# postgres15

Implement automatic primary and standby

## Primary

Example `compose.yaml` for **primary** instance.

```yaqml
services:
  db:
    image: pendragon.zone/docker/postgres15replicate
    restart: unless-stopped
    shm_size: 128mb
    environment:
      POSTGRES_PASSWORD: ${DB_ROOT_PASSWORD}
      REPLICATOR_PASSWORD: ${REPLICATOR_PASSWORD}
      MAX_CONNECTIONS: "400"

    network_mode: bridge
    ports:
      - 5432:5432

    volumes:
      - data:/var/lib/postgresql/data
      - /docker/postgres_wal:/wal_archive

volumes:
  data:
```

- Volume `/wal_archive` **must** be mapped to a location available by **all** replication participants.

- `DB_ROOT_PASSWORD` _required_, must be the same for all replication participants.

- `REPLICATOR_PASSWORD` _required_, must be the same for all replication participants.

- `UPSTREAM` **must not** be set for **primary** instance.

- `WAL_ARCHIVE` _default: `/wal_archive`_ use different location for write-ahead-logs.

- `TRIGGER_FILE` _default: `i_am_primary`_, name of the file that promotes a standby instance to primary instance, if it exists in directory `/var/lib/postgresql/data`.

- `WAL_KEEP_SIZE` _default: `1GB`_

- `REPLICATOR_NAME` _default: `replicator`_ name of user for replication.

- `MAX_CONNECTIONS` _optional_, change default value of `max_connections` configuration value.


## Standby

Example `compose.yaml` for **standby** instance.

```yaqml
services:
  db:
    image: pendragon.zone/docker/postgres15replicate
    restart: unless-stopped
    shm_size: 128mb
    environment:
      POSTGRES_PASSWORD: ${DB_ROOT_PASSWORD}
      REPLICATOR_PASSWORD: ${REPLICATOR_PASSWORD}
      UPSTREAM: ${UPSTREAM}

    network_mode: bridge
    ports:
      - 5432:5432

    volumes:
      - data:/var/lib/postgresql/data
      - /docker/postgres_wal:/wal_archive

volumes:
  data:
```

- Volume `/wal_archive` **must** be mapped to a location available by **all** replication participants.

- `DB_ROOT_PASSWORD` _required_, must be the same for all replication participants.

- `REPLICATOR_PASSWORD` _required_, must be the same for all replication participants.

- `UPSTREAM` _required_, name of the node to replicate from. Can either be **primary** or a different **standby** instance.