Containers cannot connect to each other in swarm mode in a multi-host environment

Question

I am running 3 nodes on DigitalOcean (1 GB, with private networks), and after deploying this stack, containers cannot connect to other containers using host aliases.

This is my file docker-compose.yml:

version: "3"

services:
  mongo:
    image: mongo
    ports:
      - 27017:27017
    networks:
      mynet:
        aliases:
          - mongo
    deploy:
      placement:
        constraints: [node.role == manager]

  redis:
    image: redis
    ports:
      - 6379:6379
    networks:
      mynet:
        aliases:
          - redis
    deploy:
      placement:
        constraints: [node.role == worker]

  app:
    image: node
    ports:
      - 3030:3030
    networks:
      - mynet
    depends_on:
      - redis
      - mongo
    deploy:
      mode: replicated
      replicas: 2
      placement:
        constraints: [node.role == worker]

networks:
  mynet:

Problem

root@mongo-container:/# ping mongo # works
root@mongo-container:/# ping redis # doesn't work

root@redis-container:/# ping redis # works
root@redis-container:/# ping mongo # doesn't work

root@app-container:/# ping mongo # doesn't work
root@app-container:/# ping redis # doesn't work

Configuration

daemon.json

{ "userland-proxy": false }

docker version:

Client:
 Version:      1.13.1
 API version:  1.26
 Go version:   go1.7.5
 Git commit:   092cba3
 Built:        Wed Feb  8 06:50:14 2017
 OS/Arch:      linux/amd64

Server:
 Version:      1.13.1
 API version:  1.26 (minimum version 1.12)
 Go version:   go1.7.5
 Git commit:   092cba3
 Built:        Wed Feb  8 06:50:14 2017
 OS/Arch:      linux/amd64
 Experimental: true

Any idea how to fix this?

Answer 1

This is a bug in Docker Swarm mode, and it is fixed in an upcoming release of Docker v17.04.0