Pulsar in multiprocessing mode and Ctrl-C issue about uvloop

[1st1]

No, uvloop should behave exactly as vanilla asyncio. Would it be possible for you to make a failing unittest similar to other subprocess tests in 'uvloop/tests/'?

[lsbardel]

I'm not sure how to do that! 😞

The issue occurs only when I press Ctril-C on the shell.

If I send SIGINT/SIGTERM to the main process not using Ctrl-C, everything works as expected.
You can see it yourself by running this script:

pip install git+http://github.com/quantmind/pulsar.git@coroactor#egg=pulsar uvloop
py scripy.py --io uv

where script.py is

from pulsar import MethodNotAllowed
from pulsar.apps import wsgi


def hello(environ, start_response):
    '''The WSGI_ application handler which returns an iterable
    over the "Hello World!" message.'''
    if environ['REQUEST_METHOD'] == 'GET':
        data = b'Hello World!\n'
        status = '200 OK'
        response_headers = [
            ('Content-type', 'text/plain'),
            ('Content-Length', str(len(data)))
        ]
        start_response(status, response_headers)
        return iter([data])
    else:
        raise MethodNotAllowed


def server(description=None, **kwargs):
    '''Create the :class:`.WSGIServer` running :func:`hello`.'''
    description = description or 'Pulsar Hello World Application'
    return wsgi.WSGIServer(hello, description=description, **kwargs)


if __name__ == '__main__':  # pragma nocover
    server().start()

Try to Ctrl-C and wait for about 5 seconds.
Than test with the vanilla asyncio loops

py script.py

or

py script.py --io select

[1st1]

Alright, I'll take a look in a few days!

[1st1]

I'm trying to figure out what's going on here and have some questions about how Pulsar works. Could you please point out to the place where you fork/create subprocesses for actors?

[1st1]

I see, it looks like you just instantiate multiprocessing.Process class. In asyncio, it's more reliable to use loop.subprocess_exec for that (at least that's what uvloop is tuned for).

[lsbardel]

Right, that is what I suspected.
Pulsar was born before asyncio, that is why multiprocessing module is used for process-based actors.
I will have to look into the subprocess_exec method and see what exactly does and compare with multiprocessing.

[lsbardel]

OK, using asyncio subprocess_exec fixes the issue.
Looks like the multiprocessing won't be used directly by pulsar anymore (I still need it for sharing server sockets between processes)

[1st1]

Great! I ended up rewriting how signals handling is implemented in uvloop from scratch. Maybe multiprocessing will work just fine when I'm done.

[1st1]

@lsbardel Please try uvloop 0.5.4. Ctrl-C is now being handled exactly as in asyncio.

[lsbardel]

Yes it works! Nice one.
Pulsar 1.5 will have two ways of doing multiprocessing, via asyncio subprocess or multiprocessing module. The asyncio way is better because it does not block during forking.
In any case thanks for feedback and fixes.

[1st1]

@lsbardel Thanks for confirming that everything works now! Closing this issue.