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Update to use new timeout function everywhere.

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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.
This commit is contained in:
Erik Johnston 2018-09-19 10:39:40 +01:00
parent 05b9937cd7
commit a334e1cace
4 changed files with 43 additions and 72 deletions
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4
synapse/http/client.py
View file

@ -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,
)

25
synapse/http/matrixfederationclient.py
View file

@ -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

13
synapse/notifier.py
View file

@ -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

73
synapse/util/async_helpers.py
View file

@ -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)