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python zeromq

本文轉載自   查看原文   2012-09-27 15:58   4516 

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

hwserver.py

Python代碼 復制代碼 收藏代碼
  1. #
  2. # Hello World server in Python
  3. # Binds REP socket to tcp://*:5555
  4. # Expects "Hello" from client, replies with "World"
  5. #
  6. import zmq
  7. import time
  9. context = zmq.Context()
  10. socket = context.socket(zmq.REP)
  11. socket.bind("tcp://*:5555")
  13. while True:
  14. # Wait for next request from client
  15. message = socket.recv()
  16. print "Received request: ", message
  18. # Do some 'work'
  19. time.sleep (1) # Do some 'work'
  21. # Send reply back to client
  22. socket.send("World")

hwclient.py

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  1. #
  2. # Hello World client in Python
  3. # Connects REQ socket to tcp://localhost:5555
  4. # Sends "Hello" to server, expects "World" back
  5. #
  6. import zmq
  8. context = zmq.Context()
  10. # Socket to talk to server
  11. print "Connecting to hello world server..."
  12. socket = context.socket(zmq.REQ)
  13. socket.connect ("tcp://localhost:5555")
  15. # Do 10 requests, waiting each time for a response
  16. for request in range (1,10):
  17. print "Sending request ", request,"..."
  18. socket.send ("Hello")
  20. # Get the reply.
  21. message = socket.recv()
  22. print "Received reply ", request, "[", message, "]"

問題3：zeroMQ實現一個消息層？

答：

實現一個ZeroMQ消息層需要三個步驟：

1.選擇傳輸協議

0MQ提供了4種不同的傳輸協議

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.建立基礎

由於在網絡中兩個端點是相對動態的，很難有一個穩定的單一連接點。

如果是這種情況，可以使用由0MQ提供的轉發設備。

轉發設備可以綁定2個不同端口，並且轉發消息從一個端點到另一個端點。

這樣做的話，在網絡中轉發設備能夠變成一個穩定的點，其它組件都可以去連接。

0MQ提供了3種類型的設備

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.選擇通訊模式

0MQ支持4種模式

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

均衡負載請求：

server 1

Python代碼 復制代碼 收藏代碼
  1. import zmq
  2. context = zmq.Context()
  3. socket = context.socket(zmq.REP)
  4. socket.bind("tcp://127.0.0.1:5000")
  6. while True:
  7. msg = socket.recv()
  8. print "Got", msg
  9. socket.send(msg)

server 2

Python代碼 復制代碼 收藏代碼
  1. import zmq
  2. context = zmq.Context()
  3. socket = context.socket(zmq.REP)
  4. socket.bind("tcp://127.0.0.1:6000")
  6. while True:
  7. msg = socket.recv()
  8. print "Got", msg
  9. socket.send(msg)

client

Python代碼 復制代碼 收藏代碼
  1. import zmq
  2. context = zmq.Context()
  3. socket = context.socket(zmq.REQ)
  4. socket.connect("tcp://127.0.0.1:5000")
  5. socket.connect("tcp://127.0.0.1:6000")
  7. for i in range(10):
  8. msg = "msg %s" % i
  9. socket.send(msg)
  10. print "Sending", msg
  11. msg_in = socket.recv()

會發現client的請求會被均衡的分配給兩個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

現在，如果我們要加入一個額外的server去管理我們的請求，我們將不得不修改我們的代碼。

這是非常麻煩的，我們需要讓每個client都知道有一個額外的server可以均衡請求。

為了解決這個問題，替代client直接去連接多個server的方式，client去連接轉發設備，再由轉發設備路由全部的消息給server。

Pub/Sub

在pub/sub模式下組件是松耦合的。類似於廣播電台。

一個廣播server為現場足球賽

Python代碼 復制代碼 收藏代碼
  1. import zmq
  2. from random import choice
  3. context = zmq.Context()
  4. socket = context.socket(zmq.PUB)
  5. socket.bind("tcp://127.0.0.1:5000")
  7. countries = ['netherlands','brazil','germany','portugal']
  8. events = ['yellow card', 'red card', 'goal', 'corner', 'foul']
  10. while True:
  11. msg = choice( countries ) +" "+ choice( events )
  12. print "->",msg
  13. socket.send( msg )<span style="white-space: normal;"> </span>

輸出

-> portugal corner
-> portugal yellow card
-> portugal goal
-> netherlands yellow card
-> germany yellow card
-> brazil yellow card
-> portugal goal
-> germany corner
…

一個客戶端去收聽特定的消息

Python代碼 復制代碼 收藏代碼
  1. import zmq
  3. context = zmq.Context()
  4. socket = context.socket(zmq.SUB)
  5. socket.connect("tcp://127.0.0.1:5000")
  6. socket.setsockopt(zmq.SUBSCRIBE, "netherlands")
  7. socket.setsockopt(zmq.SUBSCRIBE, "germany")
  9. while True:
  10. print socket.recv()

輸出

netherlands red card
netherlands goal
netherlands red card
germany foul
netherlands yellow card
germany foul
netherlands goal
netherlands corner
germany foul
netherlands corner
…

Pipelining

並發處理數據，其工作模式

一個工作者得到來自上游socket的消息，一旦處理完成后發送消息到下游。

Paired socket

服務器監聽某個端口，客戶端連接到這個端口，消息可以雙向流動。

server

Python代碼 復制代碼 收藏代碼
  1. import zmq
  2. context = zmq.Context()
  3. socket = context.socket(zmq.PAIR)
  4. socket.bind("tcp://127.0.0.1:5555")

client

Python代碼 復制代碼 收藏代碼
  1. import zmq
  2. context = zmq.Context()
  3. socket = context.socket(zmq.PAIR)
  4. socket.connect("tcp://127.0.0.1:5555")

ps:

推薦

http://www.zeromq.org/

http://nichol.as/zeromq-an-introduction


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