Fix spinloop during partial state sync when a prev event is in backoff (#15351)

Previously, we would spin in a tight loop until
`update_state_for_partial_state_event` stopped raising
`FederationPullAttemptBackoffError`s. Replace the spinloop with a wait
until the backoff period has expired.

Signed-off-by: Sean Quah <seanq@matrix.org>

1 files changed, 9 insertions, 4 deletions

diff --git a/tests/storage/test_event_federation.py b/tests/storage/test_event_federation.py

index 3e1984c15c..81e50bdd55 100644
--- a/tests/storage/test_event_federation.py
+++ b/tests/storage/test_event_federation.py
@@ -1143,19 +1143,24 @@ class EventFederationWorkerStoreTestCase(tests.unittest.HomeserverTestCase):
         tok = self.login("alice", "test")
         room_id = self.helper.create_room_as(room_creator=user_id, tok=tok)
 
+        failure_time = self.clock.time_msec()
         self.get_success(
             self.store.record_event_failed_pull_attempt(
                 room_id, "$failed_event_id", "fake cause"
             )
         )
 
-        event_ids_to_backoff = self.get_success(
+        event_ids_with_backoff = self.get_success(
             self.store.get_event_ids_to_not_pull_from_backoff(
                 room_id=room_id, event_ids=["$failed_event_id", "$normal_event_id"]
             )
         )
 
-        self.assertEqual(event_ids_to_backoff, ["$failed_event_id"])
+        self.assertEqual(
+            event_ids_with_backoff,
+            # We expect a 2^1 hour backoff after a single failed attempt.
+            {"$failed_event_id": failure_time + 2 * 60 * 60 * 1000},
+        )
 
     def test_get_event_ids_to_not_pull_from_backoff_retry_after_backoff_duration(
         self,
@@ -1179,14 +1184,14 @@ class EventFederationWorkerStoreTestCase(tests.unittest.HomeserverTestCase):
         # attempt (2^1 hours).
         self.reactor.advance(datetime.timedelta(hours=2).total_seconds())
 
-        event_ids_to_backoff = self.get_success(
+        event_ids_with_backoff = self.get_success(
             self.store.get_event_ids_to_not_pull_from_backoff(
                 room_id=room_id, event_ids=["$failed_event_id", "$normal_event_id"]
             )
         )
         # Since this function only returns events we should backoff from, time has
         # elapsed past the backoff range so there is no events to backoff from.
-        self.assertEqual(event_ids_to_backoff, [])
+        self.assertEqual(event_ids_with_backoff, {})
 
 
 @attr.s(auto_attribs=True)