Current File : //usr/lib/python2.7/site-packages/vdo/utils/Timeout.py
#
# Copyright (c) 2018 Red Hat, Inc.
#
# 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.
#
"""
Timeout - context manager that implements a timeout.
$Id: //eng/vdo-releases/magnesium/src/python/vdo/utils/Timeout.py#1 $
"""
import signal
########################################################################
class TimeoutError(Exception):
"""Exception raised when a block times out."""
def __init__(self, msg = None, *args, **kwargs):
super(TimeoutError, self).__init__(*args, **kwargs)
if msg is None:
msg = "timeout"
self._msg = msg
def __str__(self):
return self._msg
########################################################################
class Timeout(object):
"""Context manager for running a block of commands under a timeout.
If the block times out, a TimeoutError is raised.
Arguments:
seconds (int) - timeout in seconds
msg (str) - message to supply to TimeoutError
"""
######################################################################
# Public methods
######################################################################
######################################################################
# Overridden methods
######################################################################
def __enter__(self):
# Establish the alarm handler and set the alarm to go off.
self.__oldHandler = signal.signal(signal.SIGALRM,
lambda _signum, _frame : self._timeout())
signal.alarm(self.__seconds)
return self
######################################################################
def __exit__(self, exceptionType, exceptionValue, traceback):
# Turn off the alarm and re-establish the previous alarm handler.
signal.alarm(0)
signal.signal(signal.SIGALRM, self.__oldHandler)
# Don't suppress exceptions.
return False
######################################################################
def __init__(self, seconds, msg = None):
self.__seconds = seconds
self.__msg = msg
self.__oldHandler = None
######################################################################
# Protected methods
######################################################################
def _timeout(self):
""" Method invoked if the alarm goes off.
"""
raise TimeoutError(self.__msg)
######################################################################
# Private methods
######################################################################
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