Question

WSGI对于构建高度并发的HTTP服务器非常有用，可以支持例如但是，长轮询，通常，长时间运行的HTTP请求将在某个时候由客户端结束;要清理任何资源和打开句柄，应该通知WSGI服务器后端任何此类事件，但是，目前似乎无法在WSGI处理程序中捕获这些事件：

# pseudocode example

def application(env, start_response):
    start_response(...)

    q = Queue()
    ev_handle = register_event_handler(lambda event, arg: q.put((event, arg)))

    # ??? need to call e.g. ev_handle.unregister() when the HTTP request is terminated

    return iter(lambda: render(q.get()), None)

例如，当使用gevent.pywsgi时，相应的异常（error: [Errno 32] Broken pipe）会被抛出到gevent中的某个地方，甚至似乎都没有出现在处理程序可能看到它的任何地方：

Traceback (most recent call last):
  File "/Users/erik.allik/.virtualenvs/myproj/lib/python2.7/site-packages/gevent/pywsgi.py", line 508, in handle_one_response
    self.run_application()
  File "/Users/erik.allik/.virtualenvs/myproj/lib/python2.7/site-packages/gevent/pywsgi.py", line 495, in run_application
    self.process_result()
  File "/Users/erik.allik/.virtualenvs/myproj/lib/python2.7/site-packages/gevent/pywsgi.py", line 486, in process_result
    self.write(data)
  File "/Users/erik.allik/.virtualenvs/myproj/lib/python2.7/site-packages/gevent/pywsgi.py", line 376, in write
    self._write(data)
  File "/Users/erik.allik/.virtualenvs/myproj/lib/python2.7/site-packages/gevent/pywsgi.py", line 369, in _write
    self._sendall(data)
  File "/Users/erik.allik/.virtualenvs/myproj/lib/python2.7/site-packages/gevent/pywsgi.py", line 355, in _sendall
    self.socket.sendall(data)
  File "/Users/erik.allik/.virtualenvs/myproj/lib/python2.7/site-packages/gevent/socket.py", line 458, in sendall
    data_sent += self.send(_get_memory(data, data_sent), flags)
  File "/Users/erik.allik/.virtualenvs/myproj/lib/python2.7/site-packages/gevent/socket.py", line 435, in send
    return sock.send(data, flags)

Answer 1

看起来当请求被终止时会发生的事情是，除了（看似无法捕获的）异常回溯之外，从WSGI处理程序返回的迭代器是.close() - d。因此，可以确定何时应关闭与响应相关联的任何工人/资源/句柄。这基本上是werkzeug.wsgi.ClosingIterator所做的：

class ClosingIterator(object):
    def __init__(self, iterable, on_close):
        iterator = iter(iterable)
        self.close = on_close
    def __iter__(self):
        return self
    def __next__(self):
        return self._next()

def application(env, start_response):
    start_response(...)

    q = Queue()
    ev_handle = register_event_handler(lambda event, arg: q.put((event, arg)))

    return ClosingIterator(
        iter(lambda: render(q.get()), None),
        on_close=ev_handle.unregister
    )

然而，这并没有使错误消息/追溯变得沉默，但这似乎是可以忍受的，除非有人能提出一个解决方案，甚至可以解决这个问题。

如何在WSGI处理程序中捕获“[Errno 32] Broken pipe”

1 个答案: