Created attachment 564798 [details]
Proposed patch

Description of problem:

The worker threads in CherryPy's WSGI server can die off due to unhandled EPIPE exceptions.


Version-Release number of selected component (if applicable):

python-cherrypy2-2.3.0-11.el6.noarch


How reproducible:

Not 100% of the time, as it seems to be timing sensitive (EPIPE has to occur in the middle of a buffered write). But it can be reproduced with some looping.


Steps to Reproduce:

Minimal CherryPy server:

import pkg_resources
pkg_resources.require('CherryPy==2.3.0')
import cherrypy

class Root(object):
    def index(self):
        return '.' * 1000
    index.exposed = True

cherrypy.tree.mount(Root())
cherrypy.server.start()

Client program which triggers EPIPEs in the server:

import socket, time
while True:
    s = socket.socket()
    s.connect(('localhost', 8080))
    f = s.makefile()
    f.write('GET / HTTP/1.0\r\n\r\n')
    f.flush()
    s.close() # close without reading, to trigger EPIPE

Start the server, and then run the client and watch it kill the server.

  
Actual results:

Each worker thread will eventually die off with an exception like this:

Exception in thread CP WSGIServer Thread-9:
Traceback (most recent call last):
  File "/usr/lib64/python2.6/threading.py", line 532, in __bootstrap_inner
    self.run()
  File "/usr/lib/python2.6/site-packages/CherryPy-2.3.0-py2.6.egg/cherrypy/_cpwsgiserver.py", line 252, in run
    request.terminate()
  File "/usr/lib/python2.6/site-packages/CherryPy-2.3.0-py2.6.egg/cherrypy/_cpwsgiserver.py", line 211, in terminate
    self.wfile.close()
  File "/usr/lib64/python2.6/socket.py", line 276, in close
    self.flush()
  File "/usr/lib64/python2.6/socket.py", line 303, in flush
    self._sock.sendall(buffer(data, write_offset, buffer_size))
error: [Errno 32] Broken pipe

If you leave the above client program running for a few more seconds you will eventually see "Too many open files" in the server, which is because it is accepting connections but there are no worker threads left to handle them.


Expected results:

EPIPE is ignored and the server keeps on going.


Additional info:

Patch attached.