lib/py/src/server/TProcessPoolServer.py

#
# Licensed to the Apache Software Foundation (ASF) under one
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# distributed with this work for additional information
# regarding copyright ownership. The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License. You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
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# KIND, either express or implied. See the License for the
# specific language governing permissions and limitations
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import logging
from multiprocessing import  Process, Value, Condition, reduction

from TServer import TServer
from thrift.transport.TTransport import TTransportException


class TProcessPoolServer(TServer):
    """Server with a fixed size pool of worker subprocesses to service requests

    Note that if you need shared state between the handlers - it's up to you!
    Written by Dvir Volk, doat.com
    """
    def __init__(self, *args):
        TServer.__init__(self, *args)
        self.numWorkers = 10
        self.workers = []
        self.isRunning = Value('b', False)
        self.stopCondition = Condition()
        self.postForkCallback = None

    def setPostForkCallback(self, callback):
        if not callable(callback):
            raise TypeError("This is not a callback!")
        self.postForkCallback = callback

    def setNumWorkers(self, num):
        """Set the number of worker threads that should be created"""
        self.numWorkers = num

    def workerProcess(self):
        """Loop getting clients from the shared queue and process them"""
        if self.postForkCallback:
            self.postForkCallback()

        while self.isRunning.value:
            try:
                client = self.serverTransport.accept()
                if not client:
                  continue
                self.serveClient(client)
            except (KeyboardInterrupt, SystemExit):
                return 0
            except Exception, x:
                logging.exception(x)

    def serveClient(self, client):
        """Process input/output from a client for as long as possible"""
        itrans = self.inputTransportFactory.getTransport(client)
        otrans = self.outputTransportFactory.getTransport(client)
        iprot = self.inputProtocolFactory.getProtocol(itrans)
        oprot = self.outputProtocolFactory.getProtocol(otrans)

        try:
            while True:
                self.processor.process(iprot, oprot)
        except TTransportException, tx:
            pass
        except Exception, x:
            logging.exception(x)

        itrans.close()
        otrans.close()

    def serve(self):
        """Start workers and put into queue"""
        # this is a shared state that can tell the workers to exit when False
        self.isRunning.value = True

        # first bind and listen to the port
        self.serverTransport.listen()

        # fork the children
        for i in range(self.numWorkers):
            try:
                w = Process(target=self.workerProcess)
                w.daemon = True
                w.start()
                self.workers.append(w)
            except Exception, x:
                logging.exception(x)

        # wait until the condition is set by stop()
        while True:
            self.stopCondition.acquire()
            try:
                self.stopCondition.wait()
                break
            except (SystemExit, KeyboardInterrupt):
                break
            except Exception, x:
                logging.exception(x)

        self.isRunning.value = False

    def stop(self):
        self.isRunning.value = False
        self.stopCondition.acquire()
        self.stopCondition.notify()
        self.stopCondition.release()