Config (Traefik): Configure a Traefik reverse proxy Docker container to use muscle.local and backend.muscle.local domains

[drikusroor]

Not sure if we want this, but during yesterday's demo session I heard some people talking about not remembering the urls and port numbers to use for the application and the backend. This PR adds a Traefik container that reroutes http://localhost:3000 and http://localhost:8000 to http://muscle.local and http://backend.muscle.local, which is easier to remember (and of course you can also just type muscle.local and backend.muscle.local).

Additionally, it adds a idempotent script (./scripts/add-hosts-entries) to add the hostnames to the hostfile in /etc/hosts file, which is required Traefik to work.

[BeritJanssen]

Nice! Perhaps just "muscle" (instead of "muscle.local") might even do? Just for my understanding: where does the actual mapping of the routes to the relevant localhost ports happen? Is it in the add-hosts-entries script? I worry that the port mappings are not explicit now, so it might be a bit hocus-pocus to future developers.

[drikusroor]

Nice! Perhaps just "muscle" (instead of "muscle.local") might even do? Just for my understanding: where does the actual mapping of the routes to the relevant localhost ports happen? Is it in the add-hosts-entries script? I worry that the port mappings are not explicit now, so it might be a bit hocus-pocus to future developers.

That happens in the Traefik container (see the docker-compose.yml configuration). Traefik functions as a reverse proxy here. The add-hosts-entries script only maps the domains to 127.0.0.1. As Traefik runs on port 80 it will be hit when you send requests to 127.0.0.1 and then proxy it internally:

muscle.local => 127.0.0.1(:80) (Traefik) => localhost:8000

The only thing I'm still thinking about is how to execute the add-hosts-entries script together with docker compose up (-d --build) so that the hosts will always be up to date with the Traefik configuration.

[BeritJanssen]

Perhaps add some comments to the docker-compose then to explain what the traefik settings do?

[drikusroor]

Nice! Perhaps just "muscle" (instead of "muscle.local") might even do? Just for my understanding: where does the actual mapping of the routes to the relevant localhost ports happen? Is it in the add-hosts-entries script? I worry that the port mappings are not explicit now, so it might be a bit hocus-pocus to future developers.

I don't think the port mappings are that important. Traefik communicates with Docker and simply proxies to that specific Docker service. What might be interesting to check is to start up the newly added Traefik container (I just merged the PR) and navigate to http://localhost:8080, which is the backend interface of Traefik that shows you how the different services, load balancers, etc. are currently configured.

Also, I've added some explanation to the Wiki of how to start up the Development environment: https://github.com/Amsterdam-Music-Lab/MUSCLE/wiki/2.-Start-the-application