1

I am writing an API using ASP.NET and I have some potentially long running code from the different end points. The system uses CQRS and Event Sourcing. A Command comes into to an end point and is then published as an event using MediatR. However the Handlers are potentially long running. Since some of the Requests coming in might be sent to multiple Handlers. This process could take longer than the 12s that AWS allows before returning an Error code.

Is there a way to return a response back to the caller to say that the event has been created while still contining with the process? That is to say fire off a separate task that performs the long running piece of code, that also catches and logs errors. Then return a value back to the user saying the Event has been successfully created?

I believe that ASP.NET spins up a new instance each time a call is made, will the old instance die one a value is returned, killing the task?

I could be wrong with a number of points here, this is my knowledge gleaned from the internet but I could have missunderstood articles.

Thanks.

Tristan Trainer
  • 2,770
  • 2
  • 17
  • 33
  • Perhaps messaging is an option? You may even opt for a service bus. If so, you could take a look at my open-source service bus called [Shuttle.Esb](http://shuttle.github.io/shuttle-esb/) although there are many you could pick from. – Eben Roux May 24 '19 at 06:20

2 Answers2

1

If a new thread is running the long operation it will remain “open/live” until it finishes. Also you can configure the app pool to always be active.

There are a lot of frameworks to work with long running tasks like Hangfire.

And to keep the user updated with the status of the task you can use SignalR to push notifications to the UI

Igal23
  • 122
  • 3
  • Thank you that's really helpful, especially the extra framework might use that if it's signed off by the rest of the team or look for another one. Cheers! – Tristan Trainer May 23 '19 at 12:57
1

Yes, you should pass the long-running task off to a background process and return to the user. When the task is complete, notifiy the user with whatever mechanism is appropriate for your site.

But do not start a new thread, what you want is to have a background service running for this, and use that to manage your request.

gbjbaanb
  • 51,617
  • 12
  • 104
  • 148