645 lines
22 KiB
Python
645 lines
22 KiB
Python
# Copyright 2014-2016 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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""" Thread-local-alike tracking of log contexts within synapse
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This module provides objects and utilities for tracking contexts through
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synapse code, so that log lines can include a request identifier, and so that
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CPU and database activity can be accounted for against the request that caused
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them.
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See doc/log_contexts.rst for details on how this works.
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"""
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import logging
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import threading
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from twisted.internet import defer, threads
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logger = logging.getLogger(__name__)
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try:
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import resource
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# Python doesn't ship with a definition of RUSAGE_THREAD but it's defined
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# to be 1 on linux so we hard code it.
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RUSAGE_THREAD = 1
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# If the system doesn't support RUSAGE_THREAD then this should throw an
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# exception.
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resource.getrusage(RUSAGE_THREAD)
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def get_thread_resource_usage():
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return resource.getrusage(RUSAGE_THREAD)
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except Exception:
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# If the system doesn't support resource.getrusage(RUSAGE_THREAD) then we
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# won't track resource usage by returning None.
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def get_thread_resource_usage():
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return None
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class ContextResourceUsage(object):
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"""Object for tracking the resources used by a log context
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Attributes:
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ru_utime (float): user CPU time (in seconds)
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ru_stime (float): system CPU time (in seconds)
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db_txn_count (int): number of database transactions done
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db_sched_duration_sec (float): amount of time spent waiting for a
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database connection
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db_txn_duration_sec (float): amount of time spent doing database
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transactions (excluding scheduling time)
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evt_db_fetch_count (int): number of events requested from the database
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"""
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__slots__ = [
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"ru_stime", "ru_utime",
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"db_txn_count", "db_txn_duration_sec", "db_sched_duration_sec",
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"evt_db_fetch_count",
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]
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def __init__(self, copy_from=None):
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"""Create a new ContextResourceUsage
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Args:
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copy_from (ContextResourceUsage|None): if not None, an object to
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copy stats from
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"""
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if copy_from is None:
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self.reset()
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else:
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self.ru_utime = copy_from.ru_utime
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self.ru_stime = copy_from.ru_stime
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self.db_txn_count = copy_from.db_txn_count
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self.db_txn_duration_sec = copy_from.db_txn_duration_sec
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self.db_sched_duration_sec = copy_from.db_sched_duration_sec
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self.evt_db_fetch_count = copy_from.evt_db_fetch_count
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def copy(self):
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return ContextResourceUsage(copy_from=self)
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def reset(self):
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self.ru_stime = 0.
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self.ru_utime = 0.
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self.db_txn_count = 0
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self.db_txn_duration_sec = 0
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self.db_sched_duration_sec = 0
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self.evt_db_fetch_count = 0
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def __repr__(self):
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return ("<ContextResourceUsage ru_stime='%r', ru_utime='%r', "
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"db_txn_count='%r', db_txn_duration_sec='%r', "
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"db_sched_duration_sec='%r', evt_db_fetch_count='%r'>") % (
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self.ru_stime,
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self.ru_utime,
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self.db_txn_count,
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self.db_txn_duration_sec,
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self.db_sched_duration_sec,
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self.evt_db_fetch_count,)
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def __iadd__(self, other):
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"""Add another ContextResourceUsage's stats to this one's.
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Args:
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other (ContextResourceUsage): the other resource usage object
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"""
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self.ru_utime += other.ru_utime
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self.ru_stime += other.ru_stime
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self.db_txn_count += other.db_txn_count
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self.db_txn_duration_sec += other.db_txn_duration_sec
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self.db_sched_duration_sec += other.db_sched_duration_sec
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self.evt_db_fetch_count += other.evt_db_fetch_count
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return self
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def __isub__(self, other):
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self.ru_utime -= other.ru_utime
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self.ru_stime -= other.ru_stime
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self.db_txn_count -= other.db_txn_count
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self.db_txn_duration_sec -= other.db_txn_duration_sec
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self.db_sched_duration_sec -= other.db_sched_duration_sec
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self.evt_db_fetch_count -= other.evt_db_fetch_count
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return self
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def __add__(self, other):
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res = ContextResourceUsage(copy_from=self)
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res += other
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return res
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def __sub__(self, other):
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res = ContextResourceUsage(copy_from=self)
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res -= other
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return res
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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.
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If a parent is given when creating a new context, then:
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- logging fields are copied from the parent to the new context on entry
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- when the new context exits, the cpu usage stats are copied from the
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child to the parent
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Args:
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name (str): Name for the context for debugging.
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parent_context (LoggingContext|None): The parent of the new context
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"""
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__slots__ = [
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"previous_context", "name", "parent_context",
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"_resource_usage",
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"usage_start",
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"main_thread", "alive",
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"request", "tag",
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]
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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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def start(self):
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pass
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def stop(self):
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pass
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def add_database_transaction(self, duration_sec):
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pass
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def add_database_scheduled(self, sched_sec):
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pass
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def record_event_fetch(self, event_count):
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pass
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def __nonzero__(self):
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return False
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__bool__ = __nonzero__ # python3
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sentinel = Sentinel()
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def __init__(self, name=None, parent_context=None, request=None):
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self.previous_context = LoggingContext.current_context()
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self.name = name
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# track the resources used by this context so far
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self._resource_usage = ContextResourceUsage()
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# If alive has the thread resource usage when the logcontext last
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# became active.
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self.usage_start = None
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self.main_thread = threading.current_thread()
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self.request = None
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self.tag = ""
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self.alive = True
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self.parent_context = parent_context
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if self.parent_context is not None:
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self.parent_context.copy_to(self)
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if request is not None:
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# the request param overrides the request from the parent context
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self.request = request
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def __str__(self):
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if self.request:
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return str(self.request)
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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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Returns:
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LoggingContext: the current logging context
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"""
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return getattr(cls.thread_local, "current_context", cls.sentinel)
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@classmethod
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def set_current_context(cls, context):
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"""Set the current logging context in thread local storage
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Args:
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context(LoggingContext): The context to activate.
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Returns:
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The context that was previously active
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"""
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current = cls.current_context()
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if current is not context:
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current.stop()
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cls.thread_local.current_context = context
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context.start()
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return current
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def __enter__(self):
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"""Enters this logging context into thread local storage"""
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old_context = self.set_current_context(self)
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if self.previous_context != old_context:
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logger.warn(
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"Expected previous context %r, found %r",
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self.previous_context, old_context
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)
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self.alive = True
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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 exceptions that were thrown.
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"""
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current = self.set_current_context(self.previous_context)
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if current is not self:
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if current is self.sentinel:
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logger.warning("Expected logging context %s was lost", self)
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else:
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logger.warning(
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"Expected logging context %s but found %s", self, current
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)
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self.previous_context = None
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self.alive = False
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# if we have a parent, pass our CPU usage stats on
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if (
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self.parent_context is not None
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and hasattr(self.parent_context, '_resource_usage')
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):
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self.parent_context._resource_usage += self._resource_usage
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# reset them in case we get entered again
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self._resource_usage.reset()
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def copy_to(self, record):
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"""Copy logging fields from this context to a log record or
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another LoggingContext
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"""
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# 'request' is the only field we currently use in the logger, so that's
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# all we need to copy
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record.request = self.request
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def start(self):
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if threading.current_thread() is not self.main_thread:
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logger.warning("Started logcontext %s on different thread", self)
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return
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# If we haven't already started record the thread resource usage so
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# far
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if not self.usage_start:
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self.usage_start = get_thread_resource_usage()
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def stop(self):
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if threading.current_thread() is not self.main_thread:
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logger.warning("Stopped logcontext %s on different thread", self)
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return
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# When we stop, let's record the cpu used since we started
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if not self.usage_start:
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logger.warning(
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"Called stop on logcontext %s without calling start", self,
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)
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return
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usage_end = get_thread_resource_usage()
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self._resource_usage.ru_utime += usage_end.ru_utime - self.usage_start.ru_utime
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self._resource_usage.ru_stime += usage_end.ru_stime - self.usage_start.ru_stime
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self.usage_start = None
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def get_resource_usage(self):
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"""Get resources used by this logcontext so far.
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Returns:
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ContextResourceUsage: a *copy* of the object tracking resource
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usage so far
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"""
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# we always return a copy, for consistency
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res = self._resource_usage.copy()
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# If we are on the correct thread and we're currently running then we
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# can include resource usage so far.
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is_main_thread = threading.current_thread() is self.main_thread
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if self.alive and self.usage_start and is_main_thread:
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current = get_thread_resource_usage()
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res.ru_utime += current.ru_utime - self.usage_start.ru_utime
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res.ru_stime += current.ru_stime - self.usage_start.ru_stime
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return res
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def add_database_transaction(self, duration_sec):
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self._resource_usage.db_txn_count += 1
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self._resource_usage.db_txn_duration_sec += duration_sec
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def add_database_scheduled(self, sched_sec):
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"""Record a use of the database pool
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Args:
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sched_sec (float): number of seconds it took us to get a
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connection
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"""
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self._resource_usage.db_sched_duration_sec += sched_sec
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def record_event_fetch(self, event_count):
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"""Record a number of events being fetched from the db
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Args:
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event_count (int): number of events being fetched
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"""
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self._resource_usage.evt_db_fetch_count += event_count
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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 should never be None, but if it somehow ends up being, then
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# we end up in a death spiral of infinite loops, so let's check, for
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# robustness' sake.
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if context is not None:
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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", "new_context", "has_parent"]
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def __init__(self, new_context=None):
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if new_context is None:
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new_context = LoggingContext.sentinel
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self.new_context = new_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.set_current_context(
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self.new_context
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)
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if self.current_context:
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self.has_parent = self.current_context.previous_context is not None
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if not self.current_context.alive:
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logger.debug(
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"Entering dead context: %s",
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self.current_context,
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)
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def __exit__(self, type, value, traceback):
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"""Restores the current logging context"""
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context = LoggingContext.set_current_context(self.current_context)
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if context != self.new_context:
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if context is LoggingContext.sentinel:
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logger.warning("Expected logging context %s was lost", self.new_context)
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else:
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logger.warning(
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"Expected logging context %s but found %s",
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self.new_context,
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context,
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)
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if self.current_context is not LoggingContext.sentinel:
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if not self.current_context.alive:
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logger.debug(
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"Restoring dead context: %s",
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self.current_context,
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)
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def nested_logging_context(suffix, parent_context=None):
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"""Creates a new logging context as a child of another.
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The nested logging context will have a 'request' made up of the parent context's
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request, plus the given suffix.
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CPU/db usage stats will be added to the parent context's on exit.
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Normal usage looks like:
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with nested_logging_context(suffix):
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# ... do stuff
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Args:
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suffix (str): suffix to add to the parent context's 'request'.
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parent_context (LoggingContext|None): parent context. Will use the current context
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if None.
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Returns:
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LoggingContext: new logging context.
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"""
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if parent_context is None:
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parent_context = LoggingContext.current_context()
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return LoggingContext(
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parent_context=parent_context,
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request=parent_context.request + "-" + suffix,
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)
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def preserve_fn(f):
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"""Function decorator which wraps the function with run_in_background"""
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def g(*args, **kwargs):
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return run_in_background(f, *args, **kwargs)
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return g
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def run_in_background(f, *args, **kwargs):
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"""Calls a function, ensuring that the current context is restored after
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return from the function, and that the sentinel context is set once the
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deferred returned by the function completes.
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Useful for wrapping functions that return a deferred which you don't yield
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on (for instance because you want to pass it to deferred.gatherResults()).
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Note that if you completely discard the result, you should make sure that
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`f` doesn't raise any deferred exceptions, otherwise a scary-looking
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CRITICAL error about an unhandled error will be logged without much
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indication about where it came from.
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"""
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current = LoggingContext.current_context()
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try:
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res = f(*args, **kwargs)
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except: # noqa: E722
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# the assumption here is that the caller doesn't want to be disturbed
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# by synchronous exceptions, so let's turn them into Failures.
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return defer.fail()
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if not isinstance(res, defer.Deferred):
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return res
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if res.called and not res.paused:
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# The function should have maintained the logcontext, so we can
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# optimise out the messing about
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return res
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# The function may have reset the context before returning, so
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# we need to restore it now.
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ctx = LoggingContext.set_current_context(current)
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# The original context will be restored when the deferred
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# completes, but there is nothing waiting for it, so it will
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# get leaked into the reactor or some other function which
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# wasn't expecting it. We therefore need to reset the context
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# here.
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#
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# (If this feels asymmetric, consider it this way: we are
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# effectively forking a new thread of execution. We are
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# probably currently within a ``with LoggingContext()`` block,
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# which is supposed to have a single entry and exit point. But
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# by spawning off another deferred, we are effectively
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# adding a new exit point.)
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res.addBoth(_set_context_cb, ctx)
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return res
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def make_deferred_yieldable(deferred):
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"""Given a deferred, make it follow the Synapse logcontext rules:
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If the deferred has completed (or is not actually a Deferred), essentially
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does nothing (just returns another completed deferred with the
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result/failure).
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If the deferred has not yet completed, resets the logcontext before
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returning a deferred. Then, when the deferred completes, restores the
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current logcontext before running callbacks/errbacks.
|
|
|
|
(This is more-or-less the opposite operation to run_in_background.)
|
|
"""
|
|
if not isinstance(deferred, defer.Deferred):
|
|
return deferred
|
|
|
|
if deferred.called and not deferred.paused:
|
|
# it looks like this deferred is ready to run any callbacks we give it
|
|
# immediately. We may as well optimise out the logcontext faffery.
|
|
return deferred
|
|
|
|
# ok, we can't be sure that a yield won't block, so let's reset the
|
|
# logcontext, and add a callback to the deferred to restore it.
|
|
prev_context = LoggingContext.set_current_context(LoggingContext.sentinel)
|
|
deferred.addBoth(_set_context_cb, prev_context)
|
|
return deferred
|
|
|
|
|
|
def _set_context_cb(result, context):
|
|
"""A callback function which just sets the logging context"""
|
|
LoggingContext.set_current_context(context)
|
|
return result
|
|
|
|
|
|
def defer_to_thread(reactor, f, *args, **kwargs):
|
|
"""
|
|
Calls the function `f` using a thread from the reactor's default threadpool and
|
|
returns the result as a Deferred.
|
|
|
|
Creates a new logcontext for `f`, which is created as a child of the current
|
|
logcontext (so its CPU usage metrics will get attributed to the current
|
|
logcontext). `f` should preserve the logcontext it is given.
|
|
|
|
The result deferred follows the Synapse logcontext rules: you should `yield`
|
|
on it.
|
|
|
|
Args:
|
|
reactor (twisted.internet.base.ReactorBase): The reactor in whose main thread
|
|
the Deferred will be invoked, and whose threadpool we should use for the
|
|
function.
|
|
|
|
Normally this will be hs.get_reactor().
|
|
|
|
f (callable): The function to call.
|
|
|
|
args: positional arguments to pass to f.
|
|
|
|
kwargs: keyword arguments to pass to f.
|
|
|
|
Returns:
|
|
Deferred: A Deferred which fires a callback with the result of `f`, or an
|
|
errback if `f` throws an exception.
|
|
"""
|
|
return defer_to_threadpool(reactor, reactor.getThreadPool(), f, *args, **kwargs)
|
|
|
|
|
|
def defer_to_threadpool(reactor, threadpool, f, *args, **kwargs):
|
|
"""
|
|
A wrapper for twisted.internet.threads.deferToThreadpool, which handles
|
|
logcontexts correctly.
|
|
|
|
Calls the function `f` using a thread from the given threadpool and returns
|
|
the result as a Deferred.
|
|
|
|
Creates a new logcontext for `f`, which is created as a child of the current
|
|
logcontext (so its CPU usage metrics will get attributed to the current
|
|
logcontext). `f` should preserve the logcontext it is given.
|
|
|
|
The result deferred follows the Synapse logcontext rules: you should `yield`
|
|
on it.
|
|
|
|
Args:
|
|
reactor (twisted.internet.base.ReactorBase): The reactor in whose main thread
|
|
the Deferred will be invoked. Normally this will be hs.get_reactor().
|
|
|
|
threadpool (twisted.python.threadpool.ThreadPool): The threadpool to use for
|
|
running `f`. Normally this will be hs.get_reactor().getThreadPool().
|
|
|
|
f (callable): The function to call.
|
|
|
|
args: positional arguments to pass to f.
|
|
|
|
kwargs: keyword arguments to pass to f.
|
|
|
|
Returns:
|
|
Deferred: A Deferred which fires a callback with the result of `f`, or an
|
|
errback if `f` throws an exception.
|
|
"""
|
|
logcontext = LoggingContext.current_context()
|
|
|
|
def g():
|
|
with LoggingContext(parent_context=logcontext):
|
|
return f(*args, **kwargs)
|
|
|
|
return make_deferred_yieldable(
|
|
threads.deferToThreadPool(reactor, threadpool, g)
|
|
)
|