Config docs (#37)

* config docs

* space

* space

* shards

.circleci/config.yml

@@ -10,18 +10,36 @@ jobs:
     # See: https://circleci.com/docs/2.0/configuration-reference/#docker-machine-macos-windows-executor
     docker:
       - image: cimg/rust:1.58.1
+        environment:
+          RUST_LOG: info
+      - image: cimg/postgres:14.0
+        auth:
+          username: mydockerhub-user
+          password: $DOCKERHUB_PASSWORD
+        environment:
+          POSTGRES_USER: postgres
+          POSTGRES_DB: postgres
     # Add steps to the job
     # See: https://circleci.com/docs/2.0/configuration-reference/#steps
     steps:
       - checkout
       - restore_cache:
           key: cargo-lock-2-{{ checksum "Cargo.lock" }}
+      - run:
+          name: "Lint"
+          command: "cargo fmt --check"
+      - run:
+          name: "Install dependencies"
+          command: "sudo apt-get update && sudo apt-get install -y psmisc postgresql-contrib-12 postgresql-client-12 ruby ruby-dev libpq-dev"
       - run:
           name: "Build" 
           command: "cargo build"
       - run:
           name: "Test"
           command: "cargo test"
+      - run:
+          name: "Test end-to-end"
+          command: "bash .circleci/run_tests.sh"
       - save_cache:
           key: cargo-lock-2-{{ checksum "Cargo.lock" }}
           paths:
@@ -34,4 +52,4 @@ jobs:
 workflows:
   build:
     jobs:
-      - build
+      - build

.circleci/run_tests.sh

@@ -0,0 +1,59 @@
+#!/bin/bash
+
+set -e
+set -o xtrace
+
+psql -e -h 127.0.0.1 -p 5432 -U postgres -f tests/sharding/query_routing_setup.sql
+
+./target/debug/pgcat &
+
+sleep 1
+
+# Setup PgBench
+pgbench -i -h 127.0.0.1 -p 6432
+
+# Run it
+pgbench -h 127.0.0.1 -p 6432 -t 500 -c 2 --protocol simple
+
+# Extended protocol
+pgbench -h 127.0.0.1 -p 6432 -t 500 -c 2 --protocol extended
+
+# COPY TO STDOUT test
+psql -h 127.0.0.1 -p 6432 -c 'COPY (SELECT * FROM pgbench_accounts LIMIT 15) TO STDOUT;' > /dev/null
+
+# Query cancellation test
+(psql -h 127.0.0.1 -p 6432 -c 'SELECT pg_sleep(5)' || true) &
+killall psql -s SIGINT
+
+# Sharding insert
+psql -e -h 127.0.0.1 -p 6432 -f tests/sharding/query_routing_test_insert.sql
+
+# Sharding select
+psql -e -h 127.0.0.1 -p 6432 -f tests/sharding/query_routing_test_select.sql > /dev/null
+
+# Replica/primary selection & more sharding tests
+psql -e -h 127.0.0.1 -p 6432 -f tests/sharding/query_routing_test_primary_replica.sql > /dev/null
+
+#
+# ActiveRecord tests!
+#
+cd tests/ruby
+sudo gem install bundler
+bundle install
+ruby tests.rb
+
+cd ../../
+# Test session mode (and config reload)
+sed -i 's/pool_mode = "transaction"/pool_mode = "session"/' pgcat.toml
+
+# Reload config
+kill -SIGHUP $(pgrep pgcat)
+
+# Prepared statements that will only work in session mode
+pgbench -h 127.0.0.1 -p 6432 -t 500 -c 2 --protocol prepared
+
+# Attempt clean shut down
+killall pgcat -s SIGINT
+
+# Allow for graceful shutdown
+sleep 1

.dockerignore

@@ -0,0 +1,4 @@
+target/
+tests/
+tracing/
+.circleci/

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,38 @@
+---
+name: Bug report
+about: Create a report to help us improve
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+**Describe the bug**
+A clear and concise description of what the bug is.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Go to '...'
+2. Click on '....'
+3. Scroll down to '....'
+4. See error
+
+**Expected behavior**
+A clear and concise description of what you expected to happen.
+
+**Screenshots**
+If applicable, add screenshots to help explain your problem.
+
+**Desktop (please complete the following information):**
+ - OS: [e.g. iOS]
+ - Browser [e.g. chrome, safari]
+ - Version [e.g. 22]
+
+**Smartphone (please complete the following information):**
+ - Device: [e.g. iPhone6]
+ - OS: [e.g. iOS8.1]
+ - Browser [e.g. stock browser, safari]
+ - Version [e.g. 22]
+
+**Additional context**
+Add any other context about the problem here.

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,20 @@
+---
+name: Feature request
+about: Suggest an idea for this project
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+**Is your feature request related to a problem? Please describe.**
+A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]
+
+**Describe the solution you'd like**
+A clear and concise description of what you want to happen.
+
+**Describe alternatives you've considered**
+A clear and concise description of any alternative solutions or features you've considered.
+
+**Additional context**
+Add any other context or screenshots about the feature request here.

CONTRIBUTING.md

@@ -1,6 +1,19 @@
+## Introduction
+
 Thank you for contributing! Just a few tips here:
 
 1. `cargo fmt` your code before opening up a PR
-2. Run the "test suite" (i.e. PgBench) to make sure everything still works.
+2. Run the test suite (e.g. `pgbench`) to make sure everything still works. The tests are in `.circleci/run_tests.sh`.
+3. Performance is important, make sure there are no regressions in your branch vs. `main`.
 
 Happy hacking!
+
+## TODOs
+
+A non-exhaustive list of things that would be useful to implement:
+
+#### Client authentication
+MD5 is probably sufficient, but maybe others too.
+
+#### Admin
+Admin database for stats collection and pooler administration. PgBouncer gives us a nice example on how to do that, specifically how to implement `RowDescription` and `DataRow` messages, [example here](https://github.com/pgbouncer/pgbouncer/blob/4f9ced8e63d317a6ff45c8b0efa876b32161f6db/src/admin.c#L813).

Cargo.lock

@@ -11,6 +11,12 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "arc-swap"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c5d78ce20460b82d3fa150275ed9d55e21064fc7951177baacf86a145c4a4b1f"
+
 [[package]]
 name = "async-trait"
 version = "0.1.52"
@@ -22,6 +28,17 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "atty"
+version = "0.2.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d9b39be18770d11421cdb1b9947a45dd3f37e93092cbf377614828a319d5fee8"
+dependencies = [
+ "hermit-abi",
+ "libc",
+ "winapi",
+]
+
 [[package]]
 name = "autocfg"
 version = "1.0.1"
@@ -110,6 +127,19 @@ dependencies = [
  "generic-array",
 ]
 
+[[package]]
+name = "env_logger"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0b2cf0344971ee6c64c31be0d530793fba457d322dfec2810c453d0ef228f9c3"
+dependencies = [
+ "atty",
+ "humantime",
+ "log",
+ "regex",
+ "termcolor",
+]
+
 [[package]]
 name = "futures-channel"
 version = "0.3.19"
@@ -175,6 +205,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "humantime"
+version = "2.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9a3a5bfb195931eeb336b2a7b4d761daec841b97f947d34394601737a7bba5e4"
+
 [[package]]
 name = "instant"
 version = "0.1.12"
@@ -318,16 +354,23 @@ dependencies = [
 name = "pgcat"
 version = "0.1.0"
 dependencies = [
+ "arc-swap",
  "async-trait",
  "bb8",
  "bytes",
  "chrono",
+ "env_logger",
+ "log",
  "md-5",
+ "num_cpus",
+ "once_cell",
  "rand",
  "regex",
  "serde",
  "serde_derive",
  "sha-1",
+ "sqlparser",
+ "statsd",
  "tokio",
  "toml",
 ]
@@ -489,6 +532,24 @@ version = "1.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f2dd574626839106c320a323308629dcb1acfc96e32a8cba364ddc61ac23ee83"
 
+[[package]]
+name = "sqlparser"
+version = "0.14.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b8f192f29f4aa49e57bebd0aa05858e0a1f32dd270af36efe49edb82cbfffab6"
+dependencies = [
+ "log",
+]
+
+[[package]]
+name = "statsd"
+version = "0.15.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "df1efceb4bf2c0b5ebec94354285a43bbbed1375605bdf2ebe4132299434a330"
+dependencies = [
+ "rand",
+]
+
 [[package]]
 name = "syn"
 version = "1.0.86"
@@ -500,6 +561,15 @@ dependencies = [
  "unicode-xid",
 ]
 
+[[package]]
+name = "termcolor"
+version = "1.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2dfed899f0eb03f32ee8c6a0aabdb8a7949659e3466561fc0adf54e26d88c5f4"
+dependencies = [
+ "winapi-util",
+]
+
 [[package]]
 name = "time"
 version = "0.1.44"
@@ -590,6 +660,15 @@ version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
 
+[[package]]
+name = "winapi-util"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "70ec6ce85bb158151cae5e5c87f95a8e97d2c0c4b001223f33a334e3ce5de178"
+dependencies = [
+ "winapi",
+]
+
 [[package]]
 name = "winapi-x86_64-pc-windows-gnu"
 version = "0.4.0"

Cargo.toml

@@ -18,3 +18,10 @@ toml = "0.5"
 serde = "1"
 serde_derive = "1"
 regex = "1"
+num_cpus = "1"
+once_cell = "1"
+statsd = "0.15"
+sqlparser = "0.14"
+log = "0.4"
+arc-swap = "1"
+env_logger = "0.9"

Dockerfile

@@ -0,0 +1,11 @@
+FROM rust:1.58-slim-buster AS builder
+COPY . /app
+WORKDIR /app
+RUN cargo build --release
+
+FROM debian:buster-slim
+COPY --from=builder /app/target/release/pgcat /usr/bin/pgcat
+COPY --from=builder /app/pgcat.toml /etc/pgcat/pgcat.toml
+WORKDIR /etc/pgcat
+ENV RUST_LOG=info
+ENTRYPOINT ["/usr/bin/pgcat"]

LICENSE

@@ -1,674 +1,20 @@
-                    GNU GENERAL PUBLIC LICENSE
-                       Version 3, 29 June 2007
-
- Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
- Everyone is permitted to copy and distribute verbatim copies
- of this license document, but changing it is not allowed.
-
-                            Preamble
-
-  The GNU General Public License is a free, copyleft license for
-software and other kinds of works.
-
-  The licenses for most software and other practical works are designed
-to take away your freedom to share and change the works.  By contrast,
-the GNU General Public License is intended to guarantee your freedom to
-share and change all versions of a program--to make sure it remains free
-software for all its users.  We, the Free Software Foundation, use the
-GNU General Public License for most of our software; it applies also to
-any other work released this way by its authors.  You can apply it to
-your programs, too.
-
-  When we speak of free software, we are referring to freedom, not
-price.  Our General Public Licenses are designed to make sure that you
-have the freedom to distribute copies of free software (and charge for
-them if you wish), that you receive source code or can get it if you
-want it, that you can change the software or use pieces of it in new
-free programs, and that you know you can do these things.
-
-  To protect your rights, we need to prevent others from denying you
-these rights or asking you to surrender the rights.  Therefore, you have
-certain responsibilities if you distribute copies of the software, or if
-you modify it: responsibilities to respect the freedom of others.
-
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README.md

@@ -6,18 +6,64 @@
 
 Meow. PgBouncer rewritten in Rust, with sharding, load balancing and failover support.
 
-**Alpha**: don't use in production just yet.
+**Alpha**: looking for alpha testers, see [#35](https://github.com/levkk/pgcat/issues/35).
+
+## Features
+| **Feature**                    | **Status**            | **Comments**                                                                                                                                          |
+|--------------------------------|-----------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Transaction pooling            | :heavy_check_mark:    | Identical to PgBouncer.                                                                                                                               |
+| Session pooling                | :heavy_check_mark:    | Identical to PgBouncer.                                                                                                                               |
+| `COPY` support                 | :heavy_check_mark:    | Both `COPY TO` and `COPY FROM` are supported.                                                                                                         |
+| Query cancellation             | :heavy_check_mark:    | Supported both in transaction and session pooling modes.                                                                                              |
+| Load balancing of read queries | :heavy_check_mark:    | Using round-robin between replicas. Primary is included when `primary_reads_enabled` is enabled (default).                                            |
+| Sharding                       | :heavy_check_mark:    | Transactions are sharded using `SET SHARD TO` and `SET SHARDING KEY TO` syntax extensions; see examples below.                                        |
+| Failover                       | :heavy_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 reporting           | :heavy_check_mark:    | Statistics similar to PgBouncers are reported via StatsD.                                                                                             |
+| Live configuration reloading   | :construction_worker: | Reload config with a `SIGHUP` to the process, e.g. `kill -s SIGHUP $(pgrep pgcat)`. Not all settings can be reloaded without a restart.               |
+| Client authentication          | :x: :wrench:          | On the roadmap; currently all clients are allowed to connect and one user is used to connect to Postgres.                                             |
+
+## Deployment
+
+See `Dockerfile` for example deployment using Docker. The pooler is configured to spawn 4 workers so 4 CPUs are recommended for optimal performance.
+That setting can be adjusted to spawn as many (or as little) workers as needed.
+
+### 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`                           |
+| `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`                             |
+| `statsd_address`        | StatsD host and port. Statistics will be sent there every 15 seconds.                                                                      | `127.0.0.1:8125`                 |
+|                         |                                                                                                                                            |                                  |
+| **`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`                           |
 
 ## Local development
 
 1. Install Rust (latest stable will work great).
-2. `cargo run --release` (to get better benchmarks).
+2. `cargo build --release` (to get better benchmarks).
 3. Change the config in `pgcat.toml` to fit your setup (optional given next step).
-4. Install Postgres and run `psql -f tests/sharding/query_routing_setup.sql`
+4. Install Postgres and run `psql -f tests/sharding/query_routing_setup.sql` (user/password may be required depending on your setup)
+5. `RUST_LOG=info cargo run --release` You're ready to go!
 
 ### Tests
 
-You can just PgBench to test your changes:
+Quickest way to test your changes is to use pgbench:
 
 ```
 pgbench -i -h 127.0.0.1 -p 6432 && \
@@ -27,65 +73,154 @@ pgbench -t 1000 -p 6432 -h 127.0.0.1 --protocol extended
 
 See [sharding README](./tests/sharding/README.md) for sharding logic testing.
 
-## Features
+| **Feature**           | **Tested in CI**   | **Tested manually** | **Comments**                                                                                                             |
+|-----------------------|--------------------|---------------------|--------------------------------------------------------------------------------------------------------------------------|
+| Transaction pooling   | :heavy_check_mark: | :heavy_check_mark:  | Used by default for all tests.                                                                                           |
+| Session pooling       | :heavy_check_mark: | :heavy_check_mark:  | Tested by running pgbench with `--protocol prepared` which only works in session mode.                                   |
+| `COPY`                | :heavy_check_mark: | :heavy_check_mark:  | `pgbench -i` uses `COPY`. `COPY FROM` is tested as well.                                                                 |
+| Query cancellation    | :heavy_check_mark: | :heavy_check_mark:  | `psql -c 'SELECT pg_sleep(1000);'` and press `Ctrl-C`.                                                                   |
+| Load balancing        | :x:                | :heavy_check_mark:  | We could test this by emitting statistics for each replica and compare them.                                             |
+| Failover              | :x:                | :heavy_check_mark:  | Misconfigure a replica in `pgcat.toml` and watch it forward queries to spares. CI testing could include using Toxiproxy. |
+| Sharding              | :heavy_check_mark: | :heavy_check_mark:  | See `tests/sharding` and `tests/ruby` for an Rails/ActiveRecord example.                                                 |
+| Statistics reporting  | :x:                | :heavy_check_mark:  | Run `nc -l -u 8125` and watch the stats come in every 15 seconds.                                                        |
+| Live config reloading | :heavy_check_mark: | :heavy_check_mark:  | Run `kill -s SIGHUP $(pgrep pgcat)` and watch the config reload.                                                         |
 
-1. Session mode.
-2. Transaction mode.
-3. `COPY` protocol support.
-4. Query cancellation.
-5. Round-robin load balancing of replicas.
-6. Banlist & failover
-7. Sharding!
+## Usage
 
 ### Session mode
-Each client owns its own server for the duration of the session. Commands like `SET` are allowed.
-This is identical to PgBouncer session mode.
+In session mode, a client talks to one server for the duration of the connection. Prepared statements, `SET`, and advisory locks are supported. In terms of supported features, there is very little if any difference between session mode and talking directly to the server.
+
+To use session mode, change `pool_mode = "session"`.
 
 ### Transaction mode
-The connection is attached to the server for the duration of the transaction. `SET` will pollute the connection,
-but `SET LOCAL` works great. Identical to PgBouncer transaction mode.
+In transaction mode, a client talks to one server for the duration of a single transaction; once it's over, the server is returned to the pool. Prepared statements, `SET`, and advisory locks are not supported; alternatives are to use `SET LOCAL` and `pg_advisory_xact_lock` which are scoped to the transaction.
 
-### COPY protocol
-That one isn't particularly special, but good to mention that you can `COPY` data in and from the server
-using this pooler.
+This mode is enabled by default.
 
-### Query cancellation
-Okay, this is just basic stuff, but we support cancelling queries. If you know the Postgres protocol,
-this might be relevant given than this is a transactional pooler but if you're new to Pg, don't worry about it, it works.
+### 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.
 
-### Round-robin load balancing
-This is the novel part. PgBouncer doesn't support it and suggests we use DNS or a TCP proxy instead.
-We prefer to have everything as part of one package; arguably, it's easier to understand and optimize.
-This pooler will round-robin between multiple replicas keeping load reasonably even.
+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.
 
-### Banlist & failover
-This is where it gets even more interesting. If we fail to connect to one of the replicas or it fails a health check,
-we add it to a ban list. No more new transactions will be served by that replica for, in our case, 60 seconds. This
-gives it the opportunity to recover while clients are happily served by the remaining replicas.
+The query parser is disabled by default.
 
-This decreases error rates substantially! Worth noting here that on busy systems, if the replicas are running too hot,
-failing over could bring even more load and tip over the remaining healthy-ish replicas. In this case, a decision should be made:
-either lose 1/x of your traffic or risk losing it all eventually. Ideally you overprovision your system, so you don't necessarily need
-to make this choice :-).
-
-### Sharding
-We're implemeting Postgres' `PARTITION BY HASH` sharding function for `BIGINT` fields. This works well for tables that use `BIGSERIAL` primary key which I think is common enough these days. We can also add many more functions here, but this is a good start. See `src/sharding.rs` and `tests/sharding/partition_hash_test_setup.sql` for more details on the implementation.
-
-The biggest advantage of using this sharding function is that anyone can shard the dataset using Postgres partitions
-while also access it for both reads and writes using this pooler. No custom obscure sharding function is needed and database sharding can be done entirely in Postgres.
-
-To select the shard we want to talk to, we introduced special syntax:
+#### Query parser
+The query parser will do its best to determine where the query should go, but sometimes that's not possible. In that case, the client can select which server it wants using this custom SQL syntax:
 
 ```sql
+-- To talk to the primary for the duration of the next transaction:
+SET SERVER ROLE TO 'primary';
+
+-- To talk to the replica for the duration of the next transaction:
+SET SERVER ROLE TO 'replica';
+
+-- Let the query parser decide
+SET SERVER ROLE TO 'auto';
+
+-- Pick any server at random
+SET SERVER ROLE TO 'any';
+
+-- Reset to default configured settings
+SET SERVER ROLE TO 'default';
+```
+
+The setting will persist until it's changed again or the client disconnects.
+
+By default, all queries are routed to the first available server; `default_role` setting controls this behavior.
+
+### Failover
+All servers are checked with a `SELECT 1` query before being given to a client. If the server is not reachable, it will be banned and cannot serve any more transactions for the duration of the ban. The queries are routed to the remaining servers. If all servers become banned, the ban list is cleared: this is a safety precaution against false positives. The primary can never be banned.
+
+The ban time can be changed with `ban_time`. The default is 60 seconds.
+
+### Sharding
+We use the `PARTITION BY HASH` hashing function, the same as used by Postgres for declarative partitioning. This allows to shard the database using Postgres partitions and place the partitions on different servers (shards). Both read and write queries can be routed to the shards using this pooler.
+
+To route queries to a particular shard, we use this custom SQL syntax:
+
+```sql
+-- To talk to a shard explicitely
+SET SHARD TO '1';
+
+-- To let the pooler choose based on a value
 SET SHARDING KEY TO '1234';
 ```
 
-This sharding key will be hashed and the pooler will select a shard to use for the next transaction. If the pooler is in session mode, this sharding key will be used until it's set again or the client disconnects.
+The active shard will last until it's changed again or the client disconnects. By default, the queries are routed to shard 0.
 
+For hash function implementation, see `src/sharding.rs` and `tests/sharding/partition_hash_test_setup.sql`.
 
-## Missing
+#### ActiveRecord/Rails
+
+```ruby
+class User < ActiveRecord::Base
+end
+
+# Metadata will be fetched from shard 0
+ActiveRecord::Base.establish_connection
+
+# Grab a bunch of users from shard 1
+User.connection.execute "SET SHARD TO '1'"
+User.take(10)
+
+# Using id as the sharding key
+User.connection.execute "SET SHARDING KEY TO '1234'"
+User.find_by_id(1234)
+
+# Using geographical sharding
+User.connection.execute "SET SERVER ROLE TO 'primary'"
+User.connection.execute "SET SHARDING KEY TO '85'"
+User.create(name: "test user", email: "test@example.com", zone_id: 85)
+
+# Let the query parser figure out where the query should go.
+# We are still on shard = hash(85) % shards.
+User.connection.execute "SET SERVER ROLE TO 'auto'"
+User.find_by_email("test@example.com")
+```
+
+#### Raw SQL
+
+```sql
+-- Grab a bunch of users from shard 1
+SET SHARD TO '1';
+SELECT * FROM users LIMT 10;
+
+-- Find by id
+SET SHARDING KEY TO '1234';
+SELECT * FROM USERS WHERE id = 1234;
+
+-- Writing in a primary/replicas configuration.
+SET SHARDING ROLE TO 'primary';
+SET SHARDING KEY TO '85';
+INSERT INTO users (name, email, zome_id) VALUES ('test user', 'test@example.com', 85);
+
+SET SERVER ROLE TO 'auto'; -- let the query router figure out where the query should go
+SELECT * FROM users WHERE email = 'test@example.com'; -- shard setting lasts until set again; we are reading from the primary
+```
+
+### Statistics reporting
+
+Stats are reported using StatsD every 15 seconds. The address is configurable with `statsd_address`, the default is `127.0.0.1:8125`. The stats are very similar to what Pgbouncer reports and the names are kept to be comparable.
+
+### Live configuration reloading
+
+The config can be reloaded by sending a `kill -s SIGHUP` to the process. Not all settings are currently supported by live reload:
+
+| **Config**              | **Requires restart** |
+|-------------------------|----------------------|
+| `host`                  | yes                  |
+| `port`                  | yes                  |
+| `pool_mode`             | no                   |
+| `connect_timeout`       | yes                  |
+| `healthcheck_timeout`   | no                   |
+| `ban_time`              | no                   |
+| `statsd_address`        | yes                  |
+| `user`                  | yes                  |
+| `shards`                | yes                  |
+| `default_role`          | no                   |
+| `primary_reads_enabled` | no                   |
+| `query_parser_enabled`  | no                   |
 
-1. Authentication, ehem, this proxy is letting anyone in at the moment.
 
 ## Benchmarks
 
@@ -95,114 +230,231 @@ You can setup PgBench locally through PgCat:
 pgbench -h 127.0.0.1 -p 6432 -i
 ```
 
-Coincidenly, this uses `COPY` so you can test if that works.
+Coincidenly, this uses `COPY` so you can test if that works. Additionally, we'll be running the following PgBench configurations:
+
+1. 16 clients, 2 threads
+2. 32 clients, 2 threads
+3. 64 clients, 2 threads
+4. 128 clients, 2 threads
+
+All queries will be `SELECT` only (`-S`) just so disks don't get in the way, since the dataset will be effectively all in RAM.
+
+My setup:
+
+- 8 cores, 16 hyperthreaded (AMD Ryzen 5800X)
+- 32GB RAM (doesn't matter for this benchmark, except to prove that Postgres will fit the whole dataset into RAM)
 
 ### PgBouncer
 
+#### Config
+
+```ini
+[databases]
+shard0 = host=localhost port=5432 user=sharding_user password=sharding_user
+
+[pgbouncer]
+pool_mode = transaction
+max_client_conn = 1000
 ```
-$ pgbench -i -h 127.0.0.1 -p 6432 && pgbench -t 1000 -p 6432 -h 127.0.0.1 --protocol simple && pgbench -t 1000 -p 6432 -h 127.0.0.1 --protocol extended
-dropping old tables...
-creating tables...
-generating data...
-100000 of 100000 tuples (100%) done (elapsed 0.01 s, remaining 0.00 s)
-vacuuming...
-creating primary keys...
-done.
+
+Everything else stays default.
+
+#### Runs
+
+
+```
+$ pgbench -t 1000 -c 16 -j 2 -p 6432 -h 127.0.0.1 -S --protocol extended shard0
+
 starting vacuum...end.
-transaction type: <builtin: TPC-B (sort of)>
-scaling factor: 1
-query mode: simple
-number of clients: 1
-number of threads: 1
-number of transactions per client: 1000
-number of transactions actually processed: 1000/1000
-latency average = 1.089 ms
-tps = 918.687098 (including connections establishing)
-tps = 918.847790 (excluding connections establishing)
-starting vacuum...end.
-transaction type: <builtin: TPC-B (sort of)>
+transaction type: <builtin: select only>
 scaling factor: 1
 query mode: extended
-number of clients: 1
-number of threads: 1
+number of clients: 16
+number of threads: 2
 number of transactions per client: 1000
-number of transactions actually processed: 1000/1000
-latency average = 1.136 ms
-tps = 880.622009 (including connections establishing)
-tps = 880.769550 (excluding connections establishing)
+number of transactions actually processed: 16000/16000
+latency average = 0.155 ms
+tps = 103417.377469 (including connections establishing)
+tps = 103510.639935 (excluding connections establishing)
+
+
+$ pgbench -t 1000 -c 32 -j 2 -p 6432 -h 127.0.0.1 -S --protocol extended shard0
+
+starting vacuum...end.
+transaction type: <builtin: select only>
+scaling factor: 1
+query mode: extended
+number of clients: 32
+number of threads: 2
+number of transactions per client: 1000
+number of transactions actually processed: 32000/32000
+latency average = 0.290 ms
+tps = 110325.939785 (including connections establishing)
+tps = 110386.513435 (excluding connections establishing)
+
+
+$ pgbench -t 1000 -c 64 -j 2 -p 6432 -h 127.0.0.1 -S --protocol extended shard0
+
+starting vacuum...end.
+transaction type: <builtin: select only>
+scaling factor: 1
+query mode: extended
+number of clients: 64
+number of threads: 2
+number of transactions per client: 1000
+number of transactions actually processed: 64000/64000
+latency average = 0.692 ms
+tps = 92470.427412 (including connections establishing)
+tps = 92618.389350 (excluding connections establishing)
+
+$ pgbench -t 1000 -c 128 -j 2 -p 6432 -h 127.0.0.1 -S --protocol extended shard0
+
+starting vacuum...end.
+transaction type: <builtin: select only>
+scaling factor: 1
+query mode: extended
+number of clients: 128
+number of threads: 2
+number of transactions per client: 1000
+number of transactions actually processed: 128000/128000
+latency average = 1.406 ms
+tps = 91013.429985 (including connections establishing)
+tps = 91067.583928 (excluding connections establishing)
 ```
 
 ### PgCat
 
+#### Config
+
+The only thing that matters here is the number of workers in the Tokio pool. Make sure to set it to < than the number of your CPU cores.
+Also account for hyper-threading, so if you have that, take the number you got above and divide it by two, that way only "real" cores serving
+requests.
+
+My setup is 16 threads, 8 cores (`htop` shows as 16 CPUs), so I set the `max_workers` in Tokio to 4. Too many, and it starts conflicting with PgBench
+which is also running on the same system.
+
+#### Runs
+
 
 ```
-$ pgbench -i -h 127.0.0.1 -p 6432 && pgbench -t 1000 -p 6432 -h 127.0.0.1 --protocol simple && pgbench -t 1000 -p 6432 -h 127.0.0.1 --protocol extended
-dropping old tables...
-creating tables...
-generating data...
-100000 of 100000 tuples (100%) done (elapsed 0.01 s, remaining 0.00 s)
-vacuuming...
-creating primary keys...
-done.
+$ pgbench -t 1000 -c 16 -j 2 -p 6432 -h 127.0.0.1 -S --protocol extended
 starting vacuum...end.
-transaction type: <builtin: TPC-B (sort of)>
-scaling factor: 1
-query mode: simple
-number of clients: 1
-number of threads: 1
-number of transactions per client: 1000
-number of transactions actually processed: 1000/1000
-latency average = 1.142 ms
-tps = 875.645437 (including connections establishing)
-tps = 875.799995 (excluding connections establishing)
-starting vacuum...end.
-transaction type: <builtin: TPC-B (sort of)>
+transaction type: <builtin: select only>
 scaling factor: 1
 query mode: extended
-number of clients: 1
-number of threads: 1
+number of clients: 16
+number of threads: 2
 number of transactions per client: 1000
-number of transactions actually processed: 1000/1000
-latency average = 1.181 ms
-tps = 846.539176 (including connections establishing)
-tps = 846.713636 (excluding connections establishing)
+number of transactions actually processed: 16000/16000
+latency average = 0.164 ms
+tps = 97705.088232 (including connections establishing)
+tps = 97872.216045 (excluding connections establishing)
+
+
+$ pgbench -t 1000 -c 32 -j 2 -p 6432 -h 127.0.0.1 -S --protocol extended
+
+starting vacuum...end.
+transaction type: <builtin: select only>
+scaling factor: 1
+query mode: extended
+number of clients: 32
+number of threads: 2
+number of transactions per client: 1000
+number of transactions actually processed: 32000/32000
+latency average = 0.288 ms
+tps = 111300.488119 (including connections establishing)
+tps = 111413.107800 (excluding connections establishing)
+
+
+$ pgbench -t 1000 -c 64 -j 2 -p 6432 -h 127.0.0.1 -S --protocol extended
+
+starting vacuum...end.
+transaction type: <builtin: select only>
+scaling factor: 1
+query mode: extended
+number of clients: 64
+number of threads: 2
+number of transactions per client: 1000
+number of transactions actually processed: 64000/64000
+latency average = 0.556 ms
+tps = 115190.496139 (including connections establishing)
+tps = 115247.521295 (excluding connections establishing)
+
+$ pgbench -t 1000 -c 128 -j 2 -p 6432 -h 127.0.0.1 -S --protocol extended
+
+starting vacuum...end.
+transaction type: <builtin: select only>
+scaling factor: 1
+query mode: extended
+number of clients: 128
+number of threads: 2
+number of transactions per client: 1000
+number of transactions actually processed: 128000/128000
+latency average = 1.135 ms
+tps = 112770.562239 (including connections establishing)
+tps = 112796.502381 (excluding connections establishing)
 ```
 
 ### Direct Postgres
 
+Always good to have a base line.
+
+#### Runs
+
 ```
-$ pgbench -i -h 127.0.0.1 -p 5432 && pgbench -t 1000 -p 5432 -h 127.0.0.1 --protocol simple && pgbench -t 1000 -p
-5432 -h 127.0.0.1 --protocol extended
-Password:
-dropping old tables...
-creating tables...
-generating data...
-100000 of 100000 tuples (100%) done (elapsed 0.01 s, remaining 0.00 s)
-vacuuming...
-creating primary keys...
-done.
-Password:
+$ pgbench -t 1000 -c 16 -j 2 -p 5432 -h 127.0.0.1 -S --protocol extended shard0
+Password: 
 starting vacuum...end.
-transaction type: <builtin: TPC-B (sort of)>
-scaling factor: 1
-query mode: simple
-number of clients: 1
-number of threads: 1
-number of transactions per client: 1000
-number of transactions actually processed: 1000/1000
-latency average = 0.902 ms
-tps = 1109.014867 (including connections establishing)
-tps = 1112.318595 (excluding connections establishing)
-Password:
-starting vacuum...end.
-transaction type: <builtin: TPC-B (sort of)>
+transaction type: <builtin: select only>
 scaling factor: 1
 query mode: extended
-number of clients: 1
-number of threads: 1
+number of clients: 16
+number of threads: 2
 number of transactions per client: 1000
-number of transactions actually processed: 1000/1000
-latency average = 0.931 ms
-tps = 1074.017747 (including connections establishing)
-tps = 1077.121752 (excluding connections establishing)
-```
+number of transactions actually processed: 16000/16000
+latency average = 0.115 ms
+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: 
+starting vacuum...end.
+transaction type: <builtin: select only>
+scaling factor: 1
+query mode: extended
+number of clients: 32
+number of threads: 2
+number of transactions per client: 1000
+number of transactions actually processed: 32000/32000
+latency average = 0.212 ms
+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: 
+starting vacuum...end.
+transaction type: <builtin: select only>
+scaling factor: 1
+query mode: extended
+number of clients: 64
+number of threads: 2
+number of transactions per client: 1000
+number of transactions actually processed: 64000/64000
+latency average = 0.420 ms
+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: 
+starting vacuum...end.
+transaction type: <builtin: select only>
+scaling factor: 1
+query mode: extended
+number of clients: 128
+number of threads: 2
+number of transactions per client: 1000
+number of transactions actually processed: 128000/128000
+latency average = 0.854 ms
+tps = 149818.594087 (including connections establishing)
+tps = 150200.603049 (excluding connections establishing)
+```

pgcat.toml

@@ -29,6 +29,9 @@ healthcheck_timeout = 1000
 # For how long to ban a server if it fails a health check (seconds).
 ban_time = 60 # Seconds
 
+# Stats will be sent here
+statsd_address = "127.0.0.1:8125"
+
 #
 # User to use for authentication against the server.
 [user]
@@ -43,26 +46,53 @@ password = "sharding_user"
 # Shard 0
 [shards.0]
 
-# [ host, port ]
+# [ host, port, role ]
 servers = [
-    [ "127.0.0.1", 5432 ],
-    [ "localhost", 5432 ],
+    [ "127.0.0.1", 5432, "primary" ],
+    [ "localhost", 5432, "replica" ],
+    # [ "127.0.1.1", 5432, "replica" ],
 ]
 # Database name (e.g. "postgres")
 database = "shard0"
 
 [shards.1]
-# [ host, port ]
+# [ host, port, role ]
 servers = [
-    [ "127.0.0.1", 5432 ],
-    [ "localhost", 5432 ],
+    [ "127.0.0.1", 5432, "primary" ],
+    [ "localhost", 5432, "replica" ],
+    # [ "127.0.1.1", 5432, "replica" ],
 ]
 database = "shard1"
 
 [shards.2]
-# [ host, port ]
+# [ host, port, role ]
 servers = [
-    [ "127.0.0.1", 5432 ],
-    [ "localhost", 5432 ],
+    [ "127.0.0.1", 5432, "primary" ],
+    [ "localhost", 5432, "replica" ],
+    # [ "127.0.1.1", 5432, "replica" ],
 ]
-database = "shard2"
+database = "shard2"
+
+
+# Settings for our query routing layer.
+[query_router]
+
+# If the client doesn't specify, route traffic to
+# this role by default.
+#
+# any: round-robin between primary and replicas,
+# replica: round-robin between replicas only without touching the primary,
+# primary: all queries go to the primary unless otherwise specified.
+default_role = "any"
+
+
+# Query parser. If enabled, we'll attempt to parse
+# every incoming query to determine if it's a read or a write.
+# If it's a read query, we'll direct it to a replica. Otherwise, if it's a write,
+# we'll direct it to the primary.
+query_parser_enabled = false
+
+# If the query parser is enabled and this setting is enabled, the primary will be part of the pool of databases used for
+# load balancing of read queries. Otherwise, the primary will only be used for write
+# queries. The primary can always be explicitely selected with our custom protocol.
+primary_reads_enabled = true

src/client.rs

@@ -2,18 +2,23 @@
 /// We are pretending to the server in this scenario,
 /// and this module implements that.
 use bytes::{Buf, BufMut, BytesMut};
-use regex::Regex;
+use log::error;
 use tokio::io::{AsyncReadExt, BufReader};
-use tokio::net::tcp::{OwnedReadHalf, OwnedWriteHalf};
-use tokio::net::TcpStream;
+use tokio::net::{
+    tcp::{OwnedReadHalf, OwnedWriteHalf},
+    TcpStream,
+};
 
+use std::collections::HashMap;
+
+use crate::config::get_config;
+use crate::constants::*;
 use crate::errors::Error;
 use crate::messages::*;
 use crate::pool::{ClientServerMap, ConnectionPool};
+use crate::query_router::{Command, QueryRouter};
 use crate::server::Server;
-use crate::sharding::Sharder;
-
-const SHARDING_REGEX: &str = r"SET SHARDING KEY TO '[0-9]+';";
+use crate::stats::Reporter;
 
 /// The client state. One of these is created per client.
 pub struct Client {
@@ -43,8 +48,12 @@ pub struct Client {
     // to connect and cancel a query.
     client_server_map: ClientServerMap,
 
-    // sharding regex
-    sharding_regex: Regex,
+    // Client parameters, e.g. user, client_encoding, etc.
+    #[allow(dead_code)]
+    parameters: HashMap<String, String>,
+
+    // Statistics
+    stats: Reporter,
 }
 
 impl Client {
@@ -54,10 +63,12 @@ impl Client {
     pub async fn startup(
         mut stream: TcpStream,
         client_server_map: ClientServerMap,
-        transaction_mode: bool,
+        server_info: BytesMut,
+        stats: Reporter,
     ) -> Result<Client, Error> {
-        let sharding_regex = Regex::new(SHARDING_REGEX).unwrap();
-
+        let config = get_config();
+        let transaction_mode = config.general.pool_mode.starts_with("t");
+        drop(config);
         loop {
             // Could be StartupMessage or SSLRequest
             // which makes this variable length.
@@ -79,7 +90,7 @@ impl Client {
 
             match code {
                 // Client wants SSL. We don't support it at the moment.
-                80877103 => {
+                SSL_REQUEST_CODE => {
                     let mut no = BytesMut::with_capacity(1);
                     no.put_u8(b'N');
 
@@ -87,16 +98,16 @@ impl Client {
                 }
 
                 // Regular startup message.
-                196608 => {
+                PROTOCOL_VERSION_NUMBER => {
                     // TODO: perform actual auth.
-                    // TODO: record startup parameters client sends over.
+                    let parameters = parse_startup(bytes.clone())?;
 
                     // Generate random backend ID and secret key
                     let process_id: i32 = rand::random();
                     let secret_key: i32 = rand::random();
 
                     auth_ok(&mut stream).await?;
-                    server_parameters(&mut stream).await?;
+                    write_all(&mut stream, server_info).await?;
                     backend_key_data(&mut stream, process_id, secret_key).await?;
                     ready_for_query(&mut stream).await?;
 
@@ -113,12 +124,13 @@ impl Client {
                         process_id: process_id,
                         secret_key: secret_key,
                         client_server_map: client_server_map,
-                        sharding_regex: sharding_regex,
+                        parameters: parameters,
+                        stats: stats,
                     });
                 }
 
                 // Query cancel request.
-                80877102 => {
+                CANCEL_REQUEST_CODE => {
                     let (read, write) = stream.into_split();
 
                     let process_id = bytes.get_i32();
@@ -133,7 +145,8 @@ impl Client {
                         process_id: process_id,
                         secret_key: secret_key,
                         client_server_map: client_server_map,
-                        sharding_regex: sharding_regex,
+                        parameters: HashMap::new(),
+                        stats: stats,
                     });
                 }
 
@@ -145,78 +158,132 @@ impl Client {
     }
 
     /// Client loop. We handle all messages between the client and the database here.
-    pub async fn handle(&mut self, pool: ConnectionPool) -> Result<(), Error> {
-        // Special: cancelling existing running query
+    pub async fn handle(&mut self, mut pool: ConnectionPool) -> Result<(), Error> {
+        // The client wants to cancel a query it has issued previously.
         if self.cancel_mode {
             let (process_id, secret_key, address, port) = {
                 let guard = self.client_server_map.lock().unwrap();
+
                 match guard.get(&(self.process_id, self.secret_key)) {
                     // Drop the mutex as soon as possible.
+                    // We found the server the client is using for its query
+                    // that it wants to cancel.
                     Some((process_id, secret_key, address, port)) => (
                         process_id.clone(),
                         secret_key.clone(),
                         address.clone(),
                         port.clone(),
                     ),
+
+                    // The client doesn't know / got the wrong server,
+                    // we're closing the connection for security reasons.
                     None => return Ok(()),
                 }
             };
 
-            // TODO: pass actual server host and port somewhere.
+            // 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?);
         }
 
-        // Active shard we're talking to.
-        // The lifetime of this depends on the pool mode:
-        // - if in session mode, this lives until client disconnects or changes it,
-        // - if in transaction mode, this lives for the duration of one transaction.
-        let mut shard: Option<usize> = None;
+        let mut query_router = QueryRouter::new();
 
+        // Our custom protocol loop.
+        // We expect the client to either start a transaction with regular queries
+        // or issue commands for our sharding and server selection protocols.
         loop {
+            // Client idle, waiting for messages.
+            self.stats.client_idle(self.process_id);
+
             // Read a complete message from the client, which normally would be
             // either a `Q` (query) or `P` (prepare, extended protocol).
             // We can parse it here before grabbing a server from the pool,
             // in case the client is sending some control messages, e.g.
-            // SET sharding_context.key = '1234';
+            // SET SHARDING KEY TO 'bigint';
             let mut message = read_message(&mut self.read).await?;
 
-            // Parse for special select shard command.
-            // SET SHARDING KEY TO 'bigint';
-            match self.select_shard(message.clone(), pool.shards()).await {
-                Some(s) => {
-                    set_sharding_key(&mut self.write).await?;
-                    shard = Some(s);
+            // Handle all custom protocol commands here.
+            match query_router.try_execute_command(message.clone()) {
+                // Normal query
+                None => {
+                    if query_router.query_parser_enabled() && query_router.role() == None {
+                        query_router.infer_role(message.clone());
+                    }
+                }
+
+                Some((Command::SetShard, _)) | Some((Command::SetShardingKey, _)) => {
+                    custom_protocol_response_ok(&mut self.write, &format!("SET SHARD")).await?;
+                    continue;
+                }
+
+                Some((Command::SetServerRole, _)) => {
+                    custom_protocol_response_ok(&mut self.write, "SET SERVER ROLE").await?;
+                    continue;
+                }
+
+                Some((Command::ShowServerRole, value)) => {
+                    show_response(&mut self.write, "server role", &value).await?;
+                    continue;
+                }
+
+                Some((Command::ShowShard, value)) => {
+                    show_response(&mut self.write, "shard", &value).await?;
                     continue;
                 }
-                None => (),
             };
 
-            // The message is part of the regular protocol.
-            // self.buffer.put(message);
+            // Make sure we selected a valid shard.
+            if query_router.shard() >= pool.shards() {
+                error_response(
+                    &mut self.write,
+                    &format!(
+                        "shard '{}' is more than configured '{}'",
+                        query_router.shard(),
+                        pool.shards()
+                    ),
+                )
+                .await?;
+                continue;
+            }
 
-            // Grab a server from the pool.
-            // None = any shard
-            let connection = pool.get(shard).await.unwrap();
-            let mut proxy = connection.0;
+            // Waiting for server connection.
+            self.stats.client_waiting(self.process_id);
+
+            // Grab a server from the pool: the client issued a regular query.
+            let connection = match pool.get(query_router.shard(), query_router.role()).await {
+                Ok(conn) => conn,
+                Err(err) => {
+                    error!("Could not get connection from pool: {:?}", err);
+                    error_response(&mut self.write, "could not get connection from the pool")
+                        .await?;
+                    continue;
+                }
+            };
+
+            let mut reference = connection.0;
             let _address = connection.1;
-            let server = &mut *proxy;
+            let server = &mut *reference;
 
             // Claim this server as mine for query cancellation.
             server.claim(self.process_id, self.secret_key);
 
+            // Client active & server active
+            self.stats.client_active(self.process_id);
+            self.stats.server_active(server.process_id());
+
+            // Transaction loop. Multiple queries can be issued by the client here.
+            // The connection belongs to the client until the transaction is over,
+            // or until the client disconnects if we are in session mode.
             loop {
-                // No messages in the buffer, read one.
                 let mut message = if message.len() == 0 {
                     match read_message(&mut self.read).await {
                         Ok(message) => message,
                         Err(err) => {
                             // Client disconnected without warning.
                             if server.in_transaction() {
-                                // TODO: this is what PgBouncer does
-                                // which leads to connection thrashing.
-                                //
-                                // I think we could issue a ROLLBACK here instead.
-                                // server.mark_bad();
+                                // Client left dirty server. Clean up and proceed
+                                // without thrashing this connection.
                                 server.query("ROLLBACK; DISCARD ALL;").await?;
                             }
 
@@ -229,16 +296,26 @@ impl Client {
                     msg
                 };
 
-                let original = message.clone(); // To be forwarded to the server
+                // The message will be forwarded to the server intact. We still would like to
+                // parse it below to figure out what to do with it.
+                let original = message.clone();
+
                 let code = message.get_u8() as char;
                 let _len = message.get_i32() as usize;
 
                 match code {
+                    // ReadyForQuery
                     'Q' => {
+                        // TODO: implement retries here for read-only transactions.
                         server.send(original).await?;
 
+                        // Read all data the server has to offer, which can be multiple messages
+                        // buffered in 8196 bytes chunks.
                         loop {
+                            // TODO: implement retries here for read-only transactions.
                             let response = server.recv().await?;
+
+                            // Send server reply to the client.
                             match write_all_half(&mut self.write, response).await {
                                 Ok(_) => (),
                                 Err(err) => {
@@ -252,13 +329,24 @@ impl Client {
                             }
                         }
 
-                        // Release server
-                        if !server.in_transaction() && self.transaction_mode {
-                            shard = None;
-                            break;
+                        // Report query executed statistics.
+                        self.stats.query();
+
+                        // The transaction is over, we can release the connection back to the pool.
+                        if !server.in_transaction() {
+                            // Report transaction executed statistics.
+                            self.stats.transaction();
+
+                            // 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());
+                                break;
+                            }
                         }
                     }
 
+                    // Terminate
                     'X' => {
                         // Client closing. Rollback and clean up
                         // connection before releasing into the pool.
@@ -272,32 +360,46 @@ impl Client {
                         return Ok(());
                     }
 
+                    // Parse
+                    // The query with placeholders is here, e.g. `SELECT * FROM users WHERE email = $1 AND active = $2`.
                     'P' => {
-                        // Extended protocol, let's buffer most of it
                         self.buffer.put(&original[..]);
                     }
 
+                    // Bind
+                    // The placeholder's replacements are here, e.g. 'user@email.com' and 'true'
                     'B' => {
                         self.buffer.put(&original[..]);
                     }
 
                     // Describe
+                    // Command a client can issue to describe a previously prepared named statement.
                     'D' => {
                         self.buffer.put(&original[..]);
                     }
 
+                    // Execute
+                    // Execute a prepared statement prepared in `P` and bound in `B`.
                     'E' => {
                         self.buffer.put(&original[..]);
                     }
 
+                    // Sync
+                    // Frontend (client) is asking for the query result now.
                     'S' => {
-                        // Extended protocol, client requests sync
                         self.buffer.put(&original[..]);
+
+                        // TODO: retries for read-only transactions.
                         server.send(self.buffer.clone()).await?;
+
                         self.buffer.clear();
 
+                        // Read all data the server has to offer, which can be multiple messages
+                        // buffered in 8196 bytes chunks.
                         loop {
+                            // TODO: retries for read-only transactions
                             let response = server.recv().await?;
+
                             match write_all_half(&mut self.write, response).await {
                                 Ok(_) => (),
                                 Err(err) => {
@@ -311,10 +413,18 @@ impl Client {
                             }
                         }
 
-                        // Release server
-                        if !server.in_transaction() && self.transaction_mode {
-                            shard = None;
-                            break;
+                        // Report query executed statistics.
+                        self.stats.query();
+
+                        // 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 !server.in_transaction() {
+                            self.stats.transaction();
+
+                            if self.transaction_mode {
+                                self.stats.server_idle(server.process_id());
+                                break;
+                            }
                         }
                     }
 
@@ -325,10 +435,13 @@ impl Client {
                         server.send(original).await?;
                     }
 
+                    // CopyDone or CopyFail
+                    // Copy is done, successfully or not.
                     'c' | 'f' => {
-                        // Copy is done.
                         server.send(original).await?;
+
                         let response = server.recv().await?;
+
                         match write_all_half(&mut self.write, response).await {
                             Ok(_) => (),
                             Err(err) => {
@@ -337,53 +450,40 @@ impl Client {
                             }
                         };
 
-                        // Release the server
-                        if !server.in_transaction() && self.transaction_mode {
-                            println!("Releasing after copy done");
-                            shard = None;
-                            break;
+                        // 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 !server.in_transaction() {
+                            self.stats.transaction();
+
+                            if self.transaction_mode {
+                                self.stats.server_idle(server.process_id());
+                                break;
+                            }
                         }
                     }
 
+                    // Some unexpected message. We either did not implement the protocol correctly
+                    // or this is not a Postgres client we're talking to.
                     _ => {
-                        println!(">>> Unexpected code: {}", code);
+                        error!("Unexpected code: {}", code);
                     }
                 }
             }
 
+            // The server is no longer bound to us, we can't cancel it's queries anymore.
             self.release();
         }
     }
 
     /// Release the server from being mine. I can't cancel its queries anymore.
-    pub fn release(&mut self) {
+    pub fn release(&self) {
         let mut guard = self.client_server_map.lock().unwrap();
         guard.remove(&(self.process_id, self.secret_key));
     }
+}
 
-    async fn select_shard(&mut self, mut buf: BytesMut, shards: usize) -> Option<usize> {
-        let code = buf.get_u8() as char;
-
-        match code {
-            'Q' => (),
-            // 'P' => (),
-            _ => return None,
-        };
-
-        let len = buf.get_i32();
-        let query = String::from_utf8_lossy(&buf[..len as usize - 4 - 1]).to_ascii_uppercase(); // Don't read the ternminating null
-
-        if self.sharding_regex.is_match(&query) {
-            let shard = query.split("'").collect::<Vec<&str>>()[1];
-            match shard.parse::<i64>() {
-                Ok(shard) => {
-                    let sharder = Sharder::new(shards);
-                    Some(sharder.pg_bigint_hash(shard))
-                }
-                Err(_) => None,
-            }
-        } else {
-            None
-        }
+impl Drop for Client {
+    fn drop(&mut self) {
+        self.stats.client_disconnecting(self.process_id);
     }
 }

src/config.rs

@@ -1,16 +1,59 @@
+use arc_swap::{ArcSwap, Guard};
+use log::{error, info};
+use once_cell::sync::Lazy;
 use serde_derive::Deserialize;
 use tokio::fs::File;
 use tokio::io::AsyncReadExt;
 use toml;
 
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
+use std::sync::Arc;
 
 use crate::errors::Error;
 
+static CONFIG: Lazy<ArcSwap<Config>> = Lazy::new(|| ArcSwap::from_pointee(Config::default()));
+
+#[derive(Clone, PartialEq, Deserialize, Hash, std::cmp::Eq, Debug, Copy)]
+pub enum Role {
+    Primary,
+    Replica,
+}
+
+impl PartialEq<Option<Role>> for Role {
+    fn eq(&self, other: &Option<Role>) -> bool {
+        match other {
+            None => true,
+            Some(role) => *self == *role,
+        }
+    }
+}
+
+impl PartialEq<Role> for Option<Role> {
+    fn eq(&self, other: &Role) -> bool {
+        match *self {
+            None => true,
+            Some(role) => role == *other,
+        }
+    }
+}
+
 #[derive(Clone, PartialEq, Hash, std::cmp::Eq, Debug)]
 pub struct Address {
     pub host: String,
     pub port: String,
+    pub shard: usize,
+    pub role: Role,
+}
+
+impl Default for Address {
+    fn default() -> Address {
+        Address {
+            host: String::from("127.0.0.1"),
+            port: String::from("5432"),
+            shard: 0,
+            role: Role::Replica,
+        }
+    }
 }
 
 #[derive(Clone, PartialEq, Hash, std::cmp::Eq, Deserialize, Debug)]
@@ -19,6 +62,15 @@ pub struct User {
     pub password: String,
 }
 
+impl Default for User {
+    fn default() -> User {
+        User {
+            name: String::from("postgres"),
+            password: String::new(),
+        }
+    }
+}
+
 #[derive(Deserialize, Debug, Clone)]
 pub struct General {
     pub host: String,
@@ -28,28 +80,99 @@ pub struct General {
     pub connect_timeout: u64,
     pub healthcheck_timeout: u64,
     pub ban_time: i64,
+    pub statsd_address: String,
+}
+
+impl Default for General {
+    fn default() -> General {
+        General {
+            host: String::from("localhost"),
+            port: 5432,
+            pool_size: 15,
+            pool_mode: String::from("transaction"),
+            connect_timeout: 5000,
+            healthcheck_timeout: 1000,
+            ban_time: 60,
+            statsd_address: String::from("127.0.0.1:8125"),
+        }
+    }
 }
 
 #[derive(Deserialize, Debug, Clone)]
 pub struct Shard {
-    pub servers: Vec<(String, u16)>,
+    pub servers: Vec<(String, u16, String)>,
     pub database: String,
 }
 
+impl Default for Shard {
+    fn default() -> Shard {
+        Shard {
+            servers: vec![(String::from("localhost"), 5432, String::from("primary"))],
+            database: String::from("postgres"),
+        }
+    }
+}
+
+#[derive(Deserialize, Debug, Clone)]
+pub struct QueryRouter {
+    pub default_role: String,
+    pub query_parser_enabled: bool,
+    pub primary_reads_enabled: bool,
+}
+
+impl Default for QueryRouter {
+    fn default() -> QueryRouter {
+        QueryRouter {
+            default_role: String::from("any"),
+            query_parser_enabled: false,
+            primary_reads_enabled: true,
+        }
+    }
+}
+
 #[derive(Deserialize, Debug, Clone)]
 pub struct Config {
     pub general: General,
     pub user: User,
     pub shards: HashMap<String, Shard>,
+    pub query_router: QueryRouter,
 }
 
-pub async fn parse(path: &str) -> Result<Config, Error> {
-    // let path = Path::new(path);
+impl Default for Config {
+    fn default() -> Config {
+        Config {
+            general: General::default(),
+            user: User::default(),
+            shards: HashMap::from([(String::from("1"), Shard::default())]),
+            query_router: QueryRouter::default(),
+        }
+    }
+}
+
+impl Config {
+    pub fn show(&self) {
+        info!("Pool size: {}", self.general.pool_size);
+        info!("Pool mode: {}", self.general.pool_mode);
+        info!("Ban time: {}s", self.general.ban_time);
+        info!(
+            "Healthcheck timeout: {}ms",
+            self.general.healthcheck_timeout
+        );
+        info!("Connection timeout: {}ms", self.general.connect_timeout);
+    }
+}
+
+pub fn get_config() -> Guard<Arc<Config>> {
+    CONFIG.load()
+}
+
+/// Parse the config.
+pub async fn parse(path: &str) -> Result<(), Error> {
     let mut contents = String::new();
     let mut file = match File::open(path).await {
         Ok(file) => file,
         Err(err) => {
-            println!("> Config error: {:?}", err);
+            error!("Could not open '{}': {}", path, err.to_string());
             return Err(Error::BadConfig);
         }
     };
@@ -57,7 +180,7 @@ pub async fn parse(path: &str) -> Result<Config, Error> {
     match file.read_to_string(&mut contents).await {
         Ok(_) => (),
         Err(err) => {
-            println!("> Config error: {:?}", err);
+            error!("Could not read config file: {}", err.to_string());
             return Err(Error::BadConfig);
         }
     };
@@ -65,12 +188,84 @@ pub async fn parse(path: &str) -> Result<Config, Error> {
     let config: Config = match toml::from_str(&contents) {
         Ok(config) => config,
         Err(err) => {
-            println!("> Config error: {:?}", err);
+            error!("Could not parse config file: {}", err.to_string());
             return Err(Error::BadConfig);
         }
     };
 
-    Ok(config)
+    // Quick config sanity check.
+    for shard in &config.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);
+        }
+    }
+
+    match config.query_router.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);
+        }
+    };
+
+    CONFIG.store(Arc::new(config.clone()));
+
+    Ok(())
 }
 
 #[cfg(test)]
@@ -79,9 +274,11 @@ mod test {
 
     #[tokio::test]
     async fn test_config() {
-        let config = parse("pgcat.toml").await.unwrap();
-        assert_eq!(config.general.pool_size, 15);
-        assert_eq!(config.shards.len(), 3);
-        assert_eq!(config.shards["1"].servers[0].0, "127.0.0.1");
+        parse("pgcat.toml").await.unwrap();
+        assert_eq!(get_config().general.pool_size, 15);
+        assert_eq!(get_config().shards.len(), 3);
+        assert_eq!(get_config().shards["1"].servers[0].0, "127.0.0.1");
+        assert_eq!(get_config().shards["0"].servers[0].2, "primary");
+        assert_eq!(get_config().query_router.default_role, "any");
     }
 }

src/constants.rs

@@ -0,0 +1,22 @@
+/// Various protocol constants, as defined in
+/// https://www.postgresql.org/docs/12/protocol-message-formats.html
+/// and elsewhere in the source code.
+/// Also other constants we use elsewhere.
+
+// Used in the StartupMessage to indicate regular handshake.
+pub const PROTOCOL_VERSION_NUMBER: i32 = 196608;
+
+// SSLRequest: used to indicate we want an SSL connection.
+pub const SSL_REQUEST_CODE: i32 = 80877103;
+
+// CancelRequest: the cancel request code.
+pub const CANCEL_REQUEST_CODE: i32 = 80877102;
+
+// AuthenticationMD5Password
+pub const MD5_ENCRYPTED_PASSWORD: i32 = 5;
+
+// AuthenticationOk
+pub const AUTHENTICATION_SUCCESSFUL: i32 = 0;
+
+// ErrorResponse: A code identifying the field type; if zero, this is the message terminator and no string follows.
+pub const MESSAGE_TERMINATOR: u8 = 0;

src/errors.rs

@@ -8,4 +8,5 @@ pub enum Error {
     // ServerTimeout,
     // DirtyServer,
     BadConfig,
+    AllServersDown,
 }

src/main.rs

@@ -1,123 +1,251 @@
-// PgCat, a PostgreSQL pooler with load balancing, failover, and sharding support.
-// Copyright (C) 2022  Lev Kokotov <lev@levthe.dev>
+// Copyright (c) 2022 Lev Kokotov <lev@levthe.dev>
 
-// This program is free software: you can redistribute it and/or modify
-// it under the terms of the GNU General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
+// Permission is hereby granted, free of charge, to any person obtaining
+// a copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to
+// permit persons to whom the Software is furnished to do so, subject to
+// the following conditions:
 
-// This program is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-// GNU General Public License for more details.
+// The above copyright notice and this permission notice shall be
+// included in all copies or substantial portions of the Software.
 
-// You should have received a copy of the GNU General Public License
-// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+extern crate arc_swap;
 extern crate async_trait;
 extern crate bb8;
 extern crate bytes;
+extern crate env_logger;
+extern crate log;
 extern crate md5;
+extern crate num_cpus;
+extern crate once_cell;
 extern crate serde;
 extern crate serde_derive;
+extern crate sqlparser;
+extern crate statsd;
 extern crate tokio;
 extern crate toml;
 
+use log::{error, info};
 use tokio::net::TcpListener;
+use tokio::{
+    signal,
+    signal::unix::{signal as unix_signal, SignalKind},
+    sync::mpsc,
+};
 
 use std::collections::HashMap;
 use std::sync::{Arc, Mutex};
 
 mod client;
 mod config;
+mod constants;
 mod errors;
 mod messages;
 mod pool;
+mod query_router;
 mod server;
 mod sharding;
+mod stats;
 
 // Support for query cancellation: this maps our process_ids and
 // secret keys to the backend's.
+use config::get_config;
 use pool::{ClientServerMap, ConnectionPool};
+use stats::{Collector, Reporter};
 
 /// Main!
-#[tokio::main]
+#[tokio::main(worker_threads = 4)]
 async fn main() {
-    println!("> Welcome to PgCat! Meow.");
+    env_logger::init();
+    info!("Welcome to PgCat! Meow.");
 
-    let config = match config::parse("pgcat.toml").await {
-        Ok(config) => config,
+    // Prepare regexes
+    if !query_router::QueryRouter::setup() {
+        error!("Could not setup query router");
+        return;
+    }
+
+    let args = std::env::args().collect::<Vec<String>>();
+
+    let config_file = if args.len() == 2 {
+        args[1].to_string()
+    } else {
+        String::from("pgcat.toml")
+    };
+
+    // Prepare the config
+    match config::parse(&config_file).await {
+        Ok(_) => (),
         Err(err) => {
-            println!("> Config parse error: {:?}", err);
+            error!("Config parse error: {:?}", err);
             return;
         }
     };
 
+    let config = get_config();
+
     let addr = format!("{}:{}", config.general.host, config.general.port);
     let listener = match TcpListener::bind(&addr).await {
         Ok(sock) => sock,
         Err(err) => {
-            println!("> Error: {:?}", err);
+            error!("Listener socket error: {:?}", err);
             return;
         }
     };
 
-    println!("> Running on {}", addr);
+    info!("Running on {}", addr);
+    config.show();
 
     // Tracks which client is connected to which server for query cancellation.
     let client_server_map: ClientServerMap = Arc::new(Mutex::new(HashMap::new()));
 
-    println!("> Pool size: {}", config.general.pool_size);
-    println!("> Pool mode: {}", config.general.pool_mode);
-    println!("> Ban time: {}s", config.general.ban_time);
-    println!(
-        "> Healthcheck timeout: {}ms",
-        config.general.healthcheck_timeout
-    );
+    // Collect statistics and send them to StatsD
+    let (tx, rx) = mpsc::channel(100);
 
-    let pool = ConnectionPool::from_config(config.clone(), client_server_map.clone()).await;
-    let transaction_mode = config.general.pool_mode == "transaction";
+    tokio::task::spawn(async move {
+        let mut stats_collector = Collector::new(rx);
+        stats_collector.collect().await;
+    });
 
-    println!("> Waiting for clients...");
+    let mut pool =
+        ConnectionPool::from_config(client_server_map.clone(), Reporter::new(tx.clone())).await;
 
-    loop {
-        let pool = pool.clone();
-        let client_server_map = client_server_map.clone();
+    let server_info = match pool.validate().await {
+        Ok(info) => info,
+        Err(err) => {
+            error!("Could not validate connection pool: {:?}", err);
+            return;
+        }
+    };
 
-        let (socket, addr) = match listener.accept().await {
-            Ok((socket, addr)) => (socket, addr),
-            Err(err) => {
-                println!("> Listener: {:?}", err);
-                continue;
-            }
-        };
+    info!("Waiting for clients");
 
-        // Client goes to another thread, bye.
-        tokio::task::spawn(async move {
-            println!(
-                ">> Client {:?} connected, transaction pooling: {}",
-                addr, transaction_mode
-            );
-
-            match client::Client::startup(socket, client_server_map, transaction_mode).await {
-                Ok(mut client) => {
-                    println!(">> Client {:?} authenticated successfully!", addr);
-
-                    match client.handle(pool).await {
-                        Ok(()) => {
-                            println!(">> Client {:?} disconnected.", addr);
-                        }
-
-                        Err(err) => {
-                            println!(">> Client disconnected with error: {:?}", err);
-                            client.release();
-                        }
-                    }
-                }
+    // Main app runs here.
+    tokio::task::spawn(async move {
+        loop {
+            let pool = pool.clone();
+            let client_server_map = client_server_map.clone();
+            let server_info = server_info.clone();
+            let reporter = Reporter::new(tx.clone());
 
+            let (socket, addr) = match listener.accept().await {
+                Ok((socket, addr)) => (socket, addr),
                 Err(err) => {
-                    println!(">> Error: {:?}", err);
+                    error!("{:?}", err);
+                    continue;
                 }
             };
-        });
-    }
+
+            // Client goes to another thread, bye.
+            tokio::task::spawn(async move {
+                let start = chrono::offset::Utc::now().naive_utc();
+                match client::Client::startup(socket, client_server_map, server_info, reporter)
+                    .await
+                {
+                    Ok(mut client) => {
+                        info!("Client {:?} connected", addr);
+                        match client.handle(pool).await {
+                            Ok(()) => {
+                                let duration = chrono::offset::Utc::now().naive_utc() - start;
+
+                                info!(
+                                    "Client {:?} disconnected, session duration: {}",
+                                    addr,
+                                    format_duration(&duration)
+                                );
+                            }
+
+                            Err(err) => {
+                                error!("Client disconnected with error: {:?}", err);
+                                client.release();
+                            }
+                        }
+                    }
+
+                    Err(err) => {
+                        error!("Client failed to login: {:?}", err);
+                    }
+                };
+            });
+        }
+    });
+
+    // 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 config::parse("pgcat.toml").await {
+                Ok(_) => {
+                    get_config().show();
+                }
+                Err(err) => {
+                    error!("{:?}", err);
+                    return;
+                }
+            };
+        }
+    });
+
+    // Setup shut down sequence
+    match signal::ctrl_c().await {
+        Ok(()) => {
+            info!("Shutting down...");
+        }
+
+        Err(err) => {
+            error!("Unable to listen for shutdown signal: {}", err);
+        }
+    };
+}
+
+/// 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)
 }

src/messages.rs

@@ -1,18 +1,17 @@
-use bytes::{BufMut, BytesMut};
+/// Helper functions to send one-off protocol messages
+/// and handle TcpStream (TCP socket).
+use bytes::{Buf, BufMut, BytesMut};
 use md5::{Digest, Md5};
 use tokio::io::{AsyncReadExt, AsyncWriteExt, BufReader};
-use tokio::net::tcp::{OwnedReadHalf, OwnedWriteHalf};
-use tokio::net::TcpStream;
+use tokio::net::{
+    tcp::{OwnedReadHalf, OwnedWriteHalf},
+    TcpStream,
+};
+
+use std::collections::HashMap;
 
 use crate::errors::Error;
 
-// This is a funny one. `psql` parses this to figure out which
-// queries to send when using shortcuts, e.g. \d+.
-//
-// TODO: Actually get the version from the server itself.
-//
-const SERVER_VESION: &str = "12.9 (Ubuntu 12.9-0ubuntu0.20.04.1)";
-
 /// Tell the client that authentication handshake completed successfully.
 pub async fn auth_ok(stream: &mut TcpStream) -> Result<(), Error> {
     let mut auth_ok = BytesMut::with_capacity(9);
@@ -24,29 +23,6 @@ pub async fn auth_ok(stream: &mut TcpStream) -> Result<(), Error> {
     Ok(write_all(stream, auth_ok).await?)
 }
 
-/// Send server parameters to the client. This will tell the client
-/// what server version and what's the encoding we're using.
-pub async fn server_parameters(stream: &mut TcpStream) -> Result<(), Error> {
-    let client_encoding = BytesMut::from(&b"client_encoding\0UTF8\0"[..]);
-    let server_version =
-        BytesMut::from(&format!("server_version\0{}\0", SERVER_VESION).as_bytes()[..]);
-
-    // Client encoding
-    let len = client_encoding.len() as i32 + 4; // TODO: add more parameters here
-    let mut res = BytesMut::with_capacity(64);
-
-    res.put_u8(b'S');
-    res.put_i32(len);
-    res.put_slice(&client_encoding[..]);
-
-    let len = server_version.len() as i32 + 4;
-    res.put_u8(b'S');
-    res.put_i32(len);
-    res.put_slice(&server_version[..]);
-
-    Ok(write_all(stream, res).await?)
-}
-
 /// Give the client the process_id and secret we generated
 /// used in query cancellation.
 pub async fn backend_key_data(
@@ -62,6 +38,17 @@ pub async fn backend_key_data(
     Ok(write_all(stream, key_data).await?)
 }
 
+#[allow(dead_code)]
+pub fn simple_query(query: &str) -> BytesMut {
+    let mut res = BytesMut::from(&b"Q"[..]);
+    let query = format!("{}\0", query);
+
+    res.put_i32(query.len() as i32 + 4);
+    res.put_slice(&query.as_bytes());
+
+    res
+}
+
 /// Tell the client we're ready for another query.
 pub async fn ready_for_query(stream: &mut TcpStream) -> Result<(), Error> {
     let mut bytes = BytesMut::with_capacity(5);
@@ -104,6 +91,51 @@ pub async fn startup(stream: &mut TcpStream, user: &str, database: &str) -> Resu
     }
 }
 
+/// Parse StartupMessage parameters.
+/// e.g. user, database, application_name, etc.
+pub fn parse_startup(mut bytes: BytesMut) -> Result<HashMap<String, String>, Error> {
+    let mut result = HashMap::new();
+    let mut buf = Vec::new();
+    let mut tmp = String::new();
+
+    while bytes.has_remaining() {
+        let mut c = bytes.get_u8();
+
+        // Null-terminated C-strings.
+        while c != 0 {
+            tmp.push(c as char);
+            c = bytes.get_u8();
+        }
+
+        if tmp.len() > 0 {
+            buf.push(tmp.clone());
+            tmp.clear();
+        }
+    }
+
+    // Expect pairs of name and value
+    // and at least one pair to be present.
+    if buf.len() % 2 != 0 && buf.len() >= 2 {
+        return Err(Error::ClientBadStartup);
+    }
+
+    let mut i = 0;
+    while i < buf.len() {
+        let name = buf[i].clone();
+        let value = buf[i + 1].clone();
+        let _ = result.insert(name, value);
+        i += 2;
+    }
+
+    // Minimum required parameters
+    // I want to have the user at the very minimum, according to the protocol spec.
+    if !result.contains_key("user") {
+        return Err(Error::ClientBadStartup);
+    }
+
+    Ok(result)
+}
+
 /// Send password challenge response to the server.
 /// This is the MD5 challenge.
 pub async fn md5_password(
@@ -131,6 +163,7 @@ pub async fn md5_password(
     password.push(0);
 
     let mut message = BytesMut::with_capacity(password.len() as usize + 5);
+
     message.put_u8(b'p');
     message.put_i32(password.len() as i32 + 4);
     message.put_slice(&password[..]);
@@ -138,16 +171,151 @@ pub async fn md5_password(
     Ok(write_all(stream, message).await?)
 }
 
-pub async fn set_sharding_key(stream: &mut OwnedWriteHalf) -> Result<(), Error> {
+/// Implements a response to our custom `SET SHARDING KEY`
+/// and `SET SERVER ROLE` commands.
+/// This tells the client we're ready for the next query.
+pub async fn custom_protocol_response_ok(
+    stream: &mut OwnedWriteHalf,
+    message: &str,
+) -> Result<(), Error> {
     let mut res = BytesMut::with_capacity(25);
 
-    let set_complete = BytesMut::from(&"SET SHARDING KEY\0"[..]);
+    let set_complete = BytesMut::from(&format!("{}\0", message)[..]);
     let len = (set_complete.len() + 4) as i32;
 
+    // CommandComplete
     res.put_u8(b'C');
     res.put_i32(len);
     res.put_slice(&set_complete[..]);
 
+    // ReadyForQuery (idle)
+    res.put_u8(b'Z');
+    res.put_i32(5);
+    res.put_u8(b'I');
+
+    write_all_half(stream, res).await
+}
+
+/// Send a custom error message to the client.
+/// Tell the client we are ready for the next query and no rollback is necessary.
+/// Docs on error codes: https://www.postgresql.org/docs/12/errcodes-appendix.html
+pub async fn error_response(stream: &mut OwnedWriteHalf, message: &str) -> Result<(), Error> {
+    let mut error = BytesMut::new();
+
+    // Error level
+    error.put_u8(b'S');
+    error.put_slice(&b"FATAL\0"[..]);
+
+    // Error level (non-translatable)
+    error.put_u8(b'V');
+    error.put_slice(&b"FATAL\0"[..]);
+
+    // Error code: not sure how much this matters.
+    error.put_u8(b'C');
+    error.put_slice(&b"58000\0"[..]); // system_error, see Appendix A.
+
+    // The short error message.
+    error.put_u8(b'M');
+    error.put_slice(&format!("{}\0", message).as_bytes());
+
+    // No more fields follow.
+    error.put_u8(0);
+
+    // Ready for query, no rollback needed (I = idle).
+    let mut ready_for_query = BytesMut::new();
+
+    ready_for_query.put_u8(b'Z');
+    ready_for_query.put_i32(5);
+    ready_for_query.put_u8(b'I');
+
+    // Compose the two message reply.
+    let mut res = BytesMut::with_capacity(error.len() + ready_for_query.len() + 5);
+
+    res.put_u8(b'E');
+    res.put_i32(error.len() as i32 + 4);
+
+    res.put(error);
+    res.put(ready_for_query);
+
+    Ok(write_all_half(stream, res).await?)
+}
+
+/// Respond to a SHOW SHARD command.
+pub async fn show_response(
+    stream: &mut OwnedWriteHalf,
+    name: &str,
+    value: &str,
+) -> Result<(), Error> {
+    // A SELECT response consists of:
+    // 1. RowDescription
+    // 2. One or more DataRow
+    // 3. CommandComplete
+    // 4. ReadyForQuery
+
+    // RowDescription
+    let mut row_desc = BytesMut::new();
+
+    // Number of columns: 1
+    row_desc.put_i16(1);
+
+    // Column name
+    row_desc.put_slice(&format!("{}\0", name).as_bytes());
+
+    // Doesn't belong to any table
+    row_desc.put_i32(0);
+
+    // Doesn't belong to any table
+    row_desc.put_i16(0);
+
+    // Text
+    row_desc.put_i32(25);
+
+    // Text size = variable (-1)
+    row_desc.put_i16(-1);
+
+    // Type modifier: none that I know
+    row_desc.put_i32(0);
+
+    // Format being used: text (0), binary (1)
+    row_desc.put_i16(0);
+
+    // DataRow
+    let mut data_row = BytesMut::new();
+
+    // Number of columns
+    data_row.put_i16(1);
+
+    // Size of the column content (length of the string really)
+    data_row.put_i32(value.len() as i32);
+
+    // The content
+    data_row.put_slice(value.as_bytes());
+
+    // CommandComplete
+    let mut command_complete = BytesMut::new();
+
+    // Number of rows returned (just one)
+    command_complete.put_slice(&b"SELECT 1\0"[..]);
+
+    // The final messages sent to the client
+    let mut res = BytesMut::new();
+
+    // RowDescription
+    res.put_u8(b'T');
+    res.put_i32(row_desc.len() as i32 + 4);
+    res.put(row_desc);
+
+    // DataRow
+    res.put_u8(b'D');
+    res.put_i32(data_row.len() as i32 + 4);
+    res.put(data_row);
+
+    // CommandComplete
+    res.put_u8(b'C');
+    res.put_i32(command_complete.len() as i32 + 4);
+    res.put(command_complete);
+
+    // ReadyForQuery
     res.put_u8(b'Z');
     res.put_i32(5);
     res.put_u8(b'I');

src/pool.rs

@@ -1,36 +1,39 @@
 /// Pooling and failover and banlist.
 use async_trait::async_trait;
 use bb8::{ManageConnection, Pool, PooledConnection};
+use bytes::BytesMut;
 use chrono::naive::NaiveDateTime;
+use log::{error, info, warn};
 
-use crate::config::{Address, Config, User};
+use crate::config::{get_config, Address, Role, User};
 use crate::errors::Error;
 use crate::server::Server;
+use crate::stats::Reporter;
 
 use std::collections::HashMap;
-use std::sync::{
-    atomic::{AtomicUsize, Ordering},
-    Arc, Mutex,
-};
+use std::sync::{Arc, Mutex};
+use std::time::Instant;
 
 // Banlist: bad servers go in here.
 pub type BanList = Arc<Mutex<Vec<HashMap<Address, NaiveDateTime>>>>;
-pub type Counter = Arc<AtomicUsize>;
 pub type ClientServerMap = Arc<Mutex<HashMap<(i32, i32), (i32, i32, String, String)>>>;
 
 #[derive(Clone, Debug)]
 pub struct ConnectionPool {
     databases: Vec<Vec<Pool<ServerPool>>>,
     addresses: Vec<Vec<Address>>,
-    round_robin: Counter,
+    round_robin: usize,
     banlist: BanList,
-    healthcheck_timeout: u64,
-    ban_time: i64,
+    stats: Reporter,
 }
 
 impl ConnectionPool {
     /// Construct the connection pool from a config file.
-    pub async fn from_config(config: Config, client_server_map: ClientServerMap) -> ConnectionPool {
+    pub async fn from_config(
+        client_server_map: ClientServerMap,
+        stats: Reporter,
+    ) -> ConnectionPool {
+        let config = get_config();
         let mut shards = Vec::new();
         let mut addresses = Vec::new();
         let mut banlist = Vec::new();
@@ -42,15 +45,26 @@ impl ConnectionPool {
             .collect::<Vec<String>>();
         shard_ids.sort_by_key(|k| k.parse::<i64>().unwrap());
 
-        for shard in shard_ids {
-            let shard = &config.shards[&shard];
+        for shard_idx in shard_ids {
+            let shard = &config.shards[&shard_idx];
             let mut pools = Vec::new();
             let mut replica_addresses = Vec::new();
 
-            for server in &shard.servers {
+            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 {
                     host: server.0.clone(),
                     port: server.1.to_string(),
+                    role: role,
+                    shard: shard_idx.parse::<usize>().unwrap(),
                 };
 
                 let manager = ServerPool::new(
@@ -58,6 +72,7 @@ impl ConnectionPool {
                     config.user.clone(),
                     &shard.database,
                     client_server_map.clone(),
+                    stats.clone(),
                 );
 
                 let pool = Pool::builder()
@@ -79,92 +94,162 @@ impl ConnectionPool {
             banlist.push(HashMap::new());
         }
 
+        assert_eq!(shards.len(), addresses.len());
+        let address_len = addresses.len();
+
         ConnectionPool {
             databases: shards,
             addresses: addresses,
-            round_robin: Arc::new(AtomicUsize::new(0)),
+            round_robin: rand::random::<usize>() % address_len, // Start at a random replica
             banlist: Arc::new(Mutex::new(banlist)),
-            healthcheck_timeout: config.general.healthcheck_timeout,
-            ban_time: config.general.ban_time,
+            stats: stats,
         }
     }
 
+    /// Connect to all shards and grab server information.
+    /// Return server information we will pass to the clients
+    /// when they connect.
+    /// This also warms up the pool for clients that connect when
+    /// the pooler starts up.
+    pub async fn validate(&mut self) -> Result<BytesMut, Error> {
+        let mut server_infos = Vec::new();
+
+        for shard in 0..self.shards() {
+            for _ in 0..self.servers(shard) {
+                let connection = match self.get(shard, None).await {
+                    Ok(conn) => conn,
+                    Err(err) => {
+                        error!("Shard {} down or misconfigured: {:?}", shard, err);
+                        continue;
+                    }
+                };
+
+                let mut proxy = connection.0;
+                let _address = connection.1;
+                let server = &mut *proxy;
+
+                server_infos.push(server.server_info());
+            }
+        }
+
+        // TODO: compare server information to make sure
+        // all shards are running identical configurations.
+        if server_infos.len() == 0 {
+            return Err(Error::AllServersDown);
+        }
+
+        Ok(server_infos[0].clone())
+    }
+
     /// Get a connection from the pool.
     pub async fn get(
-        &self,
-        shard: Option<usize>,
+        &mut self,
+        shard: usize,
+        role: Option<Role>,
     ) -> Result<(PooledConnection<'_, ServerPool>, Address), Error> {
-        // Set this to false to gain ~3-4% speed.
-        let with_health_check = true;
+        let now = Instant::now();
+        let addresses = &self.addresses[shard];
 
-        let shard = match shard {
-            Some(shard) => shard,
-            None => 0, // TODO: pick a shard at random
+        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(),
         };
 
-        loop {
-            let index =
-                self.round_robin.fetch_add(1, Ordering::SeqCst) % self.databases[shard].len();
-            let address = self.addresses[shard][index].clone();
+        let exists = match role {
+            Some(role) => addresses.iter().filter(|addr| addr.role == role).count() > 0,
+            None => true,
+        };
 
-            if self.is_banned(&address, shard) {
+        if !exists {
+            error!("Requested role {:?}, but none are configured", role);
+            return Err(Error::BadConfig);
+        }
+
+        while allowed_attempts > 0 {
+            // Round-robin each client's queries.
+            // If a client only sends one query and then disconnects, it doesn't matter
+            // which replica it'll go to.
+            self.round_robin += 1;
+            let index = self.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;
+
+            if self.is_banned(address, shard, role) {
                 continue;
             }
 
             // Check if we can connect
-            // TODO: implement query wait timeout, i.e. time to get a conn from the pool
             let mut conn = match self.databases[shard][index].get().await {
                 Ok(conn) => conn,
                 Err(err) => {
-                    println!(">> Banning replica {}, error: {:?}", index, err);
-                    self.ban(&address, shard);
+                    error!("Banning replica {}, error: {:?}", index, err);
+                    self.ban(address, shard);
                     continue;
                 }
             };
 
-            if !with_health_check {
-                return Ok((conn, address));
-            }
-
             // // Check if this server is alive with a health check
             let server = &mut *conn;
+            let healthcheck_timeout = get_config().general.healthcheck_timeout;
+
+            self.stats.server_tested(server.process_id());
 
             match tokio::time::timeout(
-                tokio::time::Duration::from_millis(self.healthcheck_timeout),
+                tokio::time::Duration::from_millis(healthcheck_timeout),
                 server.query("SELECT 1"),
             )
             .await
             {
                 // Check if health check succeeded
                 Ok(res) => match res {
-                    Ok(_) => return Ok((conn, address)),
+                    Ok(_) => {
+                        self.stats.checkout_time(now.elapsed().as_micros());
+                        self.stats.server_idle(conn.process_id());
+                        return Ok((conn, address.clone()));
+                    }
                     Err(_) => {
-                        println!(
-                            ">> Banning replica {} because of failed health check",
-                            index
-                        );
-                        self.ban(&address, shard);
+                        error!("Banning replica {} because of failed health check", index);
+                        // Don't leave a bad connection in the pool.
+                        server.mark_bad();
+
+                        self.ban(address, shard);
                         continue;
                     }
                 },
                 // Health check never came back, database is really really down
                 Err(_) => {
-                    println!(
-                        ">> Banning replica {} because of health check timeout",
-                        index
-                    );
-                    self.ban(&address, shard);
+                    error!("Banning replica {} because of health check timeout", index);
+                    // Don't leave a bad connection in the pool.
+                    server.mark_bad();
+
+                    self.ban(address, shard);
                     continue;
                 }
             }
         }
+
+        return 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) {
-        println!(">> Banning {:?}", address);
+        error!("Banning {:?}", address);
         let now = chrono::offset::Utc::now().naive_utc();
         let mut guard = self.banlist.lock().unwrap();
         guard[shard].insert(address.clone(), now);
@@ -179,14 +264,25 @@ impl ConnectionPool {
 
     /// 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) -> bool {
+    pub fn is_banned(&self, address: &Address, shard: usize, role: Option<Role>) -> bool {
+        let replicas_available = match role {
+            Some(Role::Replica) => self.addresses[shard]
+                .iter()
+                .filter(|addr| addr.role == Role::Replica)
+                .count(),
+            None => self.addresses[shard].len(),
+            Some(Role::Primary) => return false, // Primary cannot be banned.
+        };
+
+        // If you're not asking for the primary,
+        // all databases are treated as replicas.
         let mut guard = self.banlist.lock().unwrap();
 
-        // Everything is banned, nothig is banned
-        if guard[shard].len() == self.databases[shard].len() {
+        // Everything is banned = nothing is banned.
+        if guard[shard].len() == replicas_available {
             guard[shard].clear();
             drop(guard);
-            println!(">> Unbanning all replicas.");
+            warn!("Unbanning all replicas.");
             return false;
         }
 
@@ -194,8 +290,9 @@ impl ConnectionPool {
         match guard[shard].get(address) {
             Some(timestamp) => {
                 let now = chrono::offset::Utc::now().naive_utc();
-                if now.timestamp() - timestamp.timestamp() > self.ban_time {
-                    // 1 minute
+                let config = get_config();
+                // Ban expired.
+                if now.timestamp() - timestamp.timestamp() > config.general.ban_time {
                     guard[shard].remove(address);
                     false
                 } else {
@@ -210,6 +307,10 @@ impl ConnectionPool {
     pub fn shards(&self) -> usize {
         self.databases.len()
     }
+
+    pub fn servers(&self, shard: usize) -> usize {
+        self.addresses[shard].len()
+    }
 }
 
 pub struct ServerPool {
@@ -217,6 +318,7 @@ pub struct ServerPool {
     user: User,
     database: String,
     client_server_map: ClientServerMap,
+    stats: Reporter,
 }
 
 impl ServerPool {
@@ -225,12 +327,14 @@ impl ServerPool {
         user: User,
         database: &str,
         client_server_map: ClientServerMap,
+        stats: Reporter,
     ) -> ServerPool {
         ServerPool {
             address: address,
             user: user,
             database: database.to_string(),
             client_server_map: client_server_map,
+            stats: stats,
         }
     }
 }
@@ -242,17 +346,36 @@ impl ManageConnection for ServerPool {
 
     /// Attempts to create a new connection.
     async fn connect(&self) -> Result<Self::Connection, Self::Error> {
-        println!(">> Creating a new connection for the pool");
+        info!(
+            "Creating a new connection to {:?} using user {:?}",
+            self.address, self.user.name
+        );
 
-        Server::startup(
-            &self.address.host,
-            &self.address.port,
-            &self.user.name,
-            &self.user.password,
+        // Put a temporary process_id into the stats
+        // for server login.
+        let process_id = rand::random::<i32>();
+        self.stats.server_login(process_id);
+
+        match Server::startup(
+            &self.address,
+            &self.user,
             &self.database,
             self.client_server_map.clone(),
+            self.stats.clone(),
         )
         .await
+        {
+            Ok(conn) => {
+                // Remove the temporary process_id from the stats.
+                self.stats.server_disconnecting(process_id);
+                Ok(conn)
+            }
+            Err(err) => {
+                // Remove the temporary process_id from the stats.
+                self.stats.server_disconnecting(process_id);
+                Err(err)
+            }
+        }
     }
 
     /// Determines if the connection is still connected to the database.

src/query_router.rs

@@ -0,0 +1,489 @@
+use crate::config::{get_config, Role};
+use crate::sharding::Sharder;
+/// Route queries automatically based on explicitely requested
+/// or implied query characteristics.
+use bytes::{Buf, BytesMut};
+use log::{debug, error};
+use once_cell::sync::OnceCell;
+use regex::RegexSet;
+use sqlparser::ast::Statement::{Query, StartTransaction};
+use sqlparser::dialect::PostgreSqlDialect;
+use sqlparser::parser::Parser;
+
+const CUSTOM_SQL_REGEXES: [&str; 5] = [
+    r"(?i)SET SHARDING KEY TO '[0-9]+'",
+    r"(?i)SET SHARD TO '[0-9]+'",
+    r"(?i)SHOW SHARD",
+    r"(?i)SET SERVER ROLE TO '(PRIMARY|REPLICA|ANY|AUTO|DEFAULT)'",
+    r"(?i)SHOW SERVER ROLE",
+];
+
+#[derive(PartialEq, Debug)]
+pub enum Command {
+    SetShardingKey,
+    SetShard,
+    ShowShard,
+    SetServerRole,
+    ShowServerRole,
+}
+
+static CUSTOM_SQL_REGEX_SET: OnceCell<RegexSet> = OnceCell::new();
+
+pub struct QueryRouter {
+    // By default, queries go here, unless we have better information
+    // about what the client wants.
+    default_server_role: Option<Role>,
+
+    // Number of shards in the cluster.
+    shards: usize,
+
+    // Which shard we should be talking to right now.
+    active_shard: Option<usize>,
+
+    // Should we be talking to a primary or a replica?
+    active_role: Option<Role>,
+
+    // Include the primary into the replica pool?
+    primary_reads_enabled: bool,
+
+    // Should we try to parse queries?
+    query_parser_enabled: bool,
+}
+
+impl QueryRouter {
+    pub fn setup() -> bool {
+        let set = match RegexSet::new(&CUSTOM_SQL_REGEXES) {
+            Ok(rgx) => rgx,
+            Err(err) => {
+                error!("QueryRouter::setup Could not compile regex set: {:?}", err);
+                return false;
+            }
+        };
+
+        match CUSTOM_SQL_REGEX_SET.set(set) {
+            Ok(_) => true,
+            Err(_) => false,
+        }
+    }
+
+    pub fn new() -> QueryRouter {
+        let config = get_config();
+
+        let default_server_role = match config.query_router.default_role.as_ref() {
+            "any" => None,
+            "primary" => Some(Role::Primary),
+            "replica" => Some(Role::Replica),
+            _ => unreachable!(),
+        };
+
+        QueryRouter {
+            default_server_role: default_server_role,
+            shards: config.shards.len(),
+
+            active_role: default_server_role,
+            active_shard: None,
+            primary_reads_enabled: config.query_router.primary_reads_enabled,
+            query_parser_enabled: config.query_router.query_parser_enabled,
+        }
+    }
+
+    /// Try to parse a command and execute it.
+    pub fn try_execute_command(&mut self, mut buf: BytesMut) -> Option<(Command, String)> {
+        let code = buf.get_u8() as char;
+
+        if code != 'Q' {
+            return None;
+        }
+
+        let len = buf.get_i32() as usize;
+        let query = String::from_utf8_lossy(&buf[..len - 5]).to_string(); // Ignore the terminating NULL.
+
+        let regex_set = match CUSTOM_SQL_REGEX_SET.get() {
+            Some(regex_set) => regex_set,
+            None => return None,
+        };
+
+        let matches: Vec<_> = regex_set.matches(&query).into_iter().collect();
+
+        if matches.len() != 1 {
+            return None;
+        }
+
+        let command = match matches[0] {
+            0 => Command::SetShardingKey,
+            1 => Command::SetShard,
+            2 => Command::ShowShard,
+            3 => Command::SetServerRole,
+            4 => Command::ShowServerRole,
+            _ => unreachable!(),
+        };
+
+        let mut value = match command {
+            Command::SetShardingKey | Command::SetShard | Command::SetServerRole => {
+                query.split("'").collect::<Vec<&str>>()[1].to_string()
+            }
+
+            Command::ShowShard => self.shard().to_string(),
+            Command::ShowServerRole => match self.active_role {
+                Some(Role::Primary) => String::from("primary"),
+                Some(Role::Replica) => String::from("replica"),
+                None => {
+                    if self.query_parser_enabled {
+                        String::from("auto")
+                    } else {
+                        String::from("any")
+                    }
+                }
+            },
+        };
+
+        match command {
+            Command::SetShardingKey => {
+                let sharder = Sharder::new(self.shards);
+                let shard = sharder.pg_bigint_hash(value.parse::<i64>().unwrap());
+                self.active_shard = Some(shard);
+                value = shard.to_string();
+            }
+
+            Command::SetShard => {
+                self.active_shard = Some(value.parse::<usize>().unwrap());
+            }
+
+            Command::SetServerRole => {
+                self.active_role = match value.to_ascii_lowercase().as_ref() {
+                    "primary" => {
+                        self.query_parser_enabled = false;
+                        Some(Role::Primary)
+                    }
+
+                    "replica" => {
+                        self.query_parser_enabled = false;
+                        Some(Role::Replica)
+                    }
+
+                    "any" => {
+                        self.query_parser_enabled = false;
+                        None
+                    }
+
+                    "auto" => {
+                        self.query_parser_enabled = true;
+                        None
+                    }
+
+                    "default" => {
+                        // TODO: reset query parser to default here.
+                        self.active_role = self.default_server_role;
+                        self.query_parser_enabled = get_config().query_router.query_parser_enabled;
+                        self.active_role
+                    }
+
+                    _ => unreachable!(),
+                };
+            }
+
+            _ => (),
+        }
+
+        Some((command, value))
+    }
+
+    /// Try to infer which server to connect to based on the contents of the query.
+    pub fn infer_role(&mut self, mut buf: BytesMut) -> bool {
+        let code = buf.get_u8() as char;
+        let len = buf.get_i32() as usize;
+
+        let query = match code {
+            'Q' => String::from_utf8_lossy(&buf[..len - 5]).to_string(),
+            'P' => {
+                let mut start = 0;
+                let mut end;
+
+                // Skip the name of the prepared statement.
+                while buf[start] != 0 && start < buf.len() {
+                    start += 1;
+                }
+                start += 1; // Skip terminating null
+
+                // Find the end of the prepared stmt (\0)
+                end = start;
+                while buf[end] != 0 && end < buf.len() {
+                    end += 1;
+                }
+
+                let query = String::from_utf8_lossy(&buf[start..end]).to_string();
+
+                query.replace("$", "") // Remove placeholders turning them into "values"
+            }
+            _ => return false,
+        };
+
+        let ast = match Parser::parse_sql(&PostgreSqlDialect {}, &query) {
+            Ok(ast) => ast,
+            Err(err) => {
+                debug!("{:?}, query: {}", err, query);
+                return false;
+            }
+        };
+
+        if ast.len() == 0 {
+            return false;
+        }
+
+        match ast[0] {
+            // All transactions go to the primary, probably a write.
+            StartTransaction { .. } => {
+                self.active_role = Some(Role::Primary);
+            }
+
+            // Likely a read-only query
+            Query { .. } => {
+                self.active_role = match self.primary_reads_enabled {
+                    false => Some(Role::Replica), // If primary should not be receiving reads, use a replica.
+                    true => None,                 // Any server role is fine in this case.
+                }
+            }
+
+            // Likely a write
+            _ => {
+                self.active_role = Some(Role::Primary);
+            }
+        };
+
+        true
+    }
+
+    /// Get the current desired server role we should be talking to.
+    pub fn role(&self) -> Option<Role> {
+        self.active_role
+    }
+
+    /// Get desired shard we should be talking to.
+    pub fn shard(&self) -> usize {
+        match self.active_shard {
+            Some(shard) => shard,
+            None => 0,
+        }
+    }
+
+    /// Reset the router back to defaults.
+    /// This must be called at the end of every transaction in transaction mode.
+    pub fn _reset(&mut self) {
+        self.active_role = self.default_server_role;
+        self.active_shard = None;
+    }
+
+    /// Should we attempt to parse queries?
+    pub fn query_parser_enabled(&self) -> bool {
+        self.query_parser_enabled
+    }
+
+    #[allow(dead_code)]
+    pub fn toggle_primary_reads(&mut self, value: bool) {
+        self.primary_reads_enabled = value;
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::messages::simple_query;
+    use bytes::BufMut;
+
+    #[test]
+    fn test_defaults() {
+        QueryRouter::setup();
+        let qr = QueryRouter::new();
+
+        assert_eq!(qr.role(), None);
+    }
+
+    #[test]
+    fn test_infer_role_replica() {
+        QueryRouter::setup();
+        let mut qr = QueryRouter::new();
+        assert!(qr.try_execute_command(simple_query("SET SERVER ROLE TO 'auto'")) != None);
+        assert_eq!(qr.query_parser_enabled(), true);
+        qr.toggle_primary_reads(false);
+
+        let queries = vec![
+            simple_query("SELECT * FROM items WHERE id = 5"),
+            simple_query(
+                "SELECT id, name, value FROM items INNER JOIN prices ON item.id = prices.item_id",
+            ),
+            simple_query("WITH t AS (SELECT * FROM items) SELECT * FROM t"),
+        ];
+
+        for query in queries {
+            // It's a recognized query
+            assert!(qr.infer_role(query));
+            assert_eq!(qr.role(), Some(Role::Replica));
+        }
+    }
+
+    #[test]
+    fn test_infer_role_primary() {
+        QueryRouter::setup();
+        let mut qr = QueryRouter::new();
+
+        let queries = vec![
+            simple_query("UPDATE items SET name = 'pumpkin' WHERE id = 5"),
+            simple_query("INSERT INTO items (id, name) VALUES (5, 'pumpkin')"),
+            simple_query("DELETE FROM items WHERE id = 5"),
+            simple_query("BEGIN"), // Transaction start
+        ];
+
+        for query in queries {
+            // It's a recognized query
+            assert!(qr.infer_role(query));
+            assert_eq!(qr.role(), Some(Role::Primary));
+        }
+    }
+
+    #[test]
+    fn test_infer_role_primary_reads_enabled() {
+        QueryRouter::setup();
+        let mut qr = QueryRouter::new();
+        let query = simple_query("SELECT * FROM items WHERE id = 5");
+        qr.toggle_primary_reads(true);
+
+        assert!(qr.infer_role(query));
+        assert_eq!(qr.role(), None);
+    }
+
+    #[test]
+    fn test_infer_role_parse_prepared() {
+        QueryRouter::setup();
+        let mut qr = QueryRouter::new();
+        qr.try_execute_command(simple_query("SET SERVER ROLE TO 'auto'"));
+        qr.toggle_primary_reads(false);
+
+        let prepared_stmt = BytesMut::from(
+            &b"WITH t AS (SELECT * FROM items WHERE name = $1) SELECT * FROM t WHERE id = $2\0"[..],
+        );
+        let mut res = BytesMut::from(&b"P"[..]);
+        res.put_i32(prepared_stmt.len() as i32 + 4 + 1 + 2);
+        res.put_u8(0);
+        res.put(prepared_stmt);
+        res.put_i16(0);
+
+        assert!(qr.infer_role(res));
+        assert_eq!(qr.role(), Some(Role::Replica));
+    }
+
+    #[test]
+    fn test_regex_set() {
+        QueryRouter::setup();
+
+        let tests = [
+            // Upper case
+            "SET SHARDING KEY TO '1'",
+            "SET SHARD TO '1'",
+            "SHOW SHARD",
+            "SET SERVER ROLE TO 'replica'",
+            "SET SERVER ROLE TO 'primary'",
+            "SET SERVER ROLE TO 'any'",
+            "SET SERVER ROLE TO 'auto'",
+            "SHOW SERVER ROLE",
+            // Lower case
+            "set sharding key to '1'",
+            "set shard to '1'",
+            "show shard",
+            "set server role to 'replica'",
+            "set server role to 'primary'",
+            "set server role to 'any'",
+            "set server role to 'auto'",
+            "show server role",
+        ];
+
+        let set = CUSTOM_SQL_REGEX_SET.get().unwrap();
+
+        for test in &tests {
+            let matches: Vec<_> = set.matches(test).into_iter().collect();
+
+            assert_eq!(matches.len(), 1);
+        }
+    }
+
+    #[test]
+    fn test_try_execute_command() {
+        QueryRouter::setup();
+        let mut qr = QueryRouter::new();
+
+        // SetShardingKey
+        let query = simple_query("SET SHARDING KEY TO '13'");
+        assert_eq!(
+            qr.try_execute_command(query),
+            Some((Command::SetShardingKey, String::from("1")))
+        );
+        assert_eq!(qr.shard(), 1);
+
+        // SetShard
+        let query = simple_query("SET SHARD TO '1'");
+        assert_eq!(
+            qr.try_execute_command(query),
+            Some((Command::SetShard, String::from("1")))
+        );
+        assert_eq!(qr.shard(), 1);
+
+        // ShowShard
+        let query = simple_query("SHOW SHARD");
+        assert_eq!(
+            qr.try_execute_command(query),
+            Some((Command::ShowShard, String::from("1")))
+        );
+
+        // SetServerRole
+        let roles = ["primary", "replica", "any", "auto", "primary"];
+        let verify_roles = [
+            Some(Role::Primary),
+            Some(Role::Replica),
+            None,
+            None,
+            Some(Role::Primary),
+        ];
+        let query_parser_enabled = [false, false, false, true, false];
+
+        for (idx, role) in roles.iter().enumerate() {
+            let query = simple_query(&format!("SET SERVER ROLE TO '{}'", role));
+            assert_eq!(
+                qr.try_execute_command(query),
+                Some((Command::SetServerRole, String::from(*role)))
+            );
+            assert_eq!(qr.role(), verify_roles[idx],);
+            assert_eq!(qr.query_parser_enabled(), query_parser_enabled[idx],);
+
+            // ShowServerRole
+            let query = simple_query("SHOW SERVER ROLE");
+            assert_eq!(
+                qr.try_execute_command(query),
+                Some((Command::ShowServerRole, String::from(*role)))
+            );
+        }
+    }
+
+    #[test]
+    fn test_enable_query_parser() {
+        QueryRouter::setup();
+        let mut qr = QueryRouter::new();
+        let query = simple_query("SET SERVER ROLE TO 'auto'");
+        qr.toggle_primary_reads(false);
+
+        assert!(qr.try_execute_command(query) != None);
+        assert!(qr.query_parser_enabled());
+        assert_eq!(qr.role(), None);
+
+        let query = simple_query("INSERT INTO test_table VALUES (1)");
+        assert_eq!(qr.infer_role(query), true);
+        assert_eq!(qr.role(), Some(Role::Primary));
+
+        let query = simple_query("SELECT * FROM test_table");
+        assert_eq!(qr.infer_role(query), true);
+        assert_eq!(qr.role(), Some(Role::Replica));
+
+        assert!(qr.query_parser_enabled());
+        let query = simple_query("SET SERVER ROLE TO 'default'");
+        assert!(qr.try_execute_command(query) != None);
+        assert!(!qr.query_parser_enabled());
+    }
+}

src/server.rs

@@ -1,43 +1,43 @@
-#![allow(dead_code)]
-#![allow(unused_variables)]
-
+use bytes::{Buf, BufMut, BytesMut};
 ///! Implementation of the PostgreSQL server (database) protocol.
 ///! Here we are pretending to the a Postgres client.
-use bytes::{Buf, BufMut, BytesMut};
+use log::{error, info};
 use tokio::io::{AsyncReadExt, BufReader};
-use tokio::net::tcp::{OwnedReadHalf, OwnedWriteHalf};
-use tokio::net::TcpStream;
+use tokio::net::{
+    tcp::{OwnedReadHalf, OwnedWriteHalf},
+    TcpStream,
+};
 
-use crate::config::Address;
+use crate::config::{Address, User};
+use crate::constants::*;
 use crate::errors::Error;
 use crate::messages::*;
+use crate::stats::Reporter;
 use crate::ClientServerMap;
 
 /// Server state.
 pub struct Server {
-    // Server host, e.g. localhost
-    host: String,
+    // Server host, e.g. localhost,
+    // port, e.g. 5432, and role, e.g. primary or replica.
+    address: Address,
 
-    // Server port: e.g. 5432
-    port: String,
-
-    // Buffered read socket
+    // Buffered read socket.
     read: BufReader<OwnedReadHalf>,
 
-    // Unbuffered write socket (our client code buffers)
+    // Unbuffered write socket (our client code buffers).
     write: OwnedWriteHalf,
 
-    // Our server response buffer
+    // Our server response buffer. We buffer data before we give it to the client.
     buffer: BytesMut,
 
-    // Server information the server sent us over on startup
+    // Server information the server sent us over on startup.
     server_info: BytesMut,
 
     // Backend id and secret key used for query cancellation.
-    backend_id: i32,
+    process_id: i32,
     secret_key: i32,
 
-    // Is the server inside a transaction at the moment.
+    // Is the server inside a transaction or idle.
     in_transaction: bool,
 
     // Is there more data for the client to read.
@@ -48,34 +48,42 @@ pub struct Server {
 
     // Mapping of clients and servers used for query cancellation.
     client_server_map: ClientServerMap,
+
+    // Server connected at.
+    connected_at: chrono::naive::NaiveDateTime,
+
+    // Reports various metrics, e.g. data sent & received.
+    stats: Reporter,
 }
 
 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 mode.
+    /// Perform the authentication and return the server in a ready for query state.
     pub async fn startup(
-        host: &str,
-        port: &str,
-        user: &str,
-        password: &str,
+        address: &Address,
+        user: &User,
         database: &str,
         client_server_map: ClientServerMap,
+        stats: Reporter,
     ) -> Result<Server, Error> {
-        let mut stream = match TcpStream::connect(&format!("{}:{}", host, port)).await {
-            Ok(stream) => stream,
-            Err(err) => {
-                println!(">> Could not connect to server: {}", err);
-                return Err(Error::SocketError);
-            }
-        };
+        let mut stream =
+            match TcpStream::connect(&format!("{}:{}", &address.host, &address.port)).await {
+                Ok(stream) => stream,
+                Err(err) => {
+                    error!("Could not connect to server: {}", err);
+                    return Err(Error::SocketError);
+                }
+            };
 
-        // Send the startup packet.
-        startup(&mut stream, user, database).await?;
+        // Send the startup packet telling the server we're a normal Postgres client.
+        startup(&mut stream, &user.name, database).await?;
 
-        let mut server_info = BytesMut::with_capacity(25);
-        let mut backend_id: i32 = 0;
+        let mut server_info = BytesMut::new();
+        let mut process_id: i32 = 0;
         let mut secret_key: i32 = 0;
 
+        // We'll be handling multiple packets, but they will all be structured the same.
+        // We'll loop here until this exchange is complete.
         loop {
             let code = match stream.read_u8().await {
                 Ok(code) => code as char,
@@ -88,16 +96,18 @@ impl Server {
             };
 
             match code {
+                // Authentication
                 'R' => {
-                    // Auth can proceed
-                    let code = match stream.read_i32().await {
-                        Ok(code) => code,
+                    // Determine which kind of authentication is required, if any.
+                    let auth_code = match stream.read_i32().await {
+                        Ok(auth_code) => auth_code,
                         Err(_) => return Err(Error::SocketError),
                     };
 
-                    match code {
-                        // MD5
-                        5 => {
+                    match auth_code {
+                        MD5_ENCRYPTED_PASSWORD => {
+                            // The salt is 4 bytes.
+                            // See: https://www.postgresql.org/docs/12/protocol-message-formats.html
                             let mut salt = vec![0u8; 4];
 
                             match stream.read_exact(&mut salt).await {
@@ -105,19 +115,20 @@ impl Server {
                                 Err(_) => return Err(Error::SocketError),
                             };
 
-                            md5_password(&mut stream, user, password, &salt[..]).await?;
+                            md5_password(&mut stream, &user.name, &user.password, &salt[..])
+                                .await?;
                         }
 
-                        // Authentication handshake complete.
-                        0 => (),
+                        AUTHENTICATION_SUCCESSFUL => (),
 
                         _ => {
-                            println!(">> Unsupported authentication mechanism: {}", code);
+                            error!("Unsupported authentication mechanism: {}", auth_code);
                             return Err(Error::ServerError);
                         }
                     }
                 }
 
+                // ErrorResponse
                 'E' => {
                     let error_code = match stream.read_u8().await {
                         Ok(error_code) => error_code,
@@ -125,46 +136,62 @@ impl Server {
                     };
 
                     match error_code {
-                        0 => (), // Terminator
+                        // No error message is present in the message.
+                        MESSAGE_TERMINATOR => (),
+
+                        // An error message will be present.
                         _ => {
+                            // Read the error message without the terminating null character.
                             let mut error = vec![0u8; len as usize - 4 - 1];
+
                             match stream.read_exact(&mut error).await {
                                 Ok(_) => (),
                                 Err(_) => return Err(Error::SocketError),
                             };
 
-                            println!(">> Server error: {}", String::from_utf8_lossy(&error));
+                            // TODO: the error message contains multiple fields; we can decode them and
+                            // present a prettier message to the user.
+                            // See: https://www.postgresql.org/docs/12/protocol-error-fields.html
+                            error!("Server error: {}", String::from_utf8_lossy(&error));
                         }
                     };
+
                     return Err(Error::ServerError);
                 }
 
+                // ParameterStatus
                 'S' => {
-                    // Parameter
                     let mut param = vec![0u8; len as usize - 4];
+
                     match stream.read_exact(&mut param).await {
                         Ok(_) => (),
                         Err(_) => return Err(Error::SocketError),
                     };
 
+                    // Save the parameter so we can pass it to the client later.
+                    // These can be server_encoding, client_encoding, server timezone, Postgres version,
+                    // and many more interesting things we should know about the Postgres server we are talking to.
                     server_info.put_u8(b'S');
                     server_info.put_i32(len);
                     server_info.put_slice(&param[..]);
                 }
 
+                // BackendKeyData
                 'K' => {
-                    // Query cancellation data.
-                    backend_id = match stream.read_i32().await {
+                    // The frontend must save these values if it wishes to be able to issue CancelRequest messages later.
+                    // See: https://www.postgresql.org/docs/12/protocol-message-formats.html
+                    process_id = match stream.read_i32().await {
                         Ok(id) => id,
-                        Err(err) => return Err(Error::SocketError),
+                        Err(_) => return Err(Error::SocketError),
                     };
 
                     secret_key = match stream.read_i32().await {
                         Ok(id) => id,
-                        Err(err) => return Err(Error::SocketError),
+                        Err(_) => return Err(Error::SocketError),
                     };
                 }
 
+                // ReadyForQuery
                 'Z' => {
                     let mut idle = vec![0u8; len as usize - 4];
 
@@ -173,34 +200,38 @@ impl Server {
                         Err(_) => return Err(Error::SocketError),
                     };
 
-                    // Startup finished
+                    // This is the last step in the client-server connection setup,
+                    // and indicates the server is ready for to query it.
                     let (read, write) = stream.into_split();
 
                     return Ok(Server {
-                        host: host.to_string(),
-                        port: port.to_string(),
+                        address: address.clone(),
                         read: BufReader::new(read),
                         write: write,
                         buffer: BytesMut::with_capacity(8196),
                         server_info: server_info,
-                        backend_id: backend_id,
+                        process_id: process_id,
                         secret_key: secret_key,
                         in_transaction: false,
                         data_available: false,
                         bad: false,
                         client_server_map: client_server_map,
+                        connected_at: chrono::offset::Utc::now().naive_utc(),
+                        stats: stats,
                     });
                 }
 
+                // We have an unexpected message from the server during this exchange.
+                // Means we implemented the protocol wrong or we're not talking to a Postgres server.
                 _ => {
-                    println!(">> Unknown code: {}", code);
+                    error!("Unknown code: {}", code);
                     return Err(Error::ProtocolSyncError);
                 }
             };
         }
     }
 
-    /// Issue a cancellation request to the server.
+    /// Issue a query cancellation request to the server.
     /// Uses a separate connection that's not part of the connection pool.
     pub async fn cancel(
         host: &str,
@@ -211,33 +242,35 @@ impl Server {
         let mut stream = match TcpStream::connect(&format!("{}:{}", host, port)).await {
             Ok(stream) => stream,
             Err(err) => {
-                println!(">> Could not connect to server: {}", err);
+                error!("Could not connect to server: {}", err);
                 return Err(Error::SocketError);
             }
         };
 
         let mut bytes = BytesMut::with_capacity(16);
         bytes.put_i32(16);
-        bytes.put_i32(80877102);
+        bytes.put_i32(CANCEL_REQUEST_CODE);
         bytes.put_i32(process_id);
         bytes.put_i32(secret_key);
 
         Ok(write_all(&mut stream, bytes).await?)
     }
 
-    /// Send data to the server from the client.
+    /// Send messages to the server from the client.
     pub async fn send(&mut self, messages: BytesMut) -> Result<(), Error> {
+        self.stats.data_sent(messages.len());
+
         match write_all_half(&mut self.write, messages).await {
             Ok(_) => Ok(()),
             Err(err) => {
-                println!(">> Terminating server because of: {:?}", err);
+                error!("Terminating server because of: {:?}", err);
                 self.bad = true;
                 Err(err)
             }
         }
     }
 
-    /// Receive data from the server in response to a client request sent previously.
+    /// Receive data from the server in response to a client request.
     /// This method must be called multiple times while `self.is_data_available()` is true
     /// in order to receive all data the server has to offer.
     pub async fn recv(&mut self) -> Result<BytesMut, Error> {
@@ -245,86 +278,96 @@ impl Server {
             let mut message = match read_message(&mut self.read).await {
                 Ok(message) => message,
                 Err(err) => {
-                    println!(">> Terminating server because of: {:?}", err);
+                    error!("Terminating server because of: {:?}", err);
                     self.bad = true;
                     return Err(err);
                 }
             };
 
-            // Buffer the message we'll forward to the client in a bit.
+            // Buffer the message we'll forward to the client later.
             self.buffer.put(&message[..]);
 
             let code = message.get_u8() as char;
             let _len = message.get_i32();
 
             match code {
+                // ReadyForQuery
                 'Z' => {
-                    // Ready for query, time to forward buffer to client.
                     let transaction_state = message.get_u8() as char;
 
                     match transaction_state {
+                        // In transaction.
                         'T' => {
                             self.in_transaction = true;
                         }
 
+                        // Idle, transaction over.
                         'I' => {
                             self.in_transaction = false;
                         }
 
-                        // Error client didn't clean up!
-                        // We shuold drop this server
+                        // Some error occured, the transaction was rolled back.
                         'E' => {
                             self.in_transaction = true;
                         }
 
+                        // Something totally unexpected, this is not a Postgres server we know.
                         _ => {
                             self.bad = true;
                             return Err(Error::ProtocolSyncError);
                         }
                     };
 
+                    // There is no more data available from the server.
                     self.data_available = false;
 
                     break;
                 }
 
+                // DataRow
                 'D' => {
+                    // More data is available after this message, this is not the end of the reply.
                     self.data_available = true;
 
-                    // Don't flush yet, the more we buffer, the faster this goes.
-                    // Up to a limit of course.
+                    // Don't flush yet, the more we buffer, the faster this goes...
+                    // up to a limit of course.
                     if self.buffer.len() >= 8196 {
                         break;
                     }
                 }
 
-                // CopyInResponse: copy is starting from client to server
+                // CopyInResponse: copy is starting from client to server.
                 'G' => break,
 
-                // CopyOutResponse: copy is starting from the server to the client
+                // CopyOutResponse: copy is starting from the server to the client.
                 'H' => {
                     self.data_available = true;
                     break;
                 }
 
-                // CopyData
+                // CopyData: we are not buffering this one because there will be many more
+                // and we don't know how big this packet could be, best not to take a risk.
                 'd' => break,
 
                 // CopyDone
-                'c' => {
-                    self.data_available = false;
-                    // Buffer until ReadyForQuery shows up
-                }
+                // Buffer until ReadyForQuery shows up, so don't exit the loop yet.
+                'c' => (),
 
-                _ => {
-                    // Keep buffering,
-                }
+                // Anything else, e.g. errors, notices, etc.
+                // Keep buffering until ReadyForQuery shows up.
+                _ => (),
             };
         }
 
         let bytes = self.buffer.clone();
+
+        // Keep track of how much data we got from the server for stats.
+        self.stats.data_received(bytes.len());
+
+        // Clear the buffer for next query.
         self.buffer.clear();
 
+        // Pass the data back to the client.
         Ok(bytes)
     }
 
@@ -354,7 +397,7 @@ impl Server {
 
     /// Indicate that this server connection cannot be re-used and must be discarded.
     pub fn mark_bad(&mut self) {
-        println!(">> Server marked bad");
+        error!("Server marked bad");
         self.bad = true;
     }
 
@@ -364,20 +407,20 @@ impl Server {
         guard.insert(
             (process_id, secret_key),
             (
-                self.backend_id,
+                self.process_id,
                 self.secret_key,
-                self.host.clone(),
-                self.port.clone(),
+                self.address.host.clone(),
+                self.address.port.clone(),
             ),
         );
     }
 
     /// Execute an arbitrary query against the server.
-    /// It will use the Simple query protocol.
+    /// It will use the simple query protocol.
     /// Result will not be returned, so this is useful for things like `SET` or `ROLLBACK`.
     pub async fn query(&mut self, query: &str) -> Result<(), Error> {
         let mut query = BytesMut::from(&query.as_bytes()[..]);
-        query.put_u8(0);
+        query.put_u8(0); // C-string terminator (NULL character).
 
         let len = query.len() as i32 + 4;
 
@@ -388,8 +431,10 @@ impl Server {
         msg.put_slice(&query[..]);
 
         self.send(msg).await?;
+
         loop {
             let _ = self.recv().await?;
+
             if !self.data_available {
                 break;
             }
@@ -399,16 +444,48 @@ impl Server {
     }
 
     /// A shorthand for `SET application_name = $1`.
+    #[allow(dead_code)]
     pub async fn set_name(&mut self, name: &str) -> Result<(), Error> {
         Ok(self
             .query(&format!("SET application_name = '{}'", name))
             .await?)
     }
 
+    /// Get the servers address.
+    #[allow(dead_code)]
     pub fn address(&self) -> Address {
-        Address {
-            host: self.host.to_string(),
-            port: self.port.to_string(),
-        }
+        self.address.clone()
+    }
+
+    pub fn process_id(&self) -> i32 {
+        self.process_id
+    }
+}
+
+impl Drop for Server {
+    /// Try to do a clean shut down. Best effort because
+    /// 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());
+
+        let mut bytes = BytesMut::with_capacity(4);
+        bytes.put_u8(b'X');
+        bytes.put_i32(4);
+
+        match self.write.try_write(&bytes) {
+            Ok(_) => (),
+            Err(_) => (),
+        };
+
+        self.bad = true;
+
+        let now = chrono::offset::Utc::now().naive_utc();
+        let duration = now - self.connected_at;
+
+        info!(
+            "Server connection closed, session duration: {}",
+            crate::format_duration(&duration)
+        );
     }
 }

src/sharding.rs

@@ -18,7 +18,7 @@ impl Sharder {
         let mut lohalf = key as u32;
         let hihalf = (key >> 32) as u32;
         lohalf ^= if key >= 0 { hihalf } else { !hihalf };
-        Self::combine(0, Self::pg_u32_hash(lohalf)) as usize % self.shards as usize
+        Self::combine(0, Self::pg_u32_hash(lohalf)) as usize % self.shards
     }
 
     #[inline]

src/stats.rs

@@ -0,0 +1,348 @@
+use log::info;
+use statsd::Client;
+/// Events collector and publisher.
+use tokio::sync::mpsc::{Receiver, Sender};
+
+use std::collections::HashMap;
+use std::time::Instant;
+
+use crate::config::get_config;
+
+#[derive(Debug, Clone, Copy)]
+enum EventName {
+    CheckoutTime,
+    Query,
+    Transaction,
+    DataSent,
+    DataReceived,
+    ClientWaiting,
+    ClientActive,
+    ClientIdle,
+    ClientDisconnecting,
+    ServerActive,
+    ServerIdle,
+    ServerTested,
+    ServerLogin,
+    ServerDisconnecting,
+}
+
+#[derive(Debug)]
+pub struct Event {
+    name: EventName,
+    value: i64,
+    process_id: Option<i32>,
+}
+
+#[derive(Clone, Debug)]
+pub struct Reporter {
+    tx: Sender<Event>,
+}
+
+impl Reporter {
+    pub fn new(tx: Sender<Event>) -> Reporter {
+        Reporter { tx: tx }
+    }
+
+    pub fn query(&self) {
+        let statistic = Event {
+            name: EventName::Query,
+            value: 1,
+            process_id: None,
+        };
+
+        let _ = self.tx.try_send(statistic);
+    }
+
+    pub fn transaction(&self) {
+        let statistic = Event {
+            name: EventName::Transaction,
+            value: 1,
+            process_id: None,
+        };
+
+        let _ = self.tx.try_send(statistic);
+    }
+
+    pub fn data_sent(&self, amount: usize) {
+        let statistic = Event {
+            name: EventName::DataSent,
+            value: amount as i64,
+            process_id: None,
+        };
+
+        let _ = self.tx.try_send(statistic);
+    }
+
+    pub fn data_received(&self, amount: usize) {
+        let statistic = Event {
+            name: EventName::DataReceived,
+            value: amount as i64,
+            process_id: None,
+        };
+
+        let _ = self.tx.try_send(statistic);
+    }
+
+    pub fn checkout_time(&self, ms: u128) {
+        let statistic = Event {
+            name: EventName::CheckoutTime,
+            value: ms as i64,
+            process_id: None,
+        };
+
+        let _ = self.tx.try_send(statistic);
+    }
+
+    pub fn client_waiting(&self, process_id: i32) {
+        let statistic = Event {
+            name: EventName::ClientWaiting,
+            value: 1,
+            process_id: Some(process_id),
+        };
+
+        let _ = self.tx.try_send(statistic);
+    }
+
+    pub fn client_active(&self, process_id: i32) {
+        let statistic = Event {
+            name: EventName::ClientActive,
+            value: 1,
+            process_id: Some(process_id),
+        };
+
+        let _ = self.tx.try_send(statistic);
+    }
+
+    pub fn client_idle(&self, process_id: i32) {
+        let statistic = Event {
+            name: EventName::ClientIdle,
+            value: 1,
+            process_id: Some(process_id),
+        };
+
+        let _ = self.tx.try_send(statistic);
+    }
+
+    pub fn client_disconnecting(&self, process_id: i32) {
+        let statistic = Event {
+            name: EventName::ClientDisconnecting,
+            value: 1,
+            process_id: Some(process_id),
+        };
+
+        let _ = self.tx.try_send(statistic);
+    }
+
+    pub fn server_active(&self, process_id: i32) {
+        let statistic = Event {
+            name: EventName::ServerActive,
+            value: 1,
+            process_id: Some(process_id),
+        };
+
+        let _ = self.tx.try_send(statistic);
+    }
+
+    pub fn server_idle(&self, process_id: i32) {
+        let statistic = Event {
+            name: EventName::ServerIdle,
+            value: 1,
+            process_id: Some(process_id),
+        };
+
+        let _ = self.tx.try_send(statistic);
+    }
+
+    pub fn server_login(&self, process_id: i32) {
+        let statistic = Event {
+            name: EventName::ServerLogin,
+            value: 1,
+            process_id: Some(process_id),
+        };
+
+        let _ = self.tx.try_send(statistic);
+    }
+
+    pub fn server_tested(&self, process_id: i32) {
+        let statistic = Event {
+            name: EventName::ServerTested,
+            value: 1,
+            process_id: Some(process_id),
+        };
+
+        let _ = self.tx.try_send(statistic);
+    }
+
+    pub fn server_disconnecting(&self, process_id: i32) {
+        let statistic = Event {
+            name: EventName::ServerDisconnecting,
+            value: 1,
+            process_id: Some(process_id),
+        };
+
+        let _ = self.tx.try_send(statistic);
+    }
+}
+
+pub struct Collector {
+    rx: Receiver<Event>,
+    client: Client,
+}
+
+impl Collector {
+    pub fn new(rx: Receiver<Event>) -> Collector {
+        Collector {
+            rx: rx,
+            client: Client::new(&get_config().general.statsd_address, "pgcat").unwrap(),
+        }
+    }
+
+    pub async fn collect(&mut self) {
+        info!("Events reporter started");
+
+        let mut stats = HashMap::from([
+            ("total_query_count", 0),
+            ("total_xact_count", 0),
+            ("total_sent", 0),
+            ("total_received", 0),
+            ("total_wait_time", 0),
+            ("maxwait_us", 0),
+            ("maxwait", 0),
+            ("cl_waiting", 0),
+            ("cl_active", 0),
+            ("cl_idle", 0),
+            ("sv_idle", 0),
+            ("sv_active", 0),
+            ("sv_login", 0),
+            ("sv_tested", 0),
+        ]);
+
+        let mut client_server_states: HashMap<i32, EventName> = HashMap::new();
+
+        let mut now = Instant::now();
+
+        loop {
+            let stat = match self.rx.recv().await {
+                Some(stat) => stat,
+                None => {
+                    info!("Events collector is shutting down");
+                    return;
+                }
+            };
+
+            // Some are counters, some are gauges...
+            match stat.name {
+                EventName::Query => {
+                    let counter = stats.entry("total_query_count").or_insert(0);
+                    *counter += stat.value;
+                }
+
+                EventName::Transaction => {
+                    let counter = stats.entry("total_xact_count").or_insert(0);
+                    *counter += stat.value;
+                }
+
+                EventName::DataSent => {
+                    let counter = stats.entry("total_sent").or_insert(0);
+                    *counter += stat.value;
+                }
+
+                EventName::DataReceived => {
+                    let counter = stats.entry("total_received").or_insert(0);
+                    *counter += stat.value;
+                }
+
+                EventName::CheckoutTime => {
+                    let counter = stats.entry("total_wait_time").or_insert(0);
+                    *counter += stat.value;
+
+                    let counter = stats.entry("maxwait_us").or_insert(0);
+
+                    // Report max time here
+                    if stat.value > *counter {
+                        *counter = stat.value;
+                    }
+
+                    let counter = stats.entry("maxwait").or_insert(0);
+                    let seconds = *counter / 1_000_000;
+
+                    if seconds > *counter {
+                        *counter = seconds;
+                    }
+                }
+
+                EventName::ClientActive
+                | EventName::ClientWaiting
+                | EventName::ClientIdle
+                | EventName::ServerActive
+                | EventName::ServerIdle
+                | EventName::ServerTested
+                | EventName::ServerLogin => {
+                    client_server_states.insert(stat.process_id.unwrap(), stat.name);
+                }
+
+                EventName::ClientDisconnecting | EventName::ServerDisconnecting => {
+                    client_server_states.remove(&stat.process_id.unwrap());
+                }
+            };
+
+            // It's been 15 seconds. If there is no traffic, it won't publish anything,
+            // but it also doesn't matter then.
+            if now.elapsed().as_secs() > 15 {
+                for (_, state) in &client_server_states {
+                    match state {
+                        EventName::ClientActive => {
+                            let counter = stats.entry("cl_active").or_insert(0);
+                            *counter += 1;
+                        }
+
+                        EventName::ClientWaiting => {
+                            let counter = stats.entry("cl_waiting").or_insert(0);
+                            *counter += 1;
+                        }
+
+                        EventName::ClientIdle => {
+                            let counter = stats.entry("cl_idle").or_insert(0);
+                            *counter += 1;
+                        }
+
+                        EventName::ServerIdle => {
+                            let counter = stats.entry("sv_idle").or_insert(0);
+                            *counter += 1;
+                        }
+
+                        EventName::ServerActive => {
+                            let counter = stats.entry("sv_active").or_insert(0);
+                            *counter += 1;
+                        }
+
+                        EventName::ServerTested => {
+                            let counter = stats.entry("sv_tested").or_insert(0);
+                            *counter += 1;
+                        }
+
+                        EventName::ServerLogin => {
+                            let counter = stats.entry("sv_login").or_insert(0);
+                            *counter += 1;
+                        }
+
+                        _ => unreachable!(),
+                    };
+                }
+
+                info!("{:?}", stats);
+
+                let mut pipeline = self.client.pipeline();
+
+                for (key, value) in stats.iter_mut() {
+                    pipeline.gauge(key, *value as f64);
+                    *value = 0;
+                }
+
+                pipeline.send(&self.client);
+
+                now = Instant::now();
+            }
+        }
+    }
+}

tests/ruby/.ruby-version

@@ -0,0 +1 @@
+2.7.1

tests/ruby/Gemfile

@@ -0,0 +1,4 @@
+source "https://rubygems.org"
+
+gem "pg"
+gem "activerecord"

tests/ruby/Gemfile.lock

@@ -0,0 +1,30 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    activemodel (7.0.2.2)
+      activesupport (= 7.0.2.2)
+    activerecord (7.0.2.2)
+      activemodel (= 7.0.2.2)
+      activesupport (= 7.0.2.2)
+    activesupport (7.0.2.2)
+      concurrent-ruby (~> 1.0, >= 1.0.2)
+      i18n (>= 1.6, < 2)
+      minitest (>= 5.1)
+      tzinfo (~> 2.0)
+    concurrent-ruby (1.1.9)
+    i18n (1.10.0)
+      concurrent-ruby (~> 1.0)
+    minitest (5.15.0)
+    pg (1.3.2)
+    tzinfo (2.0.4)
+      concurrent-ruby (~> 1.0)
+
+PLATFORMS
+  x86_64-linux
+
+DEPENDENCIES
+  activerecord
+  pg
+
+BUNDLED WITH
+   2.3.7

tests/ruby/tests.rb

@@ -1,11 +1,112 @@
-require 'pg'
+# frozen_string_literal: true
 
-conn = PG.connect(host: '127.0.0.1', port: 5433, dbname: 'test')
+require 'active_record'
 
-conn.exec( "SELECT * FROM pg_stat_activity" ) do |result|
-  puts "     PID | User             | Query"
-  result.each do |row|
-    puts " %7d | %-16s | %s " %
-      row.values_at('pid', 'usename', 'query')
+# Uncomment these two to see all queries.
+# ActiveRecord.verbose_query_logs = true
+# ActiveRecord::Base.logger = Logger.new(STDOUT)
+
+ActiveRecord::Base.establish_connection(
+  adapter: 'postgresql',
+  host: '127.0.0.1',
+  port: 6432,
+  username: 'sharding_user',
+  password: 'sharding_user',
+  database: 'rails_dev',
+  prepared_statements: false, # Transaction mode
+  advisory_locks: false # Same
+)
+
+class TestSafeTable < ActiveRecord::Base
+  self.table_name = 'test_safe_table'
+end
+
+class ShouldNeverHappenException < RuntimeError
+end
+
+class CreateSafeShardedTable < ActiveRecord::Migration[7.0]
+  # Disable transasctions or things will fly out of order!
+  disable_ddl_transaction!
+
+  SHARDS = 3
+
+  def up
+    SHARDS.times do |x|
+      # This will make this migration reversible!
+      connection.execute "SET SHARD TO '#{x.to_i}'"
+      connection.execute "SET SERVER ROLE TO 'primary'"
+
+      connection.execute <<-SQL
+        CREATE TABLE test_safe_table (
+          id BIGINT PRIMARY KEY,
+          name VARCHAR,
+          description TEXT
+        ) PARTITION BY HASH (id);
+
+        CREATE TABLE test_safe_table_data PARTITION OF test_safe_table
+        FOR VALUES WITH (MODULUS #{SHARDS.to_i}, REMAINDER #{x.to_i});
+      SQL
+    end
   end
-end
+
+  def down
+    SHARDS.times do |x|
+      connection.execute "SET SHARD TO '#{x.to_i}'"
+      connection.execute "SET SERVER ROLE TO 'primary'"
+      connection.execute 'DROP TABLE test_safe_table CASCADE'
+    end
+  end
+end
+
+SHARDS = 3
+
+2.times do
+  begin
+    CreateSafeShardedTable.migrate(:down)
+  rescue Exception
+    puts "Tables don't exist yet"
+  end
+
+  CreateSafeShardedTable.migrate(:up)
+
+  SHARDS.times do |x|
+    TestSafeTable.connection.execute "SET SHARD TO '#{x.to_i}'"
+    TestSafeTable.connection.execute "SET SERVER ROLE TO 'primary'"
+    TestSafeTable.connection.execute "TRUNCATE #{TestSafeTable.table_name}"
+  end
+
+  # Equivalent to Makara's stick_to_master! except it sticks until it's changed.
+  TestSafeTable.connection.execute "SET SERVER ROLE TO 'primary'"
+
+  200.times do |x|
+    x += 1 # Postgres ids start at 1
+    TestSafeTable.connection.execute "SET SHARDING KEY TO '#{x.to_i}'"
+    TestSafeTable.create(id: x, name: "something_special_#{x.to_i}", description: "It's a surprise!")
+  end
+
+  TestSafeTable.connection.execute "SET SERVER ROLE TO 'replica'"
+
+  100.times do |x|
+    x += 1 # 0 confuses our sharding function
+    TestSafeTable.connection.execute "SET SHARDING KEY TO '#{x.to_i}'"
+    TestSafeTable.find_by_id(x).id
+  end
+
+  # Will use the query parser to direct reads to replicas
+  TestSafeTable.connection.execute "SET SERVER ROLE TO 'auto'"
+
+  100.times do |x|
+    x += 101
+    TestSafeTable.connection.execute "SET SHARDING KEY TO '#{x.to_i}'"
+    TestSafeTable.find_by_id(x).id
+  end
+end
+
+# Test wrong shard
+TestSafeTable.connection.execute "SET SHARD TO '1'"
+begin
+  TestSafeTable.create(id: 5, name: 'test', description: 'test description')
+  raise ShouldNeverHappenException('Uh oh')
+rescue ActiveRecord::StatementInvalid
+  puts 'OK'
+end

tests/sharding/partition_hash_test_setup.sql

@@ -23,4 +23,4 @@ SELECT * FROM shard_0 ORDER BY id LIMIT 10;
 SELECT * FROM shard_1 ORDER BY id LIMIT 10;
 SELECT * FROM shard_2 ORDER BY id LIMIT 10;
 SELECT * FROM shard_3 ORDER BY id LIMIT 10;
-SELECT * FROM shard_4 ORDER BY id LIMIT 10;
+SELECT * FROM shard_4 ORDER BY id LIMIT 10;

tests/sharding/query_routing.sh

@@ -1,12 +1,19 @@
 #/bin/bash
+set -e
 
 # Setup all the shards.
-sudo service postgresql restart
+# sudo service postgresql restart
 
-psql -f query_routing_setup.sql
+echo "Giving Postgres 5 seconds to start up..."
+
+# sleep 5
+
+# psql -f query_routing_setup.sql
 
 psql -h 127.0.0.1 -p 6432 -f query_routing_test_insert.sql
 
 psql -h 127.0.0.1 -p 6432 -f query_routing_test_select.sql
 
-psql -f query_routing_test_validate.sql
+psql -e -h 127.0.0.1 -p 6432 -f query_routing_test_primary_replica.sql
+
+psql -f query_routing_test_validate.sql

tests/sharding/query_routing_setup.sql

@@ -58,4 +58,4 @@ GRANT ALL ON TABLE data TO sharding_user;
 
 \c shard2
 GRANT ALL ON SCHEMA public TO sharding_user;
-GRANT ALL ON TABLE data TO sharding_user;
+GRANT ALL ON TABLE data TO sharding_user;

tests/sharding/query_routing_test_insert.sql

@@ -1,3 +1,5 @@
+\set ON_ERROR_STOP on
+
 SET SHARDING KEY TO '1';
 INSERT INTO data (id, value) VALUES (1, 'value_1');
 
@@ -44,4 +46,10 @@ SET SHARDING KEY TO '15';
 INSERT INTO data (id, value) VALUES (15, 'value_1');
 
 SET SHARDING KEY TO '16';
-INSERT INTO data (id, value) VALUES (16, 'value_1');
+INSERT INTO data (id, value) VALUES (16, 'value_1');
+
+set sharding key to '17';
+INSERT INTO data (id, value) VALUES (17, 'value_1');
+
+SeT SHaRDInG KeY to '18';
+INSERT INTO data (id, value) VALUES (18, 'value_1');

tests/sharding/query_routing_test_primary_replica.sql

@@ -0,0 +1,153 @@
+\set ON_ERROR_STOP on
+
+SET SERVER ROLE TO 'primary';
+SET SHARDING KEY TO '1';
+INSERT INTO data (id, value) VALUES (1, 'value_1');
+
+SET SERVER ROLE TO 'replica';
+SET SHARDING KEY TO '1';
+SELECT * FROM data WHERE id = 1;
+
+---
+
+SET SERVER ROLE TO 'primary';
+SET SHARDING KEY TO '2';
+INSERT INTO data (id, value) VALUES (2, 'value_1');
+
+SET SERVER ROLE TO 'replica';
+SET SHARDING KEY TO '2';
+SELECT * FROM data WHERE id = 2;
+
+---
+
+SET SERVER ROLE TO 'primary';
+SET SHARDING KEY TO '3';
+INSERT INTO data (id, value) VALUES (3, 'value_1');
+
+SET SERVER ROLE TO 'replica';
+SET SHARDING KEY TO '3';
+SELECT * FROM data WHERE id = 3;
+
+---
+
+SET SERVER ROLE TO 'primary';
+SET SHARDING KEY TO '4';
+INSERT INTO data (id, value) VALUES (4, 'value_1');
+
+SET SERVER ROLE TO 'replica';
+SET SHARDING KEY TO '4';
+SELECT * FROM data WHERE id = 4;
+
+---
+
+SET SERVER ROLE TO 'primary';
+SET SHARDING KEY TO '5';
+INSERT INTO data (id, value) VALUES (5, 'value_1');
+
+SET SERVER ROLE TO 'replica';
+SET SHARDING KEY TO '5';
+SELECT * FROM data WHERE id = 5;
+
+---
+
+SET SERVER ROLE TO 'primary';
+SET SHARDING KEY TO '6';
+INSERT INTO data (id, value) VALUES (6, 'value_1');
+
+SET SERVER ROLE TO 'replica';
+SET SHARDING KEY TO '6';
+SELECT * FROM data WHERE id = 6;
+
+---
+
+SET SERVER ROLE TO 'primary';
+SET SHARDING KEY TO '7';
+INSERT INTO data (id, value) VALUES (7, 'value_1');
+
+SET SERVER ROLE TO 'replica';
+SET SHARDING KEY TO '7';
+SELECT * FROM data WHERE id = 7;
+
+---
+
+SET SERVER ROLE TO 'primary';
+SET SHARDING KEY TO '8';
+INSERT INTO data (id, value) VALUES (8, 'value_1');
+
+SET SERVER ROLE TO 'replica';
+SET SHARDING KEY TO '8';
+SELECT * FROM data WHERE id = 8;
+
+---
+
+SET SERVER ROLE TO 'primary';
+SET SHARDING KEY TO '9';
+INSERT INTO data (id, value) VALUES (9, 'value_1');
+
+SET SERVER ROLE TO 'replica';
+SET SHARDING KEY TO '9';
+SELECT * FROM data WHERE id = 9;
+
+---
+
+\set ON_ERROR_STOP on
+
+SET SERVER ROLE TO 'primary';
+SET SHARDING KEY TO '10';
+INSERT INTO data (id, value) VALUES (10, 'value_1');
+
+SET SERVER ROLE TO 'replica';
+SET SHARDING KEY TO '10';
+SELECT * FROM data WHERE id = 10;
+
+---
+
+SET SERVER ROLE TO 'primary';
+SET SHARDING KEY TO '11';
+INSERT INTO data (id, value) VALUES (11, 'value_1');
+
+SET SERVER ROLE TO 'replica';
+SET SHARDING KEY TO '11';
+SELECT * FROM data WHERE id = 11;
+
+---
+
+SET SERVER ROLE TO 'primary';
+SET SHARDING KEY TO '12';
+INSERT INTO data (id, value) VALUES (12, 'value_1');
+
+SET SERVER ROLE TO 'replica';
+SET SHARDING KEY TO '12';
+SELECT * FROM data WHERE id = 12;
+
+---
+
+SET SERVER ROLE TO 'primary';
+SET SHARDING KEY TO '13';
+INSERT INTO data (id, value) VALUES (13, 'value_1');
+
+SET SERVER ROLE TO 'replica';
+SET SHARDING KEY TO '13';
+SELECT * FROM data WHERE id = 13;
+
+---
+
+SET SERVER ROLE TO 'primary';
+SET SHARDING KEY TO '14';
+INSERT INTO data (id, value) VALUES (14, 'value_1');
+
+SET SERVER ROLE TO 'replica';
+SET SHARDING KEY TO '14';
+SELECT * FROM data WHERE id = 14;
+
+---
+
+SET SERVER ROLE TO 'primary';
+SELECT 1;
+
+SET SERVER ROLE TO 'replica';
+SELECT 1;
+
+set server role to 'replica';
+SeT SeRver Role TO 'PrImARY';
+select 1;

tests/sharding/query_routing_test_select.sql

@@ -1,3 +1,5 @@
+\set ON_ERROR_STOP on
+
 SET SHARDING KEY TO '1';
 SELECT * FROM data WHERE id = 1;
 
@@ -44,4 +46,4 @@ SET SHARDING KEY TO '15';
 SELECT * FROM data WHERE id = 15;
 
 SET SHARDING KEY TO '16';
-SELECT * FROM data WHERE id = 16;
+SELECT * FROM data WHERE id = 16;

tests/sharding/query_routing_test_validate.sql

@@ -8,4 +8,4 @@ SELECT * FROM data;
 
 \c shard2
 
-SELECT * FROM data;
+SELECT * FROM data;