Can anyone explain this result to me? It looks to me as though the SelectReactor is leaking file descriptors. Granted, it's a pathological case, but it's not uncommon if you're running a bunch of tests. --rich rich@black.noir.com> cat demo.py from twisted.internet.selectreactor import SelectReactor for i in xrange(1024): SelectReactor() rich@black.noir.com> python demo.py Traceback (most recent call last): File "demo.py", line 4, in <module> SelectReactor() File "/home/rich/projects/sprained/sprained-dev/lib/python2.6/site-packages/Twisted-9.0.0_r28543-py2.6-linux-x86_64.egg/twisted/internet/selectreactor.py", line 72, in __init__ posixbase.PosixReactorBase.__init__(self) File "/home/rich/projects/sprained/sprained-dev/lib/python2.6/site-packages/Twisted-9.0.0_r28543-py2.6-linux-x86_64.egg/twisted/internet/base.py", line 471, in __init__ self.installWaker() File "/home/rich/projects/sprained/sprained-dev/lib/python2.6/site-packages/Twisted-9.0.0_r28543-py2.6-linux-x86_64.egg/twisted/internet/posixbase.py", line 266, in installWaker self.waker = _Waker(self) File "/home/rich/projects/sprained/sprained-dev/lib/python2.6/site-packages/Twisted-9.0.0_r28543-py2.6-linux-x86_64.egg/twisted/internet/posixbase.py", line 128, in __init__ self.i, self.o = os.pipe() OSError: [Errno 24] Too many open files rich@black.noir.com> lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu lucid (development branch) Release: 10.04 Codename: lucid