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109 lines
3.4 KiB
Python
109 lines
3.4 KiB
Python
# Copyright (c) 2018, Ansible Project
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# Simplified BSD License (see licenses/simplified_bsd.txt or https://opensource.org/licenses/BSD-2-Clause)
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# SPDX-License-Identifier: BSD-2-Clause
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# NOTE:
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# This has been vendored from ansible.module_utils.common.file. This code has been removed from there for ansible-core 2.16.
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from __future__ import (absolute_import, division, print_function)
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__metaclass__ = type
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import os
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import stat
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import time
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import fcntl
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import sys
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from contextlib import contextmanager
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class LockTimeout(Exception):
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pass
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class FileLock:
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'''
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Currently FileLock is implemented via fcntl.flock on a lock file, however this
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behaviour may change in the future. Avoid mixing lock types fcntl.flock,
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fcntl.lockf and module_utils.common.file.FileLock as it will certainly cause
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unwanted and/or unexpected behaviour
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'''
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def __init__(self):
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self.lockfd = None
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@contextmanager
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def lock_file(self, path, tmpdir, lock_timeout=None):
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'''
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Context for lock acquisition
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'''
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try:
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self.set_lock(path, tmpdir, lock_timeout)
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yield
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finally:
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self.unlock()
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def set_lock(self, path, tmpdir, lock_timeout=None):
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'''
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Create a lock file based on path with flock to prevent other processes
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using given path.
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Please note that currently file locking only works when it's executed by
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the same user, I.E single user scenarios
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:kw path: Path (file) to lock
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:kw tmpdir: Path where to place the temporary .lock file
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:kw lock_timeout:
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Wait n seconds for lock acquisition, fail if timeout is reached.
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0 = Do not wait, fail if lock cannot be acquired immediately,
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Default is None, wait indefinitely until lock is released.
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:returns: True
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'''
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lock_path = os.path.join(tmpdir, 'ansible-{0}.lock'.format(os.path.basename(path)))
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l_wait = 0.1
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r_exception = IOError
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if sys.version_info[0] == 3:
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r_exception = BlockingIOError
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self.lockfd = open(lock_path, 'w')
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if lock_timeout <= 0:
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fcntl.flock(self.lockfd, fcntl.LOCK_EX | fcntl.LOCK_NB)
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os.chmod(lock_path, stat.S_IWRITE | stat.S_IREAD)
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return True
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if lock_timeout:
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e_secs = 0
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while e_secs < lock_timeout:
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try:
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fcntl.flock(self.lockfd, fcntl.LOCK_EX | fcntl.LOCK_NB)
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os.chmod(lock_path, stat.S_IWRITE | stat.S_IREAD)
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return True
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except r_exception:
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time.sleep(l_wait)
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e_secs += l_wait
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continue
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self.lockfd.close()
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raise LockTimeout('{0} sec'.format(lock_timeout))
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fcntl.flock(self.lockfd, fcntl.LOCK_EX)
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os.chmod(lock_path, stat.S_IWRITE | stat.S_IREAD)
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return True
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def unlock(self):
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'''
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Make sure lock file is available for everyone and Unlock the file descriptor
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locked by set_lock
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:returns: True
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'''
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if not self.lockfd:
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return True
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try:
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fcntl.flock(self.lockfd, fcntl.LOCK_UN)
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self.lockfd.close()
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except ValueError: # file wasn't opened, let context manager fail gracefully
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pass
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return True
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