New submission from Péter Szabó <[email protected]>:
Here is how to reproduce the leak in Python 2.6.4 and Python 2.7:
import gc
import socket
import ssl
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
gc.disable()
gc.collect()
count0 = gc.get_count()[0]
for i in xrange(1000):
ssl.SSLSocket(sock)
count1 = gc.get_count()[0]
# This should be less than 100 without the leak, but it is >1000.
diff = count1 - count0
assert diff < 1000, diff
The reason why the memory usage has increased is that the SSLSocket objects
contain a circular reference (self -> __init__ -> recv -> lambda -> self), and
thus Python cannot free them without garbage collection.
A side effect is that if the SSLSocket doesn't have external references, the
underlying socket._realsocket may remain unclosed for a long time (until the
garbage collection kicks in), because the SSLSocket still refers to it. Another
side effect is that when there is an exception in the wrapping in
SSLSocket.accept() (e.g. keyfile not found), then the newly accepted socket
won't get closed immediately, and the client will experience a hanging open
socket.
With gc.enable(), the leak goes away (the garbage collector finds and frees the
SSLSocket objects with circular reference). Python 3.1.1 is not affected since
it has a very different SSLSocket implementation.
Here is an easy fix: replace the self.recv = lambda ... lines in the code of
ssl.SSLSocket.__init__ with this:
import socket as socket_module
for attr in socket_module._delegate_methods:
delattr(self, attr)
See the attached patch. You can also download the patch from
http://code.google.com/p/pts-mini-gpl/source/browse/trunk/patches/pts-python2.6.4-ssl-init-memory-leak-fix.patch
----------
components: IO, Library (Lib)
files: pts-python2.6.4-ssl-init-memory-leak-fix.patch
keywords: patch
messages: 99423
nosy: Péter.Szabó
severity: normal
status: open
title: Memory leak due to circular references in ssl.SSLSocket
type: resource usage
versions: Python 2.6, Python 2.7
Added file:
http://bugs.python.org/file16234/pts-python2.6.4-ssl-init-memory-leak-fix.patch
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<http://bugs.python.org/issue7943>
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