01-setup-replication-postgres

🐘 PostgreSQL Master-Slave Replication with Docker Compose (Windows PowerShell)

This guide sets up PostgreSQL streaming replication (master-slave) using Docker Compose, powered by the Bitnami PostgreSQL image. Perfect for development and load testing environments.

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✅ Prerequisites

• Windows with Docker and Docker Compose installed
• PowerShell or Git Bash
• A Docker network named lab-net must be created:

docker network create lab-net

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📁 Directory Structure

01-setup-replication-postgres/
├── docker-compose.yml
├── README.md
└── (data is stored in Docker volumes, not inside the project folder)

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🐳 docker-compose.yml

version: '3.8'

services:
  pg-master:
    image: bitnami/postgresql:14
    container_name: pg-master
    environment:
      - POSTGRESQL_REPLICATION_MODE=master
      - POSTGRESQL_REPLICATION_USER=replicator
      - POSTGRESQL_REPLICATION_PASSWORD=example
      - POSTGRESQL_PASSWORD=example
    volumes:
      - master_data:/bitnami/postgresql
    ports:
      - '5432:5432'
    networks:
      - lab-net

  pg-slave:
    image: bitnami/postgresql:14
    container_name: pg-slave
    depends_on:
      - pg-master
    environment:
      - POSTGRESQL_REPLICATION_MODE=slave
      - POSTGRESQL_REPLICATION_USER=replicator
      - POSTGRESQL_REPLICATION_PASSWORD=example
      - POSTGRESQL_PASSWORD=example
      - POSTGRESQL_MASTER_HOST=pg-master
      - POSTGRESQL_MASTER_PORT_NUMBER=5432
    volumes:
      - slave_data:/bitnami/postgresql
    ports:
      - '5433:5432'
    networks:
      - lab-net

volumes:
  master_data:
  slave_data:

networks:
  lab-net:
    external: true

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🚀 How to Run

1. (Optional) Clean up any previous containers and volumes:

docker compose down -v

2. Start the replication cluster:

docker compose up -d

3. Verify running containers:

docker ps --filter "name=pg-"

4. Check replication status on the master:

docker exec -e PGPASSWORD=example -u postgres pg-master \
  psql -h 127.0.0.1 -U postgres -d postgres \
  -c "SELECT pid, state, client_addr FROM pg_stat_replication;"

5. Check recovery mode on the slave:

docker exec -e PGPASSWORD=example -u postgres pg-slave \
  psql -h 127.0.0.1 -U postgres -d postgres \
  -c "SELECT pg_is_in_recovery();"

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🔗 Connection Info

• localhost:5432 → write DB (pg-master)
• localhost:5433 → read-only DB (pg-slave)

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🧼 Cleanup

To stop and remove everything including volumes:

docker compose down -v

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📝 Notes

• Passwords are set to example for demo purposes. Change them for production use.
• Bitnami PostgreSQL images automatically configure replication via environment variables.
• To view logs:

docker logs pg-master
docker logs pg-slave

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Happy replicating! 🚀