config/runtime.exs

[ksmithut]

In your README, you state that this isn't compatible with Elixir Releases because you can't use this module at compile time, which makes sense. But in Elixir 11, they added a new runtime configuration file documented here. Could you document how one might use this module using this config/runtime.exs file? Or is it still not possible?

[iloveitaly]

@ksmithut interesting! Do you know where I can learn more about runtime.exs the documentation you linked to is pretty sparse. How is this different from the other configuration options?

I don't personally use releases, so your best bet is trying dotenv with runtime.exs to see if it supports runtime loading of configuration. Let me know what you find!

[ksmithut]

@iloveitaly Ya, their hex docs are very sparse... Looks like the best one I could find was their 1.11 release announcement.

So I haven't tried building it with releases, but I put this at the top of my config/runtime.exs file and it loads it in mix mode:

use Mix.Config
Dotenv.load!()

[ksmithut]

I'm still tweaking usage, I'm still pretty new to Elixir. Right now my setup isn't working with releases, but I'm diving in to get a setup that works. I'll let you know what I find.

[ksmithut]

Okay, I was able to get it to work with that tweak with one minor alteration. In my config/runtime.exs instead of use Mix.Config I used import Config, so the top of my file looked like this:

import Config
Dotenv.load!()

And it loads from my .env file just fine :)

[iloveitaly]

@ksmithut nice, that's awesome! Do you know if runtime loads in prod as well? My guess is if you are doing a Heroku-style deploy (i.e. without releases) you'd actually want Dotenv not to run in that environment.

[ksmithut]

I believe runtime loads in prod as well, though you could probably do a check for the environment before calling Dotenv.load!

[fireproofsocks]

This discussion may be useful: https://elixirforum.com/t/what-cannot-be-runtime-config/38499/9
particularly the example app linked including the runtime.exs usage here: https://gitlab.com/code-stats/code-stats/-/blob/b1cf53462a3fa34369eaa06494754c7ae38aed2a/config/runtime.exs

A couple takeaways:

• you can't use Mix.env() inside your application start (because in a release build, Mix is not available)
• it might be useful to parse the .env from inside your runtime.exs
• there might be a need for an :overwrite flag for cases where a system ENV is already set (not sure if your implementation handles this or not, but imagine SOME_VAR=xyz _build/dev/rel/myapp/bin/myapp start_iex -- the expectation is that SOME_VAR would override any SOME_VAR declared in a .env

[fireproofsocks]

In my testing, this package worked fine with releases. I included an example of this in PR #40
In short, in your runtime.exs, you can do something like this:

import Config

if config_env() != :test do
  Dotenv.load(".env")
  config :yourapp,
          db_url: System.fetch_env!("DB_URL"),
          # ... etc ...
end