network-programmingnginxdocker

Docker Network Nginx Resolver

I am trying to get rid of deprecated Docker links in my configuration. What's left is getting rid of those Bad Gateway nginx reverse proxy errors when I recreated a container.

Note: I am using Docker networks in bridge mode. (docker network create nettest)

I am using the following configuration snippet inside nginx:

location / {
      resolver 127.0.0.1 valid=30s;
      set $backend "http://confluence:8090";
      proxy_pass $backend;
  1. I started a container with hostname confluence on my Docker network with name nettest.
  2. Then I started the nginx container on network nettest.
  3. I can ping confluence from inside the nginx container
  4. confluence is listed inside the nginx container's /etc/hosts file
  5. nginx log says send() failed (111: Connection refused) while resolving, resolver: 127.0.0.1:53
  6. I tried the docker network default dns resolver 127.0.0.11 from /etc/resol.conf
  7. nginx log says confluence could not be resolved (3: Host not found)

Anybody knows how to configure nginx resolver with Docker Networks or an alternative on how to force Nginx to correctly resolve the Docker network hostname?

Solution

  • First off, you should be using the Docker embedded DNS server at 127.0.0.11.

    Your problem could be caused by 1 of the following:

    1. nginx is trying to use IPv6 (AAAA record) for the DNS queries.

      See https://stackoverflow.com/a/35516395/1529493 for the solution.

      Basically something like:

      http {
    resolver 127.0.0.11 ipv6=off;
}

      This is probably no longer a problem with Docker 1.11:

      Fix to not forward docker domain IPv6 queries to external servers (#21396)

    2. Take care that you don't accidentally override the resolver configuration directive. In my case I had in the server block resolver 8.8.8.8 8.8.4.4; from Mozilla's SSL Configuration Generator, which was overriding the resolver 127.0.0.11; in the http block. That had me scratching my head for a long time...