Mongo Express to wait for MongoDB Cluster in Docker Compose

Question

I'm trying to setup a local development with Docker Compose that has a MongoDB cluster as the database. I chose Mongo Express as the Database Admin User Interface so I can check inside the MongoDB database. It does take some time for the cluster to accept connections, I have the 3 db containers as part of the depends_on, but seems like I have to do more than that based on the Docker Compose documentation here. I can't seem to find a good example for waiting for MongoDB clusters. Has anyone figured this out already? Please share, that would be great. Thank you in advance!

Here's the docker-compose.yml file:

version: '3.9'

services:
  mongodb-primary:
    image: 'bitnami/mongodb:latest'
    environment:
      - MONGODB_ADVERTISED_HOSTNAME=mongodb-primary
      - MONGODB_REPLICA_SET_MODE=primary
      - MONGODB_ROOT_PASSWORD=password
      - MONGODB_REPLICA_SET_KEY=replicasetkey
    volumes:
      - 'mongodb_master_data:/bitnami'

  mongodb-secondary:
    image: 'bitnami/mongodb:latest'
    depends_on:
      - mongodb-primary
    environment:
      - MONGODB_ADVERTISED_HOSTNAME=mongodb-secondary
      - MONGODB_REPLICA_SET_MODE=secondary
      - MONGODB_INITIAL_PRIMARY_HOST=mongodb-primary
      - MONGODB_INITIAL_PRIMARY_PORT_NUMBER=27017
      - MONGODB_INITIAL_PRIMARY_ROOT_PASSWORD=password
      - MONGODB_REPLICA_SET_KEY=replicasetkey

  mongodb-arbiter:
    image: 'bitnami/mongodb:latest'
    depends_on:
      - mongodb-primary
    environment:
      - MONGODB_ADVERTISED_HOSTNAME=mongodb-arbiter
      - MONGODB_REPLICA_SET_MODE=arbiter
      - MONGODB_INITIAL_PRIMARY_HOST=mongodb-primary
      - MONGODB_INITIAL_PRIMARY_PORT_NUMBER=27017
      - MONGODB_INITIAL_PRIMARY_ROOT_PASSWORD=password
      - MONGODB_REPLICA_SET_KEY=replicasetkey

  dbadmin:
    image: mongo-express
    restart: always
    ports:
      - 8081:8081
    depends_on:
      - mongodb-primary
      - mongodb-secondary
      - mongodb-arbiter
    environment:
      ME_CONFIG_MONGODB_URL: mongodb://root:password@mongodb-primary:27017,mongodb-secondary:27017,mongodb-arbiter:27017?replicaSet=replicaset
      ME_CONFIG_BASICAUTH_USERNAME: admin
      ME_CONFIG_BASICAUTH_PASSWORD: mexpress

volumes:
  mongodb_master_data:
    driver: local

Answer 1

If still relevant: I suggest adding healthcheck for the mongodb you are trying connect to (probably primary-node). Example:

services:
  mongo:
    image: mongo
    restart: always
    healthcheck:
      test: echo 'db.runCommand({serverStatus:1}).ok' | mongo admin -u $MONGO_INITDB_ROOT_USERNAME -p $MONGO_INITDB_ROOT_PASSWORD --quiet | grep 1
      interval: 10s
      timeout: 10s
      retries: 3
      start_period: 20s
    environment:
      MONGO_INITDB_ROOT_USERNAME: root
      MONGO_INITDB_ROOT_PASSWORD: example