Release Configuration

While having the same Oban configuration for every environment might be fine, there are certainly times you might want to make changes for a specific environment. For example, you may want to increase or decrease a queue's concurrency.

Using Config Providers

If you are using Elixir Releases, this is straight forward to do using Module Config Providers:

defmodule MyApp.ConfigProvider do
  @moduledoc """
  Provide release configuration for Oban Queue Concurrency

  @behaviour Config.Provider

  def init(path) when is_binary(path), do: path

  def load(config, path) do
    case parse_json(path) do
      nil ->

      queues ->
        Config.Reader.merge(config, ingestion: [{Oban, [queues: queues]}])

  defp parse_json(path) do
    {:ok, _} = Application.ensure_all_started(:jason)

    if File.exists?(path) do
      |> Jason.decode!()
      |> Map.fetch!("queues")
      |> {key, value} -> {String.to_atom(key), value} end)

Our config provider ensures that the Jason app is loaded so that we can parse a JSON configuration file. Once the JSON is loaded we must extract the queues map and convert it to a keyword list where all of the keys are atoms. The use of String.to_atom/1 is safe because all of our queues names are already defined.

Then you include this in your mix.ex file, where your release is configured:

releases: [
  umbrella_app: [
    version: "0.0.1",
    applications: [
      child_app: :permanent
    config_providers: [{Path.To.ConfigProvider, "/etc/config.json"}]

Then when you release your app, you ensure that you have a JSON file mounted at whatever path you specified above and that it contains all of your desired queues:

{"queues": {"special": 1, "default": 10, "events": 20}}