
+    admin_only: bool,
 ) -> Result<(), Error> {
    // Figure out if the client wants TLS or not.
    let addr = stream.peer_addr().unwrap();
@@ -106,11 +116,21 @@ pub async fn client_entrypoint(
                write_all(&mut stream, yes).await?;

                // Negotiate TLS.
-                match startup_tls(stream, client_server_map, shutdown_event_receiver).await {
+                match startup_tls(stream, client_server_map, shutdown, admin_only).await {
                    Ok(mut client) => {
                        info!("Client {:?} connected (TLS)", addr);

-                        client.handle().await
+                        if !client.is_admin() {
+                            let _ = drain.send(1).await;
+                        }
+
+                        let result = client.handle().await;
+
+                        if !client.is_admin() {
+                            let _ = drain.send(-1).await;
+                        }
+
+                        result
                    }
                    Err(err) => Err(err),
                }
@@ -136,14 +156,25 @@ pub async fn client_entrypoint(
                            addr,
                            bytes,
                            client_server_map,
-                            shutdown_event_receiver,
+                            shutdown,
+                            admin_only,
                        )
                        .await
                        {
                            Ok(mut client) => {
                                info!("Client {:?} connected (plain)", addr);

-                                client.handle().await
+                                if !client.is_admin() {
+                                    let _ = drain.send(1).await;
+                                }
+
+                                let result = client.handle().await;
+
+                                if !client.is_admin() {
+                                    let _ = drain.send(-1).await;
+                                }
+
+                                result
                            }
                            Err(err) => Err(err),
                        }
@@ -166,14 +197,25 @@ pub async fn client_entrypoint(
                addr,
                bytes,
                client_server_map,
-                shutdown_event_receiver,
+                shutdown,
+                admin_only,
            )
            .await
            {
                Ok(mut client) => {
                    info!("Client {:?} connected (plain)", addr);

-                    client.handle().await
+                    if !client.is_admin() {
+                        let _ = drain.send(1).await;
+                    }
+
+                    let result = client.handle().await;
+
+                    if !client.is_admin() {
+                        let _ = drain.send(-1).await;
+                    }
+
+                    result
                }
                Err(err) => Err(err),
            }
@@ -184,20 +226,21 @@ pub async fn client_entrypoint(
            let (read, write) = split(stream);

            // Continue with cancel query request.
-            match Client::cancel(
-                read,
-                write,
-                addr,
-                bytes,
-                client_server_map,
-                shutdown_event_receiver,
-            )
-            .await
-            {
+            match Client::cancel(read, write, addr, bytes, client_server_map, shutdown).await {
                Ok(mut client) => {
                    info!("Client {:?} issued a cancel query request", addr);

-                    client.handle().await
+                    if !client.is_admin() {
+                        let _ = drain.send(1).await;
+                    }
+
+                    let result = client.handle().await;
+
+                    if !client.is_admin() {
+                        let _ = drain.send(-1).await;
+                    }
+
+                    result
                }

                Err(err) => Err(err),
@@ -250,7 +293,8 @@ where
 pub async fn startup_tls(
    stream: TcpStream,
    client_server_map: ClientServerMap,
-    shutdown_event_receiver: Receiver<()>,
+    shutdown: Receiver<()>,
+    admin_only: bool,
 ) -> Result<Client<ReadHalf<TlsStream<TcpStream>>, WriteHalf<TlsStream<TcpStream>>>, Error> {
    // Negotiate TLS.
    let tls = Tls::new()?;
@@ -280,7 +324,8 @@ pub async fn startup_tls(
                addr,
                bytes,
                client_server_map,
-                shutdown_event_receiver,
+                shutdown,
+                admin_only,
            )
            .await
        }
@@ -295,6 +340,10 @@ where
    S: tokio::io::AsyncRead + std::marker::Unpin,
    T: tokio::io::AsyncWrite + std::marker::Unpin,
 {
+    pub fn is_admin(&self) -> bool {
+        self.admin
+    }
+
    /// Handle Postgres client startup after TLS negotiation is complete
    /// or over plain text.
    pub async fn startup(
@@ -303,29 +352,49 @@ where
        addr: std::net::SocketAddr,
        bytes: BytesMut, // The rest of the startup message.
        client_server_map: ClientServerMap,
-        shutdown_event_receiver: Receiver<()>,
+        shutdown: Receiver<()>,
+        admin_only: bool,
    ) -> Result<Client<S, T>, Error> {
        let config = get_config();
        let stats = get_reporter();
-
-        trace!("Got StartupMessage");
        let parameters = parse_startup(bytes.clone())?;
-        let target_pool_name = match parameters.get("database") {
+
+        // These two parameters are mandatory by the protocol.
+        let pool_name = match parameters.get("database") {
            Some(db) => db,
            None => return Err(Error::ClientError),
        };

-        let target_user_name = match parameters.get("user") {
+        let username = match parameters.get("user") {
            Some(user) => user,
            None => return Err(Error::ClientError),
        };

+        let application_name = match parameters.get("application_name") {
+            Some(application_name) => application_name,
+            None => "pgcat",
+        };
+
        let admin = ["pgcat", "pgbouncer"]
            .iter()
-            .filter(|db| *db == &target_pool_name)
+            .filter(|db| *db == &pool_name)
            .count()
            == 1;

+        // Kick any client that's not admin while we're in admin-only mode.
+        if !admin && admin_only {
+            debug!(
+                "Rejecting non-admin connection to {} when in admin only mode",
+                pool_name
+            );
+            error_response_terminal(
+                &mut write,
+                &format!("terminating connection due to administrator command"),
+            )
+            .await?;
+            return Err(Error::ShuttingDown);
+        }
+
        // Generate random backend ID and secret key
        let process_id: i32 = rand::random();
        let secret_key: i32 = rand::random();
@@ -357,46 +426,56 @@ where
            Err(_) => return Err(Error::SocketError),
        };

+        // Authenticate admin user.
        let (transaction_mode, server_info) = if admin {
-            let correct_user = config.general.admin_username.as_str();
-            let correct_password = config.general.admin_password.as_str();
-
            // Compare server and client hashes.
-            let password_hash = md5_hash_password(correct_user, correct_password, &salt);
+            let password_hash = md5_hash_password(
+                &config.general.admin_username,
+                &config.general.admin_password,
+                &salt,
+            );
+
            if password_hash != password_response {
-                debug!("Password authentication failed");
-                wrong_password(&mut write, target_user_name).await?;
+                warn!("Invalid password {{ username: {:?}, pool_name: {:?}, application_name: {:?} }}", pool_name, username, application_name);
+                wrong_password(&mut write, username).await?;
+
                return Err(Error::ClientError);
            }

            (false, generate_server_info_for_admin())
-        } else {
-            let target_pool = match get_pool(target_pool_name.clone(), target_user_name.clone()) {
+        }
+        // Authenticate normal user.
+        else {
+            let pool = match get_pool(&pool_name, &username) {
                Some(pool) => pool,
                None => {
                    error_response(
                        &mut write,
                        &format!(
                            "No pool configured for database: {:?}, user: {:?}",
-                            target_pool_name, target_user_name
+                            pool_name, username
                        ),
                    )
                    .await?;
+
+                    warn!("Invalid pool name {{ username: {:?}, pool_name: {:?}, application_name: {:?} }}", pool_name, username, application_name);
                    return Err(Error::ClientError);
                }
            };
-            let transaction_mode = target_pool.settings.pool_mode == "transaction";
-            let server_info = target_pool.server_info();
+
            // Compare server and client hashes.
-            let correct_password = target_pool.settings.user.password.as_str();
-            let password_hash = md5_hash_password(&target_user_name, correct_password, &salt);
+            let password_hash = md5_hash_password(&username, &pool.settings.user.password, &salt);

            if password_hash != password_response {
-                debug!("Password authentication failed");
-                wrong_password(&mut write, &target_user_name).await?;
+                warn!("Invalid password {{ username: {:?}, pool_name: {:?}, application_name: {:?} }}", pool_name, username, application_name);
+                wrong_password(&mut write, username).await?;
+
                return Err(Error::ClientError);
            }
-            (transaction_mode, server_info)
+
+            let transaction_mode = pool.settings.pool_mode == PoolMode::Transaction;
+
+            (transaction_mode, pool.server_info())
        };

        debug!("Password authentication successful");
@@ -408,27 +487,26 @@ where

        trace!("Startup OK");

-        // Split the read and write streams
-        // so we can control buffering.
-
        return Ok(Client {
            read: BufReader::new(read),
            write: write,
            addr,
            buffer: BytesMut::with_capacity(8196),
            cancel_mode: false,
-            transaction_mode: transaction_mode,
-            process_id: process_id,
-            secret_key: secret_key,
-            client_server_map: client_server_map,
+            transaction_mode,
+            process_id,
+            secret_key,
+            client_server_map,
            parameters: parameters.clone(),
            stats: stats,
            admin: admin,
            last_address_id: None,
            last_server_id: None,
-            target_pool_name: target_pool_name.clone(),
-            target_user_name: target_user_name.clone(),
-            shutdown_event_receiver: shutdown_event_receiver,
+            pool_name: pool_name.clone(),
+            username: username.clone(),
+            application_name: application_name.to_string(),
+            shutdown,
+            connected_to_server: false,
        });
    }

@@ -439,7 +517,7 @@ where
        addr: std::net::SocketAddr,
        mut bytes: BytesMut, // The rest of the startup message.
        client_server_map: ClientServerMap,
-        shutdown_event_receiver: Receiver<()>,
+        shutdown: Receiver<()>,
    ) -> Result<Client<S, T>, Error> {
        let process_id = bytes.get_i32();
        let secret_key = bytes.get_i32();
@@ -450,17 +528,19 @@ where
            buffer: BytesMut::with_capacity(8196),
            cancel_mode: true,
            transaction_mode: false,
-            process_id: process_id,
-            secret_key: secret_key,
-            client_server_map: client_server_map,
+            process_id,
+            secret_key,
+            client_server_map,
            parameters: HashMap::new(),
            stats: get_reporter(),
            admin: false,
            last_address_id: None,
            last_server_id: None,
-            target_pool_name: String::from("undefined"),
-            target_user_name: String::from("undefined"),
-            shutdown_event_receiver: shutdown_event_receiver,
+            pool_name: String::from("undefined"),
+            username: String::from("undefined"),
+            application_name: String::from("undefined"),
+            shutdown,
+            connected_to_server: false,
        });
    }

@@ -481,7 +561,7 @@ where
                        process_id.clone(),
                        secret_key.clone(),
                        address.clone(),
-                        port.clone(),
+                        *port,
                    ),

                    // The client doesn't know / got the wrong server,
@@ -493,13 +573,18 @@ where
            // Opens a new separate connection to the server, sends the backend_id
            // and secret_key and then closes it for security reasons. No other interactions
            // take place.
-            return Ok(Server::cancel(&address, &port, process_id, secret_key).await?);
+            return Ok(Server::cancel(&address, port, process_id, secret_key).await?);
        }

        // The query router determines where the query is going to go,
        // e.g. primary, replica, which shard.
        let mut query_router = QueryRouter::new();
-        let mut round_robin = 0;
+        self.stats.client_register(
+            self.process_id,
+            self.pool_name.clone(),
+            self.username.clone(),
+            self.application_name.clone(),
+        );

        // Our custom protocol loop.
        // We expect the client to either start a transaction with regular queries
@@ -517,17 +602,40 @@ where
            // SET SHARDING KEY TO 'bigint';

            let mut message = tokio::select! {
-                _ = self.shutdown_event_receiver.recv() => {
-                    error_response_terminal(&mut self.write, &format!("terminating connection due to administrator command")).await?;
-                    return Ok(())
+                _ = self.shutdown.recv() => {
+                    if !self.admin {
+                        error_response_terminal(
+                            &mut self.write,
+                            &format!("terminating connection due to administrator command")
+                        ).await?;
+                        return Ok(())
+                    }
+
+                    // Admin clients ignore shutdown.
+                    else {
+                        read_message(&mut self.read).await?
+                    }
                },
                message_result = read_message(&mut self.read) => message_result?
            };

-            // Avoid taking a server if the client just wants to disconnect.
-            if message[0] as char == 'X' {
-                debug!("Client disconnecting");
-                return Ok(());
+            match message[0] as char {
+                // Buffer extended protocol messages even if we do not have
+                // a server connection yet. Hopefully, when we get the S message
+                // we'll be able to allocate a connection. Also, clients do not expect
+                // the server to respond to these messages so even if we were not able to
+                // allocate a connection, we wouldn't be able to send back an error message
+                // to the client so we buffer them and defer the decision to error out or not
+                // to when we get the S message
+                'P' | 'B' | 'D' | 'E' => {
+                    self.buffer.put(&message[..]);
+                    continue;
+                }
+                'X' => {
+                    debug!("Client disconnecting");
+                    return Ok(());
+                }
+                _ => (),
            }

            // Handle admin database queries.
@@ -540,18 +648,19 @@ where
            // Get a pool instance referenced by the most up-to-date
            // pointer. This ensures we always read the latest config
            // when starting a query.
-            let pool = match get_pool(self.target_pool_name.clone(), self.target_user_name.clone())
-            {
+            let pool = match get_pool(&self.pool_name, &self.username) {
                Some(pool) => pool,
                None => {
                    error_response(
                        &mut self.write,
                        &format!(
                            "No pool configured for database: {:?}, user: {:?}",
-                            self.target_pool_name, self.target_user_name
+                            self.pool_name, self.username
                        ),
                    )
                    .await?;
+
+                    warn!("Invalid pool name {{ username: {:?}, pool_name: {:?}, application_name: {:?} }}", self.pool_name, self.username, self.application_name);
                    return Err(Error::ClientError);
                }
            };
@@ -631,12 +740,7 @@ where

            // Grab a server from the pool.
            let connection = match pool
-                .get(
-                    query_router.shard(),
-                    query_router.role(),
-                    self.process_id,
-                    round_robin,
-                )
+                .get(query_router.shard(), query_router.role(), self.process_id)
                .await
            {
                Ok(conn) => {
@@ -644,9 +748,19 @@ where
                    conn
                }
                Err(err) => {
-                    error!("Could not get connection from pool: {:?}", err);
+                    // Client is attempting to get results from the server,
+                    // but we were unable to grab a connection from the pool
+                    // We'll send back an error message and clean the extended
+                    // protocol buffer
+                    if message[0] as char == 'S' {
+                        error!("Got Sync message but failed to get a connection from the pool");
+                        self.buffer.clear();
+                    }
                    error_response(&mut self.write, "could not get connection from the pool")
                        .await?;
+
+                    error!("Could not get connection from pool: {{ pool_name: {:?}, username: {:?}, shard: {:?}, role: \"{:?}\", error: \"{:?}\" }}",
+                    self.pool_name.clone(), self.username.clone(), query_router.shard(), query_router.role(), err);
                    continue;
                }
            };
@@ -655,22 +769,17 @@ where
            let address = connection.1;
            let server = &mut *reference;

-            round_robin += 1;
-
            // Server is assigned to the client in case the client wants to
            // cancel a query later.
            server.claim(self.process_id, self.secret_key);
+            self.connected_to_server = true;

-            // Update statistics.
-            if let Some(last_address_id) = self.last_address_id {
-                self.stats
-                    .client_disconnecting(self.process_id, last_address_id);
-            }
-            self.stats.client_active(self.process_id, address.id);
-            self.stats.server_active(server.process_id(), address.id);
+            // Update statistics
+            self.stats
+                .client_active(self.process_id, server.server_id());

            self.last_address_id = Some(address.id);
-            self.last_server_id = Some(server.process_id());
+            self.last_server_id = Some(server.server_id());

            debug!(
                "Client {:?} talking to server {:?}",
@@ -678,13 +787,10 @@ where
                server.address()
            );

-            // Set application_name if any.
            // TODO: investigate other parameters and set them too.
-            if self.parameters.contains_key("application_name") {
-                server
-                    .set_name(&self.parameters["application_name"])
-                    .await?;
-            }
+
+            // Set application_name.
+            server.set_name(&self.application_name).await?;

            // Transaction loop. Multiple queries can be issued by the client here.
            // The connection belongs to the client until the transaction is over,
@@ -701,12 +807,7 @@ where
                        Err(err) => {
                            // Client disconnected inside a transaction.
                            // Clean up the server and re-use it.
-                            // This prevents connection thrashing by bad clients.
-                            if server.in_transaction() {
-                                server.query("ROLLBACK").await?;
-                                server.query("DISCARD ALL").await?;
-                                server.set_name("pgcat").await?;
-                            }
+                            server.checkin_cleanup().await?;

                            return Err(err);
                        }
@@ -731,52 +832,16 @@ where
                    'Q' => {
                        debug!("Sending query to server");

-                        self.send_server_message(
-                            server,
-                            original,
-                            &address,
-                            query_router.shard(),
-                            &pool,
-                        )
-                        .await?;
-
-                        // Read all data the server has to offer, which can be multiple messages
-                        // buffered in 8196 bytes chunks.
-                        loop {
-                            let response = self
-                                .receive_server_message(
-                                    server,
-                                    &address,
-                                    query_router.shard(),
-                                    &pool,
-                                )
-                                .await?;
-
-                            // Send server reply to the client.
-                            match write_all_half(&mut self.write, response).await {
-                                Ok(_) => (),
-                                Err(err) => {
-                                    server.mark_bad();
-                                    return Err(err);
-                                }
-                            };
-
-                            if !server.is_data_available() {
-                                break;
-                            }
-                        }
-
-                        // Report query executed statistics.
-                        self.stats.query(self.process_id, address.id);
+                        self.send_and_receive_loop(code, original, server, &address, &pool)
+                            .await?;

                        if !server.in_transaction() {
                            // Report transaction executed statistics.
-                            self.stats.transaction(self.process_id, address.id);
+                            self.stats.transaction(self.process_id, server.server_id());

                            // Release server back to the pool if we are in transaction mode.
                            // If we are in session mode, we keep the server until the client disconnects.
                            if self.transaction_mode {
-                                self.stats.server_idle(server.process_id(), address.id);
                                break;
                            }
                        }
@@ -784,16 +849,7 @@ where

                    // Terminate
                    'X' => {
-                        // Client closing. Rollback and clean up
-                        // connection before releasing into the pool.
-                        // Pgbouncer closes the connection which leads to
-                        // connection thrashing when clients misbehave.
-                        if server.in_transaction() {
-                            server.query("ROLLBACK").await?;
-                            server.query("DISCARD ALL").await?;
-                            server.set_name("pgcat").await?;
-                        }
-
+                        server.checkin_cleanup().await?;
                        self.release();

                        return Ok(());
@@ -830,52 +886,40 @@ where

                        self.buffer.put(&original[..]);

-                        self.send_server_message(
-                            server,
+                        // Clone after freeze does not allocate
+                        let first_message_code = (*self.buffer.get(0).unwrap_or(&0)) as char;
+
+                        // Almost certainly true
+                        if first_message_code == 'P' {
+                            // Message layout
+                            // P followed by 32 int followed by null-terminated statement name
+                            // So message code should be in offset 0 of the buffer, first character
+                            // in prepared statement name would be index 5
+                            let first_char_in_name = *self.buffer.get(5).unwrap_or(&0);
+                            if first_char_in_name != 0 {
+                                // This is a named prepared statement
+                                // Server connection state will need to be cleared at checkin
+                                server.mark_dirty();
+                            }
+                        }
+
+                        self.send_and_receive_loop(
+                            code,
                            self.buffer.clone(),
+                            server,
                            &address,
-                            query_router.shard(),
                            &pool,
                        )
                        .await?;

                        self.buffer.clear();

-                        // Read all data the server has to offer, which can be multiple messages
-                        // buffered in 8196 bytes chunks.
-                        loop {
-                            let response = self
-                                .receive_server_message(
-                                    server,
-                                    &address,
-                                    query_router.shard(),
-                                    &pool,
-                                )
-                                .await?;
-
-                            match write_all_half(&mut self.write, response).await {
-                                Ok(_) => (),
-                                Err(err) => {
-                                    server.mark_bad();
-                                    return Err(err);
-                                }
-                            };
-
-                            if !server.is_data_available() {
-                                break;
-                            }
-                        }
-
-                        // Report query executed statistics.
-                        self.stats.query(self.process_id, address.id);
-
                        if !server.in_transaction() {
-                            self.stats.transaction(self.process_id, address.id);
+                            self.stats.transaction(self.process_id, server.server_id());

                            // Release server back to the pool if we are in transaction mode.
                            // If we are in session mode, we keep the server until the client disconnects.
                            if self.transaction_mode {
-                                self.stats.server_idle(server.process_id(), address.id);
                                break;
                            }
                        }
@@ -885,32 +929,18 @@ where
                    'd' => {
                        // Forward the data to the server,
                        // don't buffer it since it can be rather large.
-                        self.send_server_message(
-                            server,
-                            original,
-                            &address,
-                            query_router.shard(),
-                            &pool,
-                        )
-                        .await?;
+                        self.send_server_message(server, original, &address, &pool)
+                            .await?;
                    }

                    // CopyDone or CopyFail
                    // Copy is done, successfully or not.
                    'c' | 'f' => {
-                        self.send_server_message(
-                            server,
-                            original,
-                            &address,
-                            query_router.shard(),
-                            &pool,
-                        )
-                        .await?;
-
-                        let response = self
-                            .receive_server_message(server, &address, query_router.shard(), &pool)
+                        self.send_server_message(server, original, &address, &pool)
                            .await?;

+                        let response = self.receive_server_message(server, &address, &pool).await?;
+
                        match write_all_half(&mut self.write, response).await {
                            Ok(_) => (),
                            Err(err) => {
@@ -920,12 +950,11 @@ where
                        };

                        if !server.in_transaction() {
-                            self.stats.transaction(self.process_id, address.id);
+                            self.stats.transaction(self.process_id, server.server_id());

                            // Release server back to the pool if we are in transaction mode.
                            // If we are in session mode, we keep the server until the client disconnects.
                            if self.transaction_mode {
-                                self.stats.server_idle(server.process_id(), address.id);
                                break;
                            }
                        }
@@ -941,8 +970,12 @@ where

            // The server is no longer bound to us, we can't cancel it's queries anymore.
            debug!("Releasing server back into the pool");
+            server.checkin_cleanup().await?;
+            self.stats.server_idle(server.server_id());
+            self.connected_to_server = false;
+
            self.release();
-            self.stats.client_idle(self.process_id, address.id);
+            self.stats.client_idle(self.process_id);
        }
    }

@@ -952,35 +985,112 @@ where
        guard.remove(&(self.process_id, self.secret_key));
    }

+    async fn send_and_receive_loop(
+        &mut self,
+        code: char,
+        message: BytesMut,
+        server: &mut Server,
+        address: &Address,
+        pool: &ConnectionPool,
+    ) -> Result<(), Error> {
+        debug!("Sending {} to server", code);
+
+        self.send_server_message(server, message, &address, &pool)
+            .await?;
+
+        let query_start = Instant::now();
+        // Read all data the server has to offer, which can be multiple messages
+        // buffered in 8196 bytes chunks.
+        loop {
+            let response = self.receive_server_message(server, &address, &pool).await?;
+
+            match write_all_half(&mut self.write, response).await {
+                Ok(_) => (),
+                Err(err) => {
+                    server.mark_bad();
+                    return Err(err);
+                }
+            };
+
+            if !server.is_data_available() {
+                break;
+            }
+        }
+
+        // Report query executed statistics.
+        self.stats.query(
+            self.process_id,
+            server.server_id(),
+            Instant::now().duration_since(query_start).as_millis(),
+        );
+
+        Ok(())
+    }
+
    async fn send_server_message(
        &self,
        server: &mut Server,
        message: BytesMut,
        address: &Address,
-        shard: usize,
        pool: &ConnectionPool,
    ) -> Result<(), Error> {
        match server.send(message).await {
            Ok(_) => Ok(()),
            Err(err) => {
-                pool.ban(address, shard, self.process_id);
+                pool.ban(address, self.process_id);
                Err(err)
            }
        }
    }

    async fn receive_server_message(
-        &self,
+        &mut self,
        server: &mut Server,
        address: &Address,
-        shard: usize,
        pool: &ConnectionPool,
    ) -> Result<BytesMut, Error> {
-        match server.recv().await {
-            Ok(message) => Ok(message),
-            Err(err) => {
-                pool.ban(address, shard, self.process_id);
-                Err(err)
+        if pool.settings.user.statement_timeout > 0 {
+            match tokio::time::timeout(
+                tokio::time::Duration::from_millis(pool.settings.user.statement_timeout),
+                server.recv(),
+            )
+            .await
+            {
+                Ok(result) => match result {
+                    Ok(message) => Ok(message),
+                    Err(err) => {
+                        pool.ban(address, self.process_id);
+                        error_response_terminal(
+                            &mut self.write,
+                            &format!("error receiving data from server: {:?}", err),
+                        )
+                        .await?;
+                        Err(err)
+                    }
+                },
+                Err(_) => {
+                    error!(
+                        "Statement timeout while talking to {:?} with user {}",
+                        address, pool.settings.user.username
+                    );
+                    server.mark_bad();
+                    pool.ban(address, self.process_id);
+                    error_response_terminal(&mut self.write, "pool statement timeout").await?;
+                    Err(Error::StatementTimeout)
+                }
+            }
+        } else {
+            match server.recv().await {
+                Ok(message) => Ok(message),
+                Err(err) => {
+                    pool.ban(address, self.process_id);
+                    error_response_terminal(
+                        &mut self.write,
+                        &format!("error receiving data from server: {:?}", err),
+                    )
+                    .await?;
+                    Err(err)
+                }
            }
        }
    }
@@ -991,15 +1101,11 @@ impl<S, T> Drop for Client<S, T> {
        let mut guard = self.client_server_map.lock();
        guard.remove(&(self.process_id, self.secret_key));

-        // Update statistics.
-        if let Some(address_id) = self.last_address_id {
-            self.stats.client_disconnecting(self.process_id, address_id);
-
-            if let Some(process_id) = self.last_server_id {
-                self.stats.server_idle(process_id, address_id);
-            }
+        // Dirty shutdown
+        // TODO: refactor, this is not the best way to handle state management.
+        self.stats.client_disconnecting(self.process_id);
+        if self.connected_to_server && self.last_server_id.is_some() {
+            self.stats.server_idle(self.last_server_id.unwrap());
        }
-
-        // self.release();
    }
 }
--- a/src/config.rs
+++ b/src/config.rs
@@ -3,7 +3,7 @@ use arc_swap::ArcSwap;
 use log::{error, info};
 use once_cell::sync::Lazy;
 use serde_derive::{Deserialize, Serialize};
-use std::collections::{HashMap, HashSet};
+use std::collections::{BTreeMap, HashMap, HashSet};
 use std::hash::Hash;
 use std::path::Path;
 use std::sync::Arc;
@@ -12,8 +12,9 @@ use tokio::io::AsyncReadExt;
 use toml;

 use crate::errors::Error;
+use crate::pool::{ClientServerMap, ConnectionPool};
+use crate::sharding::ShardingFunction;
 use crate::tls::{load_certs, load_keys};
-use crate::{ClientServerMap, ConnectionPool};

 pub const VERSION: &str = env!("CARGO_PKG_VERSION");

@@ -23,7 +24,9 @@ static CONFIG: Lazy<ArcSwap<Config>> = Lazy::new(|| ArcSwap::from_pointee(Config
 /// Server role: primary or replica.
 #[derive(Clone, PartialEq, Serialize, Deserialize, Hash, std::cmp::Eq, Debug, Copy)]
 pub enum Role {
+    #[serde(alias = "primary", alias = "Primary")]
    Primary,
+    #[serde(alias = "replica", alias = "Replica")]
    Replica,
 }

@@ -57,13 +60,35 @@ impl PartialEq<Role> for Option<Role> {
 /// Address identifying a PostgreSQL server uniquely.
 #[derive(Clone, PartialEq, Hash, std::cmp::Eq, Debug)]
 pub struct Address {
+    /// Unique ID per addressable Postgres server.
    pub id: usize,
+
+    /// Server host.
    pub host: String,
-    pub port: String,
+
+    /// Server port.
+    pub port: u16,
+
+    /// Shard number of this Postgres server.
    pub shard: usize,
+
+    /// The name of the Postgres database.
    pub database: String,
+
+    /// Server role: replica, primary.
    pub role: Role,
+
+    /// If it's a replica, number it for reference and failover.
    pub replica_number: usize,
+
+    /// Position of the server in the pool for failover.
+    pub address_index: usize,
+
+    /// The name of the user configured to use this pool.
+    pub username: String,
+
+    /// The name of this pool (i.e. database name visible to the client).
+    pub pool_name: String,
 }

 impl Default for Address {
@@ -71,11 +96,14 @@ impl Default for Address {
        Address {
            id: 0,
            host: String::from("127.0.0.1"),
-            port: String::from("5432"),
+            port: 5432,
            shard: 0,
+            address_index: 0,
            replica_number: 0,
            database: String::from("database"),
            role: Role::Replica,
+            username: String::from("username"),
+            pool_name: String::from("pool_name"),
        }
    }
 }
@@ -84,22 +112,24 @@ impl Address {
    /// Address name (aka database) used in `SHOW STATS`, `SHOW DATABASES`, and `SHOW POOLS`.
    pub fn name(&self) -> String {
        match self.role {
-            Role::Primary => format!("{}_shard_{}_primary", self.database, self.shard),
+            Role::Primary => format!("{}_shard_{}_primary", self.pool_name, self.shard),

            Role::Replica => format!(
                "{}_shard_{}_replica_{}",
-                self.database, self.shard, self.replica_number
+                self.pool_name, self.shard, self.replica_number
            ),
        }
    }
 }

 /// PostgreSQL user.
-#[derive(Clone, PartialEq, Hash, std::cmp::Eq, Serialize, Deserialize, Debug)]
+#[derive(Clone, PartialEq, Hash, Eq, Serialize, Deserialize, Debug)]
 pub struct User {
    pub username: String,
    pub password: String,
    pub pool_size: u32,
+    #[serde(default)] // 0
+    pub statement_timeout: u64,
 }

 impl Default for User {
@@ -108,6 +138,7 @@ impl Default for User {
            username: String::from("postgres"),
            password: String::new(),
            pool_size: 15,
+            statement_timeout: 0,
        }
    }
 }
@@ -115,32 +146,81 @@ impl Default for User {
 /// General configuration.
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq)]
 pub struct General {
+    #[serde(default = "General::default_host")]
    pub host: String,
+
+    #[serde(default = "General::default_port")]
    pub port: i16,
+
    pub enable_prometheus_exporter: Option<bool>,
+    pub prometheus_exporter_port: i16,
+
+    #[serde(default = "General::default_connect_timeout")]
    pub connect_timeout: u64,
-    pub healthcheck_timeout: u64,
+
+    #[serde(default = "General::default_shutdown_timeout")]
    pub shutdown_timeout: u64,
+
+    #[serde(default = "General::default_healthcheck_timeout")]
+    pub healthcheck_timeout: u64,
+
+    #[serde(default = "General::default_healthcheck_delay")]
    pub healthcheck_delay: u64,
+
+    #[serde(default = "General::default_ban_time")]
    pub ban_time: i64,
+
+    #[serde(default)] // False
    pub autoreload: bool,
+
    pub tls_certificate: Option<String>,
    pub tls_private_key: Option<String>,
    pub admin_username: String,
    pub admin_password: String,
 }

+impl General {
+    pub fn default_host() -> String {
+        "0.0.0.0".into()
+    }
+
+    pub fn default_port() -> i16 {
+        5432
+    }
+
+    pub fn default_connect_timeout() -> u64 {
+        1000
+    }
+
+    pub fn default_shutdown_timeout() -> u64 {
+        60000
+    }
+
+    pub fn default_healthcheck_timeout() -> u64 {
+        1000
+    }
+
+    pub fn default_healthcheck_delay() -> u64 {
+        30000
+    }
+
+    pub fn default_ban_time() -> i64 {
+        60
+    }
+}
+
 impl Default for General {
    fn default() -> General {
        General {
-            host: String::from("localhost"),
-            port: 5432,
+            host: Self::default_host(),
+            port: Self::default_port(),
            enable_prometheus_exporter: Some(false),
-            connect_timeout: 5000,
-            healthcheck_timeout: 1000,
-            shutdown_timeout: 60000,
-            healthcheck_delay: 30000,
-            ban_time: 60,
+            prometheus_exporter_port: 9930,
+            connect_timeout: General::default_connect_timeout(),
+            shutdown_timeout: Self::default_shutdown_timeout(),
+            healthcheck_timeout: Self::default_healthcheck_timeout(),
+            healthcheck_delay: Self::default_healthcheck_delay(),
+            ban_time: Self::default_ban_time(),
            autoreload: false,
            tls_certificate: None,
            tls_private_key: None,
@@ -149,50 +229,166 @@ impl Default for General {
        }
    }
 }
-#[derive(Serialize, Deserialize, Debug, Clone, PartialEq)]
-pub struct Pool {
-    pub pool_mode: String,
-    pub default_role: String,
-    pub query_parser_enabled: bool,
-    pub primary_reads_enabled: bool,
-    pub sharding_function: String,
-    pub shards: HashMap<String, Shard>,
-    pub users: HashMap<String, User>,
+
+/// Pool mode:
+/// - transaction: server serves one transaction,
+/// - session: server is attached to the client.
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, Copy, Hash)]
+pub enum PoolMode {
+    #[serde(alias = "transaction", alias = "Transaction")]
+    Transaction,
+
+    #[serde(alias = "session", alias = "Session")]
+    Session,
 }
-impl Default for Pool {
-    fn default() -> Pool {
-        Pool {
-            pool_mode: String::from("transaction"),
-            shards: HashMap::from([(String::from("1"), Shard::default())]),
-            users: HashMap::default(),
-            default_role: String::from("any"),
-            query_parser_enabled: false,
-            primary_reads_enabled: true,
-            sharding_function: "pg_bigint_hash".to_string(),
+
+impl ToString for PoolMode {
+    fn to_string(&self) -> String {
+        match *self {
+            PoolMode::Transaction => "transaction".to_string(),
+            PoolMode::Session => "session".to_string(),
        }
    }
 }

+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, Hash)]
+pub struct Pool {
+    #[serde(default = "Pool::default_pool_mode")]
+    pub pool_mode: PoolMode,
+
+    pub default_role: String,
+
+    #[serde(default)] // False
+    pub query_parser_enabled: bool,
+
+    #[serde(default)] // False
+    pub primary_reads_enabled: bool,
+
+    pub connect_timeout: Option<u64>,
+
+    pub sharding_function: ShardingFunction,
+    pub shards: BTreeMap<String, Shard>,
+    pub users: BTreeMap<String, User>,
+}
+
+impl Pool {
+    pub fn default_pool_mode() -> PoolMode {
+        PoolMode::Transaction
+    }
+
+    pub fn validate(&self) -> Result<(), Error> {
+        match self.default_role.as_ref() {
+            "any" => (),
+            "primary" => (),
+            "replica" => (),
+            other => {
+                error!(
+                    "Query router default_role must be 'primary', 'replica', or 'any', got: '{}'",
+                    other
+                );
+                return Err(Error::BadConfig);
+            }
+        };
+
+        for (shard_idx, shard) in &self.shards {
+            match shard_idx.parse::<usize>() {
+                Ok(_) => (),
+                Err(_) => {
+                    error!(
+                        "Shard '{}' is not a valid number, shards must be numbered starting at 0",
+                        shard_idx
+                    );
+                    return Err(Error::BadConfig);
+                }
+            };
+            shard.validate()?;
+        }
+
+        Ok(())
+    }
+}
+
+impl Default for Pool {
+    fn default() -> Pool {
+        Pool {
+            pool_mode: Self::default_pool_mode(),
+            shards: BTreeMap::from([(String::from("1"), Shard::default())]),
+            users: BTreeMap::default(),
+            default_role: String::from("any"),
+            query_parser_enabled: false,
+            primary_reads_enabled: false,
+            sharding_function: ShardingFunction::PgBigintHash,
+            connect_timeout: None,
+        }
+    }
+}
+
+#[derive(Clone, PartialEq, Serialize, Deserialize, Debug, Hash, Eq)]
+pub struct ServerConfig {
+    pub host: String,
+    pub port: u16,
+    pub role: Role,
+}
+
 /// Shard configuration.
-#[derive(Serialize, Deserialize, Debug, Clone, PartialEq)]
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Hash, Eq)]
 pub struct Shard {
    pub database: String,
-    pub servers: Vec<(String, u16, String)>,
+    pub servers: Vec<ServerConfig>,
+}
+
+impl Shard {
+    pub fn validate(&self) -> Result<(), Error> {
+        // We use addresses as unique identifiers,
+        // let's make sure they are unique in the config as well.
+        let mut dup_check = HashSet::new();
+        let mut primary_count = 0;
+
+        if self.servers.len() == 0 {
+            error!("Shard {} has no servers configured", self.database);
+            return Err(Error::BadConfig);
+        }
+
+        for server in &self.servers {
+            dup_check.insert(server);
+
+            // Check that we define only zero or one primary.
+            match server.role {
+                Role::Primary => primary_count += 1,
+                _ => (),
+            };
+        }
+
+        if primary_count > 1 {
+            error!(
+                "Shard {} has more than on primary configured",
+                self.database
+            );
+            return Err(Error::BadConfig);
+        }
+
+        if dup_check.len() != self.servers.len() {
+            error!("Shard {} contains duplicate server configs", self.database);
+            return Err(Error::BadConfig);
+        }
+
+        Ok(())
+    }
 }

 impl Default for Shard {
    fn default() -> Shard {
        Shard {
-            servers: vec![(String::from("localhost"), 5432, String::from("primary"))],
+            servers: vec![ServerConfig {
+                host: String::from("localhost"),
+                port: 5432,
+                role: Role::Primary,
+            }],
            database: String::from("postgres"),
        }
    }
 }

-fn default_path() -> String {
-    String::from("pgcat.toml")
-}
-
 /// Configuration wrapper.
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq)]
 pub struct Config {
@@ -200,24 +396,30 @@ pub struct Config {
    // so we should always put simple fields before nested fields
    // in all serializable structs to avoid ValueAfterTable errors
    // These errors occur when the toml serializer is about to produce
-    // ambigous toml structure like the one below
+    // ambiguous toml structure like the one below
    // [main]
    // field1_under_main = 1
    // field2_under_main = 2
    // [main.subconf]
    // field1_under_subconf = 1
    // field3_under_main = 3 # This field will be interpreted as being under subconf and not under main
-    #[serde(default = "default_path")]
+    #[serde(default = "Config::default_path")]
    pub path: String,

    pub general: General,
    pub pools: HashMap<String, Pool>,
 }

+impl Config {
+    pub fn default_path() -> String {
+        String::from("pgcat.toml")
+    }
+}
+
 impl Default for Config {
    fn default() -> Config {
        Config {
-            path: String::from("pgcat.toml"),
+            path: Self::default_path(),
            general: General::default(),
            pools: HashMap::default(),
        }
@@ -233,7 +435,7 @@ impl From<&Config> for std::collections::HashMap<String, String> {
                [
                    (
                        format!("pools.{}.pool_mode", pool_name),
-                        pool.pool_mode.clone(),
+                        pool.pool_mode.to_string(),
                    ),
                    (
                        format!("pools.{}.primary_reads_enabled", pool_name),
@@ -249,7 +451,7 @@ impl From<&Config> for std::collections::HashMap<String, String> {
                    ),
                    (
                        format!("pools.{}.sharding_function", pool_name),
-                        pool.sharding_function.clone(),
+                        pool.sharding_function.to_string(),
                    ),
                    (
                        format!("pools.{:?}.shard_count", pool_name),
@@ -271,6 +473,10 @@ impl From<&Config> for std::collections::HashMap<String, String> {
        let mut static_settings = vec![
            ("host".to_string(), config.general.host.to_string()),
            ("port".to_string(), config.general.port.to_string()),
+            (
+                "prometheus_exporter_port".to_string(),
+                config.general.prometheus_exporter_port.to_string(),
+            ),
            (
                "connect_timeout".to_string(),
                config.general.connect_timeout.to_string(),
@@ -326,9 +532,10 @@ impl Config {
        };

        for (pool_name, pool_config) in &self.pools {
-            info!("--- Settings for pool {} ---", pool_name);
+            // TODO: Make this output prettier (maybe a table?)
            info!(
-                "Pool size from all users: {}",
+                "[pool: {}] Maximum user connections: {}",
+                pool_name,
                pool_config
                    .users
                    .iter()
@@ -336,14 +543,98 @@ impl Config {
                    .sum::<u32>()
                    .to_string()
            );
-            info!("Pool mode: {}", pool_config.pool_mode);
-            info!("Sharding function: {}", pool_config.sharding_function);
-            info!("Primary reads: {}", pool_config.primary_reads_enabled);
-            info!("Query router: {}", pool_config.query_parser_enabled);
-            info!("Number of shards: {}", pool_config.shards.len());
-            info!("Number of users: {}", pool_config.users.len());
+            info!(
+                "[pool: {}] Pool mode: {:?}",
+                pool_name, pool_config.pool_mode
+            );
+            let connect_timeout = match pool_config.connect_timeout {
+                Some(connect_timeout) => connect_timeout,
+                None => self.general.connect_timeout,
+            };
+            info!(
+                "[pool: {}] Connection timeout: {}ms",
+                pool_name, connect_timeout
+            );
+            info!(
+                "[pool: {}] Sharding function: {}",
+                pool_name,
+                pool_config.sharding_function.to_string()
+            );
+            info!(
+                "[pool: {}] Primary reads: {}",
+                pool_name, pool_config.primary_reads_enabled
+            );
+            info!(
+                "[pool: {}] Query router: {}",
+                pool_name, pool_config.query_parser_enabled
+            );
+            info!(
+                "[pool: {}] Number of shards: {}",
+                pool_name,
+                pool_config.shards.len()
+            );
+            info!(
+                "[pool: {}] Number of users: {}",
+                pool_name,
+                pool_config.users.len()
+            );
+
+            for user in &pool_config.users {
+                info!(
+                    "[pool: {}][user: {}] Pool size: {}",
+                    pool_name, user.1.username, user.1.pool_size,
+                );
+                info!(
+                    "[pool: {}][user: {}] Statement timeout: {}",
+                    pool_name, user.1.username, user.1.statement_timeout
+                )
+            }
        }
    }
+
+    pub fn validate(&mut self) -> Result<(), Error> {
+        // Validate TLS!
+        match self.general.tls_certificate.clone() {
+            Some(tls_certificate) => {
+                match load_certs(&Path::new(&tls_certificate)) {
+                    Ok(_) => {
+                        // Cert is okay, but what about the private key?
+                        match self.general.tls_private_key.clone() {
+                            Some(tls_private_key) => {
+                                match load_keys(&Path::new(&tls_private_key)) {
+                                    Ok(_) => (),
+                                    Err(err) => {
+                                        error!(
+                                            "tls_private_key is incorrectly configured: {:?}",
+                                            err
+                                        );
+                                        return Err(Error::BadConfig);
+                                    }
+                                }
+                            }
+
+                            None => {
+                                error!("tls_certificate is set, but the tls_private_key is not");
+                                return Err(Error::BadConfig);
+                            }
+                        };
+                    }
+
+                    Err(err) => {
+                        error!("tls_certificate is incorrectly configured: {:?}", err);
+                        return Err(Error::BadConfig);
+                    }
+                }
+            }
+            None => (),
+        };
+
+        for (_, pool) in &mut self.pools {
+            pool.validate()?;
+        }
+
+        Ok(())
+    }
 }

 /// Get a read-only instance of the configuration
@@ -380,120 +671,7 @@ pub async fn parse(path: &str) -> Result<(), Error> {
        }
    };

-    // Validate TLS!
-    match config.general.tls_certificate.clone() {
-        Some(tls_certificate) => {
-            match load_certs(&Path::new(&tls_certificate)) {
-                Ok(_) => {
-                    // Cert is okay, but what about the private key?
-                    match config.general.tls_private_key.clone() {
-                        Some(tls_private_key) => match load_keys(&Path::new(&tls_private_key)) {
-                            Ok(_) => (),
-                            Err(err) => {
-                                error!("tls_private_key is incorrectly configured: {:?}", err);
-                                return Err(Error::BadConfig);
-                            }
-                        },
-
-                        None => {
-                            error!("tls_certificate is set, but the tls_private_key is not");
-                            return Err(Error::BadConfig);
-                        }
-                    };
-                }
-
-                Err(err) => {
-                    error!("tls_certificate is incorrectly configured: {:?}", err);
-                    return Err(Error::BadConfig);
-                }
-            }
-        }
-        None => (),
-    };
-
-    for (pool_name, pool) in &config.pools {
-        match pool.sharding_function.as_ref() {
-            "pg_bigint_hash" => (),
-            "sha1" => (),
-            _ => {
-                error!(
-                    "Supported sharding functions are: 'pg_bigint_hash', 'sha1', got: '{}' in pool {} settings",
-                    pool.sharding_function,
-                    pool_name
-                );
-                return Err(Error::BadConfig);
-            }
-        };
-
-        match pool.default_role.as_ref() {
-            "any" => (),
-            "primary" => (),
-            "replica" => (),
-            other => {
-                error!(
-                    "Query router default_role must be 'primary', 'replica', or 'any', got: '{}'",
-                    other
-                );
-                return Err(Error::BadConfig);
-            }
-        };
-
-        for shard in &pool.shards {
-            // We use addresses as unique identifiers,
-            // let's make sure they are unique in the config as well.
-            let mut dup_check = HashSet::new();
-            let mut primary_count = 0;
-
-            match shard.0.parse::<usize>() {
-                Ok(_) => (),
-                Err(_) => {
-                    error!(
-                        "Shard '{}' is not a valid number, shards must be numbered starting at 0",
-                        shard.0
-                    );
-                    return Err(Error::BadConfig);
-                }
-            };
-
-            if shard.1.servers.len() == 0 {
-                error!("Shard {} has no servers configured", shard.0);
-                return Err(Error::BadConfig);
-            }
-
-            for server in &shard.1.servers {
-                dup_check.insert(server);
-
-                // Check that we define only zero or one primary.
-                match server.2.as_ref() {
-                    "primary" => primary_count += 1,
-                    _ => (),
-                };
-
-                // Check role spelling.
-                match server.2.as_ref() {
-                    "primary" => (),
-                    "replica" => (),
-                    _ => {
-                        error!(
-                            "Shard {} server role must be either 'primary' or 'replica', got: '{}'",
-                            shard.0, server.2
-                        );
-                        return Err(Error::BadConfig);
-                    }
-                };
-            }
-
-            if primary_count > 1 {
-                error!("Shard {} has more than on primary configured", &shard.0);
-                return Err(Error::BadConfig);
-            }
-
-            if dup_check.len() != shard.1.servers.len() {
-                error!("Shard {} contains duplicate server configs", &shard.0);
-                return Err(Error::BadConfig);
-            }
-        }
-    }
+    config.validate()?;

    config.path = path.to_string();

@@ -515,7 +693,7 @@ pub async fn reload_config(client_server_map: ClientServerMap) -> Result<bool, E
    let new_config = get_config();

    if old_config.pools != new_config.pools {
-        info!("Pool configuration changed, re-creating server pools");
+        info!("Pool configuration changed");
        ConnectionPool::from_config(client_server_map).await?;
        Ok(true)
    } else if old_config != new_config {
@@ -543,12 +721,12 @@ mod test {
        assert_eq!(get_config().pools["simple_db"].users.len(), 1);

        assert_eq!(
-            get_config().pools["sharded_db"].shards["0"].servers[0].0,
+            get_config().pools["sharded_db"].shards["0"].servers[0].host,
            "127.0.0.1"
        );
        assert_eq!(
-            get_config().pools["sharded_db"].shards["1"].servers[0].2,
-            "primary"
+            get_config().pools["sharded_db"].shards["1"].servers[0].role,
+            Role::Primary
        );
        assert_eq!(
            get_config().pools["sharded_db"].shards["1"].database,
@@ -566,11 +744,11 @@ mod test {
        assert_eq!(get_config().pools["sharded_db"].default_role, "any");

        assert_eq!(
-            get_config().pools["simple_db"].shards["0"].servers[0].0,
+            get_config().pools["simple_db"].shards["0"].servers[0].host,
            "127.0.0.1"
        );
        assert_eq!(
-            get_config().pools["simple_db"].shards["0"].servers[0].1,
+            get_config().pools["simple_db"].shards["0"].servers[0].port,
            5432
        );
        assert_eq!(
--- a/src/errors.rs
+++ b/src/errors.rs
@@ -11,4 +11,6 @@ pub enum Error {
    AllServersDown,
    ClientError,
    TlsError,
+    StatementTimeout,
+    ShuttingDown,
 }
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -0,0 +1,32 @@
+pub mod config;
+pub mod constants;
+pub mod errors;
+pub mod messages;
+pub mod pool;
+pub mod scram;
+pub mod server;
+pub mod sharding;
+pub mod stats;
+pub mod tls;
+
+/// Format chrono::Duration to be more human-friendly.
+///
+/// # Arguments
+///
+/// * `duration` - A duration of time
+pub fn format_duration(duration: &chrono::Duration) -> String {
+    let milliseconds = format!("{:0>3}", duration.num_milliseconds() % 1000);
+
+    let seconds = format!("{:0>2}", duration.num_seconds() % 60);
+
+    let minutes = format!("{:0>2}", duration.num_minutes() % 60);
+
+    let hours = format!("{:0>2}", duration.num_hours() % 24);
+
+    let days = duration.num_days().to_string();
+
+    format!(
+        "{}d {}:{}:{}.{}",
+        days, hours, minutes, seconds, milliseconds
+    )
+}
--- a/src/main.rs
+++ b/src/main.rs
@@ -24,6 +24,7 @@ extern crate async_trait;
 extern crate bb8;
 extern crate bytes;
 extern crate env_logger;
+extern crate exitcode;
 extern crate log;
 extern crate md5;
 extern crate num_cpus;
@@ -36,8 +37,9 @@ extern crate tokio;
 extern crate tokio_rustls;
 extern crate toml;

-use log::{debug, error, info};
+use log::{error, info, warn};
 use parking_lot::Mutex;
+use pgcat::format_duration;
 use tokio::net::TcpListener;
 use tokio::{
    signal::unix::{signal as unix_signal, SignalKind},
@@ -66,18 +68,20 @@ mod stats;
 mod tls;

 use crate::config::{get_config, reload_config, VERSION};
+use crate::errors::Error;
 use crate::pool::{ClientServerMap, ConnectionPool};
 use crate::prometheus::start_metric_server;
 use crate::stats::{Collector, Reporter, REPORTER};

 #[tokio::main(worker_threads = 4)]
 async fn main() {
-    env_logger::init();
+    env_logger::builder().format_timestamp_micros().init();
+
    info!("Welcome to PgCat! Meow. (Version {})", VERSION);

    if !query_router::QueryRouter::setup() {
        error!("Could not setup query router");
-        return;
+        std::process::exit(exitcode::CONFIG);
    }

    let args = std::env::args().collect::<Vec<String>>();
@@ -92,19 +96,22 @@ async fn main() {
        Ok(_) => (),
        Err(err) => {
            error!("Config parse error: {:?}", err);
-            return;
+            std::process::exit(exitcode::CONFIG);
        }
    };

    let config = get_config();

    if let Some(true) = config.general.enable_prometheus_exporter {
-        let http_addr_str = format!("{}:{}", config.general.host, crate::prometheus::HTTP_PORT);
+        let http_addr_str = format!(
+            "{}:{}",
+            config.general.host, config.general.prometheus_exporter_port
+        );
        let http_addr = match SocketAddr::from_str(&http_addr_str) {
            Ok(addr) => addr,
            Err(err) => {
                error!("Invalid http address: {}", err);
-                return;
+                std::process::exit(exitcode::CONFIG);
            }
        };
        tokio::task::spawn(async move {
@@ -118,7 +125,7 @@ async fn main() {
        Ok(sock) => sock,
        Err(err) => {
            error!("Listener socket error: {:?}", err);
-            return;
+            std::process::exit(exitcode::CONFIG);
        }
    };

@@ -130,125 +137,33 @@ async fn main() {
    let client_server_map: ClientServerMap = Arc::new(Mutex::new(HashMap::new()));

    // Statistics reporting.
-    let (tx, rx) = mpsc::channel(100);
-    REPORTER.store(Arc::new(Reporter::new(tx.clone())));
+    let (stats_tx, stats_rx) = mpsc::channel(100_000);
+    REPORTER.store(Arc::new(Reporter::new(stats_tx.clone())));

    // Connection pool that allows to query all shards and replicas.
    match ConnectionPool::from_config(client_server_map.clone()).await {
        Ok(_) => (),
        Err(err) => {
            error!("Pool error: {:?}", err);
-            return;
+            std::process::exit(exitcode::CONFIG);
        }
    };

-    // Statistics collector task.
-    let collector_tx = tx.clone();
-
-    // Save these for reloading
-    let reload_client_server_map = client_server_map.clone();
-    let autoreload_client_server_map = client_server_map.clone();
-
    tokio::task::spawn(async move {
-        let mut stats_collector = Collector::new(rx, collector_tx);
+        let mut stats_collector = Collector::new(stats_rx, stats_tx.clone());
        stats_collector.collect().await;
    });

-    info!("Waiting for clients");
+    info!("Config autoreloader: {}", config.general.autoreload);

-    let (shutdown_event_tx, mut shutdown_event_rx) = broadcast::channel::<()>(1);
-
-    let shutdown_event_tx_clone = shutdown_event_tx.clone();
-
-    // Client connection loop.
+    let mut autoreload_interval = tokio::time::interval(tokio::time::Duration::from_millis(15_000));
+    let autoreload_client_server_map = client_server_map.clone();
    tokio::task::spawn(async move {
-        // Creates event subscriber for shutdown event, this is dropped when shutdown event is broadcast
-        let mut listener_shutdown_event_rx = shutdown_event_tx_clone.subscribe();
        loop {
-            let client_server_map = client_server_map.clone();
+            autoreload_interval.tick().await;
+            if config.general.autoreload {
+                info!("Automatically reloading config");

-            // Listen for shutdown event and client connection at the same time
-            let (socket, addr) = tokio::select! {
-                _ = listener_shutdown_event_rx.recv() => {
-                    // Exits client connection loop which drops listener, listener_shutdown_event_rx and shutdown_event_tx_clone
-                    break;
-                }
-
-                listener_response = listener.accept() => {
-                    match listener_response {
-                        Ok((socket, addr)) => (socket, addr),
-                        Err(err) => {
-                            error!("{:?}", err);
-                            continue;
-                        }
-                    }
-                }
-            };
-
-            // Used to signal shutdown
-            let client_shutdown_handler_rx = shutdown_event_tx_clone.subscribe();
-
-            // Used to signal that the task has completed
-            let dummy_tx = shutdown_event_tx_clone.clone();
-
-            // Handle client.
-            tokio::task::spawn(async move {
-                let start = chrono::offset::Utc::now().naive_utc();
-
-                match client::client_entrypoint(
-                    socket,
-                    client_server_map,
-                    client_shutdown_handler_rx,
-                )
-                .await
-                {
-                    Ok(_) => {
-                        let duration = chrono::offset::Utc::now().naive_utc() - start;
-
-                        info!(
-                            "Client {:?} disconnected, session duration: {}",
-                            addr,
-                            format_duration(&duration)
-                        );
-                    }
-
-                    Err(err) => {
-                        debug!("Client disconnected with error {:?}", err);
-                    }
-                };
-                // Drop this transmitter so receiver knows that the task is completed
-                drop(dummy_tx);
-            });
-        }
-    });
-
-    // Reload config:
-    // kill -SIGHUP $(pgrep pgcat)
-    tokio::task::spawn(async move {
-        let mut stream = unix_signal(SignalKind::hangup()).unwrap();
-
-        loop {
-            stream.recv().await;
-
-            info!("Reloading config");
-
-            match reload_config(reload_client_server_map.clone()).await {
-                Ok(_) => (),
-                Err(_) => continue,
-            };
-
-            get_config().show();
-        }
-    });
-
-    if config.general.autoreload {
-        let mut interval = tokio::time::interval(tokio::time::Duration::from_millis(15_000));
-
-        tokio::task::spawn(async move {
-            info!("Config autoreloader started");
-
-            loop {
-                interval.tick().await;
                match reload_config(autoreload_client_server_map.clone()).await {
                    Ok(changed) => {
                        if changed {
@@ -258,82 +173,132 @@ async fn main() {
                    Err(_) => (),
                };
            }
-        });
-    }
+        }
+    });

    let mut term_signal = unix_signal(SignalKind::terminate()).unwrap();
    let mut interrupt_signal = unix_signal(SignalKind::interrupt()).unwrap();
+    let mut sighup_signal = unix_signal(SignalKind::hangup()).unwrap();
+    let (shutdown_tx, _) = broadcast::channel::<()>(1);
+    let (drain_tx, mut drain_rx) = mpsc::channel::<i32>(2048);
+    let (exit_tx, mut exit_rx) = mpsc::channel::<()>(1);

-    tokio::select! {
-        // Initiate graceful shutdown sequence on sig int
-        _ = interrupt_signal.recv() => {
-            info!("Got SIGINT, waiting for client connection drain now");
+    info!("Waiting for clients");

-            // Broadcast that client tasks need to finish
-            shutdown_event_tx.send(()).unwrap();
-            // Closes transmitter
-            drop(shutdown_event_tx);
+    let mut admin_only = false;
+    let mut total_clients = 0;

-            // This is in a loop because the first event that the receiver receives will be the shutdown event
-            // This is not what we are waiting for instead, we want the receiver to send an error once all senders are closed which is reached after the shutdown event is received
-            loop {
-                match tokio::time::timeout(
-                    tokio::time::Duration::from_millis(config.general.shutdown_timeout),
-                    shutdown_event_rx.recv(),
-                )
-                .await
-                {
-                    Ok(res) => match res {
-                        Ok(_) => {}
-                        Err(_) => break,
-                    },
-                    Err(_) => {
-                        info!("Timed out while waiting for clients to shutdown");
-                        break;
+    loop {
+        tokio::select! {
+            // Reload config:
+            // kill -SIGHUP $(pgrep pgcat)
+            _ = sighup_signal.recv() => {
+                info!("Reloading config");
+
+                match reload_config(client_server_map.clone()).await {
+                    Ok(_) => (),
+                    Err(_) => (),
+                };
+
+                get_config().show();
+            },
+
+            // Initiate graceful shutdown sequence on sig int
+            _ = interrupt_signal.recv() => {
+                info!("Got SIGINT, waiting for client connection drain now");
+                admin_only = true;
+
+                // Broadcast that client tasks need to finish
+                let _ = shutdown_tx.send(());
+                let exit_tx = exit_tx.clone();
+                let _ = drain_tx.send(0).await;
+
+                tokio::task::spawn(async move {
+                    let mut interval = tokio::time::interval(tokio::time::Duration::from_millis(config.general.shutdown_timeout));
+
+                    // First tick fires immediately.
+                    interval.tick().await;
+
+                    // Second one in the interval time.
+                    interval.tick().await;
+
+                    // We're done waiting.
+                    error!("Graceful shutdown timed out. {} active clients being closed", total_clients);
+
+                    let _ = exit_tx.send(()).await;
+                });
+            },
+
+            _ = term_signal.recv() => {
+                info!("Got SIGTERM, closing with {} clients active", total_clients);
+                break;
+            },
+
+            new_client = listener.accept() => {
+                let (socket, addr) = match new_client {
+                    Ok((socket, addr)) => (socket, addr),
+                    Err(err) => {
+                        error!("{:?}", err);
+                        continue;
                    }
+                };
+
+                let shutdown_rx = shutdown_tx.subscribe();
+                let drain_tx = drain_tx.clone();
+                let client_server_map = client_server_map.clone();
+
+                tokio::task::spawn(async move {
+                    let start = chrono::offset::Utc::now().naive_utc();
+
+                    match client::client_entrypoint(
+                        socket,
+                        client_server_map,
+                        shutdown_rx,
+                        drain_tx,
+                        admin_only,
+                    )
+                    .await
+                    {
+                        Ok(()) => {
+
+                            let duration = chrono::offset::Utc::now().naive_utc() - start;
+
+                            info!(
+                                "Client {:?} disconnected, session duration: {}",
+                                addr,
+                                format_duration(&duration)
+                            );
+                        }
+
+                        Err(err) => {
+                            match err {
+                                // Don't count the clients we rejected.
+                                Error::ShuttingDown => (),
+                                _ => {
+                                    // drain_tx.send(-1).await.unwrap();
+                                }
+                            }
+
+                            warn!("Client disconnected with error {:?}", err);
+                        }
+                    };
+                });
+            }
+
+            _ = exit_rx.recv() => {
+                break;
+            }
+
+            client_ping = drain_rx.recv() => {
+                let client_ping = client_ping.unwrap();
+                total_clients += client_ping;
+
+                if total_clients == 0 && admin_only {
+                    let _ = exit_tx.send(()).await;
                }
            }
-        },
-        _ = term_signal.recv() => (),
+        }
    }

    info!("Shutting down...");
 }
-
-/// Format chrono::Duration to be more human-friendly.
-///
-/// # Arguments
-///
-/// * `duration` - A duration of time
-fn format_duration(duration: &chrono::Duration) -> String {
-    let seconds = {
-        let seconds = duration.num_seconds() % 60;
-        if seconds < 10 {
-            format!("0{}", seconds)
-        } else {
-            format!("{}", seconds)
-        }
-    };
-
-    let minutes = {
-        let minutes = duration.num_minutes() % 60;
-        if minutes < 10 {
-            format!("0{}", minutes)
-        } else {
-            format!("{}", minutes)
-        }
-    };
-
-    let hours = {
-        let hours = duration.num_hours() % 24;
-        if hours < 10 {
-            format!("0{}", hours)
-        } else {
-            format!("{}", hours)
-        }
-    };
-
-    let days = duration.num_days().to_string();
-
-    format!("{}d {}:{}:{}", days, hours, minutes, seconds)
-}
--- a/src/messages.rs
+++ b/src/messages.rs
@@ -496,7 +496,7 @@ where
    Ok(bytes)
 }

-pub fn server_paramater_message(key: &str, value: &str) -> BytesMut {
+pub fn server_parameter_message(key: &str, value: &str) -> BytesMut {
    let mut server_info = BytesMut::new();

    let null_byte_size = 1;
--- a/src/pool.rs
+++ b/src/pool.rs
@@ -6,44 +6,91 @@ use chrono::naive::NaiveDateTime;
 use log::{debug, error, info, warn};
 use once_cell::sync::Lazy;
 use parking_lot::{Mutex, RwLock};
-use std::collections::HashMap;
+use rand::seq::SliceRandom;
+use rand::thread_rng;
+use std::collections::{HashMap, HashSet};
 use std::sync::Arc;
 use std::time::Instant;

-use crate::config::{get_config, Address, Role, Shard, User};
+use crate::config::{get_config, Address, PoolMode, Role, User};
 use crate::errors::Error;

 use crate::server::Server;
+use crate::sharding::ShardingFunction;
 use crate::stats::{get_reporter, Reporter};

+pub type ProcessId = i32;
+pub type SecretKey = i32;
+pub type ServerHost = String;
+pub type ServerPort = u16;
+
 pub type BanList = Arc<RwLock<Vec<HashMap<Address, NaiveDateTime>>>>;
-pub type ClientServerMap = Arc<Mutex<HashMap<(i32, i32), (i32, i32, String, String)>>>;
-pub type PoolMap = HashMap<(String, String), ConnectionPool>;
+pub type ClientServerMap =
+    Arc<Mutex<HashMap<(ProcessId, SecretKey), (ProcessId, SecretKey, ServerHost, ServerPort)>>>;
+pub type PoolMap = HashMap<PoolIdentifier, ConnectionPool>;
 /// The connection pool, globally available.
 /// This is atomic and safe and read-optimized.
 /// The pool is recreated dynamically when the config is reloaded.
 pub static POOLS: Lazy<ArcSwap<PoolMap>> = Lazy::new(|| ArcSwap::from_pointee(HashMap::default()));
+static POOLS_HASH: Lazy<ArcSwap<HashSet<crate::config::Pool>>> =
+    Lazy::new(|| ArcSwap::from_pointee(HashSet::default()));

+/// An identifier for a PgCat pool,
+/// a database visible to clients.
+#[derive(Hash, Debug, Clone, PartialEq, Eq)]
+pub struct PoolIdentifier {
+    // The name of the database clients want to connect to.
+    pub db: String,
+
+    /// The username the client connects with. Each user gets its own pool.
+    pub user: String,
+}
+
+impl PoolIdentifier {
+    /// Create a new user/pool identifier.
+    pub fn new(db: &str, user: &str) -> PoolIdentifier {
+        PoolIdentifier {
+            db: db.to_string(),
+            user: user.to_string(),
+        }
+    }
+}
+
+/// Pool settings.
 #[derive(Clone, Debug)]
 pub struct PoolSettings {
-    pub pool_mode: String,
-    pub shards: HashMap<String, Shard>,
+    /// Transaction or Session.
+    pub pool_mode: PoolMode,
+
+    // Number of shards.
+    pub shards: usize,
+
+    // Connecting user.
    pub user: User,
-    pub default_role: String,
+
+    // Default server role to connect to.
+    pub default_role: Option<Role>,
+
+    // Enable/disable query parser.
    pub query_parser_enabled: bool,
+
+    // Read from the primary as well or not.
    pub primary_reads_enabled: bool,
-    pub sharding_function: String,
+
+    // Sharding function.
+    pub sharding_function: ShardingFunction,
 }
+
 impl Default for PoolSettings {
    fn default() -> PoolSettings {
        PoolSettings {
-            pool_mode: String::from("transaction"),
-            shards: HashMap::from([(String::from("1"), Shard::default())]),
+            pool_mode: PoolMode::Transaction,
+            shards: 1,
            user: User::default(),
-            default_role: String::from("any"),
+            default_role: None,
            query_parser_enabled: false,
            primary_reads_enabled: true,
-            sharding_function: "pg_bigint_hash".to_string(),
+            sharding_function: ShardingFunction::PgBigintHash,
        }
    }
 }
@@ -71,6 +118,7 @@ pub struct ConnectionPool {
    /// on pool creation and save the K messages here.
    server_info: BytesMut,

+    /// Pool configuration.
    pub settings: PoolSettings,
 }

@@ -78,11 +126,41 @@ impl ConnectionPool {
    /// Construct the connection pool from the configuration.
    pub async fn from_config(client_server_map: ClientServerMap) -> Result<(), Error> {
        let config = get_config();
-        let mut new_pools = PoolMap::default();

+        let mut new_pools = HashMap::new();
        let mut address_id = 0;
+
+        let mut pools_hash = (*(*POOLS_HASH.load())).clone();
+
        for (pool_name, pool_config) in &config.pools {
-            for (_user_index, user_info) in &pool_config.users {
+            let changed = pools_hash.insert(pool_config.clone());
+
+            // There is one pool per database/user pair.
+            for (_, user) in &pool_config.users {
+                // If the pool hasn't changed, get existing reference and insert it into the new_pools.
+                // We replace all pools at the end, but if the reference is kept, the pool won't get re-created (bb8).
+                if !changed {
+                    match get_pool(&pool_name, &user.username) {
+                        Some(pool) => {
+                            info!(
+                                "[pool: {}][user: {}] has not changed",
+                                pool_name, user.username
+                            );
+                            new_pools.insert(
+                                PoolIdentifier::new(&pool_name, &user.username),
+                                pool.clone(),
+                            );
+                            continue;
+                        }
+                        None => (),
+                    }
+                }
+
+                info!(
+                    "[pool: {}][user: {}] creating new pool",
+                    pool_name, user.username
+                );
+
                let mut shards = Vec::new();
                let mut addresses = Vec::new();
                let mut banlist = Vec::new();
@@ -96,51 +174,50 @@ impl ConnectionPool {
                // Sort by shard number to ensure consistency.
                shard_ids.sort_by_key(|k| k.parse::<i64>().unwrap());

-                for shard_idx in shard_ids {
-                    let shard = &pool_config.shards[&shard_idx];
+                for shard_idx in &shard_ids {
+                    let shard = &pool_config.shards[shard_idx];
                    let mut pools = Vec::new();
                    let mut servers = Vec::new();
+                    let mut address_index = 0;
                    let mut replica_number = 0;

                    for server in shard.servers.iter() {
-                        let role = match server.2.as_ref() {
-                            "primary" => Role::Primary,
-                            "replica" => Role::Replica,
-                            _ => {
-                                error!("Config error: server role can be 'primary' or 'replica', have: '{}'. Defaulting to 'replica'.", server.2);
-                                Role::Replica
-                            }
-                        };
-
                        let address = Address {
                            id: address_id,
-                            database: pool_name.clone(),
-                            host: server.0.clone(),
-                            port: server.1.to_string(),
-                            role: role,
+                            database: shard.database.clone(),
+                            host: server.host.clone(),
+                            port: server.port,
+                            role: server.role,
+                            address_index,
                            replica_number,
                            shard: shard_idx.parse::<usize>().unwrap(),
+                            username: user.username.clone(),
+                            pool_name: pool_name.clone(),
                        };

                        address_id += 1;
+                        address_index += 1;

-                        if role == Role::Replica {
+                        if server.role == Role::Replica {
                            replica_number += 1;
                        }

                        let manager = ServerPool::new(
                            address.clone(),
-                            user_info.clone(),
+                            user.clone(),
                            &shard.database,
                            client_server_map.clone(),
                            get_reporter(),
                        );

+                        let connect_timeout = match pool_config.connect_timeout {
+                            Some(connect_timeout) => connect_timeout,
+                            None => config.general.connect_timeout,
+                        };
+
                        let pool = Pool::builder()
-                            .max_size(user_info.pool_size)
-                            .connection_timeout(std::time::Duration::from_millis(
-                                config.general.connect_timeout,
-                            ))
+                            .max_size(user.pool_size)
+                            .connection_timeout(std::time::Duration::from_millis(connect_timeout))
                            .test_on_check_out(false)
                            .build(manager)
                            .await
@@ -164,13 +241,19 @@ impl ConnectionPool {
                    stats: get_reporter(),
                    server_info: BytesMut::new(),
                    settings: PoolSettings {
-                        pool_mode: pool_config.pool_mode.clone(),
-                        shards: pool_config.shards.clone(),
-                        user: user_info.clone(),
-                        default_role: pool_config.default_role.clone(),
+                        pool_mode: pool_config.pool_mode,
+                        // shards: pool_config.shards.clone(),
+                        shards: shard_ids.len(),
+                        user: user.clone(),
+                        default_role: match pool_config.default_role.as_str() {
+                            "any" => None,
+                            "replica" => Some(Role::Replica),
+                            "primary" => Some(Role::Primary),
+                            _ => unreachable!(),
+                        },
                        query_parser_enabled: pool_config.query_parser_enabled.clone(),
                        primary_reads_enabled: pool_config.primary_reads_enabled,
-                        sharding_function: pool_config.sharding_function.clone(),
+                        sharding_function: pool_config.sharding_function,
                    },
                };

@@ -183,11 +266,14 @@ impl ConnectionPool {
                        return Err(err);
                    }
                };
-                new_pools.insert((pool_name.clone(), user_info.username.clone()), pool);
+
+                // There is one pool per database/user pair.
+                new_pools.insert(PoolIdentifier::new(&pool_name, &user.username), pool);
            }
        }

        POOLS.store(Arc::new(new_pools.clone()));
+        POOLS_HASH.store(Arc::new(pools_hash.clone()));

        Ok(())
    }
@@ -199,16 +285,9 @@ impl ConnectionPool {
    /// the pooler starts up.
    async fn validate(&mut self) -> Result<(), Error> {
        let mut server_infos = Vec::new();
-        let stats = self.stats.clone();
-
        for shard in 0..self.shards() {
-            let mut round_robin = 0;
-
-            for _ in 0..self.servers(shard) {
-                // To keep stats consistent.
-                let fake_process_id = 0;
-
-                let connection = match self.get(shard, None, fake_process_id, round_robin).await {
+            for server in 0..self.servers(shard) {
+                let connection = match self.databases[shard][server].get().await {
                    Ok(conn) => conn,
                    Err(err) => {
                        error!("Shard {} down or misconfigured: {:?}", shard, err);
@@ -216,25 +295,21 @@ impl ConnectionPool {
                    }
                };

-                let proxy = connection.0;
-                let address = connection.1;
+                let proxy = connection;
                let server = &*proxy;
                let server_info = server.server_info();

-                stats.client_disconnecting(fake_process_id, address.id);
-
                if server_infos.len() > 0 {
                    // Compare against the last server checked.
                    if server_info != server_infos[server_infos.len() - 1] {
                        warn!(
                            "{:?} has different server configuration than the last server",
-                            address
+                            proxy.address()
                        );
                    }
                }

                server_infos.push(server_info);
-                round_robin += 1;
            }
        }

@@ -244,6 +319,8 @@ impl ConnectionPool {
            return Err(Error::AllServersDown);
        }

+        // We're assuming all servers are identical.
+        // TODO: not true.
        self.server_info = server_infos[0].clone();

        Ok(())
@@ -252,73 +329,47 @@ impl ConnectionPool {
    /// Get a connection from the pool.
    pub async fn get(
        &self,
-        shard: usize,           // shard number
-        role: Option<Role>,     // primary or replica
-        process_id: i32,        // client id
-        mut round_robin: usize, // round robin offset
+        shard: usize,       // shard number
+        role: Option<Role>, // primary or replica
+        process_id: i32,    // client id
    ) -> Result<(PooledConnection<'_, ServerPool>, Address), Error> {
-        let now = Instant::now();
-        let addresses = &self.addresses[shard];
+        let mut candidates: Vec<&Address> = self.addresses[shard]
+            .iter()
+            .filter(|address| address.role == role)
+            .collect();

-        let mut allowed_attempts = match role {
-            // Primary-specific queries get one attempt, if the primary is down,
-            // nothing we should do about it I think. It's dangerous to retry
-            // write queries.
-            Some(Role::Primary) => 1,
-
-            // Replicas get to try as many times as there are replicas
-            // and connections in the pool.
-            _ => addresses.len(),
-        };
-
-        debug!("Allowed attempts for {:?}: {}", role, allowed_attempts);
-
-        let exists = match role {
-            Some(role) => addresses.iter().filter(|addr| addr.role == role).count() > 0,
-            None => true,
-        };
-
-        if !exists {
-            error!("Requested role {:?}, but none are configured", role);
-            return Err(Error::BadConfig);
-        }
+        // Random load balancing
+        candidates.shuffle(&mut thread_rng());

        let healthcheck_timeout = get_config().general.healthcheck_timeout;
        let healthcheck_delay = get_config().general.healthcheck_delay as u128;

-        while allowed_attempts > 0 {
-            // Round-robin replicas.
-            round_robin += 1;
+        while !candidates.is_empty() {
+            // Get the next candidate
+            let address = match candidates.pop() {
+                Some(address) => address,
+                None => break,
+            };

-            let index = round_robin % addresses.len();
-            let address = &addresses[index];
-
-            // Make sure you're getting a primary or a replica
-            // as per request. If no specific role is requested, the first
-            // available will be chosen.
-            if address.role != role {
-                continue;
-            }
-
-            allowed_attempts -= 1;
-
-            // Don't attempt to connect to banned servers.
-            if self.is_banned(address, shard, role) {
+            if self.is_banned(&address, role) {
+                debug!("Address {:?} is banned", address);
                continue;
            }

            // Indicate we're waiting on a server connection from a pool.
-            self.stats.client_waiting(process_id, address.id);
+            let now = Instant::now();
+            self.stats.client_waiting(process_id);

            // Check if we can connect
-            let mut conn = match self.databases[shard][index].get().await {
+            let mut conn = match self.databases[address.shard][address.address_index]
+                .get()
+                .await
+            {
                Ok(conn) => conn,
                Err(err) => {
-                    error!("Banning replica {}, error: {:?}", index, err);
-                    self.ban(address, shard, process_id);
-                    self.stats.client_disconnecting(process_id, address.id);
-                    self.stats
-                        .checkout_time(now.elapsed().as_micros(), process_id, address.id);
+                    error!("Banning instance {:?}, error: {:?}", address, err);
+                    self.ban(&address, process_id);
+                    self.stats.client_checkout_error(process_id, address.id);
                    continue;
                }
            };
@@ -330,89 +381,99 @@ impl ConnectionPool {
            let require_healthcheck =
                server.last_activity().elapsed().unwrap().as_millis() > healthcheck_delay;

+            // Do not issue a health check unless it's been a little while
+            // since we last checked the server is ok.
+            // Health checks are pretty expensive.
            if !require_healthcheck {
                self.stats
-                    .checkout_time(now.elapsed().as_micros(), process_id, address.id);
-                self.stats.server_idle(conn.process_id(), address.id);
+                    .checkout_time(now.elapsed().as_micros(), process_id, server.server_id());
+                self.stats.server_active(process_id, server.server_id());
                return Ok((conn, address.clone()));
            }

            debug!("Running health check on server {:?}", address);

-            self.stats.server_tested(server.process_id(), address.id);
+            self.stats.server_tested(server.server_id());

            match tokio::time::timeout(
                tokio::time::Duration::from_millis(healthcheck_timeout),
-                server.query(";"),
+                server.query(";"), // Cheap query as it skips the query planner
            )
            .await
            {
                // Check if health check succeeded.
                Ok(res) => match res {
                    Ok(_) => {
-                        self.stats
-                            .checkout_time(now.elapsed().as_micros(), process_id, address.id);
-                        self.stats.server_idle(conn.process_id(), address.id);
+                        self.stats.checkout_time(
+                            now.elapsed().as_micros(),
+                            process_id,
+                            conn.server_id(),
+                        );
+                        self.stats.server_active(process_id, conn.server_id());
                        return Ok((conn, address.clone()));
                    }

                    // Health check failed.
-                    Err(_) => {
-                        error!("Banning replica {} because of failed health check", index);
+                    Err(err) => {
+                        error!(
+                            "Banning instance {:?} because of failed health check, {:?}",
+                            address, err
+                        );

                        // Don't leave a bad connection in the pool.
                        server.mark_bad();

-                        self.ban(address, shard, process_id);
+                        self.ban(&address, process_id);
                        continue;
                    }
                },

                // Health check timed out.
-                Err(_) => {
-                    error!("Banning replica {} because of health check timeout", index);
+                Err(err) => {
+                    error!(
+                        "Banning instance {:?} because of health check timeout, {:?}",
+                        address, err
+                    );
                    // Don't leave a bad connection in the pool.
                    server.mark_bad();

-                    self.ban(address, shard, process_id);
+                    self.ban(&address, process_id);
                    continue;
                }
            }
        }

-        return Err(Error::AllServersDown);
+        Err(Error::AllServersDown)
    }

    /// Ban an address (i.e. replica). It no longer will serve
    /// traffic for any new transactions. Existing transactions on that replica
    /// will finish successfully or error out to the clients.
-    pub fn ban(&self, address: &Address, shard: usize, process_id: i32) {
-        self.stats.client_disconnecting(process_id, address.id);
-        self.stats
-            .checkout_time(Instant::now().elapsed().as_micros(), process_id, address.id);
-
+    pub fn ban(&self, address: &Address, client_id: i32) {
        error!("Banning {:?}", address);
+        self.stats.client_ban_error(client_id, address.id);
+
        let now = chrono::offset::Utc::now().naive_utc();
        let mut guard = self.banlist.write();
-        guard[shard].insert(address.clone(), now);
+        guard[address.shard].insert(address.clone(), now);
    }

    /// Clear the replica to receive traffic again. Takes effect immediately
    /// for all new transactions.
-    pub fn _unban(&self, address: &Address, shard: usize) {
+    pub fn _unban(&self, address: &Address) {
        let mut guard = self.banlist.write();
-        guard[shard].remove(address);
+        guard[address.shard].remove(address);
    }

    /// Check if a replica can serve traffic. If all replicas are banned,
    /// we unban all of them. Better to try then not to.
-    pub fn is_banned(&self, address: &Address, shard: usize, role: Option<Role>) -> bool {
+    pub fn is_banned(&self, address: &Address, role: Option<Role>) -> bool {
        let replicas_available = match role {
-            Some(Role::Replica) => self.addresses[shard]
+            Some(Role::Replica) => self.addresses[address.shard]
                .iter()
                .filter(|addr| addr.role == Role::Replica)
                .count(),
-            None => self.addresses[shard].len(),
+            None => self.addresses[address.shard].len(),
            Some(Role::Primary) => return false, // Primary cannot be banned.
        };

@@ -421,17 +482,17 @@ impl ConnectionPool {
        let guard = self.banlist.read();

        // Everything is banned = nothing is banned.
-        if guard[shard].len() == replicas_available {
+        if guard[address.shard].len() == replicas_available {
            drop(guard);
            let mut guard = self.banlist.write();
-            guard[shard].clear();
+            guard[address.shard].clear();
            drop(guard);
            warn!("Unbanning all replicas.");
            return false;
        }

        // I expect this to miss 99.9999% of the time.
-        match guard[shard].get(address) {
+        match guard[address.shard].get(address) {
            Some(timestamp) => {
                let now = chrono::offset::Utc::now().naive_utc();
                let config = get_config();
@@ -441,7 +502,7 @@ impl ConnectionPool {
                    drop(guard);
                    warn!("Unbanning {:?}", address);
                    let mut guard = self.banlist.write();
-                    guard[shard].remove(address);
+                    guard[address.shard].remove(address);
                    false
                } else {
                    debug!("{:?} is banned", address);
@@ -525,19 +586,21 @@ impl ManageConnection for ServerPool {

    /// Attempts to create a new connection.
    async fn connect(&self) -> Result<Self::Connection, Self::Error> {
-        info!(
-            "Creating a new connection to {:?} using user {:?}",
-            self.address.name(),
-            self.user.username
-        );
+        info!("Creating a new server connection {:?}", self.address);
+        let server_id = rand::random::<i32>();

-        // Put a temporary process_id into the stats
-        // for server login.
-        let process_id = rand::random::<i32>();
-        self.stats.server_login(process_id, self.address.id);
+        self.stats.server_register(
+            server_id,
+            self.address.id,
+            self.address.name(),
+            self.address.pool_name.clone(),
+            self.address.username.clone(),
+        );
+        self.stats.server_login(server_id);

        // Connect to the PostgreSQL server.
        match Server::startup(
+            server_id,
            &self.address,
            &self.user,
            &self.database,
@@ -547,20 +610,18 @@ impl ManageConnection for ServerPool {
        .await
        {
            Ok(conn) => {
-                // Remove the temporary process_id from the stats.
-                self.stats.server_disconnecting(process_id, self.address.id);
+                self.stats.server_idle(server_id);
                Ok(conn)
            }
            Err(err) => {
-                // Remove the temporary process_id from the stats.
-                self.stats.server_disconnecting(process_id, self.address.id);
+                self.stats.server_disconnecting(server_id);
                Err(err)
            }
        }
    }

    /// Determines if the connection is still connected to the database.
-    async fn is_valid(&self, _conn: &mut PooledConnection<'_, Self>) -> Result<(), Self::Error> {
+    async fn is_valid(&self, _conn: &mut Self::Connection) -> Result<(), Self::Error> {
        Ok(())
    }

@@ -571,20 +632,22 @@ impl ManageConnection for ServerPool {
 }

 /// Get the connection pool
-pub fn get_pool(db: String, user: String) -> Option<ConnectionPool> {
-    match get_all_pools().get(&(db, user)) {
+pub fn get_pool(db: &str, user: &str) -> Option<ConnectionPool> {
+    match get_all_pools().get(&PoolIdentifier::new(&db, &user)) {
        Some(pool) => Some(pool.clone()),
        None => None,
    }
 }

+/// Get a pointer to all configured pools.
+pub fn get_all_pools() -> HashMap<PoolIdentifier, ConnectionPool> {
+    return (*(*POOLS.load())).clone();
+}
+
+/// How many total servers we have in the config.
 pub fn get_number_of_addresses() -> usize {
    get_all_pools()
        .iter()
        .map(|(_, pool)| pool.databases())
        .sum()
 }
-
-pub fn get_all_pools() -> HashMap<(String, String), ConnectionPool> {
-    return (*(*POOLS.load())).clone();
-}
--- a/src/prometheus.rs
+++ b/src/prometheus.rs
@@ -8,9 +8,7 @@ use std::net::SocketAddr;

 use crate::config::Address;
 use crate::pool::get_all_pools;
-use crate::stats::get_stats;
-
-pub const HTTP_PORT: usize = 9930;
+use crate::stats::get_address_stats;

 struct MetricHelpType {
    help: &'static str,
@@ -166,7 +164,7 @@ impl PrometheusMetric {
 async fn prometheus_stats(request: Request<Body>) -> Result<Response<Body>, hyper::http::Error> {
    match (request.method(), request.uri().path()) {
        (&Method::GET, "/metrics") => {
-            let stats = get_stats();
+            let stats: HashMap<usize, HashMap<String, i64>> = get_address_stats();

            let mut lines = Vec::new();
            for (_, pool) in get_all_pools() {
--- a/src/query_router.rs
+++ b/src/query_router.rs
@@ -10,7 +10,7 @@ use sqlparser::parser::Parser;

 use crate::config::Role;
 use crate::pool::PoolSettings;
-use crate::sharding::{Sharder, ShardingFunction};
+use crate::sharding::Sharder;

 /// Regexes used to parse custom commands.
 const CUSTOM_SQL_REGEXES: [&str; 7] = [
@@ -55,11 +55,13 @@ pub struct QueryRouter {
    /// Include the primary into the replica pool for reads.
    primary_reads_enabled: bool,

+    /// Pool configuration.
    pool_settings: PoolSettings,
 }

 impl QueryRouter {
-    /// One-time initialization of regexes.
+    /// One-time initialization of regexes
+    /// that parse our custom SQL protocol.
    pub fn setup() -> bool {
        let set = match RegexSet::new(&CUSTOM_SQL_REGEXES) {
            Ok(rgx) => rgx,
@@ -74,10 +76,7 @@ impl QueryRouter {
            .map(|rgx| Regex::new(rgx).unwrap())
            .collect();

-        // Impossible
-        if list.len() != set.len() {
-            return false;
-        }
+        assert_eq!(list.len(), set.len());

        match CUSTOM_SQL_REGEX_LIST.set(list) {
            Ok(_) => true,
@@ -90,7 +89,8 @@ impl QueryRouter {
        }
    }

-    /// Create a new instance of the query router. Each client gets its own.
+    /// Create a new instance of the query router.
+    /// Each client gets its own.
    pub fn new() -> QueryRouter {
        QueryRouter {
            active_shard: None,
@@ -101,6 +101,7 @@ impl QueryRouter {
        }
    }

+    /// Pool settings can change because of a config reload.
    pub fn update_pool_settings(&mut self, pool_settings: PoolSettings) {
        self.pool_settings = pool_settings;
    }
@@ -136,19 +137,6 @@ impl QueryRouter {
            return None;
        }

-        let sharding_function = match self.pool_settings.sharding_function.as_ref() {
-            "pg_bigint_hash" => ShardingFunction::PgBigintHash,
-            "sha1" => ShardingFunction::Sha1,
-            _ => unreachable!(),
-        };
-
-        let default_server_role = match self.pool_settings.default_role.as_ref() {
-            "any" => None,
-            "primary" => Some(Role::Primary),
-            "replica" => Some(Role::Replica),
-            _ => unreachable!(),
-        };
-
        let command = match matches[0] {
            0 => Command::SetShardingKey,
            1 => Command::SetShard,
@@ -181,8 +169,8 @@ impl QueryRouter {

            Command::ShowShard => self.shard().to_string(),
            Command::ShowServerRole => match self.active_role {
-                Some(Role::Primary) => String::from("primary"),
-                Some(Role::Replica) => String::from("replica"),
+                Some(Role::Primary) => Role::Primary.to_string(),
+                Some(Role::Replica) => Role::Replica.to_string(),
                None => {
                    if self.query_parser_enabled {
                        String::from("auto")
@@ -200,7 +188,10 @@ impl QueryRouter {

        match command {
            Command::SetShardingKey => {
-                let sharder = Sharder::new(self.pool_settings.shards.len(), sharding_function);
+                let sharder = Sharder::new(
+                    self.pool_settings.shards,
+                    self.pool_settings.sharding_function,
+                );
                let shard = sharder.shard(value.parse::<i64>().unwrap());
                self.active_shard = Some(shard);
                value = shard.to_string();
@@ -208,7 +199,7 @@ impl QueryRouter {

            Command::SetShard => {
                self.active_shard = match value.to_ascii_uppercase().as_ref() {
-                    "ANY" => Some(rand::random::<usize>() % self.pool_settings.shards.len()),
+                    "ANY" => Some(rand::random::<usize>() % self.pool_settings.shards),
                    _ => Some(value.parse::<usize>().unwrap()),
                };
            }
@@ -236,7 +227,7 @@ impl QueryRouter {
                    }

                    "default" => {
-                        self.active_role = default_server_role;
+                        self.active_role = self.pool_settings.default_role;
                        self.query_parser_enabled = self.query_parser_enabled;
                        self.active_role
                    }
@@ -367,10 +358,10 @@ impl QueryRouter {

 #[cfg(test)]
 mod test {
-    use std::collections::HashMap;
-
    use super::*;
+    use crate::config::PoolMode;
    use crate::messages::simple_query;
+    use crate::sharding::ShardingFunction;
    use bytes::BufMut;

    #[test]
@@ -633,13 +624,13 @@ mod test {
        QueryRouter::setup();

        let pool_settings = PoolSettings {
-            pool_mode: "transaction".to_string(),
-            shards: HashMap::default(),
+            pool_mode: PoolMode::Transaction,
+            shards: 0,
            user: crate::config::User::default(),
-            default_role: Role::Replica.to_string(),
+            default_role: Some(Role::Replica),
            query_parser_enabled: true,
            primary_reads_enabled: false,
-            sharding_function: "pg_bigint_hash".to_string(),
+            sharding_function: ShardingFunction::PgBigintHash,
        };
        let mut qr = QueryRouter::new();
        assert_eq!(qr.active_role, None);
@@ -661,9 +652,6 @@ mod test {

        let q2 = simple_query("SET SERVER ROLE TO 'default'");
        assert!(qr.try_execute_command(q2) != None);
-        assert_eq!(
-            qr.active_role.unwrap().to_string(),
-            pool_settings.clone().default_role
-        );
+        assert_eq!(qr.active_role.unwrap(), pool_settings.clone().default_role);
    }
 }
--- a/src/server.rs
+++ b/src/server.rs
@@ -1,7 +1,8 @@
 /// Implementation of the PostgreSQL server (database) protocol.
 /// Here we are pretending to the a Postgres client.
 use bytes::{Buf, BufMut, BytesMut};
-use log::{debug, error, info, trace};
+use log::{debug, error, info, trace, warn};
+use std::io::Read;
 use std::time::SystemTime;
 use tokio::io::{AsyncReadExt, BufReader};
 use tokio::net::{
@@ -13,12 +14,14 @@ use crate::config::{Address, User};
 use crate::constants::*;
 use crate::errors::Error;
 use crate::messages::*;
+use crate::pool::ClientServerMap;
 use crate::scram::ScramSha256;
 use crate::stats::Reporter;
-use crate::ClientServerMap;

 /// Server state.
 pub struct Server {
+    server_id: i32,
+
    /// Server host, e.g. localhost,
    /// port, e.g. 5432, and role, e.g. primary or replica.
    address: Address,
@@ -48,6 +51,9 @@ pub struct Server {
    /// Is the server broken? We'll remote it from the pool if so.
    bad: bool,

+    /// If server connection requires a DISCARD ALL before checkin
+    needs_cleanup: bool,
+
    /// Mapping of clients and servers used for query cancellation.
    client_server_map: ClientServerMap,

@@ -68,6 +74,7 @@ impl Server {
    /// Pretend to be the Postgres client and connect to the server given host, port and credentials.
    /// Perform the authentication and return the server in a ready for query state.
    pub async fn startup(
+        server_id: i32,
        address: &Address,
        user: &User,
        database: &str,
@@ -75,7 +82,7 @@ impl Server {
        stats: Reporter,
    ) -> Result<Server, Error> {
        let mut stream =
-            match TcpStream::connect(&format!("{}:{}", &address.host, &address.port)).await {
+            match TcpStream::connect(&format!("{}:{}", &address.host, address.port)).await {
                Ok(stream) => stream,
                Err(err) => {
                    error!("Could not connect to server: {}", err);
@@ -311,11 +318,13 @@ impl Server {
                        write: write,
                        buffer: BytesMut::with_capacity(8196),
                        server_info: server_info,
+                        server_id: server_id,
                        process_id: process_id,
                        secret_key: secret_key,
                        in_transaction: false,
                        data_available: false,
                        bad: false,
+                        needs_cleanup: false,
                        client_server_map: client_server_map,
                        connected_at: chrono::offset::Utc::now().naive_utc(),
                        stats: stats,
@@ -342,7 +351,7 @@ impl Server {
    /// Uses a separate connection that's not part of the connection pool.
    pub async fn cancel(
        host: &str,
-        port: &str,
+        port: u16,
        process_id: i32,
        secret_key: i32,
    ) -> Result<(), Error> {
@@ -367,8 +376,7 @@ impl Server {

    /// Send messages to the server from the client.
    pub async fn send(&mut self, messages: BytesMut) -> Result<(), Error> {
-        self.stats
-            .data_sent(messages.len(), self.process_id, self.address.id);
+        self.stats.data_sent(messages.len(), self.server_id);

        match write_all_half(&mut self.write, messages).await {
            Ok(_) => {
@@ -440,6 +448,29 @@ impl Server {
                    break;
                }

+                // CommandComplete
+                'C' => {
+                    let mut command_tag = String::new();
+                    match message.reader().read_to_string(&mut command_tag) {
+                        Ok(_) => {
+                            // Non-exhaustive list of commands that are likely to change session variables/resources
+                            // which can leak between clients. This is a best effort to block bad clients
+                            // from poisoning a transaction-mode pool by setting inappropriate session variables
+                            match command_tag.as_str() {
+                                "SET\0" | "PREPARE\0" => {
+                                    debug!("Server connection marked for clean up");
+                                    self.needs_cleanup = true;
+                                }
+                                _ => (),
+                            }
+                        }
+
+                        Err(err) => {
+                            warn!("Encountered an error while parsing CommandTag {}", err);
+                        }
+                    }
+                }
+
                // DataRow
                'D' => {
                    // More data is available after this message, this is not the end of the reply.
@@ -477,8 +508,7 @@ impl Server {
        let bytes = self.buffer.clone();

        // Keep track of how much data we got from the server for stats.
-        self.stats
-            .data_received(bytes.len(), self.process_id, self.address.id);
+        self.stats.data_received(bytes.len(), self.server_id);

        // Clear the buffer for next query.
        self.buffer.clear();
@@ -529,7 +559,7 @@ impl Server {
                self.process_id,
                self.secret_key,
                self.address.host.clone(),
-                self.address.port.clone(),
+                self.address.port,
            ),
        );
    }
@@ -553,14 +583,45 @@ impl Server {
        Ok(())
    }

+    /// Perform any necessary cleanup before putting the server
+    /// connection back in the pool
+    pub async fn checkin_cleanup(&mut self) -> Result<(), Error> {
+        // Client disconnected with an open transaction on the server connection.
+        // Pgbouncer behavior is to close the server connection but that can cause
+        // server connection thrashing if clients repeatedly do this.
+        // Instead, we ROLLBACK that transaction before putting the connection back in the pool
+        if self.in_transaction() {
+            warn!("Server returned while still in transaction, rolling back transaction");
+            self.query("ROLLBACK").await?;
+        }
+
+        // Client disconnected but it perfromed session-altering operations such as
+        // SET statement_timeout to 1 or create a prepared statement. We clear that
+        // to avoid leaking state between clients. For performance reasons we only
+        // send `DISCARD ALL` if we think the session is altered instead of just sending
+        // it before each checkin.
+        if self.needs_cleanup {
+            warn!("Server returned with session state altered, discarding state");
+            self.query("DISCARD ALL").await?;
+            self.needs_cleanup = false;
+        }
+
+        return Ok(());
+    }
+
    /// A shorthand for `SET application_name = $1`.
-    #[allow(dead_code)]
    pub async fn set_name(&mut self, name: &str) -> Result<(), Error> {
        if self.application_name != name {
            self.application_name = name.to_string();
-            Ok(self
+            // We don't want `SET application_name` to mark the server connection
+            // as needing cleanup
+            let needs_cleanup_before = self.needs_cleanup;
+
+            let result = Ok(self
                .query(&format!("SET application_name = '{}'", name))
-                .await?)
+                .await?);
+            self.needs_cleanup = needs_cleanup_before;
+            return result;
        } else {
            Ok(())
        }
@@ -572,15 +633,21 @@ impl Server {
        self.address.clone()
    }

-    /// Get the server's unique identifier.
-    pub fn process_id(&self) -> i32 {
-        self.process_id
+    /// Get the server connection identifier
+    /// Used to uniquely identify connection in statistics
+    pub fn server_id(&self) -> i32 {
+        self.server_id
    }

    // Get server's latest response timestamp
    pub fn last_activity(&self) -> SystemTime {
        self.last_activity
    }
+
+    // Marks a connection as needing DISCARD ALL at checkin
+    pub fn mark_dirty(&mut self) {
+        self.needs_cleanup = true;
+    }
 }

 impl Drop for Server {
@@ -588,8 +655,7 @@ impl Drop for Server {
    /// the socket is in non-blocking mode, so it may not be ready
    /// for a write.
    fn drop(&mut self) {
-        self.stats
-            .server_disconnecting(self.process_id(), self.address.id);
+        self.stats.server_disconnecting(self.server_id);

        let mut bytes = BytesMut::with_capacity(4);
        bytes.put_u8(b'X');
@@ -607,7 +673,8 @@ impl Drop for Server {
        let duration = now - self.connected_at;

        info!(
-            "Server connection closed, session duration: {}",
+            "Server connection closed {:?}, session duration: {}",
+            self.address,
            crate::format_duration(&duration)
        );
    }
--- a/src/sharding.rs
+++ b/src/sharding.rs
@@ -1,3 +1,4 @@
+use serde_derive::{Deserialize, Serialize};
 /// Implements various sharding functions.
 use sha1::{Digest, Sha1};

@@ -5,12 +6,23 @@ use sha1::{Digest, Sha1};
 const PARTITION_HASH_SEED: u64 = 0x7A5B22367996DCFD;

 /// The sharding functions we support.
-#[derive(Debug, PartialEq, Copy, Clone)]
+#[derive(Debug, PartialEq, Copy, Clone, Serialize, Deserialize, Hash, std::cmp::Eq)]
 pub enum ShardingFunction {
+    #[serde(alias = "pg_bigint_hash", alias = "PgBigintHash")]
    PgBigintHash,
+    #[serde(alias = "sha1", alias = "Sha1")]
    Sha1,
 }

+impl ToString for ShardingFunction {
+    fn to_string(&self) -> String {
+        match *self {
+            ShardingFunction::PgBigintHash => "pg_bigint_hash".to_string(),
+            ShardingFunction::Sha1 => "sha1".to_string(),
+        }
+    }
+}
+
 /// The sharder.
 pub struct Sharder {
    /// Number of shards in the cluster.
--- a/src/stats.rs
+++ b/src/stats.rs
--- a/tests/docker/Dockerfile
+++ b/tests/docker/Dockerfile
@@ -0,0 +1,5 @@
+FROM rust:bullseye
+
+RUN apt-get update && apt-get install llvm-11 psmisc postgresql-contrib postgresql-client ruby ruby-dev libpq-dev python3 python3-pip lcov sudo curl -y
+RUN cargo install cargo-binutils rustfilt
+RUN rustup component add llvm-tools-preview
--- a/tests/docker/docker-compose.yml
+++ b/tests/docker/docker-compose.yml
@@ -0,0 +1,47 @@
+version: "3"
+services:
+  pg1:
+    image: postgres:14
+    network_mode: "service:main"
+    environment:
+      POSTGRES_USER: postgres
+      POSTGRES_DB: postgres
+      POSTGRES_PASSWORD: postgres
+      POSTGRES_HOST_AUTH_METHOD: scram-sha-256
+    command: ["postgres", "-c", "shared_preload_libraries=pg_stat_statements", "-c", "pg_stat_statements.track=all", "-p", "5432"]
+  pg2:
+    image: postgres:14
+    network_mode: "service:main"
+    environment:
+      POSTGRES_USER: postgres
+      POSTGRES_DB: postgres
+      POSTGRES_PASSWORD: postgres
+      POSTGRES_HOST_AUTH_METHOD: scram-sha-256
+    command: ["postgres", "-c", "shared_preload_libraries=pg_stat_statements", "-c", "pg_stat_statements.track=all", "-p", "7432"]
+  pg3:
+    image: postgres:14
+    network_mode: "service:main"
+    environment:
+      POSTGRES_USER: postgres
+      POSTGRES_DB: postgres
+      POSTGRES_PASSWORD: postgres
+      POSTGRES_HOST_AUTH_METHOD: scram-sha-256
+    command: ["postgres", "-c", "shared_preload_libraries=pg_stat_statements", "-c", "pg_stat_statements.track=all", "-p", "8432"]
+  pg4:
+    image: postgres:14
+    network_mode: "service:main"
+    environment:
+      POSTGRES_USER: postgres
+      POSTGRES_DB: postgres
+      POSTGRES_PASSWORD: postgres
+      POSTGRES_HOST_AUTH_METHOD: scram-sha-256
+    command: ["postgres", "-c", "shared_preload_libraries=pg_stat_statements", "-c", "pg_stat_statements.track=all", "-p", "9432"]
+  main:
+    build: .
+    command: ["bash", "/app/tests/docker/run.sh"]
+    environment:
+      RUSTFLAGS: "-C instrument-coverage"
+      LLVM_PROFILE_FILE: "pgcat-%m.profraw"
+    volumes:
+      - ../../:/app/
+      - /app/target/
--- a/tests/docker/run.sh
+++ b/tests/docker/run.sh
@@ -0,0 +1,21 @@
+#!/bin/bash
+
+rm /app/*.profraw || true
+rm /app/pgcat.profdata || true
+rm -rf /app/cov || true
+
+cd /app/
+
+cargo build
+cargo test --tests
+
+bash .circleci/run_tests.sh
+
+rust-profdata merge -sparse pgcat-*.profraw -o pgcat.profdata
+
+rust-cov export -ignore-filename-regex="rustc|registry" -Xdemangler=rustfilt -instr-profile=pgcat.profdata --object ./target/debug/pgcat --format lcov > ./lcov.info
+
+genhtml lcov.info --output-directory cov --prefix $(pwd)
+
+rm /app/*.profraw
+rm /app/pgcat.profdata
--- a/tests/python/tests.py
+++ b/tests/python/tests.py
@@ -14,12 +14,18 @@ PGCAT_PORT = "6432"
 def pgcat_start():
    pg_cat_send_signal(signal.SIGTERM)
    os.system("./target/debug/pgcat .circleci/pgcat.toml &")
+    time.sleep(2)


 def pg_cat_send_signal(signal: signal.Signals):
-    for proc in psutil.process_iter(["pid", "name"]):
-        if "pgcat" == proc.name():
-            os.kill(proc.pid, signal)
+    try:
+        for proc in psutil.process_iter(["pid", "name"]):
+            if "pgcat" == proc.name():
+                os.kill(proc.pid, signal)
+    except Exception as e:
+        # The process can be gone when we send this signal
+        print(e)
+
    if signal == signal.SIGTERM:
        # Returns 0 if pgcat process exists
        time.sleep(2)
@@ -27,11 +33,23 @@ def pg_cat_send_signal(signal: signal.Signals):
            raise Exception("pgcat not closed after SIGTERM")


-def connect_normal_db(
-    autocommit: bool = False,
+def connect_db(
+    autocommit: bool = True,
+    admin: bool = False,
 ) -> Tuple[psycopg2.extensions.connection, psycopg2.extensions.cursor]:
+
+    if admin:
+        user = "admin_user"
+        password = "admin_pass"
+        db = "pgcat"
+    else:
+        user = "sharding_user"
+        password = "sharding_user"
+        db = "sharded_db"
+
    conn = psycopg2.connect(
-        f"postgres://sharding_user:sharding_user@{PGCAT_HOST}:{PGCAT_PORT}/sharded_db?application_name=testing_pgcat"
+        f"postgres://{user}:{password}@{PGCAT_HOST}:{PGCAT_PORT}/{db}?application_name=testing_pgcat",
+        connect_timeout=2,
    )
    conn.autocommit = autocommit
    cur = conn.cursor()
@@ -45,7 +63,7 @@ def cleanup_conn(conn: psycopg2.extensions.connection, cur: psycopg2.extensions.


 def test_normal_db_access():
-    conn, cur = connect_normal_db()
+    conn, cur = connect_db(autocommit=False)
    cur.execute("SELECT 1")
    res = cur.fetchall()
    print(res)
@@ -53,11 +71,7 @@ def test_normal_db_access():


 def test_admin_db_access():
-    conn = psycopg2.connect(
-        f"postgres://admin_user:admin_pass@{PGCAT_HOST}:{PGCAT_PORT}/pgcat"
-    )
-    conn.autocommit = True  # BEGIN/COMMIT is not supported by admin db
-    cur = conn.cursor()
+    conn, cur = connect_db(admin=True)

    cur.execute("SHOW POOLS")
    res = cur.fetchall()
@@ -67,15 +81,14 @@ def test_admin_db_access():

 def test_shutdown_logic():

-    ##### NO ACTIVE QUERIES SIGINT HANDLING #####
+    # - - - - - - - - - - - - - - - - - -
+    # NO ACTIVE QUERIES SIGINT HANDLING
+
    # Start pgcat
    pgcat_start()

-    # Wait for server to fully start up
-    time.sleep(2)
-
    # Create client connection and send query (not in transaction)
-    conn, cur = connect_normal_db(True)
+    conn, cur = connect_db()

    cur.execute("BEGIN;")
    cur.execute("SELECT 1;")
@@ -97,17 +110,14 @@ def test_shutdown_logic():
    cleanup_conn(conn, cur)
    pg_cat_send_signal(signal.SIGTERM)

-    ##### END #####
+    # - - - - - - - - - - - - - - - - - -
+    # HANDLE TRANSACTION WITH SIGINT

-    ##### HANDLE TRANSACTION WITH SIGINT #####
    # Start pgcat
    pgcat_start()

-    # Wait for server to fully start up
-    time.sleep(2)
-
    # Create client connection and begin transaction
-    conn, cur = connect_normal_db(True)
+    conn, cur = connect_db()

    cur.execute("BEGIN;")
    cur.execute("SELECT 1;")
@@ -126,17 +136,97 @@ def test_shutdown_logic():
    cleanup_conn(conn, cur)
    pg_cat_send_signal(signal.SIGTERM)

-    ##### END #####
-
-    ##### HANDLE SHUTDOWN TIMEOUT WITH SIGINT #####
+    # - - - - - - - - - - - - - - - - - -
+    # NO NEW NON-ADMIN CONNECTIONS DURING SHUTDOWN
    # Start pgcat
    pgcat_start()

-    # Wait for server to fully start up
-    time.sleep(3)
+    # Create client connection and begin transaction
+    transaction_conn, transaction_cur = connect_db()
+
+    transaction_cur.execute("BEGIN;")
+    transaction_cur.execute("SELECT 1;")
+
+    # Send sigint to pgcat while still in transaction
+    pg_cat_send_signal(signal.SIGINT)
+    time.sleep(1)
+
+    start = time.perf_counter()
+    try:
+        conn, cur = connect_db()
+        cur.execute("SELECT 1;")
+        cleanup_conn(conn, cur)
+    except psycopg2.OperationalError as e:
+        time_taken = time.perf_counter() - start
+        if time_taken > 0.1:
+            raise Exception(
+                "Failed to reject connection within 0.1 seconds, got", time_taken, "seconds")
+        pass
+    else:
+        raise Exception("Able connect to database during shutdown")
+
+    cleanup_conn(transaction_conn, transaction_cur)
+    pg_cat_send_signal(signal.SIGTERM)
+
+    # - - - - - - - - - - - - - - - - - -
+    # ALLOW NEW ADMIN CONNECTIONS DURING SHUTDOWN
+    # Start pgcat
+    pgcat_start()
+
+    # Create client connection and begin transaction
+    transaction_conn, transaction_cur = connect_db()
+
+    transaction_cur.execute("BEGIN;")
+    transaction_cur.execute("SELECT 1;")
+
+    # Send sigint to pgcat while still in transaction
+    pg_cat_send_signal(signal.SIGINT)
+    time.sleep(1)
+
+    try:
+        conn, cur = connect_db(admin=True)
+        cur.execute("SHOW DATABASES;")
+        cleanup_conn(conn, cur)
+    except psycopg2.OperationalError as e:
+        raise Exception(e)
+
+    cleanup_conn(transaction_conn, transaction_cur)
+    pg_cat_send_signal(signal.SIGTERM)
+
+    # - - - - - - - - - - - - - - - - - -
+    # ADMIN CONNECTIONS CONTINUING TO WORK AFTER SHUTDOWN
+    # Start pgcat
+    pgcat_start()
+
+    # Create client connection and begin transaction
+    transaction_conn, transaction_cur = connect_db()
+    transaction_cur.execute("BEGIN;")
+    transaction_cur.execute("SELECT 1;")
+
+    admin_conn, admin_cur = connect_db(admin=True)
+    admin_cur.execute("SHOW DATABASES;")
+
+    # Send sigint to pgcat while still in transaction
+    pg_cat_send_signal(signal.SIGINT)
+    time.sleep(1)
+
+    try:
+        admin_cur.execute("SHOW DATABASES;")
+    except psycopg2.OperationalError as e:
+        raise Exception("Could not execute admin command:", e)
+
+    cleanup_conn(transaction_conn, transaction_cur)
+    cleanup_conn(admin_conn, admin_cur)
+    pg_cat_send_signal(signal.SIGTERM)
+
+    # - - - - - - - - - - - - - - - - - -
+    # HANDLE SHUTDOWN TIMEOUT WITH SIGINT
+
+    # Start pgcat
+    pgcat_start()

    # Create client connection and begin transaction, which should prevent server shutdown unless shutdown timeout is reached
-    conn, cur = connect_normal_db(True)
+    conn, cur = connect_db()

    cur.execute("BEGIN;")
    cur.execute("SELECT 1;")
@@ -159,7 +249,7 @@ def test_shutdown_logic():
    cleanup_conn(conn, cur)
    pg_cat_send_signal(signal.SIGTERM)

-    ##### END #####
+    # - - - - - - - - - - - - - - - - - -


 test_normal_db_access()
--- a/tests/ruby/Gemfile
+++ b/tests/ruby/Gemfile
@@ -1,6 +1,8 @@
 source "https://rubygems.org"

 gem "pg"
-gem "activerecord"
+gem "toml"
+gem "rspec"
 gem "rubocop"
-gem "toml", "~> 0.3.0"
+gem "toxiproxy"
+gem "activerecord"
--- a/tests/ruby/Gemfile.lock
+++ b/tests/ruby/Gemfile.lock
@@ -13,6 +13,7 @@ GEM
      tzinfo (~> 2.0)
    ast (2.4.2)
    concurrent-ruby (1.1.10)
+    diff-lcs (1.5.0)
    i18n (1.11.0)
      concurrent-ruby (~> 1.0)
    minitest (5.16.2)
@@ -24,6 +25,19 @@ GEM
    rainbow (3.1.1)
    regexp_parser (2.3.1)
    rexml (3.2.5)
+    rspec (3.11.0)
+      rspec-core (~> 3.11.0)
+      rspec-expectations (~> 3.11.0)
+      rspec-mocks (~> 3.11.0)
+    rspec-core (3.11.0)
+      rspec-support (~> 3.11.0)
+    rspec-expectations (3.11.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.11.0)
+    rspec-mocks (3.11.1)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.11.0)
+    rspec-support (3.11.0)
    rubocop (1.29.0)
      parallel (~> 1.10)
      parser (>= 3.1.0.0)
@@ -38,19 +52,23 @@ GEM
    ruby-progressbar (1.11.0)
    toml (0.3.0)
      parslet (>= 1.8.0, < 3.0.0)
+    toxiproxy (2.0.1)
    tzinfo (2.0.4)
      concurrent-ruby (~> 1.0)
    unicode-display_width (2.1.0)

 PLATFORMS
+  aarch64-linux
  arm64-darwin-21
  x86_64-linux

 DEPENDENCIES
  activerecord
  pg
+  rspec
  rubocop
-  toml (~> 0.3.0)
+  toml
+  toxiproxy

 BUNDLED WITH
-   2.3.7
+   2.3.21
--- a/tests/ruby/admin_spec.rb
+++ b/tests/ruby/admin_spec.rb
@@ -0,0 +1,289 @@
+# frozen_string_literal: true
+require 'uri'
+require_relative 'spec_helper'
+
+describe "Admin" do
+  let(:processes) { Helpers::Pgcat.single_instance_setup("sharded_db", 10) }
+  let(:pgcat_conn_str) { processes.pgcat.connection_string("sharded_db", "sharding_user") }
+
+  after do
+    processes.all_databases.map(&:reset)
+    processes.pgcat.shutdown
+  end
+
+  describe "SHOW STATS" do
+    context "clients connect and make one query" do
+      it "updates *_query_time and *_wait_time" do
+        connection = PG::connect("#{pgcat_conn_str}?application_name=one_query")
+        connection.async_exec("SELECT pg_sleep(0.25)")
+        connection.async_exec("SELECT pg_sleep(0.25)")
+        connection.async_exec("SELECT pg_sleep(0.25)")
+        connection.close
+
+        # wait for averages to be calculated, we shouldn't do this too often
+        sleep(15.5)
+        admin_conn = PG::connect(processes.pgcat.admin_connection_string)
+        results = admin_conn.async_exec("SHOW STATS")[0]
+        admin_conn.close
+        expect(results["total_query_time"].to_i).to be_within(200).of(750)
+        expect(results["avg_query_time"].to_i).to_not eq(0)
+
+        expect(results["total_wait_time"].to_i).to_not eq(0)
+        expect(results["avg_wait_time"].to_i).to_not eq(0)
+      end
+    end
+  end
+
+  describe "SHOW POOLS" do
+    context "bad credentials" do
+      it "does not change any stats" do
+        bad_passsword_url = URI(pgcat_conn_str)
+        bad_passsword_url.password = "wrong"
+        expect { PG::connect("#{bad_passsword_url.to_s}?application_name=bad_password") }.to raise_error(PG::ConnectionBad)
+
+        sleep(1)
+        admin_conn = PG::connect(processes.pgcat.admin_connection_string)
+        results = admin_conn.async_exec("SHOW POOLS")[0]
+        %w[cl_idle cl_active cl_waiting cl_cancel_req sv_active sv_used sv_tested sv_login maxwait].each do |s|
+          raise StandardError, "Field #{s} was expected to be 0 but found to be #{results[s]}" if results[s] != "0"
+        end
+
+        expect(results["sv_idle"]).to eq("1")
+      end
+    end
+
+    context "bad database name" do
+      it "does not change any stats" do
+        bad_db_url = URI(pgcat_conn_str)
+        bad_db_url.path = "/wrong_db"
+        expect { PG::connect("#{bad_db_url.to_s}?application_name=bad_db") }.to raise_error(PG::ConnectionBad)
+
+        sleep(1)
+        admin_conn = PG::connect(processes.pgcat.admin_connection_string)
+        results = admin_conn.async_exec("SHOW POOLS")[0]
+        %w[cl_idle cl_active cl_waiting cl_cancel_req sv_active sv_used sv_tested sv_login maxwait].each do |s|
+          raise StandardError, "Field #{s} was expected to be 0 but found to be #{results[s]}" if results[s] != "0"
+        end
+
+        expect(results["sv_idle"]).to eq("1")
+      end
+    end
+
+    context "client connects but issues no queries" do
+      it "only affects cl_idle stats" do
+        connections = Array.new(20) { PG::connect(pgcat_conn_str) }
+        sleep(1)
+        admin_conn = PG::connect(processes.pgcat.admin_connection_string)
+        results = admin_conn.async_exec("SHOW POOLS")[0]
+        %w[cl_active cl_waiting cl_cancel_req sv_active sv_used sv_tested sv_login maxwait].each do |s|
+          raise StandardError, "Field #{s} was expected to be 0 but found to be #{results[s]}" if results[s] != "0"
+        end
+        expect(results["cl_idle"]).to eq("20")
+        expect(results["sv_idle"]).to eq("1")
+
+        connections.map(&:close)
+        sleep(1.1)
+        results = admin_conn.async_exec("SHOW POOLS")[0]
+        %w[cl_active cl_idle cl_waiting cl_cancel_req sv_active sv_used sv_tested sv_login maxwait].each do |s|
+          raise StandardError, "Field #{s} was expected to be 0 but found to be #{results[s]}" if results[s] != "0"
+        end
+        expect(results["sv_idle"]).to eq("1")
+      end
+    end
+
+    context "clients connect and make one query" do
+      it "only affects cl_idle, sv_idle stats" do
+        connections = Array.new(5) { PG::connect("#{pgcat_conn_str}?application_name=one_query") }
+        connections.each do |c|
+          Thread.new { c.async_exec("SELECT pg_sleep(2.5)") }
+        end
+
+        sleep(1.1)
+        admin_conn = PG::connect(processes.pgcat.admin_connection_string)
+        results = admin_conn.async_exec("SHOW POOLS")[0]
+        %w[cl_idle cl_waiting cl_cancel_req sv_idle sv_used sv_tested sv_login maxwait].each do |s|
+          raise StandardError, "Field #{s} was expected to be 0 but found to be #{results[s]}" if results[s] != "0"
+        end
+        expect(results["cl_active"]).to eq("5")
+        expect(results["sv_active"]).to eq("5")
+
+        sleep(3)
+        results = admin_conn.async_exec("SHOW POOLS")[0]
+        %w[cl_active cl_waiting cl_cancel_req sv_active sv_used sv_tested sv_login maxwait].each do |s|
+          raise StandardError, "Field #{s} was expected to be 0 but found to be #{results[s]}" if results[s] != "0"
+        end
+        expect(results["cl_idle"]).to eq("5")
+        expect(results["sv_idle"]).to eq("5")
+
+        connections.map(&:close)
+        sleep(1)
+        results = admin_conn.async_exec("SHOW POOLS")[0]
+        %w[cl_idle cl_active cl_waiting cl_cancel_req sv_active sv_used sv_tested sv_login maxwait].each do |s|
+          raise StandardError, "Field #{s} was expected to be 0 but found to be #{results[s]}" if results[s] != "0"
+        end
+        expect(results["sv_idle"]).to eq("5")
+      end
+    end
+
+    context "client connects and opens a transaction and closes connection uncleanly" do
+      it "produces correct statistics" do
+        connections = Array.new(5) { PG::connect("#{pgcat_conn_str}?application_name=one_query") }
+        connections.each do |c|
+          Thread.new do
+            c.async_exec("BEGIN")
+            c.async_exec("SELECT pg_sleep(0.01)")
+            c.close
+          end
+        end
+
+        sleep(1.1)
+        admin_conn = PG::connect(processes.pgcat.admin_connection_string)
+        results = admin_conn.async_exec("SHOW POOLS")[0]
+        %w[cl_idle cl_active cl_waiting cl_cancel_req sv_active sv_used sv_tested sv_login maxwait].each do |s|
+          raise StandardError, "Field #{s} was expected to be 0 but found to be #{results[s]}" if results[s] != "0"
+        end
+        expect(results["sv_idle"]).to eq("5")
+      end
+    end
+
+    context "client fail to checkout connection from the pool" do
+      it "counts clients as idle" do
+        new_configs = processes.pgcat.current_config
+        new_configs["general"]["connect_timeout"] = 500
+        new_configs["general"]["ban_time"] = 1
+        new_configs["general"]["shutdown_timeout"] = 1
+        new_configs["pools"]["sharded_db"]["users"]["0"]["pool_size"] = 1
+        processes.pgcat.update_config(new_configs)
+        processes.pgcat.reload_config
+
+        threads = []
+        connections = Array.new(5) { PG::connect("#{pgcat_conn_str}?application_name=one_query") }
+        connections.each do |c|
+          threads << Thread.new { c.async_exec("SELECT pg_sleep(1)") rescue PG::SystemError }
+        end
+
+        sleep(2)
+        admin_conn = PG::connect(processes.pgcat.admin_connection_string)
+        results = admin_conn.async_exec("SHOW POOLS")[0]
+        %w[cl_active cl_waiting cl_cancel_req sv_active sv_used sv_tested sv_login maxwait].each do |s|
+          raise StandardError, "Field #{s} was expected to be 0 but found to be #{results[s]}" if results[s] != "0"
+        end
+        expect(results["cl_idle"]).to eq("5")
+        expect(results["sv_idle"]).to eq("1")
+
+        threads.map(&:join)
+        connections.map(&:close)
+      end
+    end
+
+    context "clients overwhelm server pools" do
+      let(:processes) { Helpers::Pgcat.single_instance_setup("sharded_db", 2) }
+
+      it "cl_waiting is updated to show it" do
+        threads = []
+        connections = Array.new(4) { PG::connect("#{pgcat_conn_str}?application_name=one_query") }
+        connections.each do |c|
+          threads << Thread.new { c.async_exec("SELECT pg_sleep(1.5)") }
+        end
+
+        sleep(1.1) # Allow time for stats to update
+        admin_conn = PG::connect(processes.pgcat.admin_connection_string)
+        results = admin_conn.async_exec("SHOW POOLS")[0]
+        %w[cl_idle cl_cancel_req sv_idle sv_used sv_tested sv_login maxwait].each do |s|
+          raise StandardError, "Field #{s} was expected to be 0 but found to be #{results[s]}" if results[s] != "0"
+        end
+
+        expect(results["cl_waiting"]).to eq("2")
+        expect(results["cl_active"]).to eq("2")
+        expect(results["sv_active"]).to eq("2")
+
+        sleep(2.5) # Allow time for stats to update
+        results = admin_conn.async_exec("SHOW POOLS")[0]
+        %w[cl_active cl_waiting cl_cancel_req sv_active sv_used sv_tested sv_login maxwait].each do |s|
+          raise StandardError, "Field #{s} was expected to be 0 but found to be #{results[s]}" if results[s] != "0"
+        end
+        expect(results["cl_idle"]).to eq("4")
+        expect(results["sv_idle"]).to eq("2")
+
+        threads.map(&:join)
+        connections.map(&:close)
+      end
+
+      it "show correct max_wait" do
+        threads = []
+        connections = Array.new(4) { PG::connect("#{pgcat_conn_str}?application_name=one_query") }
+        connections.each do |c|
+          threads << Thread.new { c.async_exec("SELECT pg_sleep(1.5)") }
+        end
+
+        sleep(2.5) # Allow time for stats to update
+        admin_conn = PG::connect(processes.pgcat.admin_connection_string)
+        results = admin_conn.async_exec("SHOW POOLS")[0]
+
+        expect(results["maxwait"]).to eq("1")
+        expect(results["maxwait_us"].to_i).to be_within(100_000).of(500_000)
+
+        sleep(4.5) # Allow time for stats to update
+        results = admin_conn.async_exec("SHOW POOLS")[0]
+        expect(results["maxwait"]).to eq("0")
+
+        threads.map(&:join)
+        connections.map(&:close)
+      end
+    end
+  end
+
+  describe "SHOW CLIENTS" do
+    it "reports correct number and application names" do
+      conn_str = processes.pgcat.connection_string("sharded_db", "sharding_user")
+      connections = Array.new(20) { |i| PG::connect("#{conn_str}?application_name=app#{i % 5}") }
+
+      admin_conn = PG::connect(processes.pgcat.admin_connection_string)
+      sleep(1) # Wait for stats to be updated
+
+      results = admin_conn.async_exec("SHOW CLIENTS")
+      expect(results.count).to eq(21) # count admin clients
+      expect(results.select { |c| c["application_name"] == "app3" ||  c["application_name"] == "app4" }.count).to eq(8)
+      expect(results.select { |c| c["database"] == "pgcat" }.count).to eq(1)
+
+      connections[0..5].map(&:close)
+      sleep(1) # Wait for stats to be updated
+      results = admin_conn.async_exec("SHOW CLIENTS")
+      expect(results.count).to eq(15)
+
+      connections[6..].map(&:close)
+      sleep(1) # Wait for stats to be updated
+      expect(admin_conn.async_exec("SHOW CLIENTS").count).to eq(1)
+      admin_conn.close
+    end
+
+    it "reports correct number of queries and transactions" do
+      conn_str = processes.pgcat.connection_string("sharded_db", "sharding_user")
+
+      connections = Array.new(2) { |i| PG::connect("#{conn_str}?application_name=app#{i}") }
+      connections.each do |c|
+        c.async_exec("SELECT 1")
+        c.async_exec("SELECT 2")
+        c.async_exec("SELECT 3")
+        c.async_exec("BEGIN")
+        c.async_exec("SELECT 4")
+        c.async_exec("SELECT 5")
+        c.async_exec("COMMIT")
+      end
+
+      admin_conn = PG::connect(processes.pgcat.admin_connection_string)
+      sleep(1) # Wait for stats to be updated
+
+      results = admin_conn.async_exec("SHOW CLIENTS")
+      expect(results.count).to eq(3)
+      normal_client_results = results.reject { |r| r["database"] == "pgcat" }
+      expect(normal_client_results[0]["transaction_count"]).to eq("4")
+      expect(normal_client_results[1]["transaction_count"]).to eq("4")
+      expect(normal_client_results[0]["query_count"]).to eq("7")
+      expect(normal_client_results[1]["query_count"]).to eq("7")
+
+      admin_conn.close
+      connections.map(&:close)
+    end
+  end
+end
--- a/tests/ruby/helpers/pg_instance.rb
+++ b/tests/ruby/helpers/pg_instance.rb
@@ -0,0 +1,82 @@
+require 'pg'
+require 'toxiproxy'
+
+class PgInstance
+  attr_reader :port
+  attr_reader :username
+  attr_reader :password
+  attr_reader :database_name
+
+  def initialize(port, username, password, database_name)
+    @original_port = port
+    @toxiproxy_port = 10000 + port.to_i
+    @port = @toxiproxy_port
+
+    @username = username
+    @password = password
+    @database_name = database_name
+    @toxiproxy_name = "database_#{@original_port}"
+    Toxiproxy.populate([{
+      name: @toxiproxy_name,
+      listen: "0.0.0.0:#{@toxiproxy_port}",
+      upstream: "localhost:#{@original_port}",
+    }])
+
+    # Toxiproxy server will outlive our PgInstance objects
+    # so we want to destroy our proxies before exiting
+    # Ruby finalizer is ideal for doing this
+    ObjectSpace.define_finalizer(@toxiproxy_name, proc { Toxiproxy[@toxiproxy_name].destroy })
+  end
+
+  def with_connection
+    conn = PG.connect("postgres://#{@username}:#{@password}@localhost:#{port}/#{database_name}")
+    yield conn
+  ensure
+    conn&.close
+  end
+
+  def reset
+    reset_toxics
+    reset_stats
+  end
+
+  def toxiproxy
+    Toxiproxy[@toxiproxy_name]
+  end
+
+  def take_down
+    if block_given?
+      Toxiproxy[@toxiproxy_name].toxic(:limit_data, bytes: 5).apply { yield }
+    else
+      Toxiproxy[@toxiproxy_name].toxic(:limit_data, bytes: 5).toxics.each(&:save)
+    end
+  end
+
+  def add_latency(latency)
+    if block_given?
+      Toxiproxy[@toxiproxy_name].toxic(:latency, latency: latency).apply { yield }
+    else
+      Toxiproxy[@toxiproxy_name].toxic(:latency, latency: latency).toxics.each(&:save)
+    end
+  end
+
+  def delete_proxy
+    Toxiproxy[@toxiproxy_name].delete
+  end
+
+  def reset_toxics
+    Toxiproxy[@toxiproxy_name].toxics.each(&:destroy)
+  end
+
+  def reset_stats
+    with_connection { |c| c.async_exec("SELECT pg_stat_statements_reset()") }
+  end
+
+  def count_query(query)
+    with_connection { |c| c.async_exec("SELECT SUM(calls) FROM pg_stat_statements WHERE query = '#{query}'")[0]["sum"].to_i }
+  end
+
+  def count_select_1_plus_2
+    with_connection { |c| c.async_exec("SELECT SUM(calls) FROM pg_stat_statements WHERE query = 'SELECT $1 + $2'")[0]["sum"].to_i }
+  end
+end
--- a/tests/ruby/helpers/pgcat_helper.rb
+++ b/tests/ruby/helpers/pgcat_helper.rb
@@ -0,0 +1,144 @@
+require 'json'
+require 'ostruct'
+require_relative 'pgcat_process'
+require_relative 'pg_instance'
+
+module Helpers
+  module Pgcat
+    def self.three_shard_setup(pool_name, pool_size, pool_mode="transaction")
+      user = {
+        "password" => "sharding_user",
+        "pool_size" => pool_size,
+        "statement_timeout" => 0,
+        "username" => "sharding_user"
+      }
+
+      pgcat    = PgcatProcess.new("info")
+      primary0 = PgInstance.new(5432, user["username"], user["password"], "shard0")
+      primary1 = PgInstance.new(7432, user["username"], user["password"], "shard1")
+      primary2 = PgInstance.new(8432, user["username"], user["password"], "shard2")
+
+      pgcat_cfg = pgcat.current_config
+      pgcat_cfg["pools"] = {
+        "#{pool_name}" => {
+          "default_role" => "any",
+          "pool_mode" => pool_mode,
+          "primary_reads_enabled" => false,
+          "query_parser_enabled" => false,
+          "sharding_function" => "pg_bigint_hash",
+          "shards" => {
+            "0" => { "database" => "shard0", "servers" => [["localhost", primary0.port.to_s, "primary"]] },
+            "1" => { "database" => "shard1", "servers" => [["localhost", primary1.port.to_s, "primary"]] },
+            "2" => { "database" => "shard2", "servers" => [["localhost", primary2.port.to_s, "primary"]] },
+          },
+          "users" => { "0" => user }
+        }
+      }
+      pgcat.update_config(pgcat_cfg)
+
+      pgcat.start
+      pgcat.wait_until_ready
+
+      OpenStruct.new.tap do |struct|
+        struct.pgcat = pgcat
+        struct.shards = [primary0, primary1, primary2]
+        struct.all_databases = [primary0, primary1, primary2]
+      end
+    end
+
+    def self.single_instance_setup(pool_name, pool_size, pool_mode="transaction")
+      user = {
+        "password" => "sharding_user",
+        "pool_size" => pool_size,
+        "statement_timeout" => 0,
+        "username" => "sharding_user"
+      }
+
+      pgcat = PgcatProcess.new("trace")
+      pgcat_cfg = pgcat.current_config
+
+      primary  = PgInstance.new(5432, user["username"], user["password"], "shard0")
+
+      # Main proxy configs
+      pgcat_cfg["pools"] = {
+        "#{pool_name}" => {
+          "default_role" => "primary",
+          "pool_mode" => pool_mode,
+          "primary_reads_enabled" => false,
+          "query_parser_enabled" => false,
+          "sharding_function" => "pg_bigint_hash",
+          "shards" => {
+            "0" => {
+              "database" => "shard0",
+              "servers" => [
+                ["localhost", primary.port.to_s, "primary"]
+              ]
+            },
+          },
+          "users" => { "0" => user }
+        }
+      }
+      pgcat_cfg["general"]["port"] = pgcat.port
+      pgcat.update_config(pgcat_cfg)
+      pgcat.start
+      pgcat.wait_until_ready
+
+      OpenStruct.new.tap do |struct|
+        struct.pgcat = pgcat
+        struct.primary = primary
+        struct.all_databases = [primary]
+      end
+    end
+
+    def self.single_shard_setup(pool_name, pool_size, pool_mode="transaction")
+      user = {
+        "password" => "sharding_user",
+        "pool_size" => pool_size,
+        "statement_timeout" => 0,
+        "username" => "sharding_user"
+      }
+
+      pgcat = PgcatProcess.new("info")
+      pgcat_cfg = pgcat.current_config
+
+      primary  = PgInstance.new(5432, user["username"], user["password"], "shard0")
+      replica0 = PgInstance.new(7432, user["username"], user["password"], "shard0")
+      replica1 = PgInstance.new(8432, user["username"], user["password"], "shard0")
+      replica2 = PgInstance.new(9432, user["username"], user["password"], "shard0")
+
+      # Main proxy configs
+      pgcat_cfg["pools"] = {
+        "#{pool_name}" => {
+          "default_role" => "any",
+          "pool_mode" => pool_mode,
+          "primary_reads_enabled" => false,
+          "query_parser_enabled" => false,
+          "sharding_function" => "pg_bigint_hash",
+          "shards" => {
+            "0" => {
+              "database" => "shard0",
+              "servers" => [
+                ["localhost", primary.port.to_s, "primary"],
+                ["localhost", replica0.port.to_s, "replica"],
+                ["localhost", replica1.port.to_s, "replica"],
+                ["localhost", replica2.port.to_s, "replica"]
+              ]
+            },
+          },
+          "users" => { "0" => user }
+        }
+      }
+      pgcat_cfg["general"]["port"] = pgcat.port
+      pgcat.update_config(pgcat_cfg)
+      pgcat.start
+      pgcat.wait_until_ready
+
+      OpenStruct.new.tap do |struct|
+        struct.pgcat = pgcat
+        struct.primary = primary
+        struct.replicas = [replica0, replica1, replica2]
+        struct.all_databases = [primary, replica0, replica1, replica2]
+      end
+    end
+  end
+end
--- a/tests/ruby/helpers/pgcat_process.rb
+++ b/tests/ruby/helpers/pgcat_process.rb
@@ -0,0 +1,116 @@
+require 'pg'
+require 'toml'
+require 'fileutils'
+require 'securerandom'
+
+class PgcatProcess
+  attr_reader :port
+  attr_reader :pid
+
+  def self.finalize(pid, log_filename, config_filename)
+    `kill #{pid}`
+    File.delete(config_filename) if File.exist?(config_filename)
+    File.delete(log_filename) if File.exist?(log_filename)
+  end
+
+  def initialize(log_level)
+    @env = {"RUST_LOG" => log_level}
+    @port = rand(20000..32760)
+    @log_level = log_level
+    @log_filename = "/tmp/pgcat_log_#{SecureRandom.urlsafe_base64}.log"
+    @config_filename = "/tmp/pgcat_cfg_#{SecureRandom.urlsafe_base64}.toml"
+
+    @command = "../../target/debug/pgcat #{@config_filename}"
+
+    FileUtils.cp("../../pgcat.toml", @config_filename)
+    cfg = current_config
+    cfg["general"]["port"] = @port.to_i
+    cfg["general"]["enable_prometheus_exporter"] = false
+
+    update_config(cfg)
+  end
+
+  def logs
+    File.read(@log_filename)
+  end
+
+  def update_config(config_hash)
+    @original_config = current_config
+    output_to_write = TOML::Generator.new(config_hash).body
+    output_to_write = output_to_write.gsub(/,\s*["|'](\d+)["|']\s*,/, ',\1,')
+    File.write(@config_filename, output_to_write)
+  end
+
+  def current_config
+    old_cfg = File.read(@config_filename)
+    loadable_string = old_cfg.gsub(/,\s*(\d+)\s*,/, ', "\1",')
+    TOML.load(loadable_string)
+  end
+
+  def reload_config
+    `kill -s HUP #{@pid}`
+    sleep 0.1
+  end
+
+  def start
+    raise StandardError, "Process is already started" unless @pid.nil?
+    @pid = Process.spawn(@env, @command, err: @log_filename, out: @log_filename)
+    ObjectSpace.define_finalizer(@log_filename, proc { PgcatProcess.finalize(@pid, @log_filename, @config_filename) })
+
+    return self
+  end
+
+  def wait_until_ready
+    exc = nil
+    10.times do
+      PG::connect(example_connection_string).close
+
+      return self
+    rescue => e
+      exc = e
+      sleep(0.5)
+    end
+    puts exc
+    raise StandardError, "Process #{@pid} never became ready. Logs #{logs}"
+  end
+
+  def stop
+    `kill #{@pid}`
+    sleep 0.1
+  end
+
+  def shutdown
+    stop
+    File.delete(@config_filename) if File.exist?(@config_filename)
+    File.delete(@log_filename) if File.exist?(@log_filename)
+  end
+
+  def admin_connection_string
+    cfg = current_config
+    username = cfg["general"]["admin_username"]
+    password = cfg["general"]["admin_password"]
+
+    "postgresql://#{username}:#{password}@0.0.0.0:#{@port}/pgcat"
+  end
+
+  def connection_string(pool_name, username)
+    cfg = current_config
+
+    user_idx, user_obj = cfg["pools"][pool_name]["users"].detect { |k, user| user["username"] == username }
+    password = user_obj["password"]
+
+    "postgresql://#{username}:#{password}@0.0.0.0:#{@port}/#{pool_name}"
+  end
+
+  def example_connection_string
+    cfg = current_config
+    first_pool_name = cfg["pools"].keys[0]
+
+    db_name = first_pool_name
+
+    username = cfg["pools"][first_pool_name]["users"]["0"]["username"]
+    password = cfg["pools"][first_pool_name]["users"]["0"]["password"]
+
+    "postgresql://#{username}:#{password}@0.0.0.0:#{@port}/#{db_name}?application_name=example_app"
+  end
+end
--- a/tests/ruby/load_balancing_spec.rb
+++ b/tests/ruby/load_balancing_spec.rb
@@ -0,0 +1,61 @@
+# frozen_string_literal: true
+require_relative 'spec_helper'
+
+describe "Load Balancing" do
+  let(:processes) { Helpers::Pgcat.single_shard_setup("sharded_db", 5) }
+  after do
+    processes.all_databases.map(&:reset)
+    processes.pgcat.shutdown
+  end
+
+  context "under regular circumstances" do
+    it "balances query volume between all instances" do
+      conn = PG.connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+
+      query_count = QUERY_COUNT
+      expected_share = query_count / processes.all_databases.count
+      failed_count = 0
+
+      query_count.times do
+        conn.async_exec("SELECT 1 + 2")
+      rescue
+        failed_count += 1
+      end
+
+      expect(failed_count).to eq(0)
+      processes.all_databases.map(&:count_select_1_plus_2).each do |instance_share|
+        expect(instance_share).to be_within(expected_share * MARGIN_OF_ERROR).of(expected_share)
+      end
+    end
+  end
+
+  context "when some replicas are down" do
+    it "balances query volume between working instances" do
+      conn = PG.connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+      expected_share = QUERY_COUNT / (processes.all_databases.count - 2)
+      failed_count = 0
+
+      processes[:replicas][0].take_down do
+        processes[:replicas][1].take_down do
+          QUERY_COUNT.times do
+            conn.async_exec("SELECT 1 + 2")
+          rescue
+            conn = PG.connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+            failed_count += 1
+          end
+        end
+      end
+
+      expect(failed_count).to eq(2)
+      processes.all_databases.each do |instance|
+        queries_routed = instance.count_select_1_plus_2
+        if processes.replicas[0..1].include?(instance)
+          expect(queries_routed).to eq(0)
+        else
+          expect(queries_routed).to be_within(expected_share * MARGIN_OF_ERROR).of(expected_share)
+        end
+      end
+    end
+  end
+end
+
--- a/tests/ruby/misc_spec.rb
+++ b/tests/ruby/misc_spec.rb
@@ -0,0 +1,193 @@
+# frozen_string_literal: true
+require_relative 'spec_helper'
+
+describe "Miscellaneous" do
+  let(:processes) { Helpers::Pgcat.single_shard_setup("sharded_db", 5) }
+  after do
+    processes.all_databases.map(&:reset)
+    processes.pgcat.shutdown
+  end
+
+  describe "Extended Protocol handling" do
+    it "does not send packets that client does not expect during extended protocol sequence" do
+      new_configs = processes.pgcat.current_config
+
+      new_configs["general"]["connect_timeout"] = 500
+      new_configs["general"]["ban_time"] = 1
+      new_configs["general"]["shutdown_timeout"] = 1
+      new_configs["pools"]["sharded_db"]["users"]["0"]["pool_size"] = 1
+
+      processes.pgcat.update_config(new_configs)
+      processes.pgcat.reload_config
+
+      25.times do
+        Thread.new do
+          conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+          conn.async_exec("SELECT pg_sleep(5)") rescue PG::SystemError
+        ensure
+          conn&.close
+        end
+      end
+
+      sleep(0.5)
+      conn_under_test = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+      stdout, stderr = with_captured_stdout_stderr do
+        15.times do |i|
+          conn_under_test.async_exec("SELECT 1") rescue PG::SystemError
+          conn_under_test.exec_params("SELECT #{i} + $1", [i]) rescue PG::SystemError
+          sleep 1
+        end
+      end
+
+      raise StandardError, "Libpq got unexpected messages while idle" if stderr.include?("arrived from server while idle")
+    end
+  end
+
+  describe "Pool recycling after config reload" do
+    let(:processes) { Helpers::Pgcat.three_shard_setup("sharded_db", 5) }
+
+    it "should update pools for new clients and clients that are no longer in transaction" do
+      server_conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+      server_conn.async_exec("BEGIN")
+
+      # No config change yet, client should set old configs
+      current_datebase_from_pg = server_conn.async_exec("SELECT current_database();")[0]["current_database"]
+      expect(current_datebase_from_pg).to eq('shard0')
+
+      # Swap shards
+      new_config = processes.pgcat.current_config
+      shard0 = new_config["pools"]["sharded_db"]["shards"]["0"]
+      shard1 = new_config["pools"]["sharded_db"]["shards"]["1"]
+      new_config["pools"]["sharded_db"]["shards"]["0"] = shard1
+      new_config["pools"]["sharded_db"]["shards"]["1"] = shard0
+
+      # Reload config
+      processes.pgcat.update_config(new_config)
+      processes.pgcat.reload_config
+      sleep 0.5
+
+      # Config changed but transaction is in progress, client should set old configs
+      current_datebase_from_pg = server_conn.async_exec("SELECT current_database();")[0]["current_database"]
+      expect(current_datebase_from_pg).to eq('shard0')
+      server_conn.async_exec("COMMIT")
+
+      # Transaction finished, client should get new configs
+      current_datebase_from_pg = server_conn.async_exec("SELECT current_database();")[0]["current_database"]
+      expect(current_datebase_from_pg).to eq('shard1')
+
+      # New connection should get new configs
+      server_conn.close()
+      server_conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+      current_datebase_from_pg = server_conn.async_exec("SELECT current_database();")[0]["current_database"]
+      expect(current_datebase_from_pg).to eq('shard1')
+    end
+  end
+
+  describe "Clients closing connection in the middle of transaction" do
+    it "sends a rollback to the server" do
+      conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+      conn.async_exec("SET SERVER ROLE to 'primary'")
+      conn.async_exec("BEGIN")
+      conn.close
+
+      expect(processes.primary.count_query("ROLLBACK")).to eq(1)
+    end
+  end
+
+  describe "Server version reporting" do
+    it "reports correct version for normal and admin databases" do
+      server_conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+      expect(server_conn.server_version).not_to eq(0)
+      server_conn.close
+
+      admin_conn = PG::connect(processes.pgcat.admin_connection_string)
+      expect(admin_conn.server_version).not_to eq(0)
+      admin_conn.close
+    end
+  end
+
+  describe "State clearance" do
+    context "session mode" do
+      let(:processes) { Helpers::Pgcat.single_shard_setup("sharded_db", 5, "session") }
+
+      it "Clears state before connection checkin" do
+        # Both modes of operation should not raise
+        # ERROR:  prepared statement "prepared_q" already exists
+        15.times do
+          conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+          conn.async_exec("PREPARE prepared_q (int) AS SELECT $1")
+          conn.close
+        end
+
+        conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+        initial_value = conn.async_exec("SHOW statement_timeout")[0]["statement_timeout"]
+        conn.async_exec("SET statement_timeout to 1000")
+        current_value = conn.async_exec("SHOW statement_timeout")[0]["statement_timeout"]
+        expect(conn.async_exec("SHOW statement_timeout")[0]["statement_timeout"]).to eq("1s")
+        conn.close
+      end
+
+      it "Does not send DISCARD ALL unless necessary" do
+        10.times do
+          conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+          conn.async_exec("SET SERVER ROLE to 'primary'")
+          conn.async_exec("SELECT 1")
+          conn.close
+        end
+
+        expect(processes.primary.count_query("DISCARD ALL")).to eq(0)
+
+        10.times do
+          conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+          conn.async_exec("SET SERVER ROLE to 'primary'")
+          conn.async_exec("SELECT 1")
+          conn.async_exec("SET statement_timeout to 5000")
+          conn.close
+        end
+
+        expect(processes.primary.count_query("DISCARD ALL")).to eq(10)
+      end
+    end
+
+    context "transaction mode" do
+      let(:processes) { Helpers::Pgcat.single_shard_setup("sharded_db", 5, "transaction") }
+      it "Clears state before connection checkin" do
+        # Both modes of operation should not raise
+        # ERROR:  prepared statement "prepared_q" already exists
+        15.times do
+          conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+          conn.async_exec("PREPARE prepared_q (int) AS SELECT $1")
+          conn.close
+        end
+
+        15.times do
+          conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+          conn.prepare("prepared_q", "SELECT $1")
+          conn.close
+        end
+      end
+
+      it "Does not send DISCARD ALL unless necessary" do
+        10.times do
+          conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+          conn.async_exec("SET SERVER ROLE to 'primary'")
+          conn.async_exec("SELECT 1")
+          conn.exec_params("SELECT $1", [1])
+          conn.close
+        end
+
+        expect(processes.primary.count_query("DISCARD ALL")).to eq(0)
+
+        10.times do
+          conn = PG::connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+          conn.async_exec("SET SERVER ROLE to 'primary'")
+          conn.async_exec("SELECT 1")
+          conn.async_exec("SET statement_timeout to 5000")
+          conn.close
+        end
+
+        expect(processes.primary.count_query("DISCARD ALL")).to eq(10)
+      end
+    end
+  end
+end
--- a/tests/ruby/routing_spec.rb
+++ b/tests/ruby/routing_spec.rb
@@ -0,0 +1,81 @@
+# frozen_string_literal: true
+require_relative 'spec_helper'
+
+
+describe "Routing" do
+  let(:processes) { Helpers::Pgcat.single_shard_setup("sharded_db", 5) }
+  after do
+    processes.all_databases.map(&:reset)
+    processes.pgcat.shutdown
+  end
+
+  describe "SET ROLE" do
+    context "primary" do
+      it "routes queries only to primary" do
+        conn = PG.connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+        conn.async_exec("SET SERVER ROLE to 'primary'")
+
+        query_count = 30
+        failed_count = 0
+
+        query_count.times do
+          conn.async_exec("SELECT 1 + 2")
+        rescue
+          failed_count += 1
+        end
+
+        expect(failed_count).to eq(0)
+        processes.replicas.map(&:count_select_1_plus_2).each do |instance_share|
+          expect(instance_share).to eq(0)
+        end
+
+        expect(processes.primary.count_select_1_plus_2).to eq(query_count)
+      end
+    end
+    context "replica" do
+      it "routes queries only to replicas" do
+        conn = PG.connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+        conn.async_exec("SET SERVER ROLE to 'replica'")
+
+        expected_share = QUERY_COUNT / processes.replicas.count
+        failed_count = 0
+
+        QUERY_COUNT.times do
+          conn.async_exec("SELECT 1 + 2")
+        rescue
+          failed_count += 1
+        end
+
+        expect(failed_count).to eq(0)
+
+        processes.replicas.map(&:count_select_1_plus_2).each do |instance_share|
+          expect(instance_share).to be_within(expected_share * MARGIN_OF_ERROR).of(expected_share)
+        end
+
+        expect(processes.primary.count_select_1_plus_2).to eq(0)
+      end
+    end
+
+    context "any" do
+      it "routes queries to all instances" do
+        conn = PG.connect(processes.pgcat.connection_string("sharded_db", "sharding_user"))
+        conn.async_exec("SET SERVER ROLE to 'any'")
+
+        expected_share = QUERY_COUNT / processes.all_databases.count
+        failed_count = 0
+
+        QUERY_COUNT.times do
+          conn.async_exec("SELECT 1 + 2")
+        rescue
+          failed_count += 1
+        end
+
+        expect(failed_count).to eq(0)
+
+        processes.all_databases.map(&:count_select_1_plus_2).each do |instance_share|
+          expect(instance_share).to be_within(expected_share * MARGIN_OF_ERROR).of(expected_share)
+        end
+      end
+    end
+  end
+end
--- a/tests/ruby/spec_helper.rb
+++ b/tests/ruby/spec_helper.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+require 'pg'
+require_relative 'helpers/pgcat_helper'
+
+QUERY_COUNT = 300
+MARGIN_OF_ERROR = 0.30
+
+def with_captured_stdout_stderr
+  sout = STDOUT.clone
+  serr = STDERR.clone
+  STDOUT.reopen("/tmp/out.txt", "w+")
+  STDERR.reopen("/tmp/err.txt", "w+")
+  STDOUT.sync = true
+  STDERR.sync = true
+  yield
+  return File.read('/tmp/out.txt'), File.read('/tmp/err.txt')
+ensure
+  STDOUT.reopen(sout)
+  STDERR.reopen(serr)
+end
--- a/tests/ruby/tests.rb
+++ b/tests/ruby/tests.rb
@@ -1,10 +1,6 @@
 # frozen_string_literal: true
-
-require 'active_record'
 require 'pg'
-require 'toml'
-
-$stdout.sync = true
+require 'active_record'

 # Uncomment these two to see all queries.
 # ActiveRecord.verbose_query_logs = true
@@ -115,89 +111,3 @@ begin
 rescue ActiveRecord::StatementInvalid
  puts 'OK'
 end
-
-# Test evil clients
-def poorly_behaved_client
-  conn = PG::connect("postgres://sharding_user:sharding_user@127.0.0.1:6432/sharded_db?application_name=testing_pgcat")
-  conn.async_exec 'BEGIN'
-  conn.async_exec 'SELECT 1'
-
-  conn.close
-  puts 'Bad client ok'
-end
-
-25.times do
-  poorly_behaved_client
-end
-
-
-def test_server_parameters
-  server_conn = PG::connect("postgres://sharding_user:sharding_user@127.0.0.1:6432/sharded_db?application_name=testing_pgcat")
-  raise StandardError, "Bad server version" if server_conn.server_version == 0
-  server_conn.close
-
-  admin_conn = PG::connect("postgres://admin_user:admin_pass@127.0.0.1:6432/pgcat")
-  raise StandardError, "Bad server version" if admin_conn.server_version == 0
-  admin_conn.close
-
-  puts 'Server parameters ok'
-end
-
-
-class ConfigEditor
-  def initialize
-    @original_config_text = File.read('../../.circleci/pgcat.toml')
-    text_to_load = @original_config_text.gsub("5432", "\"5432\"")
-
-    @original_configs = TOML.load(text_to_load)
-  end
-
-  def original_configs
-    TOML.load(TOML::Generator.new(@original_configs).body)
-  end
-
-  def with_modified_configs(new_configs)
-    text_to_write = TOML::Generator.new(new_configs).body
-    text_to_write = text_to_write.gsub("\"5432\"", "5432")
-    File.write('../../.circleci/pgcat.toml', text_to_write)
-    yield
-  ensure
-    File.write('../../.circleci/pgcat.toml', @original_config_text)
-  end
-
-end
-
-
-def test_reload_pool_recycling
-  admin_conn = PG::connect("postgres://admin_user:admin_pass@127.0.0.1:6432/pgcat")
-  server_conn = PG::connect("postgres://sharding_user:sharding_user@127.0.0.1:6432/sharded_db?application_name=testing_pgcat")
-
-  server_conn.async_exec("BEGIN")
-  conf_editor = ConfigEditor.new
-  new_configs = conf_editor.original_configs
-
-  # swap shards
-  new_configs["pools"]["sharded_db"]["shards"]["0"]["database"] = "shard1"
-  new_configs["pools"]["sharded_db"]["shards"]["1"]["database"] = "shard0"
-
-  raise StandardError if server_conn.async_exec("SELECT current_database();")[0]["current_database"] != 'shard0'
-  conf_editor.with_modified_configs(new_configs) { admin_conn.async_exec("RELOAD") }
-  raise StandardError if server_conn.async_exec("SELECT current_database();")[0]["current_database"] != 'shard0'
-  server_conn.async_exec("COMMIT;")
-
-  # Transaction finished, client should get new configs
-  raise StandardError if server_conn.async_exec("SELECT current_database();")[0]["current_database"] != 'shard1'
-  server_conn.close()
-
-  # New connection should get new configs
-  server_conn = PG::connect("postgres://sharding_user:sharding_user@127.0.0.1:6432/sharded_db?application_name=testing_pgcat")
-  raise StandardError if server_conn.async_exec("SELECT current_database();")[0]["current_database"] != 'shard1'
-
-ensure
-  admin_conn.async_exec("RELOAD") # Go back to old state
-  admin_conn.close
-  server_conn.close
-  puts "Pool Recycling okay!"
-end
-
-test_reload_pool_recycling
--- a/tests/sharding/query_routing_setup.sql
+++ b/tests/sharding/query_routing_setup.sql
@@ -70,23 +70,35 @@ GRANT CONNECT ON DATABASE shard2  TO other_user;
 GRANT CONNECT ON DATABASE some_db TO simple_user;

 \c shard0
+CREATE EXTENSION IF NOT EXISTS pg_stat_statements;
+GRANT EXECUTE ON FUNCTION pg_stat_statements_reset TO sharding_user;
 GRANT ALL ON SCHEMA public TO sharding_user;
 GRANT ALL ON TABLE data TO sharding_user;
 GRANT ALL ON SCHEMA public TO other_user;
 GRANT ALL ON TABLE data TO other_user;
+GRANT EXECUTE ON FUNCTION pg_stat_statements_reset TO other_user;

 \c shard1
+CREATE EXTENSION IF NOT EXISTS pg_stat_statements;
+GRANT EXECUTE ON FUNCTION pg_stat_statements_reset TO sharding_user;
 GRANT ALL ON SCHEMA public TO sharding_user;
 GRANT ALL ON TABLE data TO sharding_user;
 GRANT ALL ON SCHEMA public TO other_user;
 GRANT ALL ON TABLE data TO other_user;
+GRANT EXECUTE ON FUNCTION pg_stat_statements_reset TO other_user;
+

 \c shard2
+CREATE EXTENSION IF NOT EXISTS pg_stat_statements;
+GRANT EXECUTE ON FUNCTION pg_stat_statements_reset TO sharding_user;
 GRANT ALL ON SCHEMA public TO sharding_user;
 GRANT ALL ON TABLE data TO sharding_user;
 GRANT ALL ON SCHEMA public TO other_user;
 GRANT ALL ON TABLE data TO other_user;
+GRANT EXECUTE ON FUNCTION pg_stat_statements_reset TO other_user;

 \c some_db
+CREATE EXTENSION IF NOT EXISTS pg_stat_statements;
+GRANT EXECUTE ON FUNCTION pg_stat_statements_reset TO simple_user;
 GRANT ALL ON SCHEMA public TO simple_user;
 GRANT ALL ON TABLE data TO simple_user;
Author	SHA1	Message	Date
Mostafa Abdelraouf	3d33ccf4b0	Fix maxwait metric (#183 ) Max wait was being reported as 0 after #159 This PR fixes that and adds test	2022-10-05 21:41:09 -05:00
Lev Kokotov	7987c5ffad	Replace a few types with more developer-friendly names (#182 ) * Replace a few types with more developer-friendly names * UserPool -> PoolIdentifier	2022-10-01 10:25:59 -07:00
zainkabani	24f5eec3ea	Change sharding config to enum and move validation of configs into public functions (#178 ) Moves config validation to own functions to enable tools to use them Moves sharding config to enum Makes defaults public Make connect_timeout on pool and option which is overwritten by general connect_timeout	2022-09-28 08:50:14 -05:00
Mostafa Abdelraouf	af064ef447	Set client state to idle after error (#179 ) * Set client state to idle after error * fmt * spelling * clean up	2022-09-24 09:09:15 -07:00
Lev Kokotov	e84a6f834c	Update README.md	2022-09-23 12:24:30 -07:00
Lev Kokotov	19fd677891	Fix the pool fix (#176 ) * Always listen to the compiler * Its fine	2022-09-23 12:06:07 -07:00
Lev Kokotov	964a5e1708	Don't drop connections if DB hasn't changed (#175 ) * Don't drop connections if DB hasn't changed * Incoporate connect_timeout into the pool config * use the field	2022-09-23 11:32:05 -07:00
Mostafa Abdelraouf	d126c7424d	Log failed client logins (#173 ) * Log failed client logins * more logging * remove clones * remove	2022-09-23 09:08:38 -07:00
zainkabani	f72dac420b	Add defaults for configs (#174 ) * add statement timeout to readme * Add defaults to various configs * primary read enabled default to false	2022-09-22 23:00:46 -07:00
zainkabani	3a729bb75b	Minor refactor for configs (#172 ) * Changes shard struct to use vector of ServerConfig * Adds to query router * Change client disconnect with error message to warn instead of debug * Add warning logs for clean up actions	2022-09-22 10:07:02 -07:00
zainkabani	85cc2f4147	Update to latest library versions (#170 )	2022-09-21 13:48:33 -07:00
zainkabani	8c09ab6c20	Export pgcat objects in lib (#169 ) * Export pgcat objects in lib * fmt	2022-09-20 18:47:32 -07:00
Mostafa Abdelraouf	f7a951745c	Report Query times (#166 ) * Report avg and total query timing * Report query times * fmt	2022-09-15 02:21:45 -04:00
Mostafa Abdelraouf	4ae1bc8d32	Add SHOW CLIENTS / SHOW SERVERS + Stats refactor and tests (#159 ) * wip * Main Thread Panic when swarmed with clients * fix * fix * 1024 * fix * remove test * Add SHOW CLIENTS * revert * fmt * Refactor + tests * fmt * add test * Add SHOW SERVERS + Make PR unreviewable * prometheus * add state to clients and servers * fmt * Add application_name to server stats * Add tests for waiting clients * Docs * remove comment * comments * typo * cleanup * CI	2022-09-14 11:20:41 -04:00
Lev Kokotov	075167431d	Add Discord link (#164 ) * Add Discord link * move it up * :) * hmm * hmm * :O	2022-09-08 08:12:37 -07:00
Mostafa Abdelraouf	9514b3b2d1	Clean connection state up after protocol named prepared statement (#163 ) * Clean connection state up after protocol named prepared statement * Avoid cloning + add test * fmt	2022-09-07 20:37:17 -07:00
Lev Kokotov	6d41640ea9	Send signal even if process is gone (#162 ) * Send signal even if process is gone * hmm * hmm	2022-09-07 09:22:52 -07:00
Mostafa Abdelraouf	744ceada86	Better logging for failure to get connection from pool (#161 )	2022-09-07 08:24:07 -07:00
Mostafa Abdelraouf	a5c8dd69b2	Avoid reporting ProtocolSyncError when admin session disconnects (#160 ) * Avoid reporting ProtocolSyncError when admin session disconnects * rebuild * rebuild	2022-09-06 22:22:31 -07:00
zainkabani	6a9a4db648	Adds microsecond logging and also reformats duration to include milliseconds (#156 ) * Adds microsecond logging and also reformats duration to include milliseconds * fmt * attempt to fix cd * revert	2022-09-05 01:21:27 -07:00
Mostafa Abdelraouf	976b406468	Main Thread Panic when swarmed with clients (#158 ) * Main Thread Panic when swarmed with clients * fix * fix * 1024 * fix * remove test * Update src/client.rs * Update src/main.rs * Update src/client.rs * Update src/main.rs Co-authored-by: Lev Kokotov <levkk@users.noreply.github.com>	2022-09-05 01:21:06 -07:00
zain-kabani	417358c35d	Patch graceful shutdown bug (#157 ) * Fixes non-admin client counting error * Add log when sigterm received and log number of active clients when shutdown timeout is reached	2022-09-05 01:02:49 -07:00
Mostafa Abdelraouf	23a642f4a4	Send DISCARD ALL even if client is not in transaction (#152 ) * Send DISCARD ALL even if client is not in transaction * fmt * Added tests + avoided sending extra discard all * Adds set name logic to beginning of handle client * fmt * refactor dead code handling * Refactor reading command tag * remove unnecessary trim * Removing debugging statement * typo * typo{ * documentation * edit text * un-unwrap * run ci * run ci Co-authored-by: Zain Kabani <zain.kabani@instacart.com>	2022-09-01 20:06:55 -07:00
Mostafa Abdelraouf	7f20dc3054	Better handling extended protocol messages in the event of busy pool (#155 ) * Better handling for checkout errors during extended protocol messages * Fix specs * comment	2022-09-01 15:02:39 -07:00
Mostafa Abdelraouf	36339bd96f	Log Address information in connection create/drop (#154 ) * Log Address information in connection create/drop * run ci	2022-09-01 11:16:22 -07:00
Mostafa Abdelraouf	65b69b46d2	Allow running integration tests with coverage locally (#151 )	2022-08-30 10:43:45 -07:00
Mostafa Abdelraouf	d48c04a7fb	Ruby integration tests (#147 ) * Ruby integration tests * forgot a file * refactor * refactoring * more refactoring * remove config helper * try multiple databases * fix * more databases * Use pg stats * ports * speed * Fix tests * preload library * comment	2022-08-30 09:14:53 -07:00
zainkabani	2628dec42e	Move autoreloader to own tokio task (#148 )	2022-08-29 00:08:44 -07:00
Mostafa Abdelraouf	3bc4f9351c	Exit with failure codes if configs are bad (#146 ) * Exit with failure codes if configs are bad * fmt	2022-08-25 18:56:18 -07:00
Lev Kokotov	9d84d6f131	Graceful shutdown and refactor (#144 ) * Graceful shutdown and refactor * ok * _Graceful_ shutdown * Remove hardcoded setting * clean up * end * timeout * hmm * hmm! * bash * bash * hmm * maybe maybe * Adds tests and move non-admin connection rejection to startup (#145) * Move error response * Adds tests and removes unused variable * Adds debug log Co-authored-by: zainkabani <77307340+zainkabani@users.noreply.github.com>	2022-08-25 06:40:56 -07:00
Mostafa Abdelraouf	c054ff068d	Avoid sending `Z` packet in the middle of extended protocol packet sequence if we fail to get connection from pool (#137 ) * Failing test * maybe * try fail * try * add message * pool size * correct user * more * debug * try fix * see stdout * stick? * fix configs * modify * types * m * maybe * make tests idempotent * hopefully fails * Add client fix * revert pgcat.toml change * Fix tests	2022-08-23 11:02:23 -07:00
Lev Kokotov	5a0cea6a24	Really fix idle servers (#141 )	2022-08-22 11:56:40 -07:00
Lev Kokotov	d0e8171b1b	Fix too many idle servers (#140 ) * Fix too many idle servers * oops	2022-08-22 11:52:34 -07:00
Lev Kokotov	069d76029f	Fix incorrect routing for replicas (#139 ) * Fix incorrect routing for replicas * name	2022-08-21 22:40:49 -07:00
Lev Kokotov	902fafd8d7	Random lb (#138 )	2022-08-21 22:20:31 -07:00
Mostafa Abdelraouf	5f5b5e2543	Random instance selection (#136 ) * wip * revert some' * revert more * poor-man's integration test * remove test * fmt * --workspace * fix build * fix integration test * another stab * log * run after integration * cargo test after integration * revert * revert more * Refactor + clean up * more clean up	2022-08-21 22:15:20 -07:00
zainkabani	5948fef6cf	Minor Refactoring of re-used code and server stat reporting (#129 ) * Minor changes to stats reporting and recduce re-used code * fmt	2022-08-18 05:12:38 -07:00
Mostafa Abdelraouf	790898c20e	Add pool name and username to address object (#128 ) * Add pool name and username to address object * Fix address name * fmt	2022-08-17 08:40:47 -07:00
Pradeep Chhetri	d64f6793c1	Minor cleanup in admin command (#126 ) * Minor cleanup in admin command * Typo correction * fix when the admin query is ending with semicolon	2022-08-16 10:01:46 -07:00
Lev Kokotov	cea35db35c	Fix lost statistics (#125 ) * Lost events * more logging	2022-08-15 23:54:49 -07:00
Mostafa Abdelraouf	a3aefabb47	Add cl_idle to SHOW POOLS (#124 )	2022-08-15 20:51:37 -07:00
Lev Kokotov	3285006440	Statement timeout + replica imbalance fix (#122 ) * Statement timeout * send error message too * Correct error messages * Fix replica inbalance * disable stmt timeout by default * Redundant mark_bad * revert healthcheck delay * tests * set it to 0 * reload config again	2022-08-13 13:45:58 -07:00
Pradeep Chhetri	52303cc808	Make prometheus port configurable (#121 ) * Make prometheus port configurable * Update circleci config	2022-08-13 10:25:14 -07:00
Lev Kokotov	be254cedd9	Fix debug log (#120 )	2022-08-11 22:47:47 -07:00