Merge pull request #3572 from matrix-org/rav/linearizer_cancellation

Test and fix support for cancellation in Linearizer
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Richard van der Hoff 2018-07-20 14:44:02 +01:00 committed by GitHub
commit ff48ab8527
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3 changed files with 54 additions and 6 deletions

1
changelog.d/3572.misc Normal file
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@ -0,0 +1 @@
Merge Linearizer and Limiter

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@ -184,13 +184,13 @@ class Linearizer(object):
# key_to_defer is a map from the key to a 2 element list where
# the first element is the number of things executing, and
# the second element is a deque of deferreds for the things blocked from
# executing.
# the second element is an OrderedDict, where the keys are deferreds for the
# things blocked from executing.
self.key_to_defer = {}
@defer.inlineCallbacks
def queue(self, key):
entry = self.key_to_defer.setdefault(key, [0, collections.deque()])
entry = self.key_to_defer.setdefault(key, [0, collections.OrderedDict()])
# If the number of things executing is greater than the maximum
# then add a deferred to the list of blocked items
@ -198,12 +198,28 @@ class Linearizer(object):
# this item so that it can continue executing.
if entry[0] >= self.max_count:
new_defer = defer.Deferred()
entry[1].append(new_defer)
entry[1][new_defer] = 1
logger.info(
"Waiting to acquire linearizer lock %r for key %r", self.name, key,
)
try:
yield make_deferred_yieldable(new_defer)
except Exception as e:
if isinstance(e, CancelledError):
logger.info(
"Cancelling wait for linearizer lock %r for key %r",
self.name, key,
)
else:
logger.warn(
"Unexpected exception waiting for linearizer lock %r for key %r",
self.name, key,
)
# we just have to take ourselves back out of the queue.
del entry[1][new_defer]
raise
logger.info("Acquired linearizer lock %r for key %r", self.name, key)
entry[0] += 1
@ -238,7 +254,7 @@ class Linearizer(object):
entry[0] -= 1
if entry[1]:
next_def = entry[1].popleft()
(next_def, _) = entry[1].popitem(last=False)
# we need to run the next thing in the sentinel context.
with PreserveLoggingContext():

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@ -17,6 +17,7 @@
from six.moves import range
from twisted.internet import defer, reactor
from twisted.internet.defer import CancelledError
from synapse.util import Clock, logcontext
from synapse.util.async import Linearizer
@ -112,3 +113,33 @@ class LinearizerTestCase(unittest.TestCase):
d6 = limiter.queue(key)
with (yield d6):
pass
@defer.inlineCallbacks
def test_cancellation(self):
linearizer = Linearizer()
key = object()
d1 = linearizer.queue(key)
cm1 = yield d1
d2 = linearizer.queue(key)
self.assertFalse(d2.called)
d3 = linearizer.queue(key)
self.assertFalse(d3.called)
d2.cancel()
with cm1:
pass
self.assertTrue(d2.called)
try:
yield d2
self.fail("Expected d2 to raise CancelledError")
except CancelledError:
pass
with (yield d3):
pass