Long running task in WebAPI

Stephen described why starting essentially long running fire-and-forget tasks inside an ApiController is a bad idea.

Perhaps you should create a separate service to execute those fire-and-forget tasks. That service could be a different ApiController, a worker behind a queue, anything that can be hosted on its own and have an independent lifetime.

This would make management of the different task lifetimes much easier and separate the concerns of the long-running tasks from the ApiController's core responsibilities.

You almost never want to do this. It is almost always a big mistake.

ASP.NET (and most other servers) work on the assumption that it's safe to tear down your service once all requests have completed. So you have no guarantee that your logging will be done, or that your data will be written to disk. Particularly with the disk writes, it's entirely possible that your writes will be corrupted.

That said, if you are absolutely sure that you want to implement this extremely dangerous design, you can use the BackgroundTaskManager from my blog.

Update: I've written a blog series that goes into detail on a proper solution for request-extrinsic code. In summary, what you really want to do is move the request-extrinsic code out of ASP.NET. Introduce a durable queue and an independent processor; the ASP.NET controller action will place a request onto the queue, and the independent processor will read requests and execute them. This "processor" can be an Azure Function/WebJob, Win32 Service, etc.

Great news, there is a new solution in .NET 4.5.2 called the QueueBackgroundWorkItem API. It's really simple to use:

HostingEnvironment.QueueBackgroundWorkItem(ct => DoSomething(a, b, c));

Here's an article that describes it in detail.

https://blogs.msdn.microsoft.com/webdev/2014/06/04/queuebackgroundworkitem-to-reliably-schedule-and-run-background-processes-in-asp-net/

And here's anohter article that mentions a few other approaches not mentioned in this thread. http://www.hanselman.com/blog/HowToRunBackgroundTasksInASPNET.aspx

As pointed out by others, it is not recommended. However, whenever there is a need there is a way, so take a look at IRegisteredObject

See also

http://haacked.com/archive/2011/10/16/the-dangers-of-implementing-recurring-background-tasks-in-asp-net.aspx/