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- # -*- coding: utf-8 -*-
- # Copyright 2015, 2016 OpenMarket Ltd
- #
- # Licensed under the Apache License, Version 2.0 (the "License");
- # you may not use this file except in compliance with the License.
- # You may obtain a copy of the License at
- #
- # http://www.apache.org/licenses/LICENSE-2.0
- #
- # Unless required by applicable law or agreed to in writing, software
- # distributed under the License is distributed on an "AS IS" BASIS,
- # 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 twisted.internet import defer, reactor
- from functools import wraps
- from synapse.util.logcontext import LoggingContext, PreserveLoggingContext
- def debug_deferreds():
- """Cause all deferreds to wait for a reactor tick before running their
- callbacks. This increases the chance of getting a stack trace out of
- a defer.inlineCallback since the code waiting on the deferred will get
- a chance to add an errback before the deferred runs."""
- # Helper method for retrieving and restoring the current logging context
- # around a callback.
- def with_logging_context(fn):
- context = LoggingContext.current_context()
- def restore_context_callback(x):
- with PreserveLoggingContext(context):
- return fn(x)
- return restore_context_callback
- # We are going to modify the __init__ method of defer.Deferred so we
- # need to get a copy of the old method so we can still call it.
- old__init__ = defer.Deferred.__init__
- # We need to create a deferred to bounce the callbacks through the reactor
- # but we don't want to add a callback when we create that deferred so we
- # we create a new type of deferred that uses the old __init__ method.
- # This is safe as long as the old __init__ method doesn't invoke an
- # __init__ using super.
- class Bouncer(defer.Deferred):
- __init__ = old__init__
- # We'll add this as a callback to all Deferreds. Twisted will wait until
- # the bouncer deferred resolves before calling the callbacks of the
- # original deferred.
- def bounce_callback(x):
- bouncer = Bouncer()
- reactor.callLater(0, with_logging_context(bouncer.callback), x)
- return bouncer
- # We'll add this as an errback to all Deferreds. Twisted will wait until
- # the bouncer deferred resolves before calling the errbacks of the
- # original deferred.
- def bounce_errback(x):
- bouncer = Bouncer()
- reactor.callLater(0, with_logging_context(bouncer.errback), x)
- return bouncer
- @wraps(old__init__)
- def new__init__(self, *args, **kargs):
- old__init__(self, *args, **kargs)
- self.addCallbacks(bounce_callback, bounce_errback)
- defer.Deferred.__init__ = new__init__
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