Module is not available when running Elixir exq workers

Question

I have built an async job processing app using Elixir exq. The documentation says that I can run the application using both the terminal (with iex -S mix) or as a standalone application (with mix exq.run). When I run on the terminal, everything works fine, but when I run the standalone app, I get this message when the jobs are fetched:

16:52:55.028 [info]  Elixir.MyWorker[128f902c-dd22-4706-95a2-89dc974b95d6] start

16:52:55.045 [error] Process #PID<0.196.0> raised an exception
** (UndefinedFunctionError) function MyWorker.perform/1 is undefined (module MyWorker is not available)
    MyWorker.perform("arg1")
    (exq 0.14.0) lib/exq/worker/server.ex:186: anonymous fn/4 in Exq.Worker.Server.dispatch_work/3

16:52:55.052 [info]  Queueing job 128f902c-dd22-4706-95a2-89dc974b95d6 to retry in 24.0 seconds

What am I doing wrong?

Here is my lib/my_worker.ex file:

defmodule MyWorker do
  def perform(arg) do
    IO.puts("teste: " <> arg)
  end
end

and my mix.exs

defmodule WorkersSandbox.MixProject do
  use Mix.Project

  def project do
    [
      app: :workers_sandbox,
      version: "0.1.0",
      elixir: "~> 1.10",
      start_permanent: Mix.env() == :prod,
      deps: deps()
    ]
  end

  # Run "mix help compile.app" to learn about applications.
  def application do
    [
      applications: [:exq_ui, :exq],
      extra_applications: [:logger]
    ]
  end

  # Run "mix help deps" to learn about dependencies.
  defp deps do
    [
      {:exq, "~> 0.14.0"},
      {:jason, "~> 1.0"},
      {:exq_ui, "~> 0.11.0"},
      {:plug_cowboy, "~> 2.0"}
    ]
  end
end

and my config/config.exs:

import Config

config :exq,
  start_on_application: true,
  name: Exq,
  host: "127.0.0.1",
  port: 6379,
  # password: "",
  namespace: "exq",
  queues: [{"default", 10_000}, {"fila2", 10_000}],
  poll_timeout: 50,
  scheduler_poll_timeout: 200,
  scheduler_enable: true,
  max_retries: 25,
  mode: :default,
  shutdown_timeout: 5000

Have you tried `mix do app.start, exq.run` as https://github.com/akira/exq#standalone-exq suggests? — DNNX, Nov 07 '20 at 13:20
Yes, it worked. These instructions were updated after I opened this issue: https://github.com/akira/exq/issues/432 — Daniel Cukier, Nov 09 '20 at 15:15

score 1 · Accepted Answer · answered Nov 09 '20 at 15:17

As explained in this issue,

you should start the workers with this command:

mix do app.start, exq.run

or just

mix run --no-halt

should work in these cases. The exq.run mix task just starts the exq application, not the main app. The documentation was updated to be clear about this.

Module is not available when running Elixir exq workers

1 Answers1