Troubles with connecting NestJS container with MongoDB container

Question

I have a project with docker containers:

1. api container (NestJS)
2. mongo container

And NestJS doesn't want to connect to mongoDB but connects to mongoDB Atlas. Tried everything nothing helps(

docker-compose.yml:

api:
    image: service-api
    build:
      context: "api/."
      dockerfile: "Dockerfile"
    environment:
      NODE_ENV: production
      ME_CONFIG_MONGODB_ADMINUSERNAME: root
      ME_CONFIG_MONGODB_ADMINPASSWORD: example
      ME_CONFIG_MONGODB_URL: mongodb://root:example@mongo:27017/eshop
    networks:
      - backend
      - frontend
    depends_on:
      - 'mongo'
      - 'rabbitmq'
    ports:
      - "8802:8802"
    deploy:
      placement:
        constraints: [ node.role == manager ]
      replicas: 1
...

  mongo:
    image: mongo:6.0.2
    networks:
      - backend
    ports:
      - "27017:27017"
    environment:
      MONGO_INITDB_DATABASE: eshop
      MONGO_INITDB_ROOT_USERNAME: root
      MONGO_INITDB_ROOT_PASSWORD: example
    volumes:
      - "/opt/mongo/data/db:/data/db"
    deploy:
      placement:
        constraints: [ node.role == manager ]
      replicas: 1

NestJS app.module.ts:

const MongoModule = MongooseModule.forRoot('mongodb://root:example@mongo:27017/eshop', {
  useNewUrlParser: true,
  useUnifiedTopology: true, 
  useFindAndModify: false,
});

mongoose version: ^5.8.11

Error message:

[MongooseModule] Unable to connect to the database. Retrying (1)... +29999ms
[MongooseModule] Unable to connect to the database. Retrying (2)... +33002ms
...
[MongooseModule] Unable to connect to the database. Retrying (7)... +33002ms

Everything works in same stack, in same network, and still can't connect

Answer 1

set authSource option to admin

const MongoModule = MongooseModule.forRoot('mongodb://root:example@mongo:27017/eshop?authSource=admin', {
  useNewUrlParser: true,
  useUnifiedTopology: true, 
  useFindAndModify: false,
});