Mono does not emit ProcessExit event on SIGTERM.

[tmds]

To reproduce:

dotnet new web -o web
cd web
dotnet run

Find the pid of the dotnet run process, and send it SIGTERM from another terminal:

kill -SIGTERM <pid>

With CoreCLR, the application shuts down, and the exit code is 0:

...
info: Microsoft.Hosting.Lifetime[0]
      Application is shutting down...
$ echo $?
0

With Mono, the application keeps running, the dotnet run process gets terminated:

Terminated
$ echo $?
143

The web process is still running, you can send it SIGTERM seperately and it terminates nicely.

info: Microsoft.Hosting.Lifetime[0]
      Application is shutting down...

This difference in behavior is causing one of the source-build smoke tests to fail: dotnet/source-build#3174.

cc @akoeplinger

[akoeplinger]

Hmm it feels more like a dotnet/runtime issue to me given this is a difference between Mono and CoreCLR. Should I move the issue?

[tmds]

I was not sure where to create it. It does look like the ASP.NET app responds to SIGTERM appropriately.
You can move it to another repo if you prefer.

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[akoeplinger]

@lambdageek do you know which area we should assign this to?

[lambdageek]

@akoeplinger not sure. AppModel, maybe? Cc @vitek-karas

It will probably come back to mono, but it's not obvious to me why the behavior difference.

[jkotas]

It is most likely an issue with Mono-specific SIGTERM handler.

[jkotas]

Potential duplicate of #31656

[tmds]

I've debugged this issue. Mono doesn't install a signal handler for SIGTERM to emit the AppDomain.CurrentDomain.ProcessExit event.

CoreCLR installs it here:

runtime/src/coreclr/pal/src/exception/signal.cpp

Line 236 in 9e05d33

handle_signal(SIGTERM, sigterm_handler, &g_previous_sigterm);

This event is used by the cli to reap the child processes using its ProcessReaper class.

A simpler reproducer for the issue is:

AppDomain.CurrentDomain.ProcessExit += delegate { Console.WriteLine("Process exit"); };
Thread.Sleep(int.MaxValue);

If you send SIGTERM to this app, with CoreCLR you'll see the message get printed, and with Mono you don't.