Dynamic DNS Resolution with HAProxy and Docker - docker

Question

I'm trying to setup HAProxy inside a Docker host.
Using HAProxy 1.7 and Docker 1.12
My haproxy.cfg looks like:
# Simple configuration for an HTTP proxy listening on port 81 on all
# interfaces and forwarding requests to a single backend "servers" with a
# single server "server1" listening on 127.0.0.1:8000
global
daemon
maxconn 256
resolvers docker
# nameserver dnsmasq 127.0.0.1:53
nameserver dns 127.0.0.1:53
defaults
mode http
timeout connect 5000ms
timeout client 50000ms
timeout server 50000ms
default-server init-addr none
frontend http-in
bind *:80
default_backend www_somedomain1_com
# Define hosts
acl host_www_somedomain1_com hdr(host) -i somedomain1.com
acl host_www_somedomain1_com hdr(host) -i www.somedomain1.com
acl host_www_somedomain2_com hdr(host) -i www.somedomain2.com
## figure out which one to use
use_backend www_somedomain1_com if host_www_somedomain1_com
use_backend www_somedomain2_com if host_www_somedomain2_com
backend www_somedomain1_com
# Utilizing the Docker DNS to resolve below host
# server server1 www-somedomain1-com maxconn 32 check port 80
server server1 www-somedomain1-com resolvers docker check maxconn 32
backend www_somedomain2_com
# Utilizing the Docker DNS to resolve below host
# server server1 www-somedomain2-com maxconn 32 check resolvers docker resolve-prefer ipv4
server server1 www-somedomain2-com maxconn 32 check port 80
I want to use Docker's embedded DNS system - which, in my understanding, is only enabled when using a user defined network.
So I create a network (using the default bridge driver)
docker network create mynetwork
When I run my two named docker containers, (my-haproxy and www-somedomain1-com) I add them to that network with the --net flag.
Docker run commands:
docker run --name myhaproxy --net mynetwork -p 80:80 -d haproxy
docker run --name www-somedomain1-com --net mynetwork -d nginx
I know the Docker dns is functional because I can resolve from one container to the other when I hop on them in a bash shell. I can't get the right combo/config in HAProxy to enable the dynamic DNS resolution.
HAProxy stats page always shows the downstream backends as brown/resolution issue....
Some things that have helped:
- the "default-server init-addr none" helps pass the haproxy config check on startup.
Any guidance is greatly appreciated!

Answer 1

I think your issue is that you are using 127.0.0.1:53 for your resolver dns, when it needs to be 127.0.0.11:53 for the docker bridge network.
Here is my haproxy setup for dev docker stuff:
global
quiet
defaults
log global
mode http
option forwardfor
timeout connect 60s
timeout client 60s
timeout server 60s
default-server init-addr none
resolvers docker_resolver
nameserver dns 127.0.0.11:53
frontend https-proxy
bind 0.0.0.0:80
bind 0.0.0.0:443 ssl crt /usr/local/etc/haproxy/dev_server.pem
redirect scheme https if !{ ssl_fc }
acl is_api_server hdr(host) -i mywebsite
use_backend api_server if is_api_server
backend api_server
server haproxyapi api-server-dev:80 check inter 10s resolvers docker_resolver resolve-prefer ipv4