Merge pull request #4799 from matrix-org/rav/clean_up_replication_code

Clean ups in replication notifier
This commit is contained in:
Erik Johnston 2019-03-05 09:19:48 +00:00 committed by GitHub
commit 9e8bca5667
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2 changed files with 6 additions and 60 deletions

1
changelog.d/4799.misc Normal file
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@ -0,0 +1 @@
Clean up some replication code.

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@ -178,8 +178,6 @@ class Notifier(object):
self.remove_expired_streams, self.UNUSED_STREAM_EXPIRY_MS
)
self.replication_deferred = ObservableDeferred(defer.Deferred())
# This is not a very cheap test to perform, but it's only executed
# when rendering the metrics page, which is likely once per minute at
# most when scraping it.
@ -205,7 +203,9 @@ class Notifier(object):
def add_replication_callback(self, cb):
"""Add a callback that will be called when some new data is available.
Callback is not given any arguments.
Callback is not given any arguments. It should *not* return a Deferred - if
it needs to do any asynchronous work, a background thread should be started and
wrapped with run_as_background_process.
"""
self.replication_callbacks.append(cb)
@ -517,60 +517,5 @@ class Notifier(object):
def notify_replication(self):
"""Notify the any replication listeners that there's a new event"""
with PreserveLoggingContext():
deferred = self.replication_deferred
self.replication_deferred = ObservableDeferred(defer.Deferred())
deferred.callback(None)
# the callbacks may well outlast the current request, so we run
# them in the sentinel logcontext.
#
# (ideally it would be up to the callbacks to know if they were
# starting off background processes and drop the logcontext
# accordingly, but that requires more changes)
for cb in self.replication_callbacks:
cb()
@defer.inlineCallbacks
def wait_for_replication(self, callback, timeout):
"""Wait for an event to happen.
Args:
callback: Gets called whenever an event happens. If this returns a
truthy value then ``wait_for_replication`` returns, otherwise
it waits for another event.
timeout: How many milliseconds to wait for callback return a truthy
value.
Returns:
A deferred that resolves with the value returned by the callback.
"""
listener = _NotificationListener(None)
end_time = self.clock.time_msec() + timeout
while True:
listener.deferred = self.replication_deferred.observe()
result = yield callback()
if result:
break
now = self.clock.time_msec()
if end_time <= now:
break
listener.deferred = timeout_deferred(
listener.deferred,
timeout=(end_time - now) / 1000.,
reactor=self.hs.get_reactor(),
)
try:
with PreserveLoggingContext():
yield listener.deferred
except defer.TimeoutError:
break
except defer.CancelledError:
break
defer.returnValue(result)
for cb in self.replication_callbacks:
cb()