How can a container identify which container it is in a set of a scaled docker-compose service?

Question

I have a docker container called node that I want to scale to n containers. A given node container needs to know which container it is in the set of n

Answer 1

The latest version of docker should be able to autodiscover scaled services. For example:

services:
  app: {}
  worker: {}
  

Run scale after booting up your docker-compose:

docker-compose scale worker=10

Your app container can call the services via:

http://worker{:port}

Docker will pick a random running worker container to forward the request to.