[Python-Dev] test_socketserver failure on cygwin (original) (raw)
Neal Norwitz nnorwitz at gmail.com
Mon Aug 14 02:48:20 CEST 2006
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I'm not sure if this is a race condition in the test, the test using SocketServer inappropriately, or if the failure is exposing a problem in SocketServer.
The issue is that when the second (UDP) server is setup, there is still a child process from the first (TCP) server. So when the UDP server calls collect_children(), it gets back the pid from the TCP server, which is not in the UDP server's list and an exception is raised. In general, this is a problem, if program is using a ForkingServer and spawns it's own children, this problem can occur. This is because os.waitpid() is called with a pid of 0, rather than the individual pids in the list. I suppose that would fix the problem. Is this worth fixing? (It's a pain to handle properly because there is also use of a blocking wait.)
http://www.python.org/dev/buildbot/all/x86%20cygwin%20trunk/builds/1107/step-test/0
Add this patch corrects the problem (see below for more details):
Index: Lib/test/test_socketserver.py
--- Lib/test/test_socketserver.py (revision 51260) +++ Lib/test/test_socketserver.py (working copy) @@ -183,7 +183,11 @@
def testall(): testloop(socket.AF_INET, tcpservers, MyStreamHandler, teststream)
- time.sleep(.1)
- reap_children() testloop(socket.AF_INET, udpservers, MyDatagramHandler, testdgram)
- time.sleep(.1)
- reap_children() if hasattr(socket, 'AF_UNIX'): testloop(socket.AF_UNIX, streamservers, MyStreamHandler, teststream) # Alas, on Linux (at least) recvfrom() doesn't return a meaningful
So modifying SocketServer like this: -bash-3.1$ svn diff Lib/SocketServer.py Lib/test/test_socketserver.py Index: Lib/SocketServer.py
--- Lib/SocketServer.py (revision 51260) +++ Lib/SocketServer.py (working copy) @@ -420,6 +420,7 @@ except os.error: pid = None if not pid: break
print >> sys.__stdout__, 'pid', pid, 'active',
self.active_children self.active_children.remove(pid)
def process_request(self, request, client_address):@@ -428,6 +429,7 @@ pid = os.fork() if pid: # Parent process
print >> sys.__stdout__, 'in parent, adding', pid,
self.active_children if self.active_children is None: self.active_children = [] self.active_children.append(pid)
We see this on error (prior to the test patch above):
test_socketserver in parent, adding 3084 None pid 3084 active [3084] in parent, adding 2408 [] pid 2408 active [2408] in parent, adding 3908 [] in parent, adding 532 None pid 3908 active [532] Exception in thread Thread-12: Traceback (most recent call last): ... File "/home/neal/build/python/trunk/Lib/SocketServer.py", line 424, in collect_children self.active_children.remove(pid) ValueError: list.remove(x): x not in list
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