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fixed health check; sharding setup and tests

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This commit is contained in:
Lev Kokotov
2022-02-08 15:48:28 -08:00
parent eb682db52e
commit 9657256adf
9 changed files with 206 additions and 8 deletions
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2
README.md
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@@ -66,7 +66,7 @@ either lose 1/x of your traffic or risk losing it all eventually. Ideally you ov
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/setup.sql` for more details on the implementation.
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.

16
pgcat.toml
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@@ -32,8 +32,8 @@ ban_time = 60 # Seconds
#
# User to use for authentication against the server.
[user]
name = "lev"
password = "lev"
name = "sharding_user"
password = "sharding_user"
#
@@ -49,7 +49,7 @@ servers = [
[ "localhost", 5432 ],
]
# Database name (e.g. "postgres")
database = "lev"
database = "shard0"
[shards.1]
# [ host, port ]
@@ -57,4 +57,12 @@ servers = [
[ "127.0.0.1", 5432 ],
[ "localhost", 5432 ],
]
database = "lev"
database = "shard1"
[shards.2]
# [ host, port ]
servers = [
[ "127.0.0.1", 5432 ],
[ "localhost", 5432 ],
]
database = "shard2"

14
src/pool.rs
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@@ -185,6 +185,8 @@ impl ConnectionPool {
)
.await
{
// Check if health check succeeded
Ok(res) => match res {
Ok(_) => return Ok((conn, address)),
Err(_) => {
println!(
@@ -194,6 +196,16 @@ impl ConnectionPool {
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);
continue;
}
}
}
}
@@ -280,7 +292,7 @@ impl ManageConnection for ServerPool {
/// Attempts to create a new connection.
async fn connect(&self) -> Result<Self::Connection, Self::Error> {
println!(">> Getting new connection from the pool");
println!(">> Creating a new connection for the pool");
Server::startup(
&self.address.host,

0
tests/sharding/setup.sql → tests/sharding/partition_hash_test_setup.sql
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12
tests/sharding/query_routing.sh Normal file
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@@ -0,0 +1,12 @@
#/bin/bash
# Setup all the shards.
sudo service postgresql restart
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

61
tests/sharding/query_routing_setup.sql Normal file
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@@ -0,0 +1,61 @@
DROP DATABASE IF EXISTS shard0;
DROP DATABASE IF EXISTS shard1;
DROP DATABASE IF EXISTS shard2;
CREATE DATABASE shard0;
CREATE DATABASE shard1;
CREATE DATABASE shard2;
\c shard0
DROP TABLE IF EXISTS data CASCADE;
CREATE TABLE data (
id BIGINT,
value VARCHAR
) PARTITION BY HASH (id);
CREATE TABLE data_shard_0 PARTITION OF data FOR VALUES WITH (MODULUS 3, REMAINDER 0);
\c shard1
DROP TABLE IF EXISTS data CASCADE;
CREATE TABLE data (
id BIGINT,
value VARCHAR
) PARTITION BY HASH (id);
CREATE TABLE data_shard_1 PARTITION OF data FOR VALUES WITH (MODULUS 3, REMAINDER 1);
\c shard2
DROP TABLE IF EXISTS data CASCADE;
CREATE TABLE data (
id BIGINT,
value VARCHAR
) PARTITION BY HASH (id);
CREATE TABLE data_shard_2 PARTITION OF data FOR VALUES WITH (MODULUS 3, REMAINDER 2);
DROP ROLE IF EXISTS sharding_user;
CREATE ROLE sharding_user ENCRYPTED PASSWORD 'sharding_user' LOGIN;
GRANT CONNECT ON DATABASE shard0 TO sharding_user;
GRANT CONNECT ON DATABASE shard1 TO sharding_user;
GRANT CONNECT ON DATABASE shard2 TO sharding_user;
\c shard0
GRANT ALL ON SCHEMA public TO sharding_user;
GRANT ALL ON TABLE data TO sharding_user;
\c shard1
GRANT ALL ON SCHEMA public TO sharding_user;
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;

47
tests/sharding/query_routing_test_insert.sql Normal file
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@@ -0,0 +1,47 @@
SET SHARDING KEY TO '1';
INSERT INTO data (id, value) VALUES (1, 'value_1');
SET SHARDING KEY TO '2';
INSERT INTO data (id, value) VALUES (2, 'value_1');
SET SHARDING KEY TO '3';
INSERT INTO data (id, value) VALUES (3, 'value_1');
SET SHARDING KEY TO '4';
INSERT INTO data (id, value) VALUES (4, 'value_1');
SET SHARDING KEY TO '5';
INSERT INTO data (id, value) VALUES (5, 'value_1');
SET SHARDING KEY TO '6';
INSERT INTO data (id, value) VALUES (6, 'value_1');
SET SHARDING KEY TO '7';
INSERT INTO data (id, value) VALUES (7, 'value_1');
SET SHARDING KEY TO '8';
INSERT INTO data (id, value) VALUES (8, 'value_1');
SET SHARDING KEY TO '9';
INSERT INTO data (id, value) VALUES (9, 'value_1');
SET SHARDING KEY TO '10';
INSERT INTO data (id, value) VALUES (10, 'value_1');
SET SHARDING KEY TO '11';
INSERT INTO data (id, value) VALUES (11, 'value_1');
SET SHARDING KEY TO '12';
INSERT INTO data (id, value) VALUES (12, 'value_1');
SET SHARDING KEY TO '13';
INSERT INTO data (id, value) VALUES (13, 'value_1');
SET SHARDING KEY TO '14';
INSERT INTO data (id, value) VALUES (14, 'value_1');
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');

47
tests/sharding/query_routing_test_select.sql Normal file
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@@ -0,0 +1,47 @@
SET SHARDING KEY TO '1';
SELECT * FROM data WHERE id = 1;
SET SHARDING KEY TO '2';
SELECT * FROM data WHERE id = 2;
SET SHARDING KEY TO '3';
SELECT * FROM data WHERE id = 3;
SET SHARDING KEY TO '4';
SELECT * FROM data WHERE id = 4;
SET SHARDING KEY TO '5';
SELECT * FROM data WHERE id = 5;
SET SHARDING KEY TO '6';
SELECT * FROM data WHERE id = 6;
SET SHARDING KEY TO '7';
SELECT * FROM data WHERE id = 7;
SET SHARDING KEY TO '8';
SELECT * FROM data WHERE id = 8;
SET SHARDING KEY TO '9';
SELECT * FROM data WHERE id = 9;
SET SHARDING KEY TO '10';
SELECT * FROM data WHERE id = 10;
SET SHARDING KEY TO '11';
SELECT * FROM data WHERE id = 11;
SET SHARDING KEY TO '12';
SELECT * FROM data WHERE id = 12;
SET SHARDING KEY TO '13';
SELECT * FROM data WHERE id = 13;
SET SHARDING KEY TO '14';
SELECT * FROM data WHERE id = 14;
SET SHARDING KEY TO '15';
SELECT * FROM data WHERE id = 15;
SET SHARDING KEY TO '16';
SELECT * FROM data WHERE id = 16;

11
tests/sharding/query_routing_test_validate.sql Normal file
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@@ -0,0 +1,11 @@
\c shard0
SELECT * FROM data;
\c shard1
SELECT * FROM data;
\c shard2
SELECT * FROM data;