Viewing file:  CommandLock.py (3.32 KB) -rw-r--r--
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#
# Copyright Red Hat
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301, USA.
#
"""
CommandLock - simple process locking
$Id: //eng/vdo-releases/aluminum/src/python/vdo/vdomgmnt/CommandLock.py#2 $
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
from __future__ import unicode_literals
from vdo.utils import Command, FileLock
class CommandLockError(Exception):
"""Exception raised to indicate an error acquiring a CommandLock."""
######################################################################
# Overridden methods
######################################################################
def __init__(self, message, *args):
super(CommandLockError, self).__init__()
self._message = message.format(*args)
######################################################################
def __str__(self):
return self._message
########################################################################
class CommandLock(FileLock):
"""Simple process locking.
"""
######################################################################
# Overridden methods
######################################################################
def __enter__(self):
try:
super(CommandLock, self).__enter__()
except:
raise CommandLockError("Could not lock file {0}", self.path)
return self
######################################################################
def __init__(self, filePath, readonly=True):
super(CommandLock, self).__init__(filePath,
"r" if readonly else "r+",
timeout = 20)
######################################################################
def __repr__(self):
lst = [str(self), "["]
lst.append(','.join('='.join([key, str(getattr(self, key))])
for key in self.__dict__))
lst.append("]")
return "".join(lst)
######################################################################
def __str__(self):
return "{0}({1})".format(type(self).__name__, self.path)
######################################################################
def _createFile(self):
super(CommandLock, self)._createFile()
# For now, we default to permitting shared locks from non-root
# processes. The sysadmin may change this; we won't change the
# permissions once the file has been created.
#
# N.B.: The names may not be sanitized for use with a shell!
cmd = Command(["chmod", "644", self.path])
cmd.run()
######################################################################
# Protected methods
######################################################################
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