diff --git a/synapse/util/async.py b/synapse/util/async.py
index 0729bb2863..1df5c5600c 100644
--- a/synapse/util/async.py
+++ b/synapse/util/async.py
@@ -15,6 +15,8 @@
from twisted.internet import defer, reactor
+from twisted.internet.defer import CancelledError
+from twisted.python import failure
from .logcontext import (
PreserveLoggingContext, make_deferred_yieldable, preserve_fn
@@ -392,3 +394,68 @@ class ReadWriteLock(object):
self.key_to_current_writer.pop(key)
defer.returnValue(_ctx_manager())
+
+
+class DeferredTimeoutError(Exception):
+ """
+ This error is raised by default when a L{Deferred} times out.
+ """
+
+
+def add_timeout_to_deferred(deferred, timeout, on_timeout_cancel=None):
+ """
+ Add a timeout to a deferred by scheduling it to be cancelled after
+ timeout seconds.
+
+ 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.
+
+ Args:
+ deferred (defer.Deferred): deferred to be timed out
+ timeout (Number): seconds to time out after
+
+ 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.
+
+ 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 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
|
