MongoDB ReplicaSet Docker Configuration

readme.md

Directory Structure

app-root
  -> (src)
  -> docker-compose.yml
  -> scripts
    -> setupReplicaSet.sh

Map Hostnames

Add the following to your /etc/hosts file in order to connect to the replica set locally

127.0.0.1   mongo1
127.0.0.1   mongo2
127.0.0.1   mongo3

Start up

$ sudo chmod 755 ./scripts/setupReplicaSet.sh
$ sudo docker-compose.yml up -d

Connection URI

Based on the hostnames and ports in the docker-compose.yml and setupReplicaSet.sh files

mongodb://mongo1:27017,mongo2:27018,mongo3:27019/<DB-NAME-HERE>?replicaSet=rs0

docker-compose.yml

version: "3.1"

# Our containers
services:
  # Temporary container used to initialize the replica set
  mongo-setup:
    container_name: mongo-setup
    image: mongo
    restart: on-failure
    networks:
      default:
    volumes:
      - ./scripts:/scripts      # Ensure the './scripts' directory exists with the 'setupReplicaSet.sh' file
    entrypoint: ["/scripts/setupReplicaSet.sh"]     # Call the 'setupReplicaSet.sh' script on container init
    depends_on:     # Wait for the 3 DB containers to spin up first
      - mongo1
      - mongo2
      - mongo3
     
  mongo1:
    hostname: mongo1      # You need to map this hostname to 127.0.0.1 in your /etc/hosts file
    container_name: mongo1
    image: mongo
    expose:
      - 27017
    ports:
      - 27017:27017
    networks:
      default:
    restart: always
    volumes:
      - ./mongo-volumes/mongo1/data/db:/data/db     # Create a volume to persist data
    entrypoint: ["/usr/bin/mongod", "--bind_ip_all", "--replSet", "rs0", "--journal", "--dbpath", "/data/db", "--enableMajorityReadConcern", "false", "--port", "27017"]


  mongo2:
    hostname: mongo2      # You need to map this hostname to 127.0.0.1 in your /etc/hosts file
    container_name: mongo2
    image: mongo
    expose:
      - 27018
    ports:
      - 27018:27018
    networks:
      default:
    restart: always
    volumes:
      - ./mongo-volumes/mongo2/data/db:/data/db     # Create a volume to persist data
    entrypoint: ["/usr/bin/mongod", "--bind_ip_all", "--replSet", "rs0", "--journal", "--dbpath", "/data/db", "--enableMajorityReadConcern", "false", "--port", "27018"]

  mongo3:
    hostname: mongo3      # You need to map this hostname to 127.0.0.1 in your /etc/hosts file
    container_name: mongo3
    image: mongo
    expose:
      - 27019
    ports:
      - 27019:27019
    networks:
      default:
    restart: always
    volumes:
      - ./mongo-volumes/mongo3/data/db:/data/db     # Create a volume to persist data
    entrypoint: ["/usr/bin/mongod", "--bind_ip_all", "--replSet", "rs0", "--journal", "--dbpath", "/data/db", "--enableMajorityReadConcern", "false", "--port", "27019"]

setupReplicaSet.sh

#!/bin/bash

REPLICA_SET_NAME=rs0

MONGODB1=mongo1
MONGODB1_PORT=27017

MONGODB2=mongo2
MONGODB2_PORT=27018

MONGODB3=mongo3
MONGODB3_PORT=27019

echo "********** setupReplicaSet.sh **********"
echo ${MONGODB1}
until curl http://${MONGODB1}:${MONGODB1_PORT}/serverStatus\?text\=1 2>&1 | grep uptime | head -1; do
  printf '.'
  sleep 1
done

echo setupReplicaSet.sh time now: `date +"%T" `
mongo --host ${MONGODB1}:${MONGODB1_PORT} <<EOF
var cfg = {
  "_id": "${REPLICA_SET_NAME}",
  "members": [
    {
      "_id": 0,
      "host": "${MONGODB1}:${MONGODB1_PORT}",
      "priority": 2
    },
    {
      "_id": 1,
      "host": "${MONGODB2}:${MONGODB2_PORT}",
      "priority": 0
    },
    {
      "_id": 2,
      "host": "${MONGODB3}:${MONGODB3_PORT}",
      "priority": 0
    }
  ]
};
rs.initiate(cfg);
rs.reconfig(cfg, {force: true});
rs.secondaryOk();
rs.conf();
EOF