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https://git.anonymousland.org/anonymousland/synapse-product.git
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198 lines
6.6 KiB
Python
198 lines
6.6 KiB
Python
# Copyright 2014, 2015 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
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import threading
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import logging
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logger = logging.getLogger(__name__)
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class LoggingContext(object):
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"""Additional context for log formatting. Contexts are scoped within a
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"with" block. Contexts inherit the state of their parent contexts.
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Args:
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name (str): Name for the context for debugging.
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"""
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__slots__ = ["parent_context", "name", "__dict__"]
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thread_local = threading.local()
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class Sentinel(object):
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"""Sentinel to represent the root context"""
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__slots__ = []
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def __str__(self):
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return "sentinel"
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def copy_to(self, record):
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pass
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sentinel = Sentinel()
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def __init__(self, name=None):
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self.parent_context = None
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self.name = name
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def __str__(self):
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return "%s@%x" % (self.name, id(self))
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@classmethod
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def current_context(cls):
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"""Get the current logging context from thread local storage"""
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return getattr(cls.thread_local, "current_context", cls.sentinel)
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def __enter__(self):
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"""Enters this logging context into thread local storage"""
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if self.parent_context is not None:
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raise Exception("Attempt to enter logging context multiple times")
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self.parent_context = self.current_context()
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self.thread_local.current_context = self
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return self
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def __exit__(self, type, value, traceback):
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"""Restore the logging context in thread local storage to the state it
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was before this context was entered.
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Returns:
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None to avoid suppressing any exeptions that were thrown.
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"""
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if self.thread_local.current_context is not self:
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if self.thread_local.current_context is self.sentinel:
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logger.debug("Expected logging context %s has been lost", self)
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else:
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logger.warn(
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"Current logging context %s is not expected context %s",
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self.thread_local.current_context,
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self
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)
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self.thread_local.current_context = self.parent_context
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self.parent_context = None
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def __getattr__(self, name):
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"""Delegate member lookup to parent context"""
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return getattr(self.parent_context, name)
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def copy_to(self, record):
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"""Copy fields from this context and its parents to the record"""
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if self.parent_context is not None:
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self.parent_context.copy_to(record)
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for key, value in self.__dict__.items():
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setattr(record, key, value)
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class LoggingContextFilter(logging.Filter):
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"""Logging filter that adds values from the current logging context to each
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record.
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Args:
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**defaults: Default values to avoid formatters complaining about
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missing fields
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"""
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def __init__(self, **defaults):
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self.defaults = defaults
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def filter(self, record):
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"""Add each fields from the logging contexts to the record.
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Returns:
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True to include the record in the log output.
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"""
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context = LoggingContext.current_context()
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for key, value in self.defaults.items():
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setattr(record, key, value)
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context.copy_to(record)
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return True
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class PreserveLoggingContext(object):
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"""Captures the current logging context and restores it when the scope is
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exited. Used to restore the context after a function using
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@defer.inlineCallbacks is resumed by a callback from the reactor."""
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__slots__ = ["current_context"]
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def __enter__(self):
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"""Captures the current logging context"""
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self.current_context = LoggingContext.current_context()
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LoggingContext.thread_local.current_context = LoggingContext.sentinel
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def __exit__(self, type, value, traceback):
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"""Restores the current logging context"""
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LoggingContext.thread_local.current_context = self.current_context
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if self.current_context is not LoggingContext.sentinel:
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if self.current_context.parent_context is None:
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logger.warn(
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"Restoring dead context: %s",
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self.current_context,
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)
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class _PreservingContextDeferred(defer.Deferred):
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"""A deferred that ensures that all callbacks and errbacks are called with
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the given logging context.
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"""
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def __init__(self, context):
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self._log_context = context
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defer.Deferred.__init__(self)
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def addCallbacks(self, callback, errback=None,
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callbackArgs=None, callbackKeywords=None,
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errbackArgs=None, errbackKeywords=None):
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callback = self._wrap_callback(callback)
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errback = self._wrap_callback(errback)
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return defer.Deferred.addCallbacks(
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self, callback,
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errback=errback,
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callbackArgs=callbackArgs,
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callbackKeywords=callbackKeywords,
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errbackArgs=errbackArgs,
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errbackKeywords=errbackKeywords,
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)
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def _wrap_callback(self, f):
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def g(res, *args, **kwargs):
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with PreserveLoggingContext():
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LoggingContext.thread_local.current_context = self._log_context
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res = f(res, *args, **kwargs)
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return res
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return g
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def preserve_context_over_fn(fn, *args, **kwargs):
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"""Takes a function and invokes it with the given arguments, but removes
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and restores the current logging context while doing so.
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If the result is a deferred, call preserve_context_over_deferred before
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returning it.
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"""
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with PreserveLoggingContext():
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res = fn(*args, **kwargs)
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if isinstance(res, defer.Deferred):
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return preserve_context_over_deferred(res)
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else:
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return res
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def preserve_context_over_deferred(deferred):
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"""Given a deferred wrap it such that any callbacks added later to it will
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be invoked with the current context.
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"""
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current_context = LoggingContext.current_context()
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d = _PreservingContextDeferred(current_context)
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deferred.chainDeferred(d)
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return d
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