title: Automatically append docker container to upstream config of nginx load balancer
body: <p>I'm running Docker Compose (v2) and have a node service (website) and python based api deployed with nginx sitting in front of them. </p>
  
  <p>One thing I would like to do is be able to scale the services by adding more containers. If I know ahead of time how many containers I will have, I can hardcode the nginx upstream config with the references to the IPs of the containers which docker makes available. However, the problem is that I want the upstream nginx config to be dynamic e.g. if I add another Docker container, it simply adds appends the location of the container to the upstream list of IPs in the upstream block.</p>
  
  <p>My idea was to create a script which will automatically append the upstream servers using env variables when the containers change but I'm unsure where to start and can't find a good example. </p>