Stop a Task and Async Task

Stop a task

What happens if our task is stuck and never finishes?

While await/1 stops the task, yield/1 will leave it running. It is good to stop the task manually by calling Task.shutdown(task). The shutdown/1 function also accepts a timeout and gives the process the last chance to complete before stopping it. If it ends, we will receive the result as expected. We can also stop a process immediately by using the :brutal_kill atom as the second argument.

As we can see, using yield/1 and shutdown/1 is a bit more work than await/1. Deciding what to use depends on our use case. A task timeout often justifies an exception, in which case await/1 will be more convenient to use. Whenever we require more control over the timeout and shutdown, we can switch to yield/1 and shutdown/1. The important part is that after using async/1, we always process the result. We can do this using either await/1 or yield/1 followed by shutdown/1.

Sender example

We are going to update our sender example.

Update notify_all

For our notify_all/1 logic, we’ll use await/1 for simplicity. Now we’re going to replace Task.start/1 with Task.async/1 and use Enum.map/2 instead of Enum.each/2. This is because we want to map each email string to its corresponding Task struct. The struct is needed to retrieve the result from each process: