Commit 8e0df396 authored by Tim Peters's avatar Tim Peters

Worm around suspected Windows socket bug in Windows trigger code.

See the thread starting at
 http://mail.zope.org/pipermail/zope/2005-July/160433.html
for gory details.
parent 7f94c939
......@@ -5,6 +5,7 @@ Release date: DD-MMM-2005
Following are dates of internal releases (to support ongoing Zope 2
development) since ZODB 3.4's last public release:
- 3.4.1b2 DD-MMM-2005
- 3.4.1b1 26-Jul-2005
- 3.4.1a6 19-Jul-2005
- 3.4.1a5 12-Jul-2005
......@@ -106,6 +107,17 @@ ThreadedAsync.LoopCallback
example, debugging prints added to Python's ``asyncore.loop`` won't be lost
anymore).
Windows
-------
- (3.4.1b2) As developed in a long thread starting at
http://mail.zope.org/pipermail/zope/2005-July/160433.html
there appears to be a race bug in the Microsoft Windows socket
implementation, rarely visible in ZEO when multiple processes try to
create an "asyncore trigger" simultaneously. Windows-specific code in
``ZEO/zrpc/trigger.py`` changed to work around this bug when it occurs.
Tools
-----
......
##############################################################################
#
# Copyright (c) 2001, 2002 Zope Corporation and Contributors.
# Copyright (c) 2001-2005 Zope Corporation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
......@@ -156,27 +156,61 @@ else:
def __init__(self):
_triggerbase.__init__(self)
# Get a pair of connected sockets. The trigger is the 'w'
# end of the pair, which is connected to 'r'. 'r' is put
# in the asyncore socket map. "pulling the trigger" then
# means writing something on w, which will wake up r.
a = socket.socket() # temporary, to set up the connection
w = socket.socket()
self.trigger = w
# set TCP_NODELAY to true to avoid buffering
w.setsockopt(socket.IPPROTO_TCP, 1, 1)
# Specifying port 0 tells Windows to pick a port for us.
w = socket.socket()
# Disable buffering -- pulling the trigger sends 1 byte,
# and we want that sent immediately, to wake up asyncore's
# select() ASAP.
w.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
count = 0
while 1:
count += 1
# Bind to a local port; for efficiency, let the OS pick
# a free port for us.
# Unfortunately, stress tests showed that we may not
# be able to connect to that port ("Address already in
# use") despite that the OS picked it. This appears
# to be a race bug in the Windows socket implementation.
# So we loop until a connect() succeeds (almost always
# on the first try). See the long thread at
# http://mail.zope.org/pipermail/zope/2005-July/160433.html
# for hideous details.
a = socket.socket()
a.bind(("127.0.0.1", 0))
connect_address = a.getsockname() # assigned (host, port) pair
a.listen(1)
try:
w.connect(connect_address)
break # success
except socket.error, detail:
if detail[0] != errno.WSAEADDRINUSE:
# "Address already in use" is the only error
# I've seen on two WinXP Pro SP2 boxes, under
# Pythons 2.3.5 and 2.4.1.
raise
# (10048, 'Address already in use')
# assert count <= 2 # never triggered in Tim's tests
if count >= 10: # I've never seen it go above 2
a.close()
w.close()
raise BindError("Cannot bind trigger!")
# Close `a` and try again. Note: I originally put a short
# sleep() here, but it didn't appear to help or hurt.
a.close()
r, addr = a.accept() # r becomes asyncore's (self.)socket
a.close()
self.trigger = w
asyncore.dispatcher.__init__(self, r)
def _close(self):
# self.socket is r, self.trigger is w from __init__
# self.socket is r, and self.trigger is w, from __init__
self.socket.close()
self.trigger.close()
......
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