Docker Network Nginx Resolver

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...

Maybe you should check your container's /etc/resolv.conf

It shows your container's correct DNS config and then use that DNS server IP for resolver.

127.0.0.11 does not works in Rancher

I was running "node:12.18-alpine" with angular frontend and hit the same problem with proxy_pass.

Locally it was working with:

resolver 127.0.0.11;

As simple as that! Just execute:

$ cat /etc/resolv.conf | grep nameserver

In your container to get this ip address.

However, when deploying to kubernetes (AWS EKS) I got the very same error:

failed (111: Connection refused) while resolving, resolver: 127.0.0.11:53

Solution:

First solution was to find out the IP of the kube-dns service like below:

$ kubectl get service kube-dns -n kube-systemNAME       TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)         AGEkube-dns   ClusterIP   172.20.0.10   <none>        53/UDP,53/TCP   178d

Simple replacing IP for CLUSTER-IP worked like a charm.

Later, after some more doc digging, I find out that I could reference the service by name (which is little bit more elegant and resilient):

resolver kube-dns.kube-system valid=10s;