TaskAfter

TODO: Add description

Installation

• Available in Hex
• Documentation

Install this package by adding task_after to your list of dependencies in mix.exs:

def deps do
  [
    {:task_after, "~> 1.0.0"},
  ]
end

Global installation

To use this globally without needing to add it to your own supervision tree just add this to your configuration:

config :task_after, global_name: TaskAfter

Feel free to replace the global name of TaskAfter with anything you want. If the global name is unspecified then all usage of TaskAfter must have the :name or :pid options specified.

Local Installation

To use this locally to your application or to give distinct names so you can have different schedulars then just add the TaskAfter.Worker.start_link/1 to your supervision tree as normal, such as via:

children = [
  worker(TaskAfter.Worker, [[name: MyCustomName]]),
]

Note the 2 sets of list elements. You can have a nameless worker by leaving the name option out, such as:

children = [
  worker(TaskAfter.Worker, [[]]),
]

You will have to acquire the PID some other way, such as by querying your supervisor.

Usage

The main interface point is TaskAfter.task_after/2 and TaskAfter.task_after/3 where TaskAfter.task_after/2 just calls TaskAfter.task_after/3 with an empty set of options to use the defaults.

The arguments to TaskAfter.task_after/3 are, in this order:

1. timeout_after_ms -> integer millisecond timeout
2. callback -> The 0-arg callback function
3. opts -> Can be:
   • name: name | pid: pid -> Specify a non-global task handler, if unspecified that the application :global_name must be specified
   • id: id -> A unique id, if nil or unspecified then it is auto-generated
   • call_timeout: timeout -> Override the timeout on calling to the TaskAfter.Worker
   • no_return: true -> Do not return the id or error, just try to register and forget results otherwise
   • send_result: pid -> Sends the result of the task to the specified pid
   • send_result: :in_process -> Runs the task in the TaskAfter.Worker process to do internal work, do not use this

It can be used as in these examples:

defmodule TaskAfterTest do
  use ExUnit.Case, async: true
  doctest TaskAfter

  test "TaskAfter and forget" do
    s = self()
    {:ok, _auto_id} = TaskAfter.task_after(500, fn -> send(s, 42) end)
    assert_receive(42, 600)
  end

  test "TaskAfter and receive" do
    {:ok, _auto_id} = TaskAfter.task_after(500, fn -> 42 end, send_result: self())
    assert_receive(42, 600)
  end

  test "TaskAfter with custom id" do
    assert {:ok, :my_id} = TaskAfter.task_after(500, fn -> 42 end, id: :my_id, send_result: self())
    assert_receive(42, 600)
  end

  test "TaskAfter with custom id duplicate fails" do
    assert {:ok, :dup_id} = TaskAfter.task_after(500, fn -> 42 end, id: :dup_id, send_result: self())
    assert {:error, {:duplicate_id, :dup_id}} = TaskAfter.task_after(500, fn -> 42 end, id: :dup_id, send_result: self())
    assert_receive(42, 600)
  end

  test "TaskAfter lots of tasks" do
    assert {:ok, _} = TaskAfter.task_after(400, fn -> 400 end, send_result: self())
    assert {:ok, _} = TaskAfter.task_after(200, fn -> 200 end, send_result: self())
    assert {:ok, _} = TaskAfter.task_after(500, fn -> 500 end, send_result: self())
    assert {:ok, _} = TaskAfter.task_after(100, fn -> 100 end, send_result: self())
    assert {:ok, _} = TaskAfter.task_after(300, fn -> 300 end, send_result: self())
    assert {:ok, _} = TaskAfter.task_after(600, fn -> 600 end, send_result: self())
    assert_receive(100, 150)
    assert_receive(200, 150)
    assert_receive(300, 150)
    assert_receive(400, 150)
    assert_receive(500, 150)
    assert_receive(600, 150)
  end

  test "TaskAfter non-global by name" do
    assert {:ok, pid} = TaskAfter.Worker.start_link(name: :testing_name)
    {:ok, _auto_id} = TaskAfter.task_after(500, fn -> 42 end, send_result: self(), name: :testing_name)
    assert_receive(42, 600)
    GenServer.stop(pid)
  end

  test "TaskAfter non-global by pid" do
    assert {:ok, pid} = TaskAfter.Worker.start_link()
    assert {:ok, _auto_id} = TaskAfter.task_after(500, fn -> 42 end, send_result: self(), pid: pid)
    assert_receive(42, 600)
    GenServer.stop(pid)
  end

  test "TaskAfter in process (unsafe, can freeze the task worker if the task does not return fast)" do
    assert {:ok, pid} = TaskAfter.Worker.start_link()
    s = self()
    assert {:ok, _auto_id} = TaskAfter.task_after(500, fn -> send(s, self()) end, send_result: :in_process, pid: pid)
    assert_receive(^pid, 600)
    GenServer.stop(pid)
  end
end