diff --git a/synapse/util/async_helpers.py b/synapse/util/async_helpers.py
index 67ce9a5f39..382f0cf3f0 100644
--- a/synapse/util/async_helpers.py
+++ b/synapse/util/async_helpers.py
@@ -449,18 +449,8 @@ class ReadWriteLock:
R = TypeVar("R")
-def _cancelled_to_timed_out_error(value: R, timeout: float) -> R:
- if isinstance(value, failure.Failure):
- value.trap(CancelledError)
- raise defer.TimeoutError(timeout, "Deferred")
- return value
-
-
def timeout_deferred(
- deferred: defer.Deferred,
- timeout: float,
- reactor: IReactorTime,
- on_timeout_cancel: Optional[Callable[[Any, float], Any]] = None,
+ deferred: defer.Deferred, timeout: float, reactor: IReactorTime,
) -> defer.Deferred:
"""The in built twisted `Deferred.addTimeout` fails to time out deferreds
that have a canceller that throws exceptions. This method creates a new
@@ -469,27 +459,21 @@ def timeout_deferred(
(See https://twistedmatrix.com/trac/ticket/9534)
- NOTE: Unlike `Deferred.addTimeout`, this function returns a new deferred
+ NOTE: Unlike `Deferred.addTimeout`, this function returns a new deferred.
+
+ NOTE: the TimeoutError raised by the resultant deferred is
+ twisted.internet.defer.TimeoutError, which is *different* to the built-in
+ TimeoutError, as well as various other TimeoutErrors you might have imported.
Args:
deferred: The Deferred to potentially timeout.
timeout: Timeout in seconds
reactor: The twisted reactor to use
- on_timeout_cancel: A callable which is called immediately
- after the deferred times out, and not if this deferred is
- otherwise cancelled before the timeout.
- It takes an arbitrary value, which is the value of the deferred at
- that exact point in time (probably a CancelledError Failure), and
- the timeout.
-
- The default callable (if none is provided) will translate a
- CancelledError Failure into a defer.TimeoutError.
Returns:
- A new Deferred.
+ A new Deferred, which will errback with defer.TimeoutError on timeout.
"""
-
new_d = defer.Deferred()
timed_out = [False]
@@ -502,18 +486,23 @@ def timeout_deferred(
except: # noqa: E722, if we throw any exception it'll break time outs
logger.exception("Canceller failed during timeout")
+ # the cancel() call should have set off a chain of errbacks which
+ # will have errbacked new_d, but in case it hasn't, errback it now.
+
if not new_d.called:
- new_d.errback(defer.TimeoutError(timeout, "Deferred"))
+ new_d.errback(defer.TimeoutError("Timed out after %gs" % (timeout,)))
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)
+ def convert_cancelled(value: failure.Failure):
+ # if the orgininal deferred was cancelled, and our timeout has fired, then
+ # the reason it was cancelled was due to our timeout. Turn the CancelledError
+ # into a TimeoutError.
+ if timed_out[0] and value.check(CancelledError):
+ raise defer.TimeoutError("Timed out after %gs" % (timeout,))
return value
- deferred.addBoth(convert_cancelled)
+ deferred.addErrback(convert_cancelled)
def cancel_timeout(result):
# stop the pending call to cancel the deferred if it's been fired
|
