Python BaseHTTPServer，如何捕获/捕获“管道中断”错误？

Question

我在Python中构建了一个简短的url转换器引擎，并且看到大量的“管道破损”错误，并且很好奇在使用BaseHTTPServer类时如何最好地捕获它。这不是全部代码，但可以让您大致了解我目前正在做什么：

    from BaseHTTPServer import BaseHTTPRequestHandler, HTTPServer
    import memcache

    class clientThread(BaseHTTPRequestHandler):

            def do_GET(self):
                    content = None
                    http_code,response_txt,long_url = \
                            self.ag_trans_url(self.path,content,'GET')
                    self.http_output( http_code, response_txt, long_url )
                    return

            def http_output(self,http_code,response_txt,long_url):
                    self.send_response(http_code)
                    self.send_header('Content-type','text/plain')
                    if long_url:
                            self.send_header('Location', long_url)
                    self.end_headers()
                    if response_txt:
                            self.wfile.write(response_txt)
                    return

        def ag_trans_url(self, orig_short_url, post_action, getpost):
                short_url = 'http://foo.co' + orig_short_url

                # fetch it from memcache
                long_url = mc.get(short_url)

                # other magic happens to look it up from db if there was nothing
                # in memcache, etc
                return (302, None, log_url)

def populate_memcache()
        # connect to db, do lots of mc.set() calls

def main():
        populate_memcache()
        try:
                port = 8001
                if len(sys.argv) > 1:
                        port = int(sys.argv[1])
                server = HTTPServer(('',port), clientThread)
                #server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
                print '[',str(datetime.datetime.now()),'] short url processing has begun'

                server.serve_forever()
        except KeyboardInterrupt,SystemExit:
                print '^C received, shutting down server'
                server.socket.close()

该代码本身运行良好，但是在生产中几乎立即开始引发错误：

Traceback (most recent call last):
  File "/usr/lib/python2.5/SocketServer.py", line 222, in handle_request
    self.process_request(request, client_address)
  File "/usr/lib/python2.5/SocketServer.py", line 241, in process_request
    self.finish_request(request, client_address)
  File "/usr/lib/python2.5/SocketServer.py", line 254, in finish_request
    self.RequestHandlerClass(request, client_address, self)
  File "/usr/lib/python2.5/SocketServer.py", line 522, in __init__
    self.handle()
  File "/usr/lib/python2.5/BaseHTTPServer.py", line 316, in handle
    self.handle_one_request()
  File "/usr/lib/python2.5/BaseHTTPServer.py", line 310, in handle_one_request
    method()
  File "/opt/short_url_redirector/shorturl.py", line 38, in do_GET
    self.http_output( http_code, response_txt, long_url )
  File "/opt/short_url_redirector/shorturl.py", line 52, in http_output
    self.send_response(http_code)
  File "/usr/lib/python2.5/BaseHTTPServer.py", line 370, in send_response
    self.send_header('Server', self.version_string())
  File "/usr/lib/python2.5/BaseHTTPServer.py", line 376, in send_header
    self.wfile.write("%s: %s\r\n" % (keyword, value))
  File "/usr/lib/python2.5/socket.py", line 274, in write
    self.flush()
  File "/usr/lib/python2.5/socket.py", line 261, in flush
    self._sock.sendall(buffer)
error: (32, 'Broken pipe')

这些错误的大部分似乎源于在调用send_header（）方法时遇到的问题，其中我要写的是：

self.send_header('Location', long_url)

所以我很好奇在我的代码中尝试捕获此IO异常的地方…我是否在每个self.send_header / self.end_headers /
self.wfile.write调用周围编写try / except调用？我不时看到的另一个错误是这个错误，但不确定要监视哪个异常来捕获此错误：

Traceback (most recent call last):
  File "/usr/lib/python2.5/SocketServer.py", line 222, in handle_request
    self.process_request(request, client_address)
  File "/usr/lib/python2.5/SocketServer.py", line 241, in process_request
    self.finish_request(request, client_address)
  File "/usr/lib/python2.5/SocketServer.py", line 254, in finish_request
    self.RequestHandlerClass(request, client_address, self)
  File "/usr/lib/python2.5/SocketServer.py", line 522, in __init__
    self.handle()
  File "/usr/lib/python2.5/BaseHTTPServer.py", line 316, in handle
    self.handle_one_request()
  File "/usr/lib/python2.5/BaseHTTPServer.py", line 299, in handle_one_request
    self.raw_requestline = self.rfile.readline()
  File "/usr/lib/python2.5/socket.py", line 381, in readline
    data = self._sock.recv(self._rbufsize)
error: (104, 'Connection reset by peer')

Answer 1

“断开的管道”异常意味着您的代码试图写入另一端已关闭的套接字/管道。如果另一端是Web浏览器，则用户可能已经停止了该请求。您可以忽略回溯；它并不表示严重的问题。如果要禁止显示该消息，则可以在try_except块周围放置http_output函数中的所有代码，并根据需要记录异常。

另外，如果希望HTTP服务器一次处理多个请求，则需要服务器类使用SocketServer.ForkingMixIn和SocketServer.ThreadingMixIn类之一。有关详细信息，请查看SocketServer模块的文档。

添加：“对等连接重置”异常意味着您的代码尝试从失效的套接字读取。如果要抑制回溯，则需要扩展BaseHTTPServer类并重写handle_one_request方法以添加try
… except块。无论如何，您都将需要一个新的服务器类，以实现先前的建议，即一次处理多个请求。