第二章主要在上一章的基础上介绍了以下内容&＃xff1a;
1. ForkingMixIn
2. ThreadingMixIn
3. select.select
4. select.epoll
5. Diesel库
ForkingMixIn 和 ThreadingMixIn属于socketserver&＃xff08;python2是SocketServer&＃xff09;模块&＃xff0c;该模块能够简化编写web服务器的工作。其包含四种基本的服务器class:
TCPServer 使用TCP协议&＃xff0c;在服务器和客户端之间建立持续的连续&＃xff0c;安全&＃xff1b;
UDPServer 使用UDP协议&＃xff0c;采用数据包的方法在服务器和客户端之间传递数据&＃xff0c;有丢失包的可能&＃xff0c;但是传输速度很快&＃xff1b;
UnixStreamServer和UnixDatagramServer 比较少使用&＃xff0c; 分别与TCPServer、UDPServer相似&＃xff0c;但是基于Unix上定义的套接字&＃xff0c;在其他平台上不能使用。
图1. Servers的继承关系
以上四种类都是同步的&＃xff0c;即下一个请求开始前&＃xff0c;上一个请求必须完成。显然&＃xff0c;他们并不适用于当请求需要较长处理时间的情况。为每个请求创建单独的进程或线程的方式可以解决这个问题&＃xff0c;即实现服务器和客户端的异步通信&＃xff0c;为此socketserver模块添加了ForkingMixIn和ThreadingMixIn两个类。
为了创建一个服务&＃xff0c;首先通过继承BaseRequestHandler类并重写其handler()方法得到一个句柄类&＃xff0c;它将用来处理到达服务器的请求&＃xff1b;
class ForkingServerRequestHandler(SocketServer.BaseRequestHandler):
然后以服务器地址和上一步得到的句柄实例化前面继承自ForkingMixIn/ThreadingMixIn和TCPServer/UDPServer/UnixStreamServer/UnixDatagramServer的server&＃xff0c;
class ForkingServer(SocketServer.ForkingMixIn, SocketServer.TCPServer,):passserver &＃61; ForkingServer((SERVER_HOST, SERVER_PORT), ForkingServerRequestHandler)
注意&＃xff1a;ForkingMixIn必须写在TCPServer前面&＃xff0c;因为它重载了TCPServer类的方法。
最后&＃xff0c;调用handler_request()或者server_forever()方法来开始处理请求。
server_thread &＃61; threading.Thread(target&＃61;server.serve_forever)
值得注意的是&＃xff0c;如果server类继承自ThreadingMixIn&＃xff0c;则需要明确指定遇到异常停止时的处理方法&＃xff0c;ThreadingMixIn类定义了daemon_threads方法&＃xff0c;其指定了服务器是否需要等待直到所有线程终止&＃xff0c;默认为False。
server_thread.setDaemon(True)
下面是一个简单的例子&＃xff1a;
import osimport socketimport threadingimport SocketServerSERVER_HOST &＃61; &＃39;localhost&＃39;SERVER_PORT &＃61; 0 # tells the kernel to pick up a port dynamicallyBUF_SIZE &＃61; 1024ECHO_MSG &＃61; &＃39;Hello echo server!&＃39;class ForkedClient():""" A client to test forking server"""def __init__(self, ip, port):# Create a socketself.sock &＃61; socket.socket(socket.AF_INET, socket.SOCK_STREAM)# Connect to the serverself.sock.connect((ip, port))def run(self):""" Client playing with the server"""# Send the data to servercurrent_process_id &＃61; os.getpid()print &＃39;PID %s Sending echo message to the server : "%s"&＃39; %(current_process_id, ECHO_MSG)sent_data_length &＃61; self.sock.send(ECHO_MSG)print "Sent: %d characters, so far..." %sent_data_length# Display server responseresponse &＃61; self.sock.recv(BUF_SIZE)print "PID %s received: %s" % (current_process_id,response[5:])def shutdown(self):""" Cleanup the client socket """self.sock.close()class ForkingServerRequestHandler(SocketServer.BaseRequestHandler):def handle(self):# Send the echo back to the clientdata &＃61; self.request.recv(BUF_SIZE)current_process_id &＃61; os.getpid()response &＃61; &＃39;%s: %s&＃39; % (current_process_id, data)print "Server sending response [current_process_id: data] &＃61;[%s]" %responseself.request.send(response)
returnclass ForkingServer(SocketServer.ForkingMixIn,SocketServer.TCPServer,):"""Nothing to add here, inherited everything necessary fromparents"""passdef main():# Launch the serverserver &＃61; ForkingServer((SERVER_HOST, SERVER_PORT),ForkingServerRequestHandler)ip, port &＃61; server.server_address # Retrieve the port numberserver_thread &＃61; threading.Thread(target&＃61;server.serve_forever)server_thread.setDaemon(True) # don&＃39;t hang on exitserver_thread.start()print &＃39;Server loop running PID: %s&＃39; %os.getpid()# Launch the client(s)client1 &＃61; ForkedClient(ip, port)client1.run()client2 &＃61; ForkedClient(ip, port)client2.run()# Clean them upserver.shutdown()client1.shutdown()client2.shutdown()server.socket.close()if __name__ &＃61;&＃61; &＃39;__main__&＃39;:main()
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