Cluster

Master primary

Swarm config primary

- name: Deploy Postgres on Docker Swarm
  hosts: vps
  tasks:
    - name: Creazione config pg_hba.conf
      community.docker.docker_config:
        name: postgres-master-hba
        data: "{{ lookup('file', './config/pg_hba.conf') | b64encode }}"
        data_is_b64: true
        state: present

    - name: Creazione config postgresql.conf
      community.docker.docker_config:
        name: postgres-master-conf
        data: "{{ lookup('file', './config/postgresql.conf') | b64encode }}"
        data_is_b64: true
        state: present

    - name: Deploy Postgres service
      community.docker.docker_swarm_service:
        name: postgres-primary
        image: postgres:17
        state: present
        env:
          POSTGRES_USER: postgres
          POSTGRES_PASSWORD: postgres
          POSTGRES_DB: test
        configs:
          - config_name: postgres-master-hba
            filename: /conf-postgres/pg_hba.conf
            mode: "777"
            uid: "999"
            gid: "999"
          - config_name: postgres-master-conf
            filename: /conf-postgres/postgresql.conf
            mode: "777"
            uid: "999"
            gid: "999"
        mounts:
          - type: volume
            source: postgres-primary
            target: /var/lib/postgresql/data
        args:
          [
            "postgres",
            "-c", "config_file=/conf-postgres/postgresql.conf",
            "-c", "hba_file=/conf-postgres/pg_hba.conf"
          ]
        restart_config:
          condition: any
        placement:
          constraints:
            - node.role == manager
        networks:
          - front
        mode: replicated
        replicas: 1
        endpoint_mode: dnsrr

Slave

Swarm config replica

- name: Deploy Postgres on Docker Swarm
  hosts: vps
  tasks:
    - name: Deploy Postgres replica
      community.docker.docker_swarm_service:
        name: postgres-replica
        image: postgres:17
        user: "postgres"
        state: present
        env:
          POSTGRES_USER: postgres
          POSTGRES_PASSWORD: postgres
        mounts:
          - type: volume
            source: postgres-replica
            target: /var/lib/postgresql/data
        args:
          [
            "bash",
            "-c",
            "chown -R 999:999 /var/lib/postgresql/data && chmod 700 /var/lib/postgresql/data && \
             if [ ! -s /var/lib/postgresql/data/PG_VERSION ]; then \
               pg_basebackup -h postgres-primary -D /var/lib/postgresql/data -U postgres -Fp -Xs -P -R -S replica1; \
             fi && \
             exec postgres"
          ]
        restart_config:
          condition: any
        placement:
          constraints:
            - node.role == manager
        networks:
          - front
        mode: replicated
        replicas: 1
        endpoint_mode: dnsrr

postgresql.conf

listen_addresses = '*'
port = 5432

wal_level = replica
max_wal_senders = 10
max_replication_slots = 10
wal_keep_size = 128MB
checkpoint_timeout = 120s

# Configurazione dei log
log_destination = 'stderr'
logging_collector = off
log_statement = 'none'

Comandi Utili

CREATE ROLE replicator WITH REPLICATION LOGIN PASSWORD 'password';

pg_basebackup -h postgres-master -U replicator -D restore/  -Fp -Xs -P -R 

SELECT * FROM pg_create_physical_replication_slot('my_slot');