Use internal docker network when using HAProxy loadbalancer

A common setup is to use HAProxy as a load balancer behind two or more web servers.
In a docker test environment, you can first run the two web servers and finally run the HAProxy docker, like this:

Using HAProxy for loadbalancing 2 web servers in docker

In this blog I will share the steps I made to use HAProxy (running in a docker container) to loadbalance my web requests between two apache web servers.
I will also show how to add a health check so HAProxy will be able to detect when a webserver is down.