mongod --bind_ip using docker-compose version 2

Question

I'm trying to connect two mongodb containers running on docker using docker-compose. One container seed some data to the other using mongoimport.

However, I'm getting the following error when run mongoimport

Failed: error connecting to db server: no reachable servers

I can actually reach the mongodb container from mongo-seed since I'd appended a ping -c 3 mongodb to the CMD and the container can resolve successfully that hostname.

Below the files I'm using:

docker-compose.yml

version: '2'

services:
  mongodb:
    image: mongo:3.2
    ports:
      - "27017:27017"

  mongo-seed:
    build: ./mongo-seed

mongo-seed/Dockerfile

FROM mongo:3.2

COPY init.json /init.json
CMD ping -c 3 mongodb && mongoimport --host mongodb --db test --collection users \
   --type json --file /init.json --jsonArray

mongo-seed/init.json

[
  {
    "name": "Joe Smith",
    "email": "[email protected]",
    "age": 40,
    "admin": false
  },
  {
    "name": "Jen Ford",
    "email": "[email protected]",
    "age": 45,
    "admin": true
  }
]

And this the output of docker-compose up:

mongo-seed_1  | PING mongodb (172.18.0.2): 48 data bytes
mongo-seed_1  | 56 bytes from 172.18.0.2: icmp_seq=0 ttl=64 time=0.116 ms
mongo-seed_1  | 56 bytes from 172.18.0.2: icmp_seq=1 ttl=64 time=0.141 ms
mongo-seed_1  | 56 bytes from 172.18.0.2: icmp_seq=2 ttl=64 time=0.114 ms
mongo-seed_1  | --- mongodb ping statistics ---
mongo-seed_1  | 3 packets transmitted, 3 packets received, 0% packet loss
mongo-seed_1  | round-trip min/avg/max/stddev = 0.114/0.124/0.141/0.000 ms
mongo-seed_1  | 2016-08-09T20:34:15.728+0000    [........................] smtt.devices 0.0 B/25.5 MB (0.0%)
mongo-seed_1  | 2016-08-09T20:34:17.992+0000    [........................] smtt.devices 0.0 B/25.5 MB (0.0%)
mongo-seed_1  | 2016-08-09T20:34:17.992+0000    Failed: error connecting to db server: no reachable servers
mongo-seed_1  | 2016-08-09T20:34:17.992+0000    imported 0 documents
mongo_mongo-seed_1 exited with code 1

Any idea? What am I missing?

Answer 1

I could finally manage to get connected both containers. My findings here for documentation purposes.

Main points

• docker-compose version 2 creates a bridge network and adds all the containers to it.
• mongod is not aware of this network and therefore doesn't bind to that ip. By default, binds only to 127.0.0.1
• mongoimport could not establish connection using container name, even though it's supposed to be translated to the container ip.

Solution

• Assign an static IP for the mongodb through the explicit definition of a network
• Init mongo container with --bind_ip flag pointing to that static ip
• Use ip address instead of hostname with mongoimport

docker-compose.yml

version: '2'

services:
  mongodb:
    image: mongo:3.2
    ports:
      - "27017:27017"
    networks:
      mongo_net:
        ipv4_address: 172.16.0.1
    command: mongod --bind_ip 127.0.0.1,172.16.0.1

  mongo-seed:
    build: ./mongo-seed
    networks:
      mongo_net:
    depends_on:
      - mongodb

networks:
  mongo_net:
    driver: bridge
    ipam:
      config:
      - subnet: 172.16.0.0/24
        gateway: 172.16.0.254

mongo-seed/Dockerfile

FROM mongo:3.2

COPY init.json /init.json
CMD mongoimport --host 172.16.0.1 --db test --collection users \
   --type json --file /init.json --jsonArray