Python socket multiprocessing pool of workers

Question

I need to receive connections by sockets, read input data, do hard and long calculations and then send an answer. Queries at the same time may be a lot (ie 100) I understood, that because of GIL I can't use normal threads, and tried to use C++ with boost:threads and boost:python, and running subinterpreter of python in each thread. But anyway it's not utilised all cores 100% at the same time.

So I decided to use multiprocessing, but create a static count pool of workers to serve these requests with a queue. This way, we don't waste time to fork a process, and we will not have 100 or more processess at the same time, only static count.

I am new to Python, mostly I utilised C++

So now I have this code, but it is not working. The connection opens and immediately closes, I don't know why:

#!/usr/bin/env python   
import os
import sys
import SocketServer
import Queue
import time
import socket
import multiprocessing
from multiprocessing.reduction import reduce_handle
from multiprocessing.reduction import rebuild_handle 

class MultiprocessWorker(multiprocessing.Process):

    def __init__(self, sq):

        self.SLEEP_INTERVAL = 1

        # base class initialization
        multiprocessing.Process.__init__(self)

        # job management stuff
        self.socket_queue = sq
        self.kill_received = False

    def run(self):
        while not self.kill_received:
            try:     
                h = self.socket_queue.get_nowait()          
                fd=rebuild_handle(h)
                client_socket=socket.fromfd(fd,socket.AF_INET,socket.SOCK_STREAM)
                #client_socket.send("hellofromtheworkerprocess\r\n")
                received = client_socket.recv(1024)
                print "Recieved on client: ",received
                client_socket.close()

            except Queue.Empty:
                pass

            #Dummy timer
            time.sleep(self.SLEEP_INTERVAL)

class MyTCPHandler(SocketServer.BaseRequestHandler):
    """
    The RequestHandler class for our server.

    It is instantiated once per connection to the server, and must
    override the handle() method to implement communication to the
    client.
    """

    def handle(self):
        # self.request is the TCP socket connected to the client
        #self.data = self.request.recv(1024).strip()
        #print "{} wrote:".format(self.client_address[0])
        #print self.data
        # just send back the same data, but upper-cased
        #self.request.sendall(self.data.upper())

        #Either pipe it to worker directly like this
        #pipe_to_worker.send(h) #instanceofmultiprocessing.Pipe
        #or use a Queue :)

        h = reduce_handle(self.request.fileno())
        socket_queue.put(h)


if __name__ == "__main__":

    #Mainprocess
    address =  ('localhost', 8082)
    server = SocketServer.TCPServer(address, MyTCPHandler)
    socket_queue = multiprocessing.Queue()

    for i in range(5):
        worker = MultiprocessWorker(socket_queue)
        worker.start()

    try:
        server.serve_forever()
    except KeyboardInterrupt:
        sys.exit(0)

Answer 1

Is there a reason why you do not use

def reduce_socket(s):
    ...

def rebuild_socket(ds):
    ...

?

It seems like you could do this:

import copyreg
copyreg.pickle(type(socket.socket), reduce_socket, rebuild_socket)

and then pass the socket to the queue.

These are suggestions. Do they help?

Answer 2

try this:

def handle(self):
    h = reduce_handle(self.request.fileno())
    socket_queue.put(h)
    self.request.close()

note the self.request.close() addition.