Can't do gracefull shutdown of apllication

[vokson]

Granian 1.3.1

My goal is to make program handling http request and send them to Kafka. I use https://github.com/confluentinc/confluent-kafka-python library, which is syncronious. Thus, I have to implement infinitive loop flushing kafka queue in separate thread for each granian's worker. The loop runs while flag is_cancelled = False.
When I stop program (Ctrl-C, for example),

def shutdown_app():
   is_cancelled = True

if __name__ == "__main__":
    try:
        app.serve()
    except KeyboardInterrupt:
        pass
    finally:
        shutdown_app()

I expect granian will stop and somehow move to shutdown_app() function to give me possibility to set is_cancelled = True and stop infinite thread. Unfortunately, granian never stops, because infinite thread is included in granian worker process.

    def _stop_workers(self):
        for proc in self.procs:
            proc.terminate()

        for proc in self.procs:
            proc.join()  <<- HERE

        self.procs.clear()

If changed to proc.join(1)', after 1 sec execution moves ahead and comes in shutdown_app` function, then I can manage other stuff.

Possible solution:

1. Add callback function to class Granian, which will called before stop of worker
2. Add timeout property X to class Granian, which will be used as proc.join(X)

[gi0baro]

@vokson is that a WSGI application? For ASGI you can rely on the lifespan events to perform actions on shutdown.

Anyways, 1.4 will probably review signal handling and eventually add callbacks. In general, you can always customise what happens on the workers writing your own spawn method: for instance you can copy the code of _spawn_wsgi_worker (https://github.com/emmett-framework/granian/blob/master/granian/server.py#L284-L319) and add any code you want after the serve call (blocking til shutdown).

[vokson]

app = Granian(
    "main:main",
    interface=Interfaces.RSGI,
    loop=Loops.uvloop,
    address="0.0.0.0",
    port=PORT,
    workers=int(os.getenv("HTTP_PROCESSES", "1")),
    threads=int(os.getenv("HTTP_PROCESS_WORKERS", "1")),
)

I think, it is RSGI application. @gi0baro

[gi0baro]

@vokson understood.
RSGI might introduce also shutdown callbacks in the near future. In the meantime everything I wrote for _spawn_wsgi_worker is also true for _spawn_rsgi_worker.

[vokson]

Thank you. Let's wait shutdown callbacks functionality