From a334e1cacec5dd9c1a983415906d8ffea4a30134 Mon Sep 17 00:00:00 2001 From: Erik Johnston Date: Wed, 19 Sep 2018 10:39:40 +0100 Subject: [PATCH 1/5] Update to use new timeout function everywhere. The existing deferred timeout helper function (and the one into twisted) suffer from a bug when a deferred's canceller throws an exception, #3842. The new helper function doesn't suffer from this problem. --- synapse/http/client.py | 4 +- synapse/http/matrixfederationclient.py | 25 +++++---- synapse/notifier.py | 13 ++--- synapse/util/async_helpers.py | 73 +++++++------------------- 4 files changed, 43 insertions(+), 72 deletions(-) diff --git a/synapse/http/client.py b/synapse/http/client.py index ec339a92a..3d05f83b8 100644 --- a/synapse/http/client.py +++ b/synapse/http/client.py @@ -43,7 +43,7 @@ from twisted.web.http_headers import Headers from synapse.api.errors import Codes, HttpResponseException, SynapseError from synapse.http import cancelled_to_request_timed_out_error, redact_uri from synapse.http.endpoint import SpiderEndpoint -from synapse.util.async_helpers import add_timeout_to_deferred +from synapse.util.async_helpers import timeout_deferred from synapse.util.caches import CACHE_SIZE_FACTOR from synapse.util.logcontext import make_deferred_yieldable @@ -99,7 +99,7 @@ class SimpleHttpClient(object): request_deferred = treq.request( method, uri, agent=self.agent, data=data, headers=headers ) - add_timeout_to_deferred( + request_deferred = timeout_deferred( request_deferred, 60, self.hs.get_reactor(), cancelled_to_request_timed_out_error, ) diff --git a/synapse/http/matrixfederationclient.py b/synapse/http/matrixfederationclient.py index 530c0245a..14b12cd1c 100644 --- a/synapse/http/matrixfederationclient.py +++ b/synapse/http/matrixfederationclient.py @@ -44,7 +44,7 @@ from synapse.api.errors import ( SynapseError, ) from synapse.http.endpoint import matrix_federation_endpoint -from synapse.util.async_helpers import timeout_no_seriously +from synapse.util.async_helpers import timeout_deferred from synapse.util.logcontext import make_deferred_yieldable from synapse.util.metrics import Measure @@ -145,8 +145,14 @@ def _handle_json_response(reactor, timeout_sec, request, response): """ try: check_content_type_is_json(response.headers) + d = treq.json_content(response) - d.addTimeout(timeout_sec, reactor) + d = timeout_deferred( + d, + timeout=timeout_sec, + reactor=reactor, + ) + body = yield make_deferred_yieldable(d) except Exception as e: logger.warn( @@ -321,15 +327,10 @@ class MatrixFederationHttpClient(object): reactor=self.hs.get_reactor(), unbuffered=True ) - request_deferred.addTimeout(_sec_timeout, self.hs.get_reactor()) - # Sometimes the timeout above doesn't work, so lets hack yet - # another layer of timeouts in in the vain hope that at some - # point the world made sense and this really really really - # should work. - request_deferred = timeout_no_seriously( + request_deferred = timeout_deferred( request_deferred, - timeout=_sec_timeout * 2, + timeout=_sec_timeout, reactor=self.hs.get_reactor(), ) @@ -388,7 +389,11 @@ class MatrixFederationHttpClient(object): # :'( # Update transactions table? d = treq.content(response) - d.addTimeout(_sec_timeout, self.hs.get_reactor()) + d = timeout_deferred( + d, + timeout=_sec_timeout, + reactor=self.hs.get_reactor(), + ) body = yield make_deferred_yieldable(d) raise HttpResponseException( response.code, response.phrase, body diff --git a/synapse/notifier.py b/synapse/notifier.py index 82f391481..2d683718f 100644 --- a/synapse/notifier.py +++ b/synapse/notifier.py @@ -28,7 +28,7 @@ from synapse.types import StreamToken from synapse.util.async_helpers import ( DeferredTimeoutError, ObservableDeferred, - add_timeout_to_deferred, + timeout_deferred, ) from synapse.util.logcontext import PreserveLoggingContext, run_in_background from synapse.util.logutils import log_function @@ -337,7 +337,7 @@ class Notifier(object): # Now we wait for the _NotifierUserStream to be told there # is a new token. listener = user_stream.new_listener(prev_token) - add_timeout_to_deferred( + listener.deferred = timeout_deferred( listener.deferred, (end_time - now) / 1000., self.hs.get_reactor(), @@ -559,11 +559,12 @@ class Notifier(object): if end_time <= now: break - add_timeout_to_deferred( - listener.deferred.addTimeout, - (end_time - now) / 1000., - self.hs.get_reactor(), + listener.deferred = timeout_deferred( + listener.deferred, + timeout=(end_time - now) / 1000., + reactor=self.hs.get_reactor(), ) + try: with PreserveLoggingContext(): yield listener.deferred diff --git a/synapse/util/async_helpers.py b/synapse/util/async_helpers.py index 40c294612..2e12bcda9 100644 --- a/synapse/util/async_helpers.py +++ b/synapse/util/async_helpers.py @@ -380,23 +380,25 @@ class DeferredTimeoutError(Exception): """ -def add_timeout_to_deferred(deferred, timeout, reactor, on_timeout_cancel=None): - """ - Add a timeout to a deferred by scheduling it to be cancelled after - timeout seconds. +def _cancelled_to_timed_out_error(value, timeout): + if isinstance(value, failure.Failure): + value.trap(CancelledError) + raise DeferredTimeoutError(timeout, "Deferred") + return value - This is essentially a backport of deferred.addTimeout, which was introduced - in twisted 16.5. - If the deferred gets timed out, it errbacks with a DeferredTimeoutError, - unless a cancelable function was passed to its initialization or unless - a different on_timeout_cancel callable is provided. +def timeout_deferred(deferred, timeout, reactor, on_timeout_cancel=None): + """The in built twisted `Deferred.addTimeout` fails to time out deferreds + that have a canceller that throws exceptions. This method creates a new + deferred that wraps and times out the given deferred, correctly handling + the case where the given deferred's canceller throws. + + NOTE: Unlike `Deferred.addTimeout`, this function returns a new deferred Args: - deferred (defer.Deferred): deferred to be timed out - timeout (Number): seconds to time out after - reactor (twisted.internet.reactor): the Twisted reactor to use - + deferred (Deferred) + timeout (float): Timeout in seconds + reactor (twisted.internet.reactor): The twisted reactor to use on_timeout_cancel (callable): A callable which is called immediately after the deferred times out, and not if this deferred is otherwise cancelled before the timeout. @@ -407,47 +409,9 @@ def add_timeout_to_deferred(deferred, timeout, reactor, on_timeout_cancel=None): The default callable (if none is provided) will translate a CancelledError Failure into a DeferredTimeoutError. - """ - timed_out = [False] - def time_it_out(): - timed_out[0] = True - deferred.cancel() - - delayed_call = reactor.callLater(timeout, time_it_out) - - def convert_cancelled(value): - if timed_out[0]: - to_call = on_timeout_cancel or _cancelled_to_timed_out_error - return to_call(value, timeout) - return value - - deferred.addBoth(convert_cancelled) - - def cancel_timeout(result): - # stop the pending call to cancel the deferred if it's been fired - if delayed_call.active(): - delayed_call.cancel() - return result - - deferred.addBoth(cancel_timeout) - - -def _cancelled_to_timed_out_error(value, timeout): - if isinstance(value, failure.Failure): - value.trap(CancelledError) - raise DeferredTimeoutError(timeout, "Deferred") - return value - - -def timeout_no_seriously(deferred, timeout, reactor): - """The in build twisted deferred addTimeout (and the method above) - completely fail to time things out under some unknown circumstances. - - Lets try a different way of timing things out and maybe that will make - things work?! - - TODO: Kill this with fire. + Returns: + Deferred """ new_d = defer.Deferred() @@ -466,7 +430,8 @@ def timeout_no_seriously(deferred, timeout, reactor): def convert_cancelled(value): if timed_out[0]: - return _cancelled_to_timed_out_error(value, timeout) + to_call = on_timeout_cancel or _cancelled_to_timed_out_error + return to_call(value, timeout) return value deferred.addBoth(convert_cancelled) From 6bbe3d5732630ad7f58159d267159bda2b5bfb08 Mon Sep 17 00:00:00 2001 From: Erik Johnston Date: Wed, 19 Sep 2018 10:43:13 +0100 Subject: [PATCH 2/5] Newsfile --- changelog.d/3910 | 1 + 1 file changed, 1 insertion(+) create mode 100644 changelog.d/3910 diff --git a/changelog.d/3910 b/changelog.d/3910 new file mode 100644 index 000000000..22ec2adc3 --- /dev/null +++ b/changelog.d/3910 @@ -0,0 +1 @@ +Fix bug where things occaisonally were not being timed out correctly. From 6c48aa0256ce7dfd62e72a77b03f5bb2222473ba Mon Sep 17 00:00:00 2001 From: Erik Johnston Date: Wed, 19 Sep 2018 11:04:42 +0100 Subject: [PATCH 3/5] Run canceller first to allow it to generate correct error --- synapse/util/async_helpers.py | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/synapse/util/async_helpers.py b/synapse/util/async_helpers.py index 2e12bcda9..2b2e85ecb 100644 --- a/synapse/util/async_helpers.py +++ b/synapse/util/async_helpers.py @@ -421,11 +421,14 @@ def timeout_deferred(deferred, timeout, reactor, on_timeout_cancel=None): def time_it_out(): timed_out[0] = True + try: + deferred.cancel() + except: # noqa: E722, if we throw any exception it'll break time outs + logger.exception("Canceller failed during timeout") + if not new_d.called: new_d.errback(DeferredTimeoutError(timeout, "Deferred")) - deferred.cancel() - delayed_call = reactor.callLater(timeout, time_it_out) def convert_cancelled(value): From 9407bcf37a99ebb72eef73e19632cdcf5964c968 Mon Sep 17 00:00:00 2001 From: Erik Johnston Date: Wed, 19 Sep 2018 11:05:21 +0100 Subject: [PATCH 4/5] Replace custom DeferredTimeoutError with defer.TimeoutError --- synapse/notifier.py | 5 ++--- synapse/util/async_helpers.py | 12 +++--------- 2 files changed, 5 insertions(+), 12 deletions(-) diff --git a/synapse/notifier.py b/synapse/notifier.py index 2d683718f..2e7525b7d 100644 --- a/synapse/notifier.py +++ b/synapse/notifier.py @@ -26,7 +26,6 @@ from synapse.handlers.presence import format_user_presence_state from synapse.metrics import LaterGauge from synapse.types import StreamToken from synapse.util.async_helpers import ( - DeferredTimeoutError, ObservableDeferred, timeout_deferred, ) @@ -354,7 +353,7 @@ class Notifier(object): # Update the prev_token to the current_token since nothing # has happened between the old prev_token and the current_token prev_token = current_token - except DeferredTimeoutError: + except defer.TimeoutError: break except defer.CancelledError: break @@ -568,7 +567,7 @@ class Notifier(object): try: with PreserveLoggingContext(): yield listener.deferred - except DeferredTimeoutError: + except defer.TimeoutError: break except defer.CancelledError: break diff --git a/synapse/util/async_helpers.py b/synapse/util/async_helpers.py index 2b2e85ecb..ec7b2c967 100644 --- a/synapse/util/async_helpers.py +++ b/synapse/util/async_helpers.py @@ -374,16 +374,10 @@ class ReadWriteLock(object): defer.returnValue(_ctx_manager()) -class DeferredTimeoutError(Exception): - """ - This error is raised by default when a L{Deferred} times out. - """ - - def _cancelled_to_timed_out_error(value, timeout): if isinstance(value, failure.Failure): value.trap(CancelledError) - raise DeferredTimeoutError(timeout, "Deferred") + raise defer.TimeoutError(timeout, "Deferred") return value @@ -408,7 +402,7 @@ def timeout_deferred(deferred, timeout, reactor, on_timeout_cancel=None): the timeout. The default callable (if none is provided) will translate a - CancelledError Failure into a DeferredTimeoutError. + CancelledError Failure into a defer.TimeoutError. Returns: Deferred @@ -427,7 +421,7 @@ def timeout_deferred(deferred, timeout, reactor, on_timeout_cancel=None): logger.exception("Canceller failed during timeout") if not new_d.called: - new_d.errback(DeferredTimeoutError(timeout, "Deferred")) + new_d.errback(defer.TimeoutError(timeout, "Deferred")) delayed_call = reactor.callLater(timeout, time_it_out) From 80d2d50f4764d6662ceef86f834f845b539263e8 Mon Sep 17 00:00:00 2001 From: Erik Johnston Date: Wed, 19 Sep 2018 11:19:47 +0100 Subject: [PATCH 5/5] Fixup --- changelog.d/{3910 => 3910.bugfix} | 0 synapse/notifier.py | 5 +---- 2 files changed, 1 insertion(+), 4 deletions(-) rename changelog.d/{3910 => 3910.bugfix} (100%) diff --git a/changelog.d/3910 b/changelog.d/3910.bugfix similarity index 100% rename from changelog.d/3910 rename to changelog.d/3910.bugfix diff --git a/synapse/notifier.py b/synapse/notifier.py index 2e7525b7d..f1d92c139 100644 --- a/synapse/notifier.py +++ b/synapse/notifier.py @@ -25,10 +25,7 @@ from synapse.api.errors import AuthError from synapse.handlers.presence import format_user_presence_state from synapse.metrics import LaterGauge from synapse.types import StreamToken -from synapse.util.async_helpers import ( - ObservableDeferred, - timeout_deferred, -) +from synapse.util.async_helpers import ObservableDeferred, timeout_deferred from synapse.util.logcontext import PreserveLoggingContext, run_in_background from synapse.util.logutils import log_function from synapse.util.metrics import Measure