105 lines
3.1 KiB
Python
105 lines
3.1 KiB
Python
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##############################################################################
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#
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# Copyright (c) 2001, 2002 Zope Foundation and Contributors.
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# All Rights Reserved.
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#
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# This software is subject to the provisions of the Zope Public License,
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# Version 2.1 (ZPL). A copy of the ZPL should accompany this distribution.
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# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
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# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
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# FOR A PARTICULAR PURPOSE
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#
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##############################################################################
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import os
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import errno
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import logging
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logger = logging.getLogger("zc.lockfile")
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class LockError(Exception):
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"""Couldn't get a lock
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"""
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try:
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import fcntl
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except ImportError:
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try:
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import msvcrt
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except ImportError:
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def _lock_file(file):
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raise TypeError('No file-locking support on this platform')
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def _unlock_file(file):
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raise TypeError('No file-locking support on this platform')
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else:
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# Windows
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def _lock_file(file):
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# Lock just the first byte
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try:
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msvcrt.locking(file.fileno(), msvcrt.LK_NBLCK, 1)
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except IOError:
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raise LockError("Couldn't lock %r" % file.name)
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def _unlock_file(file):
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try:
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file.seek(0)
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msvcrt.locking(file.fileno(), msvcrt.LK_UNLCK, 1)
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except IOError:
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raise LockError("Couldn't unlock %r" % file.name)
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else:
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# Unix
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_flags = fcntl.LOCK_EX | fcntl.LOCK_NB
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def _lock_file(file):
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try:
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fcntl.flock(file.fileno(), _flags)
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except IOError:
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raise LockError("Couldn't lock %r" % file.name)
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def _unlock_file(file):
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fcntl.flock(file.fileno(), fcntl.LOCK_UN)
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class LazyHostName(object):
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"""Avoid importing socket and calling gethostname() unnecessarily"""
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def __str__(self):
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import socket
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return socket.gethostname()
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class LockFile:
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_fp = None
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def __init__(self, path, content_template='{pid}'):
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self._path = path
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try:
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# Try to open for writing without truncation:
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fp = open(path, 'r+')
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except IOError:
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# If the file doesn't exist, we'll get an IO error, try a+
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# Note that there may be a race here. Multiple processes
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# could fail on the r+ open and open the file a+, but only
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# one will get the the lock and write a pid.
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fp = open(path, 'a+')
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try:
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_lock_file(fp)
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except:
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fp.close()
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raise
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# We got the lock, record info in the file.
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self._fp = fp
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fp.write(" %s\n" % content_template.format(pid=os.getpid(),
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hostname=LazyHostName()))
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fp.truncate()
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fp.flush()
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def close(self):
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if self._fp is not None:
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_unlock_file(self._fp)
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self._fp.close()
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self._fp = None
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