pg_wal2redis

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Send Postgresql database changes to a redis instance, and keep it updated.

Far from being "production ready", but not that far. It just works.

Constraint: table must have a PK, and on a single field; composite PKs are (still) not supported

IMPORTANT: use of this code in business context is strictly forbidden unless with explicit consent.

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Small HOWTO

Change config files.

Terminal 1:

$ python3 pg_wal2redis.py

Terminal 2:

$ pgbench -i -h 127.0.0.1 -Umyuser postgres -p5445
$ pgbench    -h 127.0.0.1 -Umyuser postgres -p5445 -s10

and/or

$ psql -h 127.0.0.1 -Umyuser postgres -p5445
=# UPDATE pgbench_accounts set abalance = 777 where aid=1;

Terminal 3:

$ docker run --name some-redis -p 6379:6379 --rm  -d redis

$ docker exec -it some-redis redis-cli
127.0.0.1:6379> hgetall accounts_balance:1

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Requisites

• A running Postgresql, with logical replication enabled and wal2json plugin enabled
• A logical replication slot, as in select pg_create_logical_replication_slot('pg_wal2redis', 'wal2json');
• python 3.10
• psycopg2-binary==2.9.1
• redis===4.3.4

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TODO

• Check if transaction is committed before changing the cache