pyzmq的Polling and Sockets

  Polling and Sockets

  一个线程中有多个sokect,同时需要收发数据,zmq提供polling sockets实现，不用在recv()时阻塞。

  下面这个例程中创建一个command server来告诉worker何时退出,worker从Publisher获得订阅并打印,（'exit'时退出）。

    1.PUSH server ,命令服务

import zmq
import time
import sys
import random
from  multiprocessing import Process

def server_push(port="5556"):
    context = zmq.Context()
    socket = context.socket(zmq.PUSH)
    socket.bind("tcp://*:%s" % port)
    print "Running server on port: ", port
    # serves only 5 request and dies
    for reqnum in range(10):
        if reqnum < 6:
            socket.send("Continue")
        else:
            socket.send("Exit")
            break
        time.sleep (1) 

   2.PUB server,发布消息

def server_pub(port="5558"):
    context = zmq.Context()
    socket = context.socket(zmq.PUB)
    socket.bind("tcp://*:%s" % port)
    publisher_id = random.randrange(0,9999)
    print "Running server on port: ", port
    # serves only 5 request and dies
    for reqnum in range(10):
        # Wait for next request from client
        topic = random.randrange(8,10)
        messagedata = "server#%s" % publisher_id
        print "%s %s" % (topic, messagedata)
        socket.send("%d %s" % (topic, messagedata))
        time.sleep(1) 

   3.客户端

def client(port_push, port_sub):
    context = zmq.Context()
    socket_pull = context.socket(zmq.PULL)
    socket_pull.connect ("tcp://localhost:%s" % port_push)
    print "Connected to server with port %s" % port_push
    socket_sub = context.socket(zmq.SUB)
    socket_sub.connect ("tcp://localhost:%s" % port_sub)
    socket_sub.setsockopt(zmq.SUBSCRIBE, "9")
    print "Connected to publisher with port %s" % port_sub
    # 初始化Poller
    poller = zmq.Poller()
    poller.register(socket_pull, zmq.POLLIN)
    poller.register(socket_sub, zmq.POLLIN)
    # Work on requests from both server and publisher
    should_continue = True
    while should_continue:
        socks = dict(poller.poll())
        if socket_pull in socks and socks[socket_pull] == zmq.POLLIN:
            message = socket_pull.recv()
            print "Recieved control command: %s" % message
            if message == "Exit": 
                print "Recieved exit command, client will stop recieving messages"
                should_continue = False

        if socket_sub in socks and socks[socket_sub] == zmq.POLLIN:
            string = socket_sub.recv()
            topic, messagedata = string.split()
            print "Processing ... ", topic, messagedata

 运行

if __name__ == "__main__":
    # Now we can run a few servers 
    server_push_port = "5556"
    server_pub_port = "5558"
    Process(target=server_push, args=(server_push_port,)).start()
    Process(target=server_pub, args=(server_pub_port,)).start()
    Process(target=client, args=(server_push_port,server_pub_port,)).start()

看一下api

poll(timeout=None)

Poll the registered 0MQ or native fds for I/O.

Parameters: Returns: Return type:

timeout (float, int) – The timeout in milliseconds. If None, no timeout (infinite). This is in milliseconds to be compatible with select.poll().

events – The list of events that are ready to be processed. This is a list of tuples of the form (socket, event), where the 0MQ Socket or integer fd is the first element, and the poll event mask (POLLIN, POLLOUT) is the second. It is common to callevents = dict(poller.poll()), which turns the list of tuples into a mapping ofsocket : event.

list of tuples

  至于POLLIN，POLLOUT：

• flag (int, default=POLLIN|POLLOUT) – 0MQ poll flags. If flag|POLLIN, recv events will be flushed. If flag|POLLOUT, send events will be flushed. Both flags can be set at once, which is the default.

  如此这般，不停的轮询注册在poller中的sockter状态,类似与java nio中将channel注册到selector。发现某个socket数据接收就绪(POLLIN),执行业务代码。 

 

  但是，用'if '的处理方式有点丑，所以pyzmq提供实现tornador ioloop的IOStream 的类：ZMQStream 来处理polling event,并且这样就可以使用回调。

  首先,安装tornador : pip install tornado

 然后，改造上面的代码：

import zmq
import time
import sys
import random
from  multiprocessing import Process

from zmq.eventloop import ioloop, zmqstream
ioloop.install()

    ioloop.install()用来告诉tornador.ioloop.IOLoop使用zmq的poller。

    PUSH server和PUB server的代码不用改

    把2个处理业务的函数拎出来做回调

def getcommand(msg):
	print "Received control command: %s" % msg
	if msg[0] == "Exit":
		print "Received exit command, client will stop receiving messages"
		should_continue = False
		ioloop.IOLoop.instance().stop()#退出请停止
        
def process_message(msg):
	print "Processing ... %s" % msg

    客户端改成这样:

def client(port_push, port_sub):    
	context = zmq.Context()
	socket_pull = context.socket(zmq.PULL)
	socket_pull.connect ("tcp://localhost:%s" % port_push)
	stream_pull = zmqstream.ZMQStream(socket_pull)
	stream_pull.on_recv(getcommand)
	print "Connected to server with port %s" % port_push
	
	socket_sub = context.socket(zmq.SUB)
	socket_sub.connect ("tcp://localhost:%s" % port_sub)
	socket_sub.setsockopt(zmq.SUBSCRIBE, "9")
	stream_sub = zmqstream.ZMQStream(socket_sub)
	stream_sub.on_recv(process_message)
	print "Connected to publisher with port %s" % port_sub
	ioloop.IOLoop.instance().start()
	print "Worker has stopped processing messages."


if __name__ == "__main__":
    # Now we can run a few servers 
    server_push_port = "5556"
    server_pub_port = "5558"
    Process(target=server_push, args=(server_push_port,)).start()
    Process(target=server_pub, args=(server_pub_port,)).start()
    Process(target=client, args=(server_push_port,server_pub_port,)).start()

    将原来的socket装饰成zmqstream，然后将ioloop实例run起来,其它就不需要我操心了，妥妥的傻瓜式。