Why do service fabric templates use Thread.Sleep instead of Task.Delay?

Question

When I create a new service fabric application with a stateless aps.net core service, why is this line of code in the main method of the service?

// prevents this host process from terminating so services keep running
Thread.Sleep(Timeout.Infinite)

Obviously as the code comment above the actual code says, this is to prevent the host process from terminating. But why not make the main method return an async Task instead of void to be able to use await Task.Delay()? From my understanding the latter would be better because the main thread would be put back into the thread pool to actually do something useful and not just sit there doing nothing other than waiting.

The code a couple of lines above leads me to believe that this is just a leftover from when the main method could not return an async Task.

ServiceRuntime.RegisterServiceAsync("FirstStatelessApiType",
    context => new FirstStatelessApi(context)).GetAwaiter().GetResult();

(GetAwaiter().GetResult() would also be unnccessary if the method would just return an async Task as it could then be awaited)

Edit: I have already tested switching from void Mainto async Task Main and using await Task.Delay(Timeout.Infinite) instead of Thread.Sleep and did not see a difference in the behavior of my service (api endpoints were still running and working as expected)

Answer 1

But why not make the main method return an async Task instead of void to be able to use await Task.Delay()? From my understanding the latter would be better because the main thread would be put back into the thread pool to actually do something useful and not just sit there doing nothing other than waiting.

That's not actually what happens when async Task Main is used. What actually happens is that the main thread is (synchronously) blocked on the Task returned from Main; this is to prevent the process from exiting.

The code a couple of lines above leads me to believe that this is just a leftover from when the main method could not return an async Task.

This is a good point, and I would use async Task Main and use await instead of blocking anywhere. The code would essentially behave the same, but it would look more correct.