Demo

A small project to demonstrate how Phoenix channels may be used.

How do I start with a Phoenix app?

mix phx.new demo --no-html --no-webpack --no-gettext --no-ecto

This will help us keep the app small and maintanable while getting rid of stuff we would never use. Perhaps the --no-ecto flag may be left out if we're sure that we'll need to use a database.

Then I immediately go in to config/*.exs and change use Mix.Config to import Config as that's the standard in latest Elixir.

I also remove all the comments, since they are like "You don't say":

# Configures the endpoint
config :demo, DemoWeb.Endpoint,
  ...

Then I remove all the prod.secret.exs stuff, because Elixir has a better support for release configs: [https://elixir-lang.org/getting-started/mix-otp/config-and-releases.html]

I actually don't leave too much of the config Phoenix generated, because it enforces bad practices. That's how I usually treat it:

• config.exs is where the main part of the configuration is with dev defaults
• this way I don't really need a dev.exs, but I like the convenience of import_config "#{Mix.env()}.exs", so I just leave the file empty (except for the import Config line)
• if I need some other config for testing, then put it in test.exs
• prod.exs holds anything that's related to production and not a secret
• I deal with secrets through Elixir releases mentioned above

I then remove most of the comments from the files in parallel to a cleanup.

Delete the <app_name>.ex, because it's empty and of no use. Plain noise. I usually get rid of the ErrorView (note that it's also referenced in the config) and, in fact, all the views, because I'm not doing any actual FE. While we're there, delete the controllers directory and remove all the unnecessary part from demo_web.ex. And there's the static files exposed in the generated DemoWeb.Endpoint. I've got no statics, so I remove them. I'd also get rid of the sessions stuff, because again, it assumes my app is going to be used from a browser. I removed Plug.Head and Plug.MethodOverride from my endpoint, because I don't need them right now, maybe never.

Since we removed ErrorView, we have to handle errors somehow. For start, we can add use Plug.ErrorHandler to our router (make sure to put it before use Phoenix.Router) and implement a generic handle_errors/2 call inside it.

Now we can also remove most of the test directory. Leave support and test_helper.exs. Then I run mix test to see if it all compiles. It does.

Finally I initialize the Elixir release with mix release.init, then immediately remove env.bat.eex, because of reasons. Then add config/releases.exs with whatever secret we have (currently it's the endpoint secret key base).

I lied, I also make sure to fetch the endpoint's port and hostname from the environment.

Now test if the application can be released.

MIX_ENV=prod mix release
SECRET_KEY_BASE=$(mix phx.gen.secret) PORT=8888 _build/prod/rel/demo/bin/demo start_iex

works like a charm.