This gist has a detailed explanation on how to setup a master-slave replication with Postgres using docker.

Master configuration

Create replication_user

CREATE USER replication_user NOSUPERUSER;ALTER USER replication_user WITH REPLICATION;ALTER USER replication_user WITH PASSWORD 'CHANGEME';

postgresql.conf

Edit or add these lines:

listen_addresses = '*'   # It can be more specific with the listen IPwal_level = hot_standby  max_wal_sender = 5       #  Specifies the maximum number of concurrent connections from standby serversssl = offarchive_mode = on   archive_command = "cp %p /path/to/archive/%f"

pg_hba.conf

Let's suppose that 192.168.0.2/32 is the IP of the slave and replication_user is the replication user.

case no authentication is required

 host  replication   replication_user   192.168.0.2/32      trust

case authentication using password

 host  replication   replication_user   192.168.0.2/32      scram-sha-256 # or MD5

Slave configuration

Let's suppose that the Master IP is: 192.168.0.1 and the port is the default (5432).

listen_addresses = '*'primary_conninfo = 'user=replication_user password=CHANGEME host=192.168.0.1 port=5432'hot_standby = on

Making the configuration persistent

You can use docker volumes (or for kubernetes).Start by creating the configuration files in the local machine that start the containers and then:

docker run --rm --name IMAGE_NAME -v /local/path/to/postgresql.conf:/etc/postgresql/postgresql.conf -v /local/path/to/pg_hba.conf:/var/lib/postgresql/data/pg_hba.conf CONTAINER_NAME

The same for the slaves.

sources:

https://wiki.postgresql.org/wiki/Streaming_Replication

https://gist.github.com/avshabanov/eb8e03a050c79f8e77420b06f9b4abe5