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92 lines
3.3 KiB
Python
92 lines
3.3 KiB
Python
10 years ago
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"""Lowest-common-denominator implementations of platform functionality."""
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from __future__ import absolute_import, division, print_function, with_statement
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import errno
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import socket
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from tornado.platform import interface
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class Waker(interface.Waker):
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"""Create an OS independent asynchronous pipe.
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For use on platforms that don't have os.pipe() (or where pipes cannot
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be passed to select()), but do have sockets. This includes Windows
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and Jython.
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"""
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def __init__(self):
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# Based on Zope async.py: http://svn.zope.org/zc.ngi/trunk/src/zc/ngi/async.py
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self.writer = socket.socket()
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# Disable buffering -- pulling the trigger sends 1 byte,
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# and we want that sent immediately, to wake up ASAP.
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self.writer.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
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count = 0
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while 1:
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count += 1
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# Bind to a local port; for efficiency, let the OS pick
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# a free port for us.
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# Unfortunately, stress tests showed that we may not
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# be able to connect to that port ("Address already in
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# use") despite that the OS picked it. This appears
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# to be a race bug in the Windows socket implementation.
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# So we loop until a connect() succeeds (almost always
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# on the first try). See the long thread at
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# http://mail.zope.org/pipermail/zope/2005-July/160433.html
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# for hideous details.
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a = socket.socket()
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a.bind(("127.0.0.1", 0))
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a.listen(1)
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connect_address = a.getsockname() # assigned (host, port) pair
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try:
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self.writer.connect(connect_address)
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break # success
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except socket.error as detail:
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if (not hasattr(errno, 'WSAEADDRINUSE') or
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detail[0] != errno.WSAEADDRINUSE):
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# "Address already in use" is the only error
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# I've seen on two WinXP Pro SP2 boxes, under
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# Pythons 2.3.5 and 2.4.1.
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raise
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# (10048, 'Address already in use')
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# assert count <= 2 # never triggered in Tim's tests
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if count >= 10: # I've never seen it go above 2
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a.close()
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self.writer.close()
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raise socket.error("Cannot bind trigger!")
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# Close `a` and try again. Note: I originally put a short
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# sleep() here, but it didn't appear to help or hurt.
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a.close()
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self.reader, addr = a.accept()
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self.reader.setblocking(0)
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self.writer.setblocking(0)
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a.close()
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self.reader_fd = self.reader.fileno()
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def fileno(self):
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return self.reader.fileno()
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def write_fileno(self):
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return self.writer.fileno()
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def wake(self):
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try:
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self.writer.send(b"x")
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except (IOError, socket.error):
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pass
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def consume(self):
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try:
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while True:
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result = self.reader.recv(1024)
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if not result:
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break
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except (IOError, socket.error):
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pass
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def close(self):
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self.reader.close()
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self.writer.close()
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