Provide a mechanism to inject a custom status handler

[carrascoacd]

Problem

In order to support Traefik we need to listen in the same port the h1 health checks, more info here traefik/traefik#6211

Expected outcome

Add a way to inject a custom status handler, so we can listen for h1 requests in the same port using the desired handler.

Let me know if it works for you in order to update the doc as well or if you have another solution.

The configuration could be:

config :grpc,
       :status_handler,
       {"/status", Phoenix.Endpoint.Cowboy2Handler, {My.Endpoint, []}}

[carrascoacd]

@tony612 could you review it when you have time, please?

[polvalente]

@carrascoacd is this still relevant?

[polvalente]

I think we should avoid using global config as per the general library guidelines for Elixir. Instead, we should accept this through opts.

Is this able to be passed down already, or would something more need to change?

[carrascoacd]

Hi @polvalente, thanks for answering. This is something we still need. Let me try injecting the configuration using opts and check if it works.

[carrascoacd]

@polvalente I managed to get it working in that way. When starting the server under a Supervisor we get something like this:

    status_handler = {"/status", Plug.Cowboy.Handler, {GrpcEx.StatusHandler, []}}
    children = [
      supervisor(GRPC.Server.Supervisor, [{GrpcEx.Endpoint, 50051, adapter_opts: [status_handler: status_handler]}])
    ]

Let me know if it works for you and I'll submit the changes.

[polvalente]

Yes! This is what I had in mind.
The benefit of doing it this way is that 2 processes can be started with different configs

[carrascoacd]

Great, much better. I've submitted the change!