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# mypidfile.py - functions for properly locking a PIDFile
#
# Copyright (C) 2010-2021 Arthur de Jong
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library 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
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301 USA
import errno
import fcntl
import os
import cfg
class MyPIDLockFile(object):
"""A PIDFile for use with the daemon module.
This class that locks the PIDFile with fcntl.lockf().
"""
def __init__(self, path):
self.path = path
def __enter__(self):
"""Lock the PID file and write the process ID to the file."""
# create the directory for the pidfile if needed
piddir = os.path.dirname(self.path)
if not os.path.isdir(piddir):
os.mkdir(piddir)
if cfg.uid is not None:
u, gid = cfg.get_usergid()
os.chown(piddir, u.u.pw_uid, gid)
fd = os.open(self.path, os.O_RDWR | os.O_CREAT, 0o644)
try:
fcntl.lockf(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
pidfile = os.fdopen(fd, 'w')
except Exception:
os.close(fd)
raise
pidfile.write('%d\n' % os.getpid())
pidfile.truncate()
pidfile.flush()
self.pidfile = pidfile
return self
def __exit__(self, exc_type, exc_value, traceback):
"""Release the lock (close the lockfile)."""
fcntl.lockf(self.pidfile.fileno(), fcntl.LOCK_UN)
self.pidfile.close()
del self.pidfile
def is_locked(self):
"""Check whether the file is already present and locked."""
try:
fd = os.open(self.path, os.O_RDWR, 0o644)
# Python doesn't seem to have F_TEST so we'll just try to lock
fcntl.lockf(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
# if we're here we must have aquired the lock
fcntl.lockf(fd, fcntl.LOCK_UN)
return False
except (IOError, OSError) as e:
if e.errno == errno.ENOENT:
return False
if e.errno in (errno.EACCES, errno.EAGAIN):
return True
raise
finally:
if 'fd' in locals():
os.close(fd)
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