diff options
Diffstat (limited to 'synapse/util/logcontext.py')
| -rw-r--r-- | synapse/util/logcontext.py | 199 |
1 files changed, 127 insertions, 72 deletions
diff --git a/synapse/util/logcontext.py b/synapse/util/logcontext.py index 6c83eb213d..e086e12213 100644 --- a/synapse/util/logcontext.py +++ b/synapse/util/logcontext.py @@ -12,6 +12,16 @@ # See the License for the specific language governing permissions and # limitations under the License. +""" Thread-local-alike tracking of log contexts within synapse + +This module provides objects and utilities for tracking contexts through +synapse code, so that log lines can include a request identifier, and so that +CPU and database activity can be accounted for against the request that caused +them. + +See doc/log_contexts.rst for details on how this works. +""" + from twisted.internet import defer import threading @@ -32,7 +42,7 @@ try: def get_thread_resource_usage(): return resource.getrusage(RUSAGE_THREAD) -except: +except Exception: # If the system doesn't support resource.getrusage(RUSAGE_THREAD) then we # won't track resource usage by returning None. def get_thread_resource_usage(): @@ -42,13 +52,17 @@ except: class LoggingContext(object): """Additional context for log formatting. Contexts are scoped within a "with" block. + Args: name (str): Name for the context for debugging. """ __slots__ = [ - "previous_context", "name", "usage_start", "usage_end", "main_thread", - "__dict__", "tag", "alive", + "previous_context", "name", "ru_stime", "ru_utime", + "db_txn_count", "db_txn_duration_ms", "db_sched_duration_ms", + "usage_start", "usage_end", + "main_thread", "alive", + "request", "tag", ] thread_local = threading.local() @@ -73,8 +87,12 @@ class LoggingContext(object): def add_database_transaction(self, duration_ms): pass + def add_database_scheduled(self, sched_ms): + pass + def __nonzero__(self): return False + __bool__ = __nonzero__ # python3 sentinel = Sentinel() @@ -84,9 +102,17 @@ class LoggingContext(object): self.ru_stime = 0. self.ru_utime = 0. self.db_txn_count = 0 - self.db_txn_duration = 0. + + # ms spent waiting for db txns, excluding scheduling time + self.db_txn_duration_ms = 0 + + # ms spent waiting for db txns to be scheduled + self.db_sched_duration_ms = 0 + self.usage_start = None + self.usage_end = None self.main_thread = threading.current_thread() + self.request = None self.tag = "" self.alive = True @@ -95,7 +121,11 @@ class LoggingContext(object): @classmethod def current_context(cls): - """Get the current logging context from thread local storage""" + """Get the current logging context from thread local storage + + Returns: + LoggingContext: the current logging context + """ return getattr(cls.thread_local, "current_context", cls.sentinel) @classmethod @@ -145,11 +175,13 @@ class LoggingContext(object): self.alive = False def copy_to(self, record): - """Copy fields from this context to the record""" - for key, value in self.__dict__.items(): - setattr(record, key, value) + """Copy logging fields from this context to a log record or + another LoggingContext + """ - record.ru_utime, record.ru_stime = self.get_resource_usage() + # 'request' is the only field we currently use in the logger, so that's + # all we need to copy + record.request = self.request def start(self): if threading.current_thread() is not self.main_thread: @@ -184,7 +216,16 @@ class LoggingContext(object): def add_database_transaction(self, duration_ms): self.db_txn_count += 1 - self.db_txn_duration += duration_ms / 1000. + self.db_txn_duration_ms += duration_ms + + def add_database_scheduled(self, sched_ms): + """Record a use of the database pool + + Args: + sched_ms (int): number of milliseconds it took us to get a + connection + """ + self.db_sched_duration_ms += sched_ms class LoggingContextFilter(logging.Filter): @@ -251,80 +292,94 @@ class PreserveLoggingContext(object): ) -class _PreservingContextDeferred(defer.Deferred): - """A deferred that ensures that all callbacks and errbacks are called with - the given logging context. - """ - def __init__(self, context): - self._log_context = context - defer.Deferred.__init__(self) - - def addCallbacks(self, callback, errback=None, - callbackArgs=None, callbackKeywords=None, - errbackArgs=None, errbackKeywords=None): - callback = self._wrap_callback(callback) - errback = self._wrap_callback(errback) - return defer.Deferred.addCallbacks( - self, callback, - errback=errback, - callbackArgs=callbackArgs, - callbackKeywords=callbackKeywords, - errbackArgs=errbackArgs, - errbackKeywords=errbackKeywords, - ) +def preserve_fn(f): + """Function decorator which wraps the function with run_in_background""" + def g(*args, **kwargs): + return run_in_background(f, *args, **kwargs) + return g - def _wrap_callback(self, f): - def g(res, *args, **kwargs): - with PreserveLoggingContext(self._log_context): - res = f(res, *args, **kwargs) - return res - return g +def run_in_background(f, *args, **kwargs): + """Calls a function, ensuring that the current context is restored after + return from the function, and that the sentinel context is set once the + deferred returned by the function completes. -def preserve_context_over_fn(fn, *args, **kwargs): - """Takes a function and invokes it with the given arguments, but removes - and restores the current logging context while doing so. + Useful for wrapping functions that return a deferred which you don't yield + on (for instance because you want to pass it to deferred.gatherResults()). - If the result is a deferred, call preserve_context_over_deferred before - returning it. + Note that if you completely discard the result, you should make sure that + `f` doesn't raise any deferred exceptions, otherwise a scary-looking + CRITICAL error about an unhandled error will be logged without much + indication about where it came from. """ - with PreserveLoggingContext(): - res = fn(*args, **kwargs) - - if isinstance(res, defer.Deferred): - return preserve_context_over_deferred(res) - else: + current = LoggingContext.current_context() + try: + res = f(*args, **kwargs) + except: # noqa: E722 + # the assumption here is that the caller doesn't want to be disturbed + # by synchronous exceptions, so let's turn them into Failures. + return defer.fail() + + if not isinstance(res, defer.Deferred): return res + if res.called and not res.paused: + # The function should have maintained the logcontext, so we can + # optimise out the messing about + return res -def preserve_context_over_deferred(deferred, context=None): - """Given a deferred wrap it such that any callbacks added later to it will - be invoked with the current context. + # 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 context is None: - context = LoggingContext.current_context() - d = _PreservingContextDeferred(context) - deferred.chainDeferred(d) - return d + 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 -def preserve_fn(f): - """Ensures that function is called with correct context and that context is - restored after return. Useful for wrapping functions that return a deferred - which you don't yield on. - """ - current = LoggingContext.current_context() + # 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 g(*args, **kwargs): - with PreserveLoggingContext(current): - res = f(*args, **kwargs) - if isinstance(res, defer.Deferred): - return preserve_context_over_deferred( - res, context=LoggingContext.sentinel - ) - else: - return res - return g + +def _set_context_cb(result, context): + """A callback function which just sets the logging context""" + LoggingContext.set_current_context(context) + return result # modules to ignore in `logcontext_tracer` |