MongoDB Replica Set Setup using Docker Compose

This guide explains how to set up a MongoDB replica set using Docker Compose.

Prerequisites

• Docker installed on your machine
• Docker Compose installed on your machine

Directory Structure

Ensure your directory structure looks like this:

.
├── docker-compose.yaml
├── setup
│   ├── Dockerfile
│   ├── rsconf.js
│   └── setup.sh

Files

docker-compose.yaml

version: '3'

services:
  node1:
    image: mongo
    ports:
      - 70001:27017
    volumes:
      - $HOME/mongoclusterdata/node1:/data/mongodb
    networks:
      - mongo-network
    command: mongod --replSet rs-lab-01
  node2:
    image: mongo
    ports:
      - 70002:27017
    volumes:
      - $HOME/mongoclusterdata/node2:/data/mongodb
    networks:
      - mongo-network
    command: mongod --replSet rs-lab-01
    depends_on:
      - node1 
  node3:
    image: mongo
    ports:
      - 70003:27017
    volumes:
      - $HOME/mongoclusterdata/node3:/data/mongodb
    networks:
      - mongo-network
    command: mongod --replSet rs-lab-01
    depends_on:
      - node2
  setup-rs:
    image: "setup-rs"
    networks:
      - mongo-network
    build: ./setup
    depends_on:
      - node1

networks:
  mongo-network:
    driver: bridge

setup/Dockerfile

FROM mongo

# Create App Directory
WORKDIR /usr/src/configs

# Install App Dependencies
COPY rsconf.js .
COPY setup.sh .

CMD ["./setup.sh"]

setup/rsconf.js

// Initiate Replicaset
rs.initiate({
    _id: "rs-lab-01",
    version: 1,
    members: [{
            _id: 0,
            host: "node1:27017"
        },
        {
            _id: 1,
            host: "node2:27017"
        },
        {
            _id: 2,
            host: "node3:27017"
        }
    ]
});

// Show Existing Configuration
rs.conf()

setup/setup.sh

#!/bin/bash
echo ******************************************************
echo Starting Replicaset
echo ******************************************************
# Sleep to wait for all mongo nodes to be ready
sleep 10 | echo Sleeping 
# Run script to initiate Replicaset
mongo mongodb://node1:27017 rsconf.js

Setup and Usage

1. Navigate to your project directory:

   cd path/to/your/project

2. Create the necessary directories for data storage:

   mkdir -p $HOME/mongoclusterdata/node1
   mkdir -p $HOME/mongoclusterdata/node2
   mkdir -p $HOME/mongoclusterdata/node3

3. Build and start the Docker containers:

   docker-compose up --build

   This command will:

   • Build the setup-rs image from the Dockerfile.
   • Start the MongoDB nodes and the setup container.
   • The setup container will initiate the replica set after the nodes are up and running.

4. Verify the replica set:

   After running the containers, you can connect to any of the MongoDB nodes and check the replica set configuration:

   mongo --port 70001

   Then, run:

   rs.status()

   This should show the status of the replica set with all three nodes.

Stopping the Containers

To stop and remove the containers, run:

docker-compose down

This will stop the running containers and remove them, but it will keep the data in the $HOME/mongoclusterdata directory.

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