def imageBuildLock(self, image, blocking=True, timeout=None):
'''
Context manager to use for locking new image builds.
Obtains a write lock for the specified image. A thread of control
using this API may have only one image locked at a time. A new
znode is created with the next highest build number. This build
number is returned to the caller.
:param str image: Name of the image to lock
:param bool blocking: Whether or not to block on trying to
acquire the lock
:param int timeout: When blocking, how long to wait for the lock
to get acquired. None, the default, waits forever.
:returns: A integer to use for the new build id.
:raises: TimeoutException if we failed to acquire the lock when
blocking with a timeout. ZKLockException if we are not blocking
and could not get the lock, or a lock is already held.
'''
if self._current_lock:
raise npe.ZKLockException("A lock is already held.")
try:
yield self._getImageBuildLock(image, blocking, timeout)
finally:
if self._current_lock:
self._current_lock.release()
self._current_lock = None
def _getImageLock(self, image, blocking=True, timeout=None):
# If we don't already have a znode for this image, create it.
image_lock = self._imageLockPath(image)
try:
self.client.ensure_path(self._imagePath(image))
self._current_lock = Lock(self.client, image_lock)
have_lock = self._current_lock.acquire(blocking, timeout)
except kze.LockTimeout:
raise npe.TimeoutException("Timeout trying to acquire lock %s" %
image_lock)
# If we aren't blocking, it's possible we didn't get the lock
# because someone else has it.
if not have_lock:
raise npe.ZKLockException("Did not get lock on %s" % image_lock)
def _getImageBuildLock(self, image, blocking=True, timeout=None):
lock_path = self._imageBuildLockPath(image)
try:
lock = Lock(self.client, lock_path)
have_lock = lock.acquire(blocking, timeout)
except kze.LockTimeout:
raise npe.TimeoutException(
"Timeout trying to acquire lock %s" % lock_path)
# If we aren't blocking, it's possible we didn't get the lock
# because someone else has it.
if not have_lock:
raise npe.ZKLockException("Did not get lock on %s" % lock_path)
return lock