github.com/immutable/pglogrepl

pglogrepl

pglogrepl is a Go package for PostgreSQL logical replication.

pglogrepl uses package github.com/jackc/pgx/v5/pgconn as its underlying PostgreSQL connection.

Proper use of this package requires understanding the underlying PostgreSQL concepts. See https://www.postgresql.org/docs/current/protocol-replication.html.

Example

In example/pglogrepl_demo, there is an example demo program that connects to a database and logs all messages sent over logical replication. In example/pgphysrepl_demo, there is an example demo program that connects to a database and logs all messages sent over physical replication.

Testing

Testing requires a user with replication permission, a database to replicate, access allowed in pg_hba.conf, and logical replication enabled in postgresql.conf.

Create a database:

create database pglogrepl;

Create a user:

create user pglogrepl with replication password 'secret';

If you're using PostgreSQL 15 or newer grant access to the public schema, just for these tests:

grant all on schema public to pglogrepl;

Add a replication line to your pg_hba.conf:

host replication pglogrepl 127.0.0.1/32 md5

Change the following settings in your postgresql.conf:

wal_level=logical
max_wal_senders=5
max_replication_slots=5

To run the tests set PGLOGREPL_TEST_CONN_STRING environment variable with a replication connection string (URL or DSN).

Since the base backup would request postgres to create a backup tar and stream it, this test cn be disabled with

PGLOGREPL_SKIP_BASE_BACKUP=true

Example:

PGLOGREPL_TEST_CONN_STRING=postgres://pglogrepl:secret@127.0.0.1/pglogrepl?replication=database go test