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Add some debug to keep track of client state desynchronisation

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Fixes https://github.com/element-hq/crypto-internal/issues/179
This commit is contained in:
Richard van der Hoff 2024-02-22 15:54:32 +00:00
parent 657b8cc75c
commit bc435f7d9d
1 changed files with 138 additions and 0 deletions
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138
synapse/handlers/sync.py
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@ -88,6 +88,10 @@ if TYPE_CHECKING:
logger = logging.getLogger(__name__)
# Logging for https://github.com/matrix-org/matrix-spec/issues/1209 and
# https://github.com/element-hq/synapse/issues/16940
client_state_desync_logger = logging.getLogger("synapse.client_state_desync_debug")
# Counts the number of times we returned a non-empty sync. `type` is one of
# "initial_sync", "full_state_sync" or "incremental_sync", `lazy_loaded` is
# "true" or "false" depending on if the request asked for lazy loaded members or
@ -1214,6 +1218,12 @@ class SyncHandler:
previous_timeline_end={},
lazy_load_members=lazy_load_members,
)
if client_state_desync_logger.isEnabledFor(logging.DEBUG):
await self._log_client_state_desync(
room_id, None, state_ids, timeline_state, lazy_load_members
)
return state_ids
async def _compute_state_delta_for_incremental_sync(
@ -1359,6 +1369,15 @@ class SyncHandler:
lazy_load_members=lazy_load_members,
)
if client_state_desync_logger.isEnabledFor(logging.DEBUG):
await self._log_client_state_desync(
room_id,
since_token,
state_ids,
timeline_state,
lazy_load_members,
)
return state_ids
async def _find_missing_partial_state_memberships(
@ -1475,6 +1494,125 @@ class SyncHandler:
return additional_state_ids
async def _log_client_state_desync(
self,
room_id: str,
since_token: Optional[StreamToken],
sync_response_state_state: StateMap[str],
sync_response_timeline_state: StateMap[str],
lazy_load_members: bool,
) -> None:
"""
Logging to see how often the client's state gets out of sync with the
actual current state of the room.
There are few different potential failure modes here:
* State resolution can cause changes in the state of the room that don't
directly correspond to events with the corresponding (type, state_key).
https://github.com/matrix-org/matrix-spec/issues/1209 discusses this in
more detail.
* Even where there is an event that causes a given state change, Synapse
may not serve it to the client, since it works on state at specific points
in the DAG, rather than "current state".
See https://github.com/element-hq/synapse/issues/16940.
* Lazy-loading adds more complexity, as it means that events that would
normally be served via the `state` part of an incremental sync are filtered
out.
To try to get a handle on this, let's put ourselves in the shoes of a client,
and compare the state they will calculate against the actual current state.
"""
# We only care about membership events.
state_filter = StateFilter.from_types(types=(("m.room.member", None),))
if since_token is None:
if lazy_load_members:
# For initial syncs with lazy-loading enabled, there's not too much
# concern here. We know the client will do a `/members` query before
# doing any encryption, so what sync returns isn't too important.
#
# (Of course, then `/members` might also return an incomplete list, but
# that's a separate problem.)
return
# For regular initial syncs, compare the returned response with the actual
# current state.
client_calculated_state = {}
client_calculated_state.update(sync_response_state_state)
client_calculated_state.update(sync_response_timeline_state)
else:
# For an incremental (gappy or otherwise) sync, let's assume the client has
# a complete membership list as of the last sync (or rather, at
# `since_token`, which is the closest approximation we have to it
# right now), and see what they would calculate as the current state given
# this sync update.
client_calculated_state = dict(
await self.get_state_at(
room_id,
stream_position=since_token,
state_filter=state_filter,
await_full_state=False,
)
)
client_calculated_state.update(sync_response_state_state)
client_calculated_state.update(sync_response_timeline_state)
current_state = await self._state_storage_controller.get_current_state_ids(
room_id, state_filter=state_filter, await_full_state=False
)
missing_users = await self._calculate_missing_members(
current_state, client_calculated_state
)
if missing_users:
client_state_desync_logger.debug(
"client state discrepancy in incremental sync in room %s: missing users %s",
room_id,
missing_users,
)
async def _calculate_missing_members(
self,
actual_state: StateMap[str],
client_calculated_state: StateMap[str],
) -> List[str]:
"""Helper for `_log_client_state_desync`: calculates the difference in
joined members between two state maps.
Returns:
A list of user IDs
"""
missing_users = []
async def event_id_to_membership(event_id: Optional[str]) -> Optional[str]:
if event_id is None:
return None
event = await self.store.get_event(event_id, allow_none=True)
if event is None:
return "MISSING_EVENT"
return event.membership
# Check for joined members in the actual state that are missing or have a
# different membership in the actual state.
for (event_type, state_key), actual_event_id in actual_state.items():
if event_type != EventTypes.Member:
continue
calculated_event_id = client_calculated_state.get((event_type, state_key))
if calculated_event_id != actual_event_id:
actual_membership = event_id_to_membership(actual_event_id)
calculated_membership = event_id_to_membership(calculated_event_id)
if (
actual_membership == Membership.JOIN
and calculated_membership != Membership.JOIN
):
missing_users.append(state_key)
return missing_users
async def unread_notifs_for_room_id(
self, room_id: str, sync_config: SyncConfig
) -> RoomNotifCounts: