Not able to connect mongo with replica set to mongo compass

Question

I am trying to create local setup of mongo with 3 repilca nodes
I have create docker compose file which contains 3 mongo nodes. but when i am unable to connect to mongo with compass, its throwing ENOTFOUND errror.
mongo connection string -
mongodb://localhost:27017/
mongodb://mongo1:27017/
mongodb://:27017/

version: '3'
services:
  

  mongo1:
    image: mongo:4.4
    container_name: mongo1
    ports:
      - "27017:27017"
    networks:
      - elk-net
    volumes:
      - ./data/mongo1:/data/db
    command: mongod --replSet rs0 --bind_ip_all

  mongo2:
    image: mongo:4.4
    container_name: mongo2
    ports:
      - "27018:27017"
    networks:
      - elk-net
    volumes:
      - ./data/mongo2:/data/db
    command: mongod --replSet rs0 --bind_ip_all

  mongo3:
    image: mongo:4.4
    container_name: mongo3
    ports:
      - "27019:27017"
    networks:
      - elk-net
    volumes:
      - ./data/mongo3:/data/db
    command: mongod --replSet rs0 --bind_ip_all

  

networks:
  elk-net:

Answer 1

You can find below a working solution for MongoDB replica set (It contains 2 replicas). The docker-compose.yml has several useful comments.

docker-compose.yml:

version: "3.8"

services:
  mongo1:
    image: mongo:4.4.5
    hostname: mongo1
    networks:
      - mongo_net
    # The following variables won't be used due to set entrypoint section
    # The replica-set sets automatically, but the admin user has to be set
    # only one time when you use new deploy.
    # I guess it can be automated, but I didn't have time for it...
    # Eg.:
    #    docker exec -it <docker-container-id> mongo
    #    use admin
    #    db.createUser({ user: "admin", pwd: "admin_pwd", roles: [ { role: "userAdminAnyDatabase", db: "admin" } ] })
    environment:
      - MONGO_INITDB_DATABASE=test_db
      - MONGO_INITDB_ROOT_USERNAME=admin
      - MONGO_INITDB_ROOT_PASSWORD=admin_pwd
      - MONGO_DATA_DIR=/data/db
    volumes:
      - mongo-1:/data/db
      - ./docker-entrypoint-mongo.sh:/data/docker-entrypoint.sh
    # Probably the expose is not needed because the services can
    # communicate via any port inside Docker Network.
    expose:
      - 27017
    entrypoint:
      - bash
      - -c
      - |
        chmod +x /data/docker-entrypoint.sh
        exec /data/docker-entrypoint.sh
    healthcheck:
      test: test $$(echo "rs.initiate({_id:'my-replica-set',members:[{_id:0,host:\"mongo1:27017\"},{_id:1,host:\"mongo2:27017\"}]}).ok || rs.status().ok" | mongo --quiet ) -eq 1
      interval: 10s
      start_period: 30s

  mongo2:
    image: mongo:4.4.5
    hostname: mongo2
    networks:
      - mongo_net
    environment:
      - MONGO_INITDB_DATABASE=test_db
      - MONGO_INITDB_ROOT_USERNAME=admin
      - MONGO_INITDB_ROOT_PASSWORD=admin_pwd
      - MONGO_DATA_DIR=/data/db
    volumes:
      - mongo-2:/data/db
      - ./docker-entrypoint-mongo.sh:/data/docker-entrypoint.sh
    expose:
      - 27017
    entrypoint:
      - bash
      - -c
      - |
        chmod +x /data/docker-entrypoint.sh
        exec /data/docker-entrypoint.sh

volumes:
  mongo-1:
  mongo-2:

networks:
  mongo_net: {}

docker-entrypoint-mongo.sh:

mongod "--enableMajorityReadConcern" "false" "--journal" "--dbpath" "/data/db" "--replSet" "my-replica-set" "--bind_ip_all"

The connection string for MongoDB replica-set:

mongodb://mongo1:27017,mongo2:27017/?replicaSet=my-replica-set