Synnefo » snf-ganeti

	lib/utils/livelock.py \

from ganeti.utils.livelock import *

#

#

# Copyright (C) 2014 Google 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.

"""Lockfiles to prove liveliness

When requesting resources, like locks, from wconfd, requesters have

to provide the name of a file they own an exclusive lock on, to prove

that they are still alive. Provide methods to obtain such a file.

"""

import fcntl

import os

import struct

import time

from ganeti import pathutils

class LiveLock(object):

  """Utility for a lockfile needed to request resources from WconfD.

  """

  def __init__(self, name=None):

    if name is None:

      name = "pid%d_" % os.getpid()

    # to avoid reusing existing lock files, extend name

    # by the current time

    name = "%s_%d" % (name, int(time.time()))

    fname = os.path.join(pathutils.LIVELOCK_DIR, name)

    self.lockfile = open(fname, 'w')

    fcntl.fcntl(self.lockfile, fcntl.F_SETLKW,

                struct.pack('hhllhh', fcntl.F_WRLCK, 0, 0, 0, 0, 0))

  def close(self):

    """Close the lockfile and clean it up.

    """

    self.lockfile.close()

    os.remove(self.lockfile.name)