MongoDB Replica Set with Docker

This repository sets up a MongoDB replica set using Docker Compose. It includes:

• Three MongoDB nodes (Primary, Secondary, Secondary)
• Replica set initialization script
• Mongo Express for UI-based DB access

🔗 If you want to load balance reads across secondaries, check out the companion project:
👉 haproxy-mongodb-balancer

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📦 Requirements

1. Generate the shared replica set key file (for internal authentication):

   openssl rand -base64 756 > replica.key
   sudo chown 999:999 replica.key
   chmod 600 replica.key

2. Create Docker network (shared across services):

docker network create \
  --driver=bridge \
  --subnet=192.168.22.0/24 \
  --ip-range=192.168.22.0/24 \
  --gateway=192.168.22.254 \
  connet

3. Environment variables: Copy the example and edit as needed:

4. cp .env.example .env

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🚀 Getting Started

docker compose up -d
docker compose ps
# down containers with volumes
docker compose down

Replica set will auto-init via mongo_rs_init.sh once all nodes are healthy.

Mongo Express will be available at http://localhost:8081

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🔧 Services Overview

Service	Role	Port
mongodb1	Primary	27017
mongodb2	Secondary	27017
mongodb3	Secondary	27017
mongo-express	Web UI	8081
mongo-init	Init script	—

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📖 Documentation

Full setup, TLS configuration, replication testing, and troubleshooting guides:

📚 Wiki Home »

• Setup Instructions
• Mongo Express & Replica Set
• TLS Configuration (Recommended)
• Replica Set Testing & Failover
• Troubleshooting

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📌 Notes

• This setup uses keyFile authentication (no TLS by default).
• MongoDB 8.0+ requires TLS for certain modes (e.g., sendKeyFile).