Task (Elixir)

Tasks can be started either with an anonymous function or using the Module-Function-Arguments (MFA) form.

A plain receive waits forever if no matching message arrives.

Use an after clause to avoid blocking indefinitely (this is basically a timeout in Erlang).

receive do
  {^pid, :result, value} ->
    value
after
  2000 ->
    raise "Timed out!"
end

• Prevents hanging when a process crashes or takes too long.
• Timeout is specified in milliseconds.

• Default timeout: 5 seconds
• Raises an exception if the task doesn't finish in time.

Task.await(task)
# default: 5000 ms

Task.await(task, 7000)
# custom timeout

Task.await(task, :infinity)
# wait forever

Unlike `Task.await`, `Task.yield` lets you poll a task without crashing on timeout.

Returns:

• `{:ok, result}` → task completed
• `nil` → timeout expired

case Task.yield(task, 5000) do
  {:ok, result} ->
    result

  nil ->
    Logger.warn("Timed out!")
    Task.shutdown(task)
end

Useful for:

• Long-running background work.
• Periodically checking task completion.
• Gracefully shutting down stalled tasks.

Stops a running task.

• Returns `{:ok, result}` if the task finishes while shutting down.
• Returns `nil` if it doesn't.

Often used together with `Task.yield`.

Instead of hardcoding milliseconds, use Erlang's :timer helpers.

:timer.seconds(5)   ;; 5000
:timer.minutes(5)   ;; 300000
:timer.hours(5)     ;; 18000000

Task.await(task, :timer.seconds(7))

This makes timeout values easier to read and maintain.