Development environment with read replicas

In order to test the PostgreSQL read replicas that can be configured, it's needed to run the development environment with read replicas. This guide explains which changes to made specifically.

Docker compose

Replace the first part of your docker-compose.dev.yml with the following:

services:
  db:
    image: pgvector/pgvector:pg18
    ports:
      - "127.0.0.1:5432:5432"
    environment:
      POSTGRES_USER: ${DATABASE_USER:-baserow}
      POSTGRES_PASSWORD: ${DATABASE_PASSWORD:?}
      POSTGRES_DB: ${DATABASE_NAME:-baserow}
      PGDATA: /var/lib/postgresql/data
    volumes:
      - pgdata-primary:/var/lib/postgresql/data
      - ./docs/development/init/primary-init.sh:/docker-entrypoint-initdb.d/primary-init.sh:ro
    command: >
      postgres -c wal_level=replica
               -c max_wal_senders=10
               -c wal_keep_size=1GB
               -c hot_standby=on
               -c listen_addresses='*'
    networks:
      - local

  db-replica-1:
    image: pgvector/pgvector:pg18
    ports:
      - "127.0.0.1:5433:5432"
    environment:
      POSTGRES_USER: ${DATABASE_USER:-baserow}
      POSTGRES_PASSWORD: ${DATABASE_PASSWORD:?}
      REPLICATION_PASSWORD: ${REPLICATION_PASSWORD:-replicatorpass}
      PGDATA: /var/lib/postgresql/data
    volumes:
      - pgdata-replica-1:/var/lib/postgresql/data
      - ./docs/development/init/replica-entrypoint.sh:/scripts/replica-entrypoint.sh:ro
    user: postgres
    depends_on:
      - db
    entrypoint: [ "/scripts/replica-entrypoint.sh" ]
    networks:
      - local

  db-replica-2:
    image: pgvector/pgvector:pg18
    ports:
      - "127.0.0.1:5434:5432"
    environment:
      POSTGRES_USER: ${DATABASE_USER:-baserow}
      POSTGRES_PASSWORD: ${DATABASE_PASSWORD:?}
      REPLICATION_PASSWORD: ${REPLICATION_PASSWORD:-replicatorpass}
      PGDATA: /var/lib/postgresql/data
    volumes:
      - pgdata-replica-2:/var/lib/postgresql/data
      - ./docs/development/init/replica-entrypoint.sh:/scripts/replica-entrypoint.sh:ro
    user: postgres
    depends_on:
      - db
    entrypoint: [ "/scripts/replica-entrypoint.sh" ]
    networks:
      - local

Add the following to the end of the file:

volumes:
  pgdata-primary:
  pgdata-replica-1:
  pgdata-replica-2:

Then execute:

chmod +x ./docs/development/init/primary-init.sh
chmod +x ./docs/development/init/replica-entrypoint.sh

Restart your dev environment and observe that the read-only replications are accessible. They're available on port 5433 and 5434 with the same password you're using the same username and password as the writer db.

Saveroom configuration

Add the following to .env.docker-dev (when running with just dc-dev) and restart the dev environment. This configures Saveroom to use the read-only replicas for read queries. When the backend runs on the host (just dev, .env.local), use localhost with ports 5433 and 5434 instead of the container host names.

PGDATA is pinned because PostgreSQL 18 images default to a versioned data directory and the replica entrypoint expects /var/lib/postgresql/data.

DATABASE_READ_1_NAME="baserow"
DATABASE_READ_1_USER="baserow"
DATABASE_READ_1_PASSWORD="baserow"
DATABASE_READ_1_HOST="db-replica-1"
DATABASE_READ_1_PORT="5432"
DATABASE_READ_2_NAME="baserow"
DATABASE_READ_2_USER="baserow"
DATABASE_READ_2_PASSWORD="baserow"
DATABASE_READ_2_HOST="db-replica-2"
DATABASE_READ_2_PORT="5432"