How to stop mix to hard code a Node name for application release?

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1

I got an application where I’d like to start the node with a (long) name dynamically determined during runtime based on the computer’s IP address. However when I run mix release the application is given a node at compile time. I can’t for the life of me get anything useful out the mix release docs

So my question is, how do configure my project to not start the system with a pre-defined node.

Bonus question would be why does mix release hard code a node name? Won’t it make it impossible to differentiate between two nodes of the same application?

This is mostly what’s in my mix.exs

defmodule Elevator.MixProject do
  use Mix.Project

  def project do
    [
      app: :elevator,
      version: "0.8.0",
      elixir: "~> 1.13",
      start_permanent: Mix.env() == :prod,
      env: Mix.env(),
      releases: [
        win_debug: [
          include_executables_for: [:windows],
          applications: [runtime_tools: :permanent],
          path: "releases/win_debug/"
        ],
        lab_debug: [
          include_executables_for: [:unix],
          applications: [runtime_tools: :permanent],
          path: "releases/lab_debug/"
        ]
      ]
    ]
  end

  def application() do
    [
      extra_applications: [:logger, :runtime_tools],
      mod: {Main, []}
      # Switch with Main to simulate single elevator
      # mod: {ElevatorSimul, []}
    ]
  end
end
2

After trawling through elixir repos on Github for hints, I got a working solution by creating a file rel/env.bat.eex with the lines:

@echo off
set RELEASE_DISTRIBUTION=none

This disables the application from starting up Node, so that we can manually control it via Node.start/3

I also got a file rel/env.sh.eex that I assume will apply the same changes on Linux.

#!/bin/sh

export RELEASE_DISTRIBUTION=none
1 Like
3

You could also have used

mix release --init

It creates the rel folder and files automatically

2 Likes
4 
C:\Users\UlrikHD\Documents\test> mix release --init
** (Mix) Could not invoke task "release": 1 error found!
--init : Unknown option

It’s mix release.init as of elixir 1.18 (just in case someone stumbles over it)

Thanks for the tip though, it might help others that stumbles over a similar problem

1 Like