72 lines
2.8 KiB
Python
72 lines
2.8 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2015, 2016 OpenMarket Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from twisted.internet import defer, reactor
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from functools import wraps
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from synapse.util.logcontext import LoggingContext, PreserveLoggingContext
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def debug_deferreds():
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"""Cause all deferreds to wait for a reactor tick before running their
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callbacks. This increases the chance of getting a stack trace out of
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a defer.inlineCallback since the code waiting on the deferred will get
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a chance to add an errback before the deferred runs."""
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# Helper method for retrieving and restoring the current logging context
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# around a callback.
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def with_logging_context(fn):
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context = LoggingContext.current_context()
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def restore_context_callback(x):
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with PreserveLoggingContext(context):
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return fn(x)
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return restore_context_callback
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# We are going to modify the __init__ method of defer.Deferred so we
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# need to get a copy of the old method so we can still call it.
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old__init__ = defer.Deferred.__init__
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# We need to create a deferred to bounce the callbacks through the reactor
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# but we don't want to add a callback when we create that deferred so we
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# we create a new type of deferred that uses the old __init__ method.
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# This is safe as long as the old __init__ method doesn't invoke an
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# __init__ using super.
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class Bouncer(defer.Deferred):
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__init__ = old__init__
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# We'll add this as a callback to all Deferreds. Twisted will wait until
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# the bouncer deferred resolves before calling the callbacks of the
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# original deferred.
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def bounce_callback(x):
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bouncer = Bouncer()
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reactor.callLater(0, with_logging_context(bouncer.callback), x)
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return bouncer
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# We'll add this as an errback to all Deferreds. Twisted will wait until
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# the bouncer deferred resolves before calling the errbacks of the
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# original deferred.
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def bounce_errback(x):
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bouncer = Bouncer()
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reactor.callLater(0, with_logging_context(bouncer.errback), x)
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return bouncer
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@wraps(old__init__)
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def new__init__(self, *args, **kargs):
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old__init__(self, *args, **kargs)
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self.addCallbacks(bounce_callback, bounce_errback)
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defer.Deferred.__init__ = new__init__
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