Repository: matrix-org/synapse

Issue:
Add concept of StatelessContext
This allows us to lazily load state on the master process as required
(when using workers). The advantage of this is that in the common case
the master doesn't need the full state of the events to persist them.

We keep the concept of an EventContext that has the current_state_ids
and prev_state_ids attributes, to avoid having to rewrite a lot of code.
Instead, we shift the necessary functions to accept StatelessContext.

Supersedes #2999

---

I don't know whether it would be better to completely remove `current_state_ids` from `StatelessContext` or not.


Discussion:

Resolving patch:
diff --git a/synapse/storage/push_rule.py b/synapse/storage/push_rule.py
--- a/synapse/storage/push_rule.py
+++ b/synapse/storage/push_rule.py
@@ -21,7 +21,6 @@
 
 from twisted.internet import defer
 
-from synapse.api.constants import EventTypes
 from synapse.push.baserules import list_with_base_rules
 from synapse.storage.appservice import ApplicationServiceWorkerStore
 from synapse.storage.pusher import PusherWorkerStore
@@ -250,18 +249,6 @@ def _bulk_get_push_rules_for_room(self, room_id, state_group, current_state_ids,
             if uid in local_users_in_room:
                 user_ids.add(uid)
 
-        forgotten = yield self.who_forgot_in_room(
-            event.room_id, on_invalidate=cache_context.invalidate,
-        )
-
-        for row in forgotten:
-            user_id = row["user_id"]
-            event_id = row["event_id"]
-
-            mem_id = current_state_ids.get((EventTypes.Member, user_id), None)
-            if event_id == mem_id:
-                user_ids.discard(user_id)
-
         rules_by_user = yield self.bulk_get_push_rules(
             user_ids, on_invalidate=cache_context.invalidate,
         )
diff --git a/synapse/storage/roommember.py b/synapse/storage/roommember.py
--- a/synapse/storage/roommember.py
+++ b/synapse/storage/roommember.py
@@ -461,18 +461,6 @@ def _get_joined_hosts(self, room_id, state_group, current_state_ids, state_entry
     def _get_joined_hosts_cache(self, room_id):
         return _JoinedHostsCache(self, room_id)
 
-    @cached()
-    def who_forgot_in_room(self, room_id):
-        return self._simple_select_list(
-            table="room_memberships",
-            retcols=("user_id", "event_id"),
-            keyvalues={
-                "room_id": room_id,
-                "forgotten": 1,
-            },
-            desc="who_forgot"
-        )
-
 
 class RoomMemberStore(RoomMemberWorkerStore):
     def __init__(self, db_conn, hs):
@@ -581,9 +569,6 @@ def f(txn):
             txn.execute(sql, (user_id, room_id))
 
             txn.call_after(self.did_forget.invalidate, (user_id, room_id))
-            self._invalidate_cache_and_stream(
-                txn, self.who_forgot_in_room, (room_id,)
-            )
         return self.runInteraction("forget_membership", f)
 
     @cachedInlineCallbacks(num_args=2)
diff --git a/synapse/visibility.py b/synapse/visibility.py
--- a/synapse/visibility.py
+++ b/synapse/visibility.py
@@ -24,7 +24,6 @@
 from synapse.api.constants import EventTypes, Membership
 from synapse.events.utils import prune_event
 from synapse.types import get_domain_from_id
-from synapse.util.logcontext import make_deferred_yieldable, preserve_fn
 
 logger = logging.getLogger(__name__)
 
@@ -76,19 +75,6 @@ def filter_events_for_client(store, user_id, events, is_peeking=False,
         types=types,
     )
 
-    forgotten = yield make_deferred_yieldable(defer.gatherResults([
-        defer.maybeDeferred(
-            preserve_fn(store.who_forgot_in_room),
-            room_id,
-        )
-        for room_id in frozenset(e.room_id for e in events)
-    ], consumeErrors=True))
-
-    # Set of membership event_ids that have been forgotten
-    event_id_forgotten = frozenset(
-        row["event_id"] for rows in forgotten for row in rows
-    )
-
     ignore_dict_content = yield store.get_global_account_data_by_type_for_user(
         "m.ignored_user_list", user_id,
     )
@@ -177,10 +163,7 @@ def allowed(event):
         if membership is None:
             membership_event = state.get((EventTypes.Member, user_id), None)
             if membership_event:
-                # XXX why do we do this?
-                # https://github.com/matrix-org/synapse/issues/3350
-                if membership_event.event_id not in event_id_forgotten:
-                    membership = membership_event.membership
+                membership = membership_event.membership
 
         # if the user was a member of the room at the time of the event,
         # they can see it.


Test patch: