Make `handle_new_client_event` throws `PartialStateConflictError` (#14665)

Then adapts calling code to retry when needed so it doesn't 500
to clients.

Signed-off-by: Mathieu Velten <mathieuv@matrix.org>
Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>

changelog.d/14665.misc

@@ -0,0 +1 @@
+Change `handle_new_client_event` signature so that a 429 does not reach clients on `PartialStateConflictError`, and internally retry when needed instead.

synapse/handlers/federation.py

@@ -1343,7 +1343,16 @@ class FederationHandler:
             )
 
             EventValidator().validate_builder(builder)
-            event, context = await self.event_creation_handler.create_new_client_event(
+
+            # Try several times, it could fail with PartialStateConflictError
+            # in send_membership_event, cf comment in except block.
+            max_retries = 5
+            for i in range(max_retries):
+                try:
+                    (
+                        event,
+                        context,
+                    ) = await self.event_creation_handler.create_new_client_event(
                         builder=builder
                     )
 
@@ -1359,9 +1368,13 @@ class FederationHandler:
 
                     try:
                         validate_event_for_room_version(event)
-                await self._event_auth_handler.check_auth_rules_from_context(event)
+                        await self._event_auth_handler.check_auth_rules_from_context(
+                            event
+                        )
                     except AuthError as e:
-                logger.warning("Denying new third party invite %r because %s", event, e)
+                        logger.warning(
+                            "Denying new third party invite %r because %s", event, e
+                        )
                         raise e
 
                     await self._check_signature(event, context)
@@ -1369,6 +1382,14 @@ class FederationHandler:
                     # We retrieve the room member handler here as to not cause a cyclic dependency
                     member_handler = self.hs.get_room_member_handler()
                     await member_handler.send_membership_event(None, event, context)
+
+                    break
+                except PartialStateConflictError as e:
+                    # Persisting couldn't happen because the room got un-partial stated
+                    # in the meantime and context needs to be recomputed, so let's do so.
+                    if i == max_retries - 1:
+                        raise e
+                    pass
         else:
             destinations = {x.split(":", 1)[-1] for x in (sender_user_id, room_id)}
 
@@ -1400,7 +1421,15 @@ class FederationHandler:
             room_version_obj, event_dict
         )
 
-        event, context = await self.event_creation_handler.create_new_client_event(
+        # Try several times, it could fail with PartialStateConflictError
+        # in send_membership_event, cf comment in except block.
+        max_retries = 5
+        for i in range(max_retries):
+            try:
+                (
+                    event,
+                    context,
+                ) = await self.event_creation_handler.create_new_client_event(
                     builder=builder
                 )
                 event, context = await self.add_display_name_to_third_party_invite(
@@ -1417,12 +1446,22 @@ class FederationHandler:
 
                 # We need to tell the transaction queue to send this out, even
                 # though the sender isn't a local user.
-        event.internal_metadata.send_on_behalf_of = get_domain_from_id(event.sender)
+                event.internal_metadata.send_on_behalf_of = get_domain_from_id(
+                    event.sender
+                )
 
                 # We retrieve the room member handler here as to not cause a cyclic dependency
                 member_handler = self.hs.get_room_member_handler()
                 await member_handler.send_membership_event(None, event, context)
 
+                break
+            except PartialStateConflictError as e:
+                # Persisting couldn't happen because the room got un-partial stated
+                # in the meantime and context needs to be recomputed, so let's do so.
+                if i == max_retries - 1:
+                    raise e
+                pass
+
     async def add_display_name_to_third_party_invite(
         self,
         room_version_obj: RoomVersion,

synapse/handlers/message.py

@@ -37,7 +37,6 @@ from synapse.api.errors import (
     AuthError,
     Codes,
     ConsentNotGivenError,
-    LimitExceededError,
     NotFoundError,
     ShadowBanError,
     SynapseError,
@@ -999,6 +998,11 @@ class EventCreationHandler:
                         event.internal_metadata.stream_ordering,
                     )
 
+        # Try several times, it could fail with PartialStateConflictError
+        # in handle_new_client_event, cf comment in except block.
+        max_retries = 5
+        for i in range(max_retries):
+            try:
                 event, context = await self.create_event(
                     requester,
                     event_dict,
@@ -1054,6 +1058,14 @@ class EventCreationHandler:
                     ignore_shadow_ban=ignore_shadow_ban,
                 )
 
+                break
+            except PartialStateConflictError as e:
+                # Persisting couldn't happen because the room got un-partial stated
+                # in the meantime and context needs to be recomputed, so let's do so.
+                if i == max_retries - 1:
+                    raise e
+                pass
+
         # we know it was persisted, so must have a stream ordering
         assert ev.internal_metadata.stream_ordering
         return ev, ev.internal_metadata.stream_ordering
@@ -1356,7 +1368,7 @@ class EventCreationHandler:
 
         Raises:
             ShadowBanError if the requester has been shadow-banned.
-            SynapseError(503) if attempting to persist a partial state event in
+            PartialStateConflictError if attempting to persist a partial state event in
                 a room that has been un-partial stated.
         """
         extra_users = extra_users or []
@@ -1418,7 +1430,6 @@ class EventCreationHandler:
         # We now persist the event (and update the cache in parallel, since we
         # don't want to block on it).
         event, context = events_and_context[0]
-        try:
         result, _ = await make_deferred_yieldable(
             gather_results(
                 (
@@ -1431,21 +1442,11 @@ class EventCreationHandler:
                     ),
                     run_in_background(
                         self.cache_joined_hosts_for_events, events_and_context
-                        ).addErrback(
+                    ).addErrback(log_failure, "cache_joined_hosts_for_event failed"),
-                            log_failure, "cache_joined_hosts_for_event failed"
-                        ),
                 ),
                 consumeErrors=True,
             )
         ).addErrback(unwrapFirstError)
-        except PartialStateConflictError as e:
-            # The event context needs to be recomputed.
-            # Turn the error into a 429, as a hint to the client to try again.
-            logger.info(
-                "Room %s was un-partial stated while persisting client event.",
-                event.room_id,
-            )
-            raise LimitExceededError(msg=e.msg, errcode=e.errcode, retry_after_ms=0)
 
         return result
 
@@ -2011,6 +2012,11 @@ class EventCreationHandler:
         members = await self.store.get_local_users_in_room(room_id)
         for user_id in members:
             requester = create_requester(user_id, authenticated_entity=self.server_name)
+            try:
+                # Try several times, it could fail with PartialStateConflictError
+                # in handle_new_client_event, cf comment in except block.
+                max_retries = 5
+                for i in range(max_retries):
                     try:
                         event, context = await self.create_event(
                             requester,
@@ -2032,6 +2038,14 @@ class EventCreationHandler:
                             ratelimit=False,
                             ignore_shadow_ban=True,
                         )
+
+                        break
+                    except PartialStateConflictError as e:
+                        # Persisting couldn't happen because the room got un-partial stated
+                        # in the meantime and context needs to be recomputed, so let's do so.
+                        if i == max_retries - 1:
+                            raise e
+                        pass
                 return True
             except AuthError:
                 logger.info(

synapse/handlers/room.py

@@ -62,6 +62,7 @@ from synapse.events.utils import copy_and_fixup_power_levels_contents
 from synapse.handlers.relations import BundledAggregations
 from synapse.module_api import NOT_SPAM
 from synapse.rest.admin._base import assert_user_is_admin
+from synapse.storage.databases.main.events import PartialStateConflictError
 from synapse.streams import EventSource
 from synapse.types import (
     JsonDict,
@@ -207,6 +208,11 @@ class RoomCreationHandler:
 
         new_room_id = self._generate_room_id()
 
+        # Try several times, it could fail with PartialStateConflictError
+        # in _upgrade_room, cf comment in except block.
+        max_retries = 5
+        for i in range(max_retries):
+            try:
                 # Check whether the user has the power level to carry out the upgrade.
                 # `check_auth_rules_from_context` will check that they are in the room and have
                 # the required power level to send the tombstone event.
@@ -227,7 +233,9 @@ class RoomCreationHandler:
                     },
                 )
                 validate_event_for_room_version(tombstone_event)
-        await self._event_auth_handler.check_auth_rules_from_context(tombstone_event)
+                await self._event_auth_handler.check_auth_rules_from_context(
+                    tombstone_event
+                )
 
                 # Upgrade the room
                 #
@@ -247,6 +255,17 @@ class RoomCreationHandler:
                 )
 
                 return ret
+            except PartialStateConflictError as e:
+                # Clean up the cache so we can retry properly
+                self._upgrade_response_cache.unset((old_room_id, user_id))
+                # Persisting couldn't happen because the room got un-partial stated
+                # in the meantime and context needs to be recomputed, so let's do so.
+                if i == max_retries - 1:
+                    raise e
+                pass
+
+        # This is to satisfy mypy and should never happen
+        raise PartialStateConflictError()
 
     async def _upgrade_room(
         self,

synapse/handlers/room_batch.py

@@ -375,6 +375,8 @@ class RoomBatchHandler:
         # Events are sorted by (topological_ordering, stream_ordering)
         # where topological_ordering is just depth.
         for (event, context) in reversed(events_to_persist):
+            # This call can't raise `PartialStateConflictError` since we forbid
+            # use of the historical batch API during partial state
             await self.event_creation_handler.handle_new_client_event(
                 await self.create_requester_for_user_id_from_app_service(
                     event.sender, app_service_requester.app_service

synapse/handlers/room_member.py

@@ -34,6 +34,7 @@ from synapse.events.snapshot import EventContext
 from synapse.handlers.profile import MAX_AVATAR_URL_LEN, MAX_DISPLAYNAME_LEN
 from synapse.logging import opentracing
 from synapse.module_api import NOT_SPAM
+from synapse.storage.databases.main.events import PartialStateConflictError
 from synapse.types import (
     JsonDict,
     Requester,
@@ -392,6 +393,11 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
                 event_pos = await self.store.get_position_for_event(existing_event_id)
                 return existing_event_id, event_pos.stream
 
+        # Try several times, it could fail with PartialStateConflictError,
+        # in handle_new_client_event, cf comment in except block.
+        max_retries = 5
+        for i in range(max_retries):
+            try:
                 event, context = await self.event_creation_handler.create_event(
                     requester,
                     {
@@ -418,12 +424,16 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
                     StateFilter.from_types([(EventTypes.Member, None)])
                 )
 
-        prev_member_event_id = prev_state_ids.get((EventTypes.Member, user_id), None)
+                prev_member_event_id = prev_state_ids.get(
+                    (EventTypes.Member, user_id), None
+                )
 
                 if event.membership == Membership.JOIN:
                     newly_joined = True
                     if prev_member_event_id:
-                prev_member_event = await self.store.get_event(prev_member_event_id)
+                        prev_member_event = await self.store.get_event(
+                            prev_member_event_id
+                        )
                         newly_joined = prev_member_event.membership != Membership.JOIN
 
                     # Only rate-limit if the user actually joined the room, otherwise we'll end
@@ -434,19 +444,31 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
                             requester, key=room_id, update=False
                         )
                 with opentracing.start_active_span("handle_new_client_event"):
-            result_event = await self.event_creation_handler.handle_new_client_event(
+                    result_event = (
+                        await self.event_creation_handler.handle_new_client_event(
                             requester,
                             events_and_context=[(event, context)],
                             extra_users=[target],
                             ratelimit=ratelimit,
                         )
+                    )
 
                 if event.membership == Membership.LEAVE:
                     if prev_member_event_id:
-                prev_member_event = await self.store.get_event(prev_member_event_id)
+                        prev_member_event = await self.store.get_event(
+                            prev_member_event_id
+                        )
                         if prev_member_event.membership == Membership.JOIN:
                             await self._user_left_room(target, room_id)
 
+                break
+            except PartialStateConflictError as e:
+                # Persisting couldn't happen because the room got un-partial stated
+                # in the meantime and context needs to be recomputed, so let's do so.
+                if i == max_retries - 1:
+                    raise e
+                pass
+
         # we know it was persisted, so should have a stream ordering
         assert result_event.internal_metadata.stream_ordering
         return result_event.event_id, result_event.internal_metadata.stream_ordering
@@ -1234,6 +1256,8 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
             ratelimit: Whether to rate limit this request.
         Raises:
             SynapseError if there was a problem changing the membership.
+            PartialStateConflictError: if attempting to persist a partial state event in
+                a room that has been un-partial stated.
         """
         target_user = UserID.from_string(event.state_key)
         room_id = event.room_id
@@ -1863,6 +1887,11 @@ class RoomMemberMasterHandler(RoomMemberHandler):
             list(previous_membership_event.auth_event_ids()) + prev_event_ids
         )
 
+        # Try several times, it could fail with PartialStateConflictError
+        # in handle_new_client_event, cf comment in except block.
+        max_retries = 5
+        for i in range(max_retries):
+            try:
                 event, context = await self.event_creation_handler.create_event(
                     requester,
                     event_dict,
@@ -1873,11 +1902,22 @@ class RoomMemberMasterHandler(RoomMemberHandler):
                 )
                 event.internal_metadata.out_of_band_membership = True
 
-        result_event = await self.event_creation_handler.handle_new_client_event(
+                result_event = (
+                    await self.event_creation_handler.handle_new_client_event(
                         requester,
                         events_and_context=[(event, context)],
                         extra_users=[UserID.from_string(target_user)],
                     )
+                )
+
+                break
+            except PartialStateConflictError as e:
+                # Persisting couldn't happen because the room got un-partial stated
+                # in the meantime and context needs to be recomputed, so let's do so.
+                if i == max_retries - 1:
+                    raise e
+                pass
+
         # we know it was persisted, so must have a stream ordering
         assert result_event.internal_metadata.stream_ordering
 

synapse/util/caches/response_cache.py

@@ -167,12 +167,10 @@ class ResponseCache(Generic[KV]):
             # the should_cache bit, we leave it in the cache for now and schedule
             # its removal later.
             if self.timeout_sec and context.should_cache:
-                self.clock.call_later(
+                self.clock.call_later(self.timeout_sec, self.unset, key)
-                    self.timeout_sec, self._result_cache.pop, key, None
-                )
             else:
                 # otherwise, remove the result immediately.
-                self._result_cache.pop(key, None)
+                self.unset(key)
             return r
 
         # make sure we do this *after* adding the entry to result_cache,
@@ -181,6 +179,14 @@ class ResponseCache(Generic[KV]):
         result.addBoth(on_complete)
         return entry
 
+    def unset(self, key: KV) -> None:
+        """Remove the cached value for this key from the cache, if any.
+
+        Args:
+            key: key used to remove the cached value
+        """
+        self._result_cache.pop(key, None)
+
     async def wrap(
         self,
         key: KV,