On Mon, Feb 20, 2012 at 8:09 PM, Eric Larson <[email protected]> wrote:
> CherryPy provides a bus that allows you to add events to the web server > process. It is specified pretty clearly and CherryPy recently made it > available as a standalone package, Magicbus ( > https://bitbucket.org/cherrypy/magicbus/overview). Specifically it allows > you to send events on different signals the main server process might get. > You can also use it for a general bus within the app server, but at its > most basic level, the goal was to make the stop/start/restart events easy > to hook into. > > I've found it to be really helpful for managing processes and wrote a > simple supervisor-ish app called Dad using it ( > http://bitbucket.org/elarson/dad). > Thanks for the pointer -- that looks pretty neat I would be more interested though, in defining an extension to the WSGI standard A rough example of what I am talking about: If I take the wsgiref doc, here's an example of a minimal wsgi application (myapp.py): from wsgiref.simple_server import make_server def hello_world_app(environ, start_response): status = '200 OK' # HTTP Status headers = [('Content-type', 'text/plain')] start_response(status, headers) return ["Hello World"] def main(): return make_server('', 8000, hello_world_app) That module can be run by any web server out there that understands WSGI. For instance, with gunicorn I can do: $ gunicorn myapp:main What I am talking about is a second entry point for the shutdown - example: from wsgiref.simple_server import make_server def hello_world_app(environ, start_response): status = '200 OK' # HTTP Status headers = [('Content-type', 'text/plain')] start_response(status, headers) return ["Hello World"] def main(): return make_server('', 8000, hello_world_app) def shutdown(): # or maybe something else as an argument I don't know do_some_cleanup() And point the shutdown callable to a web server: $ gunicorn myapp:main myapp:shutdown If this is defined in the WSGI standard it means any wsgi web server could call shutdown() , not only gunicorn Cheers Tarek > HTH > > Eric > > -- > Eric Larson > > > On Monday, February 20, 2012 at 10:03 AM, Tarek Ziadé wrote: > > > Hello > > > > I need to be able to call a function when the web application shuts down > (SIGTERM/SIGINT) -- the use case is to stop a background thread. > > > > I am currently using signals because it seems to be the most clean way > to do this. atexit is much trickier since you don't know when it's going to > get called and you might try to call objects that were garbage collected > unless you hack something to keep references alive. > > > > But signals are also tricky beasts since you may compete with other code > that are listening to them. For instance mod_wsgi don't like apps that have > signal handlers. > > > > Anyways, the bottom line is that the cleanest way to do this -- as per > Chris McDonough idea, would be to introduce in the WSGI protocol a > "shutdown" function the servers would be obligated to call before exiting. > > > > I am not sure yet about its arguments, maybe a signum + frame or simply > an exit code... > > > > But how do you like the idea ? That would solve for me the problem of > having to deal differently here depending on if I am called with mod_wsgi > or gunicorn or xxx > > > > > > Cheers > > Tarek > > > > -- > > Tarek Ziadé | http://ziade.org > > _______________________________________________ > > Web-SIG mailing list > > [email protected] (mailto:[email protected]) > > Web SIG: http://www.python.org/sigs/web-sig > > Unsubscribe: > http://mail.python.org/mailman/options/web-sig/eric%40ionrock.org > > > > -- Tarek Ziadé | http://ziade.org
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