Speed up updating state in large rooms (#15971)

This should speed up updating state in rooms with lots of state.

1 files changed, 0 insertions, 122 deletions

diff --git a/synapse/storage/databases/main/roommember.py b/synapse/storage/databases/main/roommember.py
index 582875c91a..fff259f74c 100644
--- a/synapse/storage/databases/main/roommember.py
+++ b/synapse/storage/databases/main/roommember.py
@@ -13,7 +13,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
-from itertools import chain
 from typing import (
     TYPE_CHECKING,
     AbstractSet,
@@ -57,15 +56,12 @@ from synapse.types import (
     StrCollection,
     get_domain_from_id,
 )
-from synapse.util.async_helpers import Linearizer
-from synapse.util.caches import intern_string
 from synapse.util.caches.descriptors import _CacheContext, cached, cachedList
 from synapse.util.iterutils import batch_iter
 from synapse.util.metrics import Measure
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer
-    from synapse.state import _StateCacheEntry
 
 logger = logging.getLogger(__name__)
 
@@ -91,10 +87,6 @@ class RoomMemberWorkerStore(EventsWorkerStore, CacheInvalidationWorkerStore):
     ):
         super().__init__(database, db_conn, hs)
 
-        # Used by `_get_joined_hosts` to ensure only one thing mutates the cache
-        # at a time. Keyed by room_id.
-        self._joined_host_linearizer = Linearizer("_JoinedHostsCache")
-
         self._server_notices_mxid = hs.config.servernotices.server_notices_mxid
 
         if (
@@ -1057,120 +1049,6 @@ class RoomMemberWorkerStore(EventsWorkerStore, CacheInvalidationWorkerStore):
             "get_current_hosts_in_room_ordered", get_current_hosts_in_room_ordered_txn
         )
 
-    async def get_joined_hosts(
-        self, room_id: str, state: StateMap[str], state_entry: "_StateCacheEntry"
-    ) -> FrozenSet[str]:
-        state_group: Union[object, int] = state_entry.state_group
-        if not state_group:
-            # If state_group is None it means it has yet to be assigned a
-            # state group, i.e. we need to make sure that calls with a state_group
-            # of None don't hit previous cached calls with a None state_group.
-            # To do this we set the state_group to a new object as object() != object()
-            state_group = object()
-
-        assert state_group is not None
-        with Measure(self._clock, "get_joined_hosts"):
-            return await self._get_joined_hosts(
-                room_id, state_group, state, state_entry=state_entry
-            )
-
-    @cached(num_args=2, max_entries=10000, iterable=True)
-    async def _get_joined_hosts(
-        self,
-        room_id: str,
-        state_group: Union[object, int],
-        state: StateMap[str],
-        state_entry: "_StateCacheEntry",
-    ) -> FrozenSet[str]:
-        # We don't use `state_group`, it's there so that we can cache based on
-        # it. However, its important that its never None, since two
-        # current_state's with a state_group of None are likely to be different.
-        #
-        # The `state_group` must match the `state_entry.state_group` (if not None).
-        assert state_group is not None
-        assert state_entry.state_group is None or state_entry.state_group == state_group
-
-        # We use a secondary cache of previous work to allow us to build up the
-        # joined hosts for the given state group based on previous state groups.
-        #
-        # We cache one object per room containing the results of the last state
-        # group we got joined hosts for. The idea is that generally
-        # `get_joined_hosts` is called with the "current" state group for the
-        # room, and so consecutive calls will be for consecutive state groups
-        # which point to the previous state group.
-        cache = await self._get_joined_hosts_cache(room_id)
-
-        # If the state group in the cache matches, we already have the data we need.
-        if state_entry.state_group == cache.state_group:
-            return frozenset(cache.hosts_to_joined_users)
-
-        # Since we'll mutate the cache we need to lock.
-        async with self._joined_host_linearizer.queue(room_id):
-            if state_entry.state_group == cache.state_group:
-                # Same state group, so nothing to do. We've already checked for
-                # this above, but the cache may have changed while waiting on
-                # the lock.
-                pass
-            elif state_entry.prev_group == cache.state_group:
-                # The cached work is for the previous state group, so we work out
-                # the delta.
-                assert state_entry.delta_ids is not None
-                for (typ, state_key), event_id in state_entry.delta_ids.items():
-                    if typ != EventTypes.Member:
-                        continue
-
-                    host = intern_string(get_domain_from_id(state_key))
-                    user_id = state_key
-                    known_joins = cache.hosts_to_joined_users.setdefault(host, set())
-
-                    event = await self.get_event(event_id)
-                    if event.membership == Membership.JOIN:
-                        known_joins.add(user_id)
-                    else:
-                        known_joins.discard(user_id)
-
-                        if not known_joins:
-                            cache.hosts_to_joined_users.pop(host, None)
-            else:
-                # The cache doesn't match the state group or prev state group,
-                # so we calculate the result from first principles.
-                #
-                # We need to fetch all hosts joined to the room according to `state` by
-                # inspecting all join memberships in `state`. However, if the `state` is
-                # relatively recent then many of its events are likely to be held in
-                # the current state of the room, which is easily available and likely
-                # cached.
-                #
-                # We therefore compute the set of `state` events not in the
-                # current state and only fetch those.
-                current_memberships = (
-                    await self._get_approximate_current_memberships_in_room(room_id)
-                )
-                unknown_state_events = {}
-                joined_users_in_current_state = []
-
-                for (type, state_key), event_id in state.items():
-                    if event_id not in current_memberships:
-                        unknown_state_events[type, state_key] = event_id
-                    elif current_memberships[event_id] == Membership.JOIN:
-                        joined_users_in_current_state.append(state_key)
-
-                joined_user_ids = await self.get_joined_user_ids_from_state(
-                    room_id, unknown_state_events
-                )
-
-                cache.hosts_to_joined_users = {}
-                for user_id in chain(joined_user_ids, joined_users_in_current_state):
-                    host = intern_string(get_domain_from_id(user_id))
-                    cache.hosts_to_joined_users.setdefault(host, set()).add(user_id)
-
-            if state_entry.state_group:
-                cache.state_group = state_entry.state_group
-            else:
-                cache.state_group = object()
-
-        return frozenset(cache.hosts_to_joined_users)
-
     async def _get_approximate_current_memberships_in_room(
         self, room_id: str
     ) -> Mapping[str, Optional[str]]: