diff options
| -rw-r--r-- | synapse/util/async.py | 24 | ||||
| -rw-r--r-- | tests/util/test_linearizer.py | 28 |
2 files changed, 46 insertions, 6 deletions
diff --git a/synapse/util/async.py b/synapse/util/async.py index bb252f75d7..0fd5b42523 100644 --- a/synapse/util/async.py +++ b/synapse/util/async.py @@ -203,7 +203,26 @@ class Linearizer(object): except: logger.exception("Unexpected exception in Linearizer") - logger.info("Acquired linearizer lock %r for key %r", self.name, key) + logger.info("Acquired linearizer lock %r for key %r", self.name, + key) + + # if the code holding the lock completes synchronously, then it + # will recursively run the next claimant on the list. That can + # relatively rapidly lead to stack exhaustion. This is essentially + # the same problem as http://twistedmatrix.com/trac/ticket/9304. + # + # In order to break the cycle, we add a cheeky sleep(0) here to + # ensure that we fall back to the reactor between each iteration. + # + # (There's no particular need for it to happen before we return + # the context manager, but it needs to happen while we hold the + # lock, and the context manager's exit code must be synchronous, + # so actually this is the only sensible place. + yield run_on_reactor() + + else: + logger.info("Acquired uncontended linearizer lock %r for key %r", + self.name, key) @contextmanager def _ctx_manager(): @@ -211,7 +230,8 @@ class Linearizer(object): yield finally: logger.info("Releasing linearizer lock %r for key %r", self.name, key) - new_defer.callback(None) + with PreserveLoggingContext(): + new_defer.callback(None) current_d = self.key_to_defer.get(key) if current_d is new_defer: self.key_to_defer.pop(key, None) diff --git a/tests/util/test_linearizer.py b/tests/util/test_linearizer.py index afcba482f9..793a88e462 100644 --- a/tests/util/test_linearizer.py +++ b/tests/util/test_linearizer.py @@ -12,8 +12,7 @@ # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. - - +from synapse.util import async, logcontext from tests import unittest from twisted.internet import defer @@ -38,7 +37,28 @@ class LinearizerTestCase(unittest.TestCase): with cm1: self.assertFalse(d2.called) - self.assertTrue(d2.called) - with (yield d2): pass + + def test_lots_of_queued_things(self): + # we have one slow thing, and lots of fast things queued up behind it. + # it should *not* explode the stack. + linearizer = Linearizer() + + @defer.inlineCallbacks + def func(i, sleep=False): + with logcontext.LoggingContext("func(%s)" % i) as lc: + with (yield linearizer.queue("")): + self.assertEqual( + logcontext.LoggingContext.current_context(), lc) + if sleep: + yield async.sleep(0) + + self.assertEqual( + logcontext.LoggingContext.current_context(), lc) + + func(0, sleep=True) + for i in xrange(1, 100): + func(i) + + return func(1000) |