def acquire(self, timeout=60):
'''Locks the token cache for this key and username.
If the token cache is already locked, waits until it is
released. Throws an exception when the lock cannot be acquired
after ``timeout`` seconds.
'''
# Check whether there is a PID file already with our PID in
# it.
lockpid = self.get_lock_pid()
if lockpid == os.getpid():
LOG.debug('The lock is ours, continuing')
return
# Figure out the lock filename
lock = self.get_lock_name()
LOG.debug('Acquiring lock %s' % lock)
# Try to obtain the lock
start_time = time.time()
while True:
try:
os.makedirs(lock)
break
except OSError:
# If the path doesn't exist, the error isn't that it
# can't be created because someone else has got the
# lock. Just bail out then.
if not os.path.exists(lock):
LOG.error('Unable to acquire lock %s, aborting' %
lock)
raise
if time.time() - start_time >= timeout:
# Timeout has passed, bail out
raise LockingError('Unable to acquire lock ' +
'%s, aborting' % lock)
# Wait for a bit, then try again
LOG.debug('Unable to acquire lock, waiting')
time.sleep(0.1)
# Write the PID file
LOG.debug('Lock acquired, writing our PID')
pidfile = open(self.pidfile_name, 'w')
try:
pidfile.write('%s' % os.getpid())
finally:
pidfile.close()
def release(self):
'''Unlocks the token cache for this key.'''
# Figure out the lock filename
lock = self.get_lock_name()
if not os.path.exists(lock):
LOG.warn('Trying to release non-existing lock %s' % lock)
return
# If the PID file isn't ours, abort.
lockpid = self.get_lock_pid()
if lockpid and lockpid != os.getpid():
raise LockingError(('Lock %s is NOT ours, but belongs ' +
'to PID %i, unable to release.') % (lock, lockpid))
LOG.debug('Releasing lock %s' % lock)
# Remove the PID file and the lock directory
pidfile = self.pidfile_name
if os.path.exists(pidfile):
os.remove(pidfile)
os.removedirs(lock)
