Question

我在Python中构建了一个简短的url翻译器引擎，我看到了一个“破管”错误的TON，我很好奇如何在使用BaseHTTPServer类时最好地捕获它。这不是整个代码，而是让您了解到目前为止我在做什么：

    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()

代码本身效果很好，但在生产中几乎立即开始抛出错误：

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')

这些错误中的大部分似乎源于调用send_header（）方法时遇到的问题，我写的所有内容都是：

self.send_header('Location', long_url)

所以我很好奇在我的代码中试图捕获此IO异常的位置...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就是这个错误，但不确定要注意哪个例外甚至是这个：

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

这似乎是SocketServer中的一个错误，请参阅此链接Python Bug: 14574

修复（在Python 2.7中适用于我）是覆盖SocketServer.StreamRequestHandler finish（）方法，如下所示：

...
def finish(self,*args,**kw):
  try:
    if not self.wfile.closed:
      self.wfile.flush()
      self.wfile.close()
  except socket.error:
    pass
  self.rfile.close()

  #Don't call the base class finish() method as it does the above
  #return SocketServer.StreamRequestHandler.finish(self)

Answer 2

“破损管道”异常意味着您的代码尝试写入另一端已关闭的套接字/管道。如果另一端是Web浏览器，则用户可能已停止该请求。你可以忽略回溯;它并不表示存在严重问题。如果要抑制消息，可以在http_output函数的所有代码周围放置一个try ... except块，如果愿意，可以记录异常。

此外，如果您希望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：“通过对等重置连接”异常意味着您的代码尝试从死套接字读取。如果要禁止回溯，则需要扩展BaseHTTPServer类并覆盖handle_one_request方法以添加try ... except块。无论如何，您将需要一个新的服务器类，以实现有关一次处理多个请求的早期建议。

Answer 3

在我的应用程序中，错误未在finish()中发生，它发生在handle()中。此修复程序捕获broken pipe错误：

class MyHTTPRequestHandler(BaseHTTPServer.BaseHTTPRequestHandler):

    ...

    def handle(self):
        try:
            BaseHTTPServer.BaseHTTPRequestHandler.handle(self)
        except socket.error:
            pass

Python BaseHTTPServer，如何捕获/捕获“破管”错误？

3 个答案: