python zeromq

python examples https://github.com/imatix/zguide/tree/master/examples/Python

hwserver.py

Python代码 ​​

​​

1. #
2. # Hello World server in Python
3. # Binds REP socket to tcp://*:5555
4. # Expects "Hello" from client, replies with "World"
6. import zmq
7. import time
8. context = zmq.Context()
9. socket = context.socket(zmq.REP)
10. socket.bind("tcp://*:5555")
11. while True:
12. # Wait for next request from client
13. message = socket.recv()
14. print "Received request: ", message
15. # Do some 'work'
16. time.sleep (1) # Do some 'work'
17. # Send reply back to client
18. socket.send("World")

#
#   Hello World server in Python
#   Binds REP socket to tcp://*:5555
#   Expects "Hello" from client, replies with "World"
#
import zmq
import time

context = zmq.Context()
socket = context.socket(zmq.REP)
socket.bind("tcp://*:5555")

while True:
    #  Wait for next request from client
    message = socket.recv()
    print "Received request: ", message

    #  Do some 'work'
    time.sleep (1)        #   Do some 'work'

    #  Send reply back to client
    socket.send("World")      

hwclient.py

2. # Hello World client in Python
3. # Connects REQ socket to tcp://localhost:5555
4. # Sends "Hello" to server, expects "World" back
8. # Socket to talk to server
9. print "Connecting to hello world server..."
10. socket = context.socket(zmq.REQ)
11. socket.connect ("tcp://localhost:5555")
12. # Do 10 requests, waiting each time for a response
13. for request in range (1,10):
14. print "Sending request ", request,"..."
15. socket.send ("Hello")
16. # Get the reply.
18. print "Received reply ", request, "[", message, "]"

#
#   Hello World client in Python
#   Connects REQ socket to tcp://localhost:5555
#   Sends "Hello" to server, expects "World" back
#
import zmq

context = zmq.Context()

#  Socket to talk to server
print "Connecting to hello world server..."
socket = context.socket(zmq.REQ)
socket.connect ("tcp://localhost:5555")

#  Do 10 requests, waiting each time for a response
for request in range (1,10):
    print "Sending request ", request,"..."
    socket.send ("Hello")

    #  Get the reply.
    message = socket.recv()
    print "Received reply ", request, "[", message, "]"      

问题3：zeroMQ实现一个消息层？

答：

实现一个ZeroMQ消息层需要三个步骤：

1.选择传输协议

0MQ提供了4种不同的传输协议

​​INPROC​​ an In-Process communication model

​​IPC​​ an Inter-Process communication model

​​MULTICAST​​ multicast via PGM, possibly encapsulated in UDP

​​TCP​​ a network based transport

2.建立基础

由于在网络中两个端点是相对动态的，很难有一个稳定的单一连接点。

如果是这种情况，可以使用由0MQ提供的转发设备。

转发设备可以绑定2个不同端口，并且转发消息从一个端点到另一个端点。

这样做的话，在网络中转发设备能够变成一个稳定的点，其它组件都可以去连接。

0MQ提供了3种类型的设备

​​QUEUE​​, a forwarder for the request/response messaging pattern

​​FORWARDER​​, a forwarder for the publish/subscribe messaging pattern

​​STREAMER​​, a forwarder for the pipelined messaging pattern

3.选择通讯模式

0MQ支持4种模式

​​REQUEST/REPLY​​, bidirectional, load balanced and state based

​​PUBLISH/SUBSCRIBE​​, publish to multiple recipients at once

​​UPSTREAM / DOWNSTREAM​​, distribute data to nodes arranged in a pipeline

​​PAIR​​, communication exclusively between peers

Req/Rep

均衡负载请求：

server 1

4. socket.bind("tcp://127.0.0.1:5000")
6. msg = socket.recv()
7. print "Got", msg
8. socket.send(msg)

import zmq
context = zmq.Context()
socket = context.socket(zmq.REP)
socket.bind("tcp://127.0.0.1:5000")

while True:
    msg = socket.recv()
    print "Got", msg
    socket.send(msg)      

server 2

4. socket.bind("tcp://127.0.0.1:6000")

import zmq
context = zmq.Context()
socket = context.socket(zmq.REP)
socket.bind("tcp://127.0.0.1:6000")

while True:
    msg = socket.recv()
    print "Got", msg
    socket.send(msg)      

client

4. socket.connect("tcp://127.0.0.1:5000")
5. socket.connect("tcp://127.0.0.1:6000")
6. for i in range(10):
7. msg = "msg %s" % i
9. print "Sending", msg
10. msg_in = socket.recv()

import zmq
context = zmq.Context()
socket = context.socket(zmq.REQ)
socket.connect("tcp://127.0.0.1:5000")
socket.connect("tcp://127.0.0.1:6000")

for i in range(10):
    msg = "msg %s" % i
    socket.send(msg)
    print "Sending", msg
    msg_in = socket.recv()      

会发现client的请求会被均衡的分配给两个server

Example client output:

Sending msg 0

Sending msg 1

Sending msg 2

Sending msg 3

Sending msg 4

Sending msg 5

Sending msg 6

Sending msg 7

Sending msg 8

Sending msg 9

Example output server 1 at port 5000:

Got msg 0

Got msg 2

Got msg 4

Got msg 6

Got msg 8

Example output server 2 at port 6000:

Got msg 1

Got msg 3

Got msg 5

Got msg 7

Got msg 9

现在，如果我们要加入一个额外的server去管理我们的请求，我们将不得不修改我们的代码。

这是非常麻烦的，我们需要让每个client都知道有一个额外的server可以均衡请求。

为了解决这个问题，替代client直接去连接多个server的方式，client去连接转发设备，再由转发设备路由全部的消息给server。

Pub/Sub

在pub/sub模式下组件是松耦合的。类似于广播电台。

一个广播server为现场足球赛

2. from random import choice
4. socket = context.socket(zmq.PUB)
6. countries = ['netherlands','brazil','germany','portugal']
7. events = ['yellow card', 'red card', 'goal', 'corner', 'foul']
9. msg = choice( countries ) +" "+ choice( events )
10. print "->",msg
11. socket.send( msg )<span style="white-space: normal;"> </span>

import zmq
from random import choice
context = zmq.Context()
socket = context.socket(zmq.PUB)
socket.bind("tcp://127.0.0.1:5000")

countries = ['netherlands','brazil','germany','portugal']
events = ['yellow card', 'red card', 'goal', 'corner', 'foul']

while True:
    msg = choice( countries ) +" "+ choice( events )
    print "->",msg
    socket.send( msg )      

输出

-> portugal corner

-> portugal yellow card

-> portugal goal

-> netherlands yellow card

-> germany yellow card

-> brazil yellow card

-> germany corner

…

一个客户端去收听特定的消息

3. socket = context.socket(zmq.SUB)
5. socket.setsockopt(zmq.SUBSCRIBE, "netherlands")
6. socket.setsockopt(zmq.SUBSCRIBE, "germany")
8. print socket.recv()

import zmq

context = zmq.Context()
socket = context.socket(zmq.SUB)
socket.connect("tcp://127.0.0.1:5000")
socket.setsockopt(zmq.SUBSCRIBE, "netherlands")
socket.setsockopt(zmq.SUBSCRIBE, "germany")

while True:
    print  socket.recv()      

netherlands red card

netherlands goal

germany foul

netherlands yellow card

netherlands corner

Pipelining

并发处理数据，其工作模式

一个工作者得到来自上游socket的消息，一旦处理完成后发送消息到下游。

Paired socket

服务器监听某个端口，客户端连接到这个端口，消息可以双向流动。

server

3. socket = context.socket(zmq.PAIR)
4. socket.bind("tcp://127.0.0.1:5555")

import zmq
context = zmq.Context()
socket = context.socket(zmq.PAIR)
socket.bind("tcp://127.0.0.1:5555")      

4. socket.connect("tcp://127.0.0.1:5555")

import zmq
context = zmq.Context()
socket = context.socket(zmq.PAIR)
socket.connect("tcp://127.0.0.1:5555")