pyzmq的Monitor Queue

    前面讲过zmq的device,用来充当客户端与服务端的中间件,以增加灵活性，让服务端也变成可插拔。然而device是zmq封装好的，怎样才能一窥内部的数据流呢？看图

    一看这图就明白了，MonitoredQueue在创建Queue同时，还提供第3个PUB socket来发布途经这个Queue的进出信息。

import time
import zmq
from zmq.devices.basedevice import ProcessDevice
from zmq.devices.monitoredqueuedevice import MonitoredQueue
from zmq.utils.strtypes import asbytes
from multiprocessing import Process
import random

frontend_port = 5559
backend_port = 5560
monitor_port = 5562
number_of_workers = 2

   创建这个MonitorQueue

def monitordevice():
    in_prefix=asbytes('in')
    out_prefix=asbytes('out')
    monitoringdevice = MonitoredQueue(zmq.XREP, zmq.XREQ, zmq.PUB, in_prefix, out_prefix)
    
    monitoringdevice.bind_in("tcp://127.0.0.1:%d" % frontend_port)
    monitoringdevice.bind_out("tcp://127.0.0.1:%d" % backend_port)
    monitoringdevice.bind_mon("tcp://127.0.0.1:%d" % monitor_port)
    
    monitoringdevice.setsockopt_in(zmq.HWM, 1)
    monitoringdevice.setsockopt_out(zmq.HWM, 1)
    monitoringdevice.start()  
    print "Program: Monitoring device has started"

   REP server

def server(backend_port):
    print "Program: Server connecting to device"
    context = zmq.Context()
    socket = context.socket(zmq.REP)
    socket.connect("tcp://127.0.0.1:%s" % backend_port)
    server_id = random.randrange(1,10005)
    while True:
        message = socket.recv()
        print "Server: Received - %s" % message  
        socket.send("Response from server #%s" % server_id)

   REQ client

def client(frontend_port, client_id):
    print "Program: Worker #%s connecting to device" % client_id
    context = zmq.Context()
    socket = context.socket(zmq.REQ)
    socket.connect("tcp://127.0.0.1:%s" % frontend_port)
    request_num = 1
    socket.send ("Request #%s from client#%s" % (request_num, client_id))
    #  Get the reply.
    message = socket.recv_multipart()
    print "Client: Received - %s" % message

   最后来一个SUB客户端接收从MonitorQueue的PUB端发布的消息

def monitor():
    print "Starting monitoring process"
    context = zmq.Context()
    socket = context.socket(zmq.SUB)
    print "Collecting updates from server..."
    socket.connect ("tcp://127.0.0.1:%s" % monitor_port)
    socket.setsockopt(zmq.SUBSCRIBE, "")
    while True:
        string = socket.recv_multipart()
        print "Monitoring Client: %s" % string

   然后在不同进程中分别启动以上各项

monitoring_p = Process(target=monitordevice)
monitoring_p.start()  
server_p = Process(target=server, args=(backend_port,))
server_p.start()  
monitorclient_p = Process(target=monitor)
monitorclient_p.start()  
time.sleep(2)   

for client_id in range(number_of_workers):
    Process(target=client, args=(frontend_port, client_id,)).start()

time.sleep(10)
server_p.terminate()
monitorclient_p.terminate()
monitoring_p.terminate()

    如此即可观察到路过Queue的数据流。

    整个过程简单明了，没有什么弯弯绕,感觉zmq上手还是很容易的。