TaskAfter

This is a library to call a function after a set delay. Usage is as simple as: TaskAfter.task_after(500, fn -> do_something_after_500_ms() end)

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

You can also cancel a task via TaskAfter.cancel_task_after/1 and TaskAfter.cancel_task_after/2 where TaskAfter.cancel_task_after/1 just defaults to having an empty opts list.

The arguments to TaskAfter.cancel_task_after/2 are, in this order:

1. task_id -> A task id
2. opts -> Can be:
   • name: name | pid: pid -> Specify a non-global task handler, if unspecified that the application :global_name must be specified
   • 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
   • run_result: pid -> Sends the result of the task to the specified pid after running it as an async task while returning the Task
   • run_result: :in_process -> Runs the task in the TaskAfter.Worker process to do internal work, do not use this, returns the value directly though
   • run_result: :async -> Runs the task as an async task and dismisses the result while returning the Task
   • run_result: nil -> Default: Does not run the task now, just cancels it immediately, returns the callback function

You can change a task via TaskAfter.change_task_after/2.

The arguments to TaskAfter.change_task_after/2 are, in this order:

1. task_id -> A task ID
2. opts -> Can be:

• name: name | pid: pid -> Specify a non-global task handler, if unspecified that the application :global_name must be specified
• call_timeout: timeout -> Override the timeout on calling to the TaskAfter.Worker*noreturn: true-> Do not return the id or error, just try to register and forget results otherwise *callback: fun-> Change the callback to this function *timeout_after_ms: timeout-> Change the timeout to this new value *send_result: pid-> Sends the result of the task to the specified pid after running it as an async task *send_result: :in_process-> Runs the task in theTaskAfter.Workerprocess to do internal work, do not use this *send_result: :async-> **Default**: Runs the task as an async task and dismisses the result *recreate: true-> If this is passed in thencallback,timeout_after_ms, andsend_result**must** be specified to be able to recreate the task if it is already elapsed. Note: Of course if the task has already run then changing a setting on it won't do anything unlessrecreate: trueis passed in. Note: Whenrecreate: trueis used thencallback,timeout_after_ms, andsend_resultcan be passed in their value wrapped in a tagged:defaulttuple liketimeout_after_ms: {:default, 500}` and it will not change the existing value if not recreating but will use the value if it is. They can be used as in these examples/tests: ```elixir test “TaskAfter and forget” do s = self() assert {:ok, _auto_id} = TaskAfter.task_after(500, fn -> send(s, 42) end) assert_receive(42, 600) end test “TaskAfter and receive” do assert {: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.taskafter(400, fn -> 400 end, send_result: self()) assert {:ok, } = TaskAfter.taskafter(200, fn -> 200 end, send_result: self()) assert {:ok, } = TaskAfter.taskafter(500, fn -> 500 end, send_result: self()) assert {:ok, } = TaskAfter.taskafter(100, fn -> 100 end, send_result: self()) assert {:ok, } = TaskAfter.taskafter(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 test “TaskAfter and cancel timer, do not run the callback” do cb = fn -> 42 end assert {:ok, auto_id} = TaskAfter.task_after(500, cb) assert {:ok, ^cb} = TaskAfter.cancel_task_after(auto_id) end test “TaskAfter and cancel timer, but its already been run or does not exist” do assert {:error, {:does_not_exist, :none}} = TaskAfter.cancel_task_after(:none) assert {:ok, auto_id} = TaskAfter.task_after(0, fn -> 42 end, send_result: self()) assert_receive(42, 100) assert {:error, {:does_not_exist, ^auto_id}} = TaskAfter.cancel_task_after(auto_id) end test “TaskAfter and cancel but also run the callback in process (unsafe again)” do assert {:ok, auto_id} = TaskAfter.task_after(500, fn -> 42 end) assert {:ok, 42} = TaskAfter.cancel_task_after(auto_id, run_result: :in_process) end test “TaskAfter and cancel but also run the callback async” do s = self() assert {:ok, auto_id} = TaskAfter.task_after(500, fn -> send(s, 42) end) assert {:ok, :task} = TaskAfter.cancel_task_after(auto_id, run_result: :async) assert_receive(42, 600) end test “TaskAfter and cancel but also run the callback async while returning result to pid” do s = self() assert {:ok, auto_id} = TaskAfter.task_after(500, fn -> 42 end) assert {:ok, :task} = TaskAfter.cancel_task_after(auto_id, run_result: s) assert_receive(42, 600) end test “TaskAfter and crash” do s = self() len = &length/1 d = len.([]) assert {:ok, _auto_id0} = TaskAfter.task_after(100, fn -> send(s, 21) end) assert {:ok, _auto_id1} = TaskAfter.task_after(250, fn -> send(s, 1/d) end) assert {:ok, _auto_id2} = TaskAfter.task_after(500, fn -> send(s, 42) end) assert_receive(42, 600) assert_receive(21, 1) assert :no_message = (receive do m -> m after 1 -> :no_message end) end test “TaskAfter and replace callback without recreate” do assert {:ok, auto_id} = TaskAfter.task_after(500, fn -> 1 end, send_result: self()) assert {:ok, ^auto_id} = TaskAfter.change_task_after(auto_id, callback: fn -> 2 end) assert_receive(2, 600) assert {:error, {:does_not_exist, ^auto_id}} = TaskAfter.change_task_after(auto_id, callback: fn -> 3 end) end test “TaskAfter and replace callback and timeout with recreate” do assert {:ok, auto_id} = TaskAfter.task_after(500, fn -> 1 end, send_result: self()) assert {:ok, ^auto_id} = TaskAfter.change_task_after(auto_id, recreate_if_necessary: true, timeout_after_ms: 500, send_result: self(), callback: fn -> 2 end) assert_receive(2, 600) assert {:ok, ^auto_id} = TaskAfter.change_task_after(auto_id, recreate_if_necessary: true, timeout_after_ms: 500, send_result: self(), callback: fn -> 3 end) assert_receive(3, 600) end test “TaskAfter and replace callback without timeout with recreate” do assert {:ok, auto_id} = TaskAfter.task_after(500, fn -> 1 end, send_result: self()) assert {:ok, ^auto_id} = TaskAfter.change_task_after(auto_id, recreate_if_necessary: true, timeout_after_ms: 500, send_result: self(), callback: fn -> 2 end) assert_receive(2, 600) assert {:ok, ^auto_id} = TaskAfter.change_task_after(auto_id, recreate_if_necessary: true, timeout_after_ms: {:default, 500}, send_result: self(), callback: fn -> 3 end) assert_receive(3, 600) end test “TaskAfter and replace timeout without recreate” do assert {:ok, auto_id} = TaskAfter.task_after(200, fn -> 1 end, send_result: self()) assert {:ok, ^auto_id} = TaskAfter.change_task_after(auto_id, timeout_after_ms: 500) assert :no_message = (receive do m -> m after 300 -> :no_message end) assert_receive(1, 600) end ```