Distillery: sasl.app does not exist or cannot be loaded

Questions / Help
1

Hi folks,

An Elixir beginner here. I’m reading the Programming Elixir 1.6 book and I’m in chapter 20, at using Distillery to release the app. Things are a bit outdated but I managed to find my way until this point where calling: mix distillery.release --env=prod is failing with this error messasge:
==> Invalid application `:sasl`! The file sasl.app does not exist or cannot be loaded.

I’m using elixir: "~> 1.15" and {:distillery, "~>2.0"} in my mix.exs.

I tried {:distillery, "~>2.1"} with no success. Looked up online and couldn’t find much information to help root cause the issue. Any clue what I’m missing here? Thanks!

❯ mix distillery.init

An example config file has been placed in rel/config.exs, review it,
make edits as needed/desired, and then run `mix distillery.release` to build the release

❯ mix distillery.release --env=prod
==> Assembling release..
==> Building release sequence_supervisor:0.1.0 using environment prod
==> Invalid application `:sasl`! The file sasl.app does not exist or cannot be loaded.

❯ iex --version
IEx 1.15.7 (compiled with Erlang/OTP 26)

❯ elixir --version
Erlang/OTP 27 [erts-15.1] [source] [64-bit] [smp:10:10] [ds:10:10:10] [async-threads:1] [jit] [dtrace]

Elixir 1.15.7 (compiled with Erlang/OTP 26)

❯ mix --version
Erlang/OTP 27 [erts-15.1] [source] [64-bit] [smp:10:10] [ds:10:10:10] [async-threads:1] [jit] [dtrace]

Mix 1.15.7 (compiled with Erlang/OTP 26)
2

Distillery is no longer used for elixir releases, as elixir has its own release tool these days: mix release — Mix v1.18.1

I would recommend to just take a look at documentation and try to adapt your project to elixir releases.

If that doesn’t work, I might guess the culprit most probably is the OTP version, in that book should be specified what OTP and elixir versions were used, stick to them and everything should work in theory.

1 Like
3

Yup, mix release worked for me.

4

mix release is a really wonderful tool, but it doesn’t support hot code upgrades while Distillery does.

So if you want to use Distillery here are the steps that you need:

  1. Use Erlang/OTP 24 because Distillery is not compatible with OTP 25

  2. Use Elixir version 1.14 or earlier. If you use a later version, you will not be able to run the IEx console in Distillery release. I suppose the reason is here and after Elixir 1.14 module IEx.CLI was refactored

Here is my tool-versions file from the brilliant asdf version manager:

erlang 24.3.4.17
elixir 1.14.5
  1. Create config/config.exs file with this content:
import Config
  1. Also don’t forget to use appropriate elixir version in project function from the mix.exs file, for example:
  def project do
    [
      app: :sequence,
      version: "0.1.0",
      elixir: "~> 1.14",
      start_permanent: Mix.env() == :prod,
      deps: deps()
    ]
  end

Yes, I also read this wonderful book and encountered the same problem :slight_smile:

  1. Use mix task which starts from the distillery prefix, for example: mix distillery.init and mix distillery.release --env=prod (my Distillery version is 2.1.1)

With all this, I was able to successfully complete the entire chapter of the book.

3 Likes
5

While there‘s no built in support it can be added by third parties: Castle - Hot-Code Upgrade Support for Elixir

2 Likes
6

I had to skip that chapter unfortunately. The release process is still not clear to me. I’ll try your suggestion though!
Wondering how common it is to downgrade Elixir/Erlang in prod applications?

7

Sometimes, this occurs just like it does with any other application in a different stack. However, it is usually common practice to use Docker and simply redeploy the container with the previous version.

I apologize; at first, I misunderstood the question.

It depends. we usually strive to use the latest versions of Elixir/Erlang. However, if it’s a critical system, there might be a compromise: using hot code updates but sticking to slightly older versions of Elixir/Erlang.

One way or another, I haven’t encountered the use of hot code updates in production. Typically, Docker containers are used along with the latest versions of Elixir/Erlang. Nevertheless, it was useful to get acquainted with this mechanism and experiment with it in the context of this chapter of the book.

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