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File Content: `rhnLockfile.py`

#
# Copyright (c) 2008--2016 Red Hat, Inc.
#
# This software is licensed to you under the GNU General Public License,
# version 2 (GPLv2). There is NO WARRANTY for this software, express or
# implied, including the implied warranties of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE. You should have received a copy of GPLv2
# along with this software; if not, see
# http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt.
#
# Red Hat trademarks are not licensed under GPLv2. No permission is
# granted to use or replicate Red Hat trademarks that are incorporated
# in this software or its documentation.
#

import os
import sys
import fcntl
from errno import EWOULDBLOCK, EEXIST
from rhn.i18n import bstr
import fcntl

class LockfileLockedException(Exception):
    """thrown ONLY when pid file is locked."""
    pass

class Lockfile:

    """class that provides simple access to a PID-style lockfile.

    methods: __init__(lockfile), acquire(), and release()
    NOTE: currently acquires upon init
    The *.pid file will be acquired, or an LockfileLockedException is raised.
    """

    def __init__(self, lockfile, pid=None):
        """create (if need be), and acquire lock on lockfile

        lockfile example: '/var/run/up2date.pid'
        """

        # cleanup the path and assign it.
        self.lockfile = os.path.abspath(
                          os.path.expanduser(
                            os.path.expandvars(lockfile)))

        self.pid = pid
        if not self.pid:
            self.pid = os.getpid()

        # create the directory structure
        dirname = os.path.dirname(self.lockfile)
        if not os.path.exists(dirname):
            try:
                os.makedirs(dirname)
            except OSError:
                e = sys.exc_info()[1]
                if hasattr(e, 'errno') and e.errno == EEXIST:
                    # race condition... dirname exists now.
                    pass
                else:
                    raise

        # open the file -- non-destructive read-write, unless it needs
        # to be created XXX: potential race condition upon create?
        self.f = os.open(self.lockfile, os.O_RDWR|os.O_CREAT|os.O_SYNC)
        self.acquire()

    def acquire(self):
        """acquire the lock; else raise LockfileLockedException."""

        try:
            fcntl.flock(self.f, fcntl.LOCK_EX|fcntl.LOCK_NB)
        except IOError:
            if sys.exc_info()[1].errno == EWOULDBLOCK:
                raise LockfileLockedException(
                  "cannot acquire lock on %s." % self.lockfile, None, sys.exc_info()[2])
            else:
                raise
        # unlock upon exit
        fcntl.fcntl(self.f, fcntl.F_SETFD, 1)
        # truncate and write the pid
        os.ftruncate(self.f, 0)
        os.write(self.f, bstr(str(self.pid) + '\n'))

    def release(self):
        # Remove the lock file
        os.unlink(self.lockfile)
        fcntl.flock(self.f, fcntl.LOCK_UN)
        os.close(self.f)


def main():
    """test code"""

    try:
        L = Lockfile('./test.pid')
    except LockfileLockedException:
        sys.stderr.write("%s\n" % sys.exc_info()[1])
        sys.exit(-1)
    else:
        print("lock acquired ")
        print("...sleeping for 10 seconds")
        import time
        time.sleep(10)
        L.release()
        print("lock released ")

if __name__ == '__main__':
    # test code
    sys.exit(main() or 0)

Name	Size	Permission
__pycache__	---	0755
actions	---	0755
SSL.py	11053 bytes	0644
SmartIO.py	2164 bytes	0644
UserDictCase.py	3034 bytes	0644
__init__.py	132 bytes	0644
connections.py	9712 bytes	0644
i18n.py	1773 bytes	0644
nonblocking.py	2427 bytes	0644
rhnLockfile.py	3427 bytes	0644
rpclib.py	24298 bytes	0644
tb.py	836 bytes	0644
transports.py	31979 bytes	0644

File Content: rhnLockfile.py

File Content: `rhnLockfile.py`