Thanks Gavin Good to know how things are done at your end. thanks! However, why is Twisted not internally using SO_REUSEPORT ? Is there any plan to integrate it inside twisted so that application need not worry about it ?
The problem with code mentioned here: http://stackoverflow.com/questions/10077745/twistedweb-on-multicore-multiprocessor is that the requests are not equally distributed across all processes. This imbalance leads to underutilization of CPU cores. This issue is also discussed on https://lwn.net/Articles/542629/ and that this is not an issue with SO_REUSEPORT Does it mean that Twisted is using single listening socket and all processes accept() on that socket ? thanks On Wed, Jun 10, 2015 at 2:23 AM, Gavin Panella <ga...@gromper.net> wrote: > On 10 June 2015 at 03:01, Sagar Dixit <sagar.di...@gmail.com> wrote: > > Hi, > > > > I am exploring Twisted Web for my RESTful application. My application > > is stateless and involves storing and retrieving objects based on > > Object-ID. This application will run on beefy (multicore, lots of > > memory) machine. However, not all APIs that the application issues to > > underlying storage are async and hence I cannot fully utilize > > Deferreds > > Which means, there will some blocking calls and hence my primary > > interest is to use Twisted Web in multiprocessing mode > > > > I came across > > > http://stackoverflow.com/questions/10077745/twistedweb-on-multicore-multiprocessor > > > > However, I am not sure if it is the "correct" way of doing things. > > > > Hence I had some questions around it: > > > > 1. Is there an interface (similar to defertoThread) which allows me to > > execute a blocking call in a separate process ? > > > > 2. Does reactor synchronize access of all processes to the shared > > listen socket ? > > > > 3. Is there a sample code I can refer to where the application is > > spawning subprocesses to handle HTTP requests ? > > We've used SO_REUSEPORT (which is briefly mentioned on the SO page you > linked to) in order to run multiple processes. On a recentish Linux the > following approach has worked well for us: > > # Make a socket with SO_REUSEPORT set so that we can run multiple web > # applications. This is easier to do from outside of Twisted as there's > # not yet official support for setting socket options. > s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) > s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) > # The following might not work on older kernels, or SO_REUSEPORT > # might not be available if Python was compiled with older headers. > # In the former case you're out of luck, but you can define the > # header yourself if it's missing from Python's socket module. > s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1) > > # Listen on all interfaces on port 1234. > s.bind(('0.0.0.0', 1234)) > > # Use a backlog of 50, which seems to be fairly common. > s.listen(50) > > # Adopt this socket into something more Twisty. > endpoint = AdoptedStreamServerEndpoint(reactor, s.fileno(), s.family) > > # Prevent garbage collection. This is something we discovered we > # needed, and is perhaps something that AdoptedStreamServerEndpoint > # ought to do itself. > endpoint.socket = s > > # Create a service with the endpoint. > service = OurService(site_endpoint) > > (Derived from src/maasserver/eventloop.py in MAAS.) > > We then use Upstart (Ubuntu 14.10 and before) or systemd (Ubuntu 15.04) > to run multiple processes. For us this mean 4, but you can have as many > or as few as you need, for example 1 process per CPU core. I like this > approach because we can use the system's facilities for process > supervision instead of cobbling together our own. > > One caveat is that the processes are running concurrently. If you're > modifiying shared resources you'll want to consider explicit locking > where before you might have been safe with Twisted' single-threadedness. > > Gavin. > > _______________________________________________ > Twisted-web mailing list > Twisted-web@twistedmatrix.com > http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-web > -- ssdixit
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