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![Richard van der Hoff](/assets/img/avatar_default.png)
Sentry will catch the errors if they happen, so that should be good enough, and woun't make things explode if we hit the error condition.
680 lines
22 KiB
Python
680 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",
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"ru_utime",
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"db_txn_count",
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"db_txn_duration_sec",
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"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 = 0.0
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self.ru_utime = 0.0
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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 (
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"<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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) % (
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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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)
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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",
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"name",
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"parent_context",
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"_resource_usage",
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"usage_start",
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"main_thread",
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"alive",
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"request",
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"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,
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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 self.parent_context is not None and hasattr(
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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("Called stop on logcontext %s without calling start", self)
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return
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utime_delta, stime_delta = self._get_cputime()
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self._resource_usage.ru_utime += utime_delta
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self._resource_usage.ru_stime += stime_delta
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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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utime_delta, stime_delta = self._get_cputime()
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res.ru_utime += utime_delta
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res.ru_stime += stime_delta
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return res
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def _get_cputime(self):
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"""Get the cpu usage time so far
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Returns: Tuple[float, float]: seconds in user mode, seconds in system mode
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"""
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current = get_thread_resource_usage()
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utime_delta = current.ru_utime - self.usage_start.ru_utime
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stime_delta = current.ru_stime - self.usage_start.ru_stime
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# sanity check
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if utime_delta < 0:
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logger.error(
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"utime went backwards! %f < %f",
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current.ru_utime,
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self.usage_start.ru_utime,
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)
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utime_delta = 0
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if stime_delta < 0:
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logger.error(
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"stime went backwards! %f < %f",
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current.ru_stime,
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self.usage_start.ru_stime,
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)
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stime_delta = 0
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return utime_delta, stime_delta
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def add_database_transaction(self, duration_sec):
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if duration_sec < 0:
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raise ValueError("DB txn time can only be non-negative")
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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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if sched_sec < 0:
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raise ValueError("DB scheduling time can only be non-negative")
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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(self.new_context)
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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("Entering dead context: %s", self.current_context)
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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("Restoring dead context: %s", self.current_context)
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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, 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:
|
|
# The function should have maintained the logcontext, so we can
|
|
# optimise out the messing about
|
|
return res
|
|
|
|
# The function may have reset the context before returning, so
|
|
# we need to restore it now.
|
|
ctx = LoggingContext.set_current_context(current)
|
|
|
|
# The original context will be restored when the deferred
|
|
# completes, but there is nothing waiting for it, so it will
|
|
# get leaked into the reactor or some other function which
|
|
# wasn't expecting it. We therefore need to reset the context
|
|
# here.
|
|
#
|
|
# (If this feels asymmetric, consider it this way: we are
|
|
# effectively forking a new thread of execution. We are
|
|
# probably currently within a ``with LoggingContext()`` block,
|
|
# which is supposed to have a single entry and exit point. But
|
|
# by spawning off another deferred, we are effectively
|
|
# adding a new exit point.)
|
|
res.addBoth(_set_context_cb, ctx)
|
|
return res
|
|
|
|
|
|
def make_deferred_yieldable(deferred):
|
|
"""Given a deferred, make it follow the Synapse logcontext rules:
|
|
|
|
If the deferred has completed (or is not actually a Deferred), essentially
|
|
does nothing (just returns another completed deferred with the
|
|
result/failure).
|
|
|
|
If the deferred has not yet completed, resets the logcontext before
|
|
returning a deferred. Then, when the deferred completes, restores the
|
|
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))
|