def mergeJoinDispatch(self, event, obj):
""" Performs a merge join on the pending fan-in dispatches.
@param event: an event that is being merge joined (destination state must be a fan in)
@return: a list (possibly empty) of FSMContext instances
"""
# this assertion comes from _queueDispatchFanIn - we never want fan-out info in a fan-in context
assert not self.get(constants.GEN_PARAM)
assert not self.get(constants.FORK_PARAM)
# the work package index is stored in the url of the Task/FSMContext
index = self.get(constants.INDEX_PARAM)
self.logger.debug('Index: %s', index)
taskNameBase = self.getTaskName(event, fanIn=True)
# see comment (***) in self._queueDispatchFanIn
#
# in the case of failing to acquire a read lock (due to failed release of write lock)
# we have decided to keep retrying
raiseOnFail = False
if self._getTaskRetryLimit() is not None:
raiseOnFail = (self._getTaskRetryLimit() > self.__obj[constants.RETRY_COUNT_PARAM])
rwlock = ReadWriteLock(taskNameBase, self)
rwlock.acquireReadLock(index, raiseOnFail=raiseOnFail)
# and return the FSMContexts list
class FSMContextList(list):
""" A list that supports .logger.info(), .logger.warning() etc.for fan-in actions """
def __init__(self, context, contexts, guarded=False):
""" setup a self.logger for fan-in actions """
super(FSMContextList, self).__init__(contexts)
self.logger = Logger(context)
self.instanceName = context.instanceName
self.guarded = guarded
# see comment (A) in self._queueDispatchFanIn(...)
time.sleep(constants.DATASTORE_ASYNCRONOUS_INDEX_WRITE_WAIT_TIME)
# the following step ensure that fan-in only ever operates one time over a list of data
# the entity is created in State.dispatch(...) _after_ all the actions have executed
# successfully
khash = knuthHash(index)
self.logger.debug('knuthHash of index: %s', khash)
workIndex = '%s-%d' % (taskNameBase, khash)
if obj[constants.RETRY_COUNT_PARAM] > 0:
semaphore = RunOnceSemaphore(workIndex, self)
if semaphore.readRunOnceSemaphore(payload=self.__obj[constants.TASK_NAME_PARAM]):
self.logger.info("Fan-in idempotency guard for workIndex '%s', not processing any work items.",
workIndex)
return FSMContextList(self, [], guarded=True) # don't operate over the data again
# fetch all the work packages in the current group for processing
query = _FantasmFanIn.all(namespace='') \
.filter('workIndex =', workIndex) \
.order('__key__')
# construct a list of FSMContexts
contexts = [self.clone(replaceData=r.context) for r in query]
return FSMContextList(self, contexts)
def test_acquireReadLock_before_acquireWriteLock(self):
lock = ReadWriteLock('foo', self.context)
index = lock.currentIndex()
self.assertEqual(None, memcache.get(lock.lockKey(index)))
lock.acquireReadLock(index)
self.assertEqual(None, memcache.get(lock.lockKey(index)))
self.assertEqual([], self.loggingDouble.messages['debug'])
self.assertEqual([], self.loggingDouble.messages['critical'])
def test_acquireReadLock_before_acquireWriteLock(self):
lock = ReadWriteLock('foo', self.context)
index = lock.currentIndex()
self.assertEqual(None, memcache.get(lock.lockKey(index)))
lock.acquireReadLock(index)
self.assertEqual(None, memcache.get(lock.lockKey(index)))
self.assertEqual([], self.loggingDouble.messages['debug'])
self.assertEqual([], self.loggingDouble.messages['critical'])
def test_acquireWriteLock_failure(self):
lock = ReadWriteLock('foo', self.context)
index = lock.currentIndex()
self.assertEqual(None, memcache.get(lock.lockKey(index)))
lock.acquireWriteLock(index) # need to call before acquireReadLock
self.assertEqual(65537, memcache.get(lock.lockKey(index)))
lock.acquireReadLock(index)
self.assertEqual(32769, memcache.get(lock.lockKey(index)))
self.assertRaises(FanInWriteLockFailureRuntimeError, lock.acquireWriteLock, index)
def test_acquireWriteLock_failure(self):
lock = ReadWriteLock('foo', self.context)
index = lock.currentIndex()
self.assertEqual(None, memcache.get(lock.lockKey(index)))
lock.acquireWriteLock(index) # need to call before acquireReadLock
self.assertEqual('65537', memcache.get(lock.lockKey(index)))
lock.acquireReadLock(index)
self.assertEqual('32769', memcache.get(lock.lockKey(index)))
self.assertRaises(FanInWriteLockFailureRuntimeError,
lock.acquireWriteLock, index)
def test_acquireReadLock_gave_up(self):
lock = ReadWriteLock('foo', self.context)
index = lock.currentIndex()
self.assertEqual(None, memcache.get(lock.lockKey(index)))
lock.acquireWriteLock(index)
self.assertEqual(65537, memcache.get(lock.lockKey(index)))
lock.acquireReadLock(index)
self.assertEqual(32769, memcache.get(lock.lockKey(index)))
self.assertEqual(["Tried to acquire read lock 'foo-lock-3626764237' 1 times...",
"Tried to acquire read lock 'foo-lock-3626764237' 2 times..."],
self.loggingDouble.messages['debug'])
self.assertEqual(["Gave up waiting for all fan-in work items with read lock 'foo-lock-3626764237'."],
self.loggingDouble.messages['critical'])
def test_acquireReadLock_gave_up(self):
lock = ReadWriteLock('foo', self.context)
index = lock.currentIndex()
self.assertEqual(None, memcache.get(lock.lockKey(index)))
lock.acquireWriteLock(index)
self.assertEqual('65537', memcache.get(lock.lockKey(index)))
lock.acquireReadLock(index)
self.assertEqual('32769', memcache.get(lock.lockKey(index)))
self.assertEqual([
"Tried to acquire read lock 'foo-lock-3626764237' 1 times...",
"Tried to acquire read lock 'foo-lock-3626764237' 2 times..."
], self.loggingDouble.messages['debug'])
self.assertEqual([
"Gave up waiting for all fan-in work items with read lock 'foo-lock-3626764237'."
], self.loggingDouble.messages['critical'])
def test_acquireReadLock_one_wait_iter(self):
lock = ReadWriteLock('foo', self.context)
index = lock.currentIndex()
self.assertEqual(None, memcache.get(lock.lockKey(index)))
lock.acquireWriteLock(index)
self.assertEqual(65537, memcache.get(lock.lockKey(index)))
def sleepAndRelease(seconds): # pylint: disable=W0613
lock.releaseWriteLock(index)
mock('time.sleep', returns_func=sleepAndRelease, tracker=None)
lock.acquireReadLock(index)
self.assertEqual(32768, memcache.get(lock.lockKey(index)))
self.assertEqual(["Tried to acquire read lock 'foo-lock-3626764237' 1 times..."],
self.loggingDouble.messages['debug'])
self.assertEqual(["Gave up waiting for all fan-in work items with read lock 'foo-lock-3626764237'."],
self.loggingDouble.messages['critical'])
def test_acquireReadLock_one_wait_iter(self):
lock = ReadWriteLock('foo', self.context)
index = lock.currentIndex()
self.assertEqual(None, memcache.get(lock.lockKey(index)))
lock.acquireWriteLock(index)
self.assertEqual('65537', memcache.get(lock.lockKey(index)))
def sleepAndRelease(seconds): # pylint: disable-msg=W0613
lock.releaseWriteLock(index)
mock('time.sleep', returns_func=sleepAndRelease, tracker=None)
lock.acquireReadLock(index)
self.assertEqual('32768', memcache.get(lock.lockKey(index)))
self.assertEqual(
["Tried to acquire read lock 'foo-lock-3626764237' 1 times..."],
self.loggingDouble.messages['debug'])
self.assertEqual([
"Gave up waiting for all fan-in work items with read lock 'foo-lock-3626764237'."
], self.loggingDouble.messages['critical'])
