How to Safely Implement Fire-and-Forget Async Methods in ASP.NET MVC?

Safe implementation of Fire-and-Forget asynchronous method in ASP.NET MVC: handling unhandled exceptions

This article explores the possible risks and best practices when implementing the "fire-and-forget" pattern of asynchronous methods in ASP.NET MVC, focusing on how to handle unobserved exceptions. This is a common question.

While synchronous methods can be wrapped for execution in a separate thread using Task.Run or TaskFactory.StartNew, asynchronous methods present unique challenges. Directly calling an asynchronous method without proper error handling can lead to unobserved exceptions, requiring a more comprehensive approach to address this issue.

One solution is to use a custom wrapper method like:

<code class="language-csharp">private async void DeleteFooWrapperAsync()
{
    try
    {
        await DeleteFooAsync();
    }
    catch(Exception exception)
    {
        m_log.Error("DeleteFooAsync failed: " + exception.ToString());
    }
}</code>

This method can be called within TaskFactory.StartNew and provides a safer way to handle exceptions. However, this requires writing custom wrapper code for each asynchronous method to be executed.

Another option (suggested by Stephen Cleary) is to use the BackgroundTaskManager component. This approach allows registering both synchronous and asynchronous work and handling exceptions via TaskScheduler.UnobservedTaskException:

<code class="language-csharp">BackgroundTaskManager.Run(() => DeleteFooAsync());</code>

It is important to note that "fire-and-forget" should be used with caution. If the result of DeleteFooAsync is important, it is recommended to wait for the task to complete. However, if such a pattern is indeed required, these solutions provide efficient ways to handle unobserved exceptions and prevent potential system failures.

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