Postgres cluster with streaming replication and pgpool

pgpool.yaml

version: '3.8'

services:

  pgmaster:
    image: bitnami/postgresql:latest
    ports:
      - 5432
    volumes:
      - pgmaster_data:/bitnami/postgresql
    environment:
      - POSTGRESQL_REPLICATION_MODE=master
      - POSTGRESQL_REPLICATION_USER=postgres
      - POSTGRESQL_REPLICATION_PASSWORD=s3cret
      - POSTGRESQL_PASSWORD=s3cret
      - POSTGRESQL_DATABASE=platform

  pgslave:
    image: bitnami/postgresql:latest
    ports:
      - 5432
    depends_on:
      - pgmaster
    environment:
      - POSTGRESQL_REPLICATION_MODE=slave
      - POSTGRESQL_REPLICATION_USER=postgres
      - POSTGRESQL_REPLICATION_PASSWORD=s3cret
      - POSTGRESQL_MASTER_HOST=pgmaster
      - POSTGRESQL_PASSWORD=s3cret

  pgpool:
    image: docker.io/bitnami/pgpool:latest
    ports:
      - 5432:5432
    depends_on:
      - pgmaster
    volumes:
      - ./pgpool.conf:/config/pgpool.conf
    environment:
      - PGPOOL_USER_CONF_FILE=/config/pgpool.conf
      - PGPOOL_BACKEND_NODES=0:pgmaster:5432:4:master:ALWAYS_MASTER,1:pgslave:5432:6:replica1
      - PGPOOL_SR_CHECK_USER=postgres
      - PGPOOL_SR_CHECK_PASSWORD=s3cret
      - PGPOOL_ENABLE_LDAP=no
      - PGPOOL_POSTGRES_USERNAME=postgres
      - PGPOOL_POSTGRES_PASSWORD=s3cret
      - PGPOOL_ADMIN_USERNAME=admin
      - PGPOOL_ADMIN_PASSWORD=s3cret
      - PGPOOL_ENABLE_LOAD_BALANCING=yes
      - PGPOOL_ENABLE_STATEMENT_LOAD_BALANCING=yes
      - PGPOOL_NUM_INIT_CHILDREN=10
      - PGPOOL_MAX_POOL=1
      - PGPOOL_EXTRA_FLAGS=-d

volumes:
  pgmaster_data:

Hello @petre-c The env variable is used to define the nodes in pgPool cluster. You can see more detailed info here: https://github.com/bitnami/containers/blob/a5510700758f036fc681f43eea79c33d49c8e11a/bitnami/pgpool/4/debian-12/rootfs/opt/bitnami/scripts/libpgpool.sh#L179-L192.
To illustrate the example this specific line 0:pgmaster:5432:4:master:ALWAYS_MASTER,1:pgslave:5432:6:replica1 describes a 2 nodes cluster:

1. Master

• NodeID=0
• Host=pgmaster
• Port=5432
• Weight=4 (40%)
• DataDir=master

2. Replica

• NodeID=1
• Host=pgslave
• Port=5432
• Weight=6 (60%)
• DataDir =replica1

As per the code: https://github.com/bitnami/containers/blob/main/bitnami/pgpool/4/debian-12/rootfs/opt/bitnami/scripts/libpgpool.sh#L401-L427, it will result in pgpool config snippet as follows:

backend_hostname0 = 'pgmaster'
backend_port0 = 5432
backend_weight0 = 4
backend_data_directory0 = 'master'

backend_hostname1 = 'pgslave'
backend_port1 = 5432
backend_weight1 = 6
backend_data_directory1 = 'replica1'

You can see an example of this in the docs: https://www.pgpool.net/docs/latest/en/html/example-replication-mode.html#EXAMPLE-REPLICATION-MODE-BACKEND-SETTINGS