Docker DNS getaddrinfo ENOTFOUND

Question

I am running docker-compose with node:4.2.1-wheezy and dnsdock containers.

I have DOCKER_OPTS="--dns 172.17.42.1" inside /etc/default/docker.

When I run node -e "require('dns').resolve('host_name_here')" inside my node.js container the host is resolved correctly through the 172.17.42.1 dns server.

But when I run node -e "require('dns').lookup('host_name_here')" it fails with ENOTFOUND error.

And the problem is that http.request uses dns.lookup instead of dns.resolve.

The docs say that dns.lookup calls getaddrinfo. And as far as I understand getaddrinfo caches /etc/resolv.conf and maybe it caches empty /etc/resolv.conf (but cat /etc/resolv.conf prints nameserver 172.17.42.1).

I really have no idea how to resolve this issue. What can cause such behavior?

Update 1.

docker -v
Docker version 1.7.1, build 786b29d

docker-compose -v
docker-compose version: 1.4.2

Update 2.

I updated all things to the latest versions (docker 1.9.0, docker-compose 1.5.0 and node up to 5.0.0) but the issue still persists.

So this is the docker-compose.yml that reproduces the issue:

dnsdock:
  image: tonistiigi/dnsdock
  volumes:
    - /var/run/docker.sock:/run/docker.sock
  ports:
    - "172.17.42.1:53:53/udp"
  environment:
    - DNSDOCK_ALIAS=dns.org
node:
  image: node:5.0.0-wheezy
  command: node -e "setTimeout(function () { var dns = require('dns'); dns.resolve('dns.org', console.log.bind(console, 'resolve')); dns.lookup('dns.org', console.log.bind(console, 'lookup')); }, 5000)"
  dns: 172.17.42.1

You should replace 172.17.42.1 with IP of your docker0 interface. The setTimeout(..., 5000) is needed because node container may start before dnsdock.

This is my docker-compose up output:

Creating test_node_1
Creating test_dnsdock_1
Attaching to test_node_1, test_dnsdock_1
dnsdock_1 | 2015/11/07 09:29:44 Added service: 3653951cff40c06c04b9ab3f5d2fc94ccc19305eaac7ba1a545ce1dbab3e3e17 {test_dnsdock_1 dnsdock 172.17.42.3 -1 [dns.org]}
dnsdock_1 | 2015/11/07 09:29:44 Added service: 36577feea136bc713f77b64b2a6a9712cd509c47ca55427f6749308cc5a4b140 {test_node_1 node 172.17.42.2 -1 []}
node_1    | resolve null [ '172.17.42.3' ]
node_1    | lookup { [Error: getaddrinfo ENOTFOUND dns.org]
node_1    |   code: 'ENOTFOUND',
node_1    |   errno: 'ENOTFOUND',
node_1    |   syscall: 'getaddrinfo',
node_1    |   hostname: 'dns.org' }
dnsdock_1 | 2015/11/07 09:29:49 Stopped service: 36577feea136bc713f77b64b2a6a9712cd509c47ca55427f6749308cc5a4b140
test_node_1 exited with code 0

Answer 1

For a better dns lookup, you could consider using a network overlay, as presented in "Docker Overlay Networks: That was Easy"

It uses a KV (Key/Value) store bases on Consul, and a swarm cluster where you can register your nodes.

You can the build an overlay network

eval "$(docker-machine env --swarm c0-master)"
docker network create -d overlay myStack1

And use it to run an image:

docker run -d --name web --net myStack1 nginx
docker run -itd --name shell1 --net myStack1 alpine /bin/sh

Both of these containers will be attached to the same network, and be discoverable by container name (regardless of start order).
Further, when a container is restarted it will remain discoverable without cascading restarts.