Merge pull request #1060 from matrix-org/erikj/state_ids

Assign state groups in state handler.

16 files changed, 217 insertions, 173 deletions

diff --git a/synapse/api/auth.py b/synapse/api/auth.py
index f26e585623..dcda40863f 100644
--- a/synapse/api/auth.py
+++ b/synapse/api/auth.py
@@ -66,7 +66,7 @@ class Auth(object):
     @defer.inlineCallbacks
     def check_from_context(self, event, context, do_sig_check=True):
         auth_events_ids = yield self.compute_auth_events(
-            event, context.current_state_ids, for_verification=True,
+            event, context.prev_state_ids, for_verification=True,
         )
         auth_events = yield self.store.get_events(auth_events_ids)
         auth_events = {
@@ -281,11 +281,13 @@ class Auth(object):
         with Measure(self.clock, "check_host_in_room"):
             latest_event_ids = yield self.store.get_latest_event_ids_in_room(room_id)
 
-            group, curr_state_ids = yield self.state.resolve_state_groups(
+            entry = yield self.state.resolve_state_groups(
                 room_id, latest_event_ids
             )
 
-            ret = yield self.store.is_host_joined(room_id, host, group, curr_state_ids)
+            ret = yield self.store.is_host_joined(
+                room_id, host, entry.state_group, entry.state
+            )
             defer.returnValue(ret)
 
     def check_event_sender_in_room(self, event, auth_events):
@@ -852,7 +854,7 @@ class Auth(object):
 
     @defer.inlineCallbacks
     def add_auth_events(self, builder, context):
-        auth_ids = yield self.compute_auth_events(builder, context.current_state_ids)
+        auth_ids = yield self.compute_auth_events(builder, context.prev_state_ids)
 
         auth_events_entries = yield self.store.add_event_hashes(
             auth_ids
diff --git a/synapse/events/snapshot.py b/synapse/events/snapshot.py
index c75afd02d8..e895b1c450 100644
--- a/synapse/events/snapshot.py
+++ b/synapse/events/snapshot.py
@@ -15,8 +15,9 @@
 
 
 class EventContext(object):
-    def __init__(self, current_state_ids=None):
-        self.current_state_ids = current_state_ids
+    def __init__(self):
+        self.current_state_ids = None
+        self.prev_state_ids = None
         self.state_group = None
         self.rejected = False
         self.push_actions = []
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index a7ea8fb98f..8e61d74b13 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -222,7 +222,7 @@ class FederationHandler(BaseHandler):
                 # joined the room. Don't bother if the user is just
                 # changing their profile info.
                 newly_joined = True
-                prev_state_id = context.current_state_ids.get(
+                prev_state_id = context.prev_state_ids.get(
                     (event.type, event.state_key)
                 )
                 if prev_state_id:
@@ -835,12 +835,12 @@ class FederationHandler(BaseHandler):
 
         self.replication_layer.send_pdu(new_pdu, destinations)
 
-        state_ids = context.current_state_ids.values()
+        state_ids = context.prev_state_ids.values()
         auth_chain = yield self.store.get_auth_chain(set(
             [event.event_id] + state_ids
         ))
 
-        state = yield self.store.get_events(context.current_state_ids.values())
+        state = yield self.store.get_events(context.prev_state_ids.values())
 
         defer.returnValue({
             "state": state.values(),
@@ -1333,7 +1333,7 @@ class FederationHandler(BaseHandler):
 
         if not auth_events:
             auth_events_ids = yield self.auth.compute_auth_events(
-                event, context.current_state_ids, for_verification=True,
+                event, context.prev_state_ids, for_verification=True,
             )
             auth_events = yield self.store.get_events(auth_events_ids)
             auth_events = {
@@ -1432,6 +1432,11 @@ class FederationHandler(BaseHandler):
         current_state = set(e.event_id for e in auth_events.values())
         event_auth_events = set(e_id for e_id, _ in event.auth_events)
 
+        if event.is_state():
+            event_key = (event.type, event.state_key)
+        else:
+            event_key = None
+
         if event_auth_events - current_state:
             have_events = yield self.store.have_events(
                 event_auth_events - current_state
@@ -1537,8 +1542,12 @@ class FederationHandler(BaseHandler):
 
                 context.current_state_ids.update({
                     k: a.event_id for k, a in auth_events.items()
+                    if k != event_key
+                })
+                context.prev_state_ids.update({
+                    k: a.event_id for k, a in auth_events.items()
                 })
-                context.state_group = None
+                context.state_group = self.store.get_next_state_group()
 
         if different_auth and not event.internal_metadata.is_outlier():
             logger.info("Different auth after resolution: %s", different_auth)
@@ -1560,7 +1569,7 @@ class FederationHandler(BaseHandler):
             if do_resolution:
                 # 1. Get what we think is the auth chain.
                 auth_ids = yield self.auth.compute_auth_events(
-                    event, context.current_state_ids
+                    event, context.prev_state_ids
                 )
                 local_auth_chain = yield self.store.get_auth_chain(auth_ids)
 
@@ -1618,8 +1627,12 @@ class FederationHandler(BaseHandler):
 
                 context.current_state_ids.update({
                     k: a.event_id for k, a in auth_events.items()
+                    if k != event_key
+                })
+                context.prev_state_ids.update({
+                    k: a.event_id for k, a in auth_events.items()
                 })
-                context.state_group = None
+                context.state_group = self.store.get_next_state_group()
 
         try:
             self.auth.check(event, auth_events=auth_events)
@@ -1855,7 +1868,7 @@ class FederationHandler(BaseHandler):
             event.content["third_party_invite"]["signed"]["token"]
         )
         original_invite = None
-        original_invite_id = context.current_state_ids.get(key)
+        original_invite_id = context.prev_state_ids.get(key)
         if original_invite_id:
             original_invite = yield self.store.get_event(
                 original_invite_id, allow_none=True
@@ -1893,7 +1906,7 @@ class FederationHandler(BaseHandler):
         signed = event.content["third_party_invite"]["signed"]
         token = signed["token"]
 
-        invite_event_id = context.current_state_ids.get(
+        invite_event_id = context.prev_state_ids.get(
             (EventTypes.ThirdPartyInvite, token,)
         )
 
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index e2f4387f60..3577db0595 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -272,7 +272,7 @@ class MessageHandler(BaseHandler):
         If so, returns the version of the event in context.
         Otherwise, returns None.
         """
-        prev_event_id = context.current_state_ids.get((event.type, event.state_key))
+        prev_event_id = context.prev_state_ids.get((event.type, event.state_key))
         prev_event = yield self.store.get_event(prev_event_id, allow_none=True)
         if not prev_event:
             return
@@ -808,8 +808,8 @@ class MessageHandler(BaseHandler):
         event = builder.build()
 
         logger.debug(
-            "Created event %s with current state: %s",
-            event.event_id, context.current_state_ids,
+            "Created event %s with state: %s",
+            event.event_id, context.prev_state_ids,
         )
 
         defer.returnValue(
@@ -904,7 +904,7 @@ class MessageHandler(BaseHandler):
 
         if event.type == EventTypes.Redaction:
             auth_events_ids = yield self.auth.compute_auth_events(
-                event, context.current_state_ids, for_verification=True,
+                event, context.prev_state_ids, for_verification=True,
             )
             auth_events = yield self.store.get_events(auth_events_ids)
             auth_events = {
@@ -924,7 +924,7 @@ class MessageHandler(BaseHandler):
                         "You don't have permission to redact events"
                     )
 
-        if event.type == EventTypes.Create and context.current_state_ids:
+        if event.type == EventTypes.Create and context.prev_state_ids:
             raise AuthError(
                 403,
                 "Changing the room create event is forbidden",
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index dd4b90ee24..3ba5335af7 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -93,7 +93,7 @@ class RoomMemberHandler(BaseHandler):
             ratelimit=ratelimit,
         )
 
-        prev_member_event_id = context.current_state_ids.get(
+        prev_member_event_id = context.prev_state_ids.get(
             (EventTypes.Member, target.to_string()),
             None
         )
@@ -341,7 +341,7 @@ class RoomMemberHandler(BaseHandler):
 
         if event.membership == Membership.JOIN:
             if requester.is_guest:
-                guest_can_join = yield self._can_guest_join(context.current_state_ids)
+                guest_can_join = yield self._can_guest_join(context.prev_state_ids)
                 if not guest_can_join:
                     # This should be an auth check, but guests are a local concept,
                     # so don't really fit into the general auth process.
@@ -355,7 +355,7 @@ class RoomMemberHandler(BaseHandler):
             ratelimit=ratelimit,
         )
 
-        prev_member_event_id = context.current_state_ids.get(
+        prev_member_event_id = context.prev_state_ids.get(
             (EventTypes.Member, event.state_key),
             None
         )
diff --git a/synapse/push/bulk_push_rule_evaluator.py b/synapse/push/bulk_push_rule_evaluator.py
index 51cb21ee9d..6ff9a06de1 100644
--- a/synapse/push/bulk_push_rule_evaluator.py
+++ b/synapse/push/bulk_push_rule_evaluator.py
@@ -87,7 +87,7 @@ class BulkPushRuleEvaluator:
         )
 
         room_members = yield self.store.get_joined_users_from_context(
-            event.room_id, context.state_group, context.current_state_ids
+            event, context
         )
 
         evaluator = PushRuleEvaluatorForEvent(event, len(room_members))
diff --git a/synapse/replication/resource.py b/synapse/replication/resource.py
index 533676814a..1ed9034bcb 100644
--- a/synapse/replication/resource.py
+++ b/synapse/replication/resource.py
@@ -40,7 +40,6 @@ STREAM_NAMES = (
     ("backfill",),
     ("push_rules",),
     ("pushers",),
-    ("state",),
     ("caches",),
     ("to_device",),
 )
@@ -131,7 +130,6 @@ class ReplicationResource(Resource):
         backfill_token = yield self.store.get_current_backfill_token()
         push_rules_token, room_stream_token = self.store.get_push_rules_stream_token()
         pushers_token = self.store.get_pushers_stream_token()
-        state_token = self.store.get_state_stream_token()
         caches_token = self.store.get_cache_stream_token()
 
         defer.returnValue(_ReplicationToken(
@@ -143,7 +141,7 @@ class ReplicationResource(Resource):
             backfill_token,
             push_rules_token,
             pushers_token,
-            state_token,
+            0,  # State stream is no longer a thing
             caches_token,
             int(stream_token.to_device_key),
         ))
@@ -193,7 +191,6 @@ class ReplicationResource(Resource):
         yield self.receipts(writer, current_token, limit, request_streams)
         yield self.push_rules(writer, current_token, limit, request_streams)
         yield self.pushers(writer, current_token, limit, request_streams)
-        yield self.state(writer, current_token, limit, request_streams)
         yield self.caches(writer, current_token, limit, request_streams)
         yield self.to_device(writer, current_token, limit, request_streams)
         self.streams(writer, current_token, request_streams)
@@ -369,25 +366,6 @@ class ReplicationResource(Resource):
             ))
 
     @defer.inlineCallbacks
-    def state(self, writer, current_token, limit, request_streams):
-        current_position = current_token.state
-
-        state = request_streams.get("state")
-
-        if state is not None:
-            state_groups, state_group_state = (
-                yield self.store.get_all_new_state_groups(
-                    state, current_position, limit
-                )
-            )
-            writer.write_header_and_rows("state_groups", state_groups, (
-                "position", "room_id", "event_id"
-            ))
-            writer.write_header_and_rows("state_group_state", state_group_state, (
-                "position", "type", "state_key", "event_id"
-            ))
-
-    @defer.inlineCallbacks
     def caches(self, writer, current_token, limit, request_streams):
         current_position = current_token.caches
 
diff --git a/synapse/replication/slave/storage/events.py b/synapse/replication/slave/storage/events.py
index b14ed4d2d8..cbebd5b2f7 100644
--- a/synapse/replication/slave/storage/events.py
+++ b/synapse/replication/slave/storage/events.py
@@ -123,6 +123,7 @@ class SlavedEventStore(BaseSlavedStore):
     get_state_groups_ids = DataStore.get_state_groups_ids.__func__
     get_state_ids_for_event = DataStore.get_state_ids_for_event.__func__
     get_state_ids_for_events = DataStore.get_state_ids_for_events.__func__
+    get_joined_users_from_state = DataStore.get_joined_users_from_state.__func__
     get_joined_users_from_context = DataStore.get_joined_users_from_context.__func__
     _get_joined_users_from_context = (
         RoomMemberStore.__dict__["_get_joined_users_from_context"]
diff --git a/synapse/state.py b/synapse/state.py
index daec983dc9..b31bbcdbd2 100644
--- a/synapse/state.py
+++ b/synapse/state.py
@@ -43,11 +43,35 @@ SIZE_OF_CACHE = int(1000 * CACHE_SIZE_FACTOR)
 EVICTION_TIMEOUT_SECONDS = 60 * 60
 
 
+_NEXT_STATE_ID = 1
+
+
+def _gen_state_id():
+    global _NEXT_STATE_ID
+    s = "X%d" % (_NEXT_STATE_ID,)
+    _NEXT_STATE_ID += 1
+    return s
+
+
 class _StateCacheEntry(object):
-    def __init__(self, state, state_group, ts):
+    __slots__ = ["state", "state_group", "state_id"]
+
+    def __init__(self, state, state_group):
         self.state = state
         self.state_group = state_group
 
+        # The `state_id` is a unique ID we generate that can be used as ID for
+        # this collection of state. Usually this would be the same as the
+        # state group, but on worker instances we can't generate a new state
+        # group each time we resolve state, so we generate a separate one that
+        # isn't persisted and is used solely for caches.
+        # `state_id` is either a state_group (and so an int) or a string. This
+        # ensures we don't accidentally persist a state_id as a stateg_group
+        if state_group:
+            self.state_id = state_group
+        else:
+            self.state_id = _gen_state_id()
+
 
 class StateHandler(object):
     """ Responsible for doing state conflict resolution.
@@ -93,7 +117,8 @@ class StateHandler(object):
         if not latest_event_ids:
             latest_event_ids = yield self.store.get_latest_event_ids_in_room(room_id)
 
-        _, state = yield self.resolve_state_groups(room_id, latest_event_ids)
+        ret = yield self.resolve_state_groups(room_id, latest_event_ids)
+        state = ret.state
 
         if event_type:
             event_id = state.get((event_type, state_key))
@@ -116,7 +141,8 @@ class StateHandler(object):
         if not latest_event_ids:
             latest_event_ids = yield self.store.get_latest_event_ids_in_room(room_id)
 
-        _, state = yield self.resolve_state_groups(room_id, latest_event_ids)
+        ret = yield self.resolve_state_groups(room_id, latest_event_ids)
+        state = ret.state
 
         if event_type:
             defer.returnValue(state.get((event_type, state_key)))
@@ -127,9 +153,9 @@ class StateHandler(object):
     @defer.inlineCallbacks
     def get_current_user_in_room(self, room_id):
         latest_event_ids = yield self.store.get_latest_event_ids_in_room(room_id)
-        group, state_ids = yield self.resolve_state_groups(room_id, latest_event_ids)
-        joined_users = yield self.store.get_joined_users_from_context(
-            room_id, group, state_ids
+        entry = yield self.resolve_state_groups(room_id, latest_event_ids)
+        joined_users = yield self.store.get_joined_users_from_state(
+            room_id, entry.state_id, entry.state
         )
         defer.returnValue(joined_users)
 
@@ -154,52 +180,73 @@ class StateHandler(object):
             # state. Certainly store.get_current_state won't return any, and
             # persisting the event won't store the state group.
             if old_state:
-                context.current_state_ids = {
+                context.prev_state_ids = {
                     (s.type, s.state_key): s.event_id for s in old_state
                 }
+                if event.is_state():
+                    context.current_state_events = dict(context.prev_state_ids)
+                    key = (event.type, event.state_key)
+                    context.current_state_events[key] = event.event_id
+                else:
+                    context.current_state_events = context.prev_state_ids
             else:
                 context.current_state_ids = {}
+                context.prev_state_ids = {}
             context.prev_state_events = []
-            context.state_group = None
+            context.state_group = self.store.get_next_state_group()
             defer.returnValue(context)
 
         if old_state:
-            context.current_state_ids = {
+            context.prev_state_ids = {
                 (s.type, s.state_key): s.event_id for s in old_state
             }
-            context.state_group = None
+            context.state_group = self.store.get_next_state_group()
 
             if event.is_state():
                 key = (event.type, event.state_key)
-                if key in context.current_state_ids:
-                    replaces = context.current_state_ids[key]
+                if key in context.prev_state_ids:
+                    replaces = context.prev_state_ids[key]
                     if replaces != event.event_id:  # Paranoia check
                         event.unsigned["replaces_state"] = replaces
+                context.current_state_ids = dict(context.prev_state_ids)
+                context.current_state_ids[key] = event.event_id
+            else:
+                context.current_state_ids = context.prev_state_ids
 
             context.prev_state_events = []
             defer.returnValue(context)
 
         if event.is_state():
-            ret = yield self.resolve_state_groups(
+            entry = yield self.resolve_state_groups(
                 event.room_id, [e for e, _ in event.prev_events],
                 event_type=event.type,
                 state_key=event.state_key,
             )
         else:
-            ret = yield self.resolve_state_groups(
+            entry = yield self.resolve_state_groups(
                 event.room_id, [e for e, _ in event.prev_events],
             )
 
-        group, curr_state = ret
+        curr_state = entry.state
 
-        context.current_state_ids = curr_state
-        context.state_group = group if not event.is_state() else None
+        context.prev_state_ids = curr_state
+        if event.is_state():
+            context.state_group = self.store.get_next_state_group()
+        else:
+            if entry.state_group is None:
+                entry.state_group = self.store.get_next_state_group()
+                entry.state_id = entry.state_group
+            context.state_group = entry.state_group
 
         if event.is_state():
             key = (event.type, event.state_key)
-            if key in context.current_state_ids:
-                replaces = context.current_state_ids[key]
+            if key in context.prev_state_ids:
+                replaces = context.prev_state_ids[key]
                 event.unsigned["replaces_state"] = replaces
+            context.current_state_ids = dict(context.prev_state_ids)
+            context.current_state_ids[key] = event.event_id
+        else:
+            context.current_state_ids = context.prev_state_ids
 
         context.prev_state_events = []
         defer.returnValue(context)
@@ -231,16 +278,15 @@ class StateHandler(object):
         if len(group_names) == 1:
             name, state_list = state_groups_ids.items().pop()
 
-            defer.returnValue((name, state_list,))
+            defer.returnValue(_StateCacheEntry(
+                state=state_list,
+                state_group=name,
+            ))
 
         if self._state_cache is not None:
             cache = self._state_cache.get(group_names, None)
             if cache:
-                cache.ts = self.clock.time_msec()
-
-                defer.returnValue(
-                    (cache.state_group, cache.state,)
-                )
+                defer.returnValue(cache)
 
         logger.info(
             "Resolving state for %s with %d groups", room_id, len(state_groups_ids)
@@ -284,17 +330,22 @@ class StateHandler(object):
             if new_state_event_ids == frozenset(e_id for e_id in events):
                 state_group = sg
                 break
+        if state_group is None:
+            # Worker instances don't have access to this method, but we want
+            # to set the state_group on the main instance to increase cache
+            # hits.
+            if hasattr(self.store, "get_next_state_group"):
+                state_group = self.store.get_next_state_group()
+
+        cache = _StateCacheEntry(
+            state=new_state,
+            state_group=state_group,
+        )
 
         if self._state_cache is not None:
-            cache = _StateCacheEntry(
-                state=new_state,
-                state_group=state_group,
-                ts=self.clock.time_msec()
-            )
-
             self._state_cache[group_names] = cache
 
-        defer.returnValue((state_group, new_state,))
+        defer.returnValue(cache)
 
     def resolve_events(self, state_sets, event):
         logger.info(
diff --git a/synapse/storage/__init__.py b/synapse/storage/__init__.py
index 4f4c723c5b..6c32773f25 100644
--- a/synapse/storage/__init__.py
+++ b/synapse/storage/__init__.py
@@ -115,7 +115,7 @@ class DataStore(RoomMemberStore, RoomStore,
         )
 
         self._transaction_id_gen = IdGenerator(db_conn, "sent_transactions", "id")
-        self._state_groups_id_gen = StreamIdGenerator(db_conn, "state_groups", "id")
+        self._state_groups_id_gen = IdGenerator(db_conn, "state_groups", "id")
         self._access_tokens_id_gen = IdGenerator(db_conn, "access_tokens", "id")
         self._refresh_tokens_id_gen = IdGenerator(db_conn, "refresh_tokens", "id")
         self._event_reports_id_gen = IdGenerator(db_conn, "event_reports", "id")
diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index 5cbe8c5978..1a7d4c5199 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -271,39 +271,28 @@ class EventsStore(SQLBaseStore):
                 len(events_and_contexts)
             )
 
-        state_group_id_manager = self._state_groups_id_gen.get_next_mult(
-            len(events_and_contexts)
-        )
         with stream_ordering_manager as stream_orderings:
-            with state_group_id_manager as state_group_ids:
-                for (event, context), stream, state_group_id in zip(
-                    events_and_contexts, stream_orderings, state_group_ids
-                ):
-                    event.internal_metadata.stream_ordering = stream
-                    # Assign a state group_id in case a new id is needed for
-                    # this context. In theory we only need to assign this
-                    # for contexts that have current_state and aren't outliers
-                    # but that make the code more complicated. Assigning an ID
-                    # per event only causes the state_group_ids to grow as fast
-                    # as the stream_ordering so in practise shouldn't be a problem.
-                    context.new_state_group_id = state_group_id
-
-                chunks = [
-                    events_and_contexts[x:x + 100]
-                    for x in xrange(0, len(events_and_contexts), 100)
-                ]
+            for (event, context), stream, in zip(
+                events_and_contexts, stream_orderings
+            ):
+                event.internal_metadata.stream_ordering = stream
 
-                for chunk in chunks:
-                    # We can't easily parallelize these since different chunks
-                    # might contain the same event. :(
-                    yield self.runInteraction(
-                        "persist_events",
-                        self._persist_events_txn,
-                        events_and_contexts=chunk,
-                        backfilled=backfilled,
-                        delete_existing=delete_existing,
-                    )
-                    persist_event_counter.inc_by(len(chunk))
+            chunks = [
+                events_and_contexts[x:x + 100]
+                for x in xrange(0, len(events_and_contexts), 100)
+            ]
+
+            for chunk in chunks:
+                # We can't easily parallelize these since different chunks
+                # might contain the same event. :(
+                yield self.runInteraction(
+                    "persist_events",
+                    self._persist_events_txn,
+                    events_and_contexts=chunk,
+                    backfilled=backfilled,
+                    delete_existing=delete_existing,
+                )
+                persist_event_counter.inc_by(len(chunk))
 
     @_retry_on_integrity_error
     @defer.inlineCallbacks
@@ -312,19 +301,17 @@ class EventsStore(SQLBaseStore):
                        delete_existing=False):
         try:
             with self._stream_id_gen.get_next() as stream_ordering:
-                with self._state_groups_id_gen.get_next() as state_group_id:
-                    event.internal_metadata.stream_ordering = stream_ordering
-                    context.new_state_group_id = state_group_id
-                    yield self.runInteraction(
-                        "persist_event",
-                        self._persist_event_txn,
-                        event=event,
-                        context=context,
-                        current_state=current_state,
-                        backfilled=backfilled,
-                        delete_existing=delete_existing,
-                    )
-                    persist_event_counter.inc()
+                event.internal_metadata.stream_ordering = stream_ordering
+                yield self.runInteraction(
+                    "persist_event",
+                    self._persist_event_txn,
+                    event=event,
+                    context=context,
+                    current_state=current_state,
+                    backfilled=backfilled,
+                    delete_existing=delete_existing,
+                )
+                persist_event_counter.inc()
         except _RollbackButIsFineException:
             pass
 
@@ -528,7 +515,7 @@ class EventsStore(SQLBaseStore):
                 # Add an entry to the ex_outlier_stream table to replicate the
                 # change in outlier status to our workers.
                 stream_order = event.internal_metadata.stream_ordering
-                state_group_id = context.state_group or context.new_state_group_id
+                state_group_id = context.state_group
                 self._simple_insert_txn(
                     txn,
                     table="ex_outlier_stream",
diff --git a/synapse/storage/roommember.py b/synapse/storage/roommember.py
index cab1660830..6ab10db328 100644
--- a/synapse/storage/roommember.py
+++ b/synapse/storage/roommember.py
@@ -354,7 +354,8 @@ class RoomMemberStore(SQLBaseStore):
             desc="who_forgot"
         )
 
-    def get_joined_users_from_context(self, room_id, state_group, state_ids):
+    def get_joined_users_from_context(self, event, context):
+        state_group = context.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
@@ -363,12 +364,24 @@ class RoomMemberStore(SQLBaseStore):
             state_group = object()
 
         return self._get_joined_users_from_context(
-            room_id, state_group, state_ids
+            event.room_id, state_group, context.current_state_ids, event=event,
+        )
+
+    def get_joined_users_from_state(self, room_id, state_group, state_ids):
+        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()
+
+        return self._get_joined_users_from_context(
+            room_id, state_group, state_ids,
         )
 
     @cachedInlineCallbacks(num_args=2, cache_context=True)
     def _get_joined_users_from_context(self, room_id, state_group, current_state_ids,
-                                       cache_context):
+                                       cache_context, event=None):
         # We don't use `state_group`, its 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.
@@ -393,7 +406,13 @@ class RoomMemberStore(SQLBaseStore):
             desc="_get_joined_users_from_context",
         )
 
-        defer.returnValue(set(row["user_id"] for row in rows))
+        users_in_room = set(row["user_id"] for row in rows)
+        if event is not None and event.type == EventTypes.Member:
+            if event.membership == Membership.JOIN:
+                if event.event_id in member_event_ids:
+                    users_in_room.add(event.state_key)
+
+        defer.returnValue(users_in_room)
 
     def is_host_joined(self, room_id, host, state_group, state_ids):
         if not state_group:
diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index b1d461fef5..ec551b0b4f 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -83,6 +83,14 @@ class StateStore(SQLBaseStore):
             for group, event_id_map in group_to_ids.items()
         })
 
+    def _have_persisted_state_group_txn(self, txn, state_group):
+        txn.execute(
+            "SELECT count(*) FROM state_groups WHERE id = ?",
+            (state_group,)
+        )
+        row = txn.fetchone()
+        return row and row[0]
+
     def _store_mult_state_groups_txn(self, txn, events_and_contexts):
         state_groups = {}
         for event, context in events_and_contexts:
@@ -92,22 +100,19 @@ class StateStore(SQLBaseStore):
             if context.current_state_ids is None:
                 continue
 
-            if context.state_group is not None:
-                state_groups[event.event_id] = context.state_group
+            state_groups[event.event_id] = context.state_group
+
+            if self._have_persisted_state_group_txn(txn, context.state_group):
+                logger.info("Already persisted state_group: %r", context.state_group)
                 continue
 
             state_event_ids = dict(context.current_state_ids)
 
-            if event.is_state():
-                state_event_ids[(event.type, event.state_key)] = event.event_id
-
-            state_group = context.new_state_group_id
-
             self._simple_insert_txn(
                 txn,
                 table="state_groups",
                 values={
-                    "id": state_group,
+                    "id": context.state_group,
                     "room_id": event.room_id,
                     "event_id": event.event_id,
                 },
@@ -118,7 +123,7 @@ class StateStore(SQLBaseStore):
                 table="state_groups_state",
                 values=[
                     {
-                        "state_group": state_group,
+                        "state_group": context.state_group,
                         "room_id": event.room_id,
                         "type": key[0],
                         "state_key": key[1],
@@ -127,7 +132,6 @@ class StateStore(SQLBaseStore):
                     for key, state_id in state_event_ids.items()
                 ],
             )
-            state_groups[event.event_id] = state_group
 
         self._simple_insert_many_txn(
             txn,
@@ -527,5 +531,5 @@ class StateStore(SQLBaseStore):
             "get_all_new_state_groups", get_all_new_state_groups_txn
         )
 
-    def get_state_stream_token(self):
-        return self._state_groups_id_gen.get_current_token()
+    def get_next_state_group(self):
+        return self._state_groups_id_gen.get_next()
diff --git a/tests/replication/slave/storage/test_events.py b/tests/replication/slave/storage/test_events.py
index 218cb24889..44e859b5d1 100644
--- a/tests/replication/slave/storage/test_events.py
+++ b/tests/replication/slave/storage/test_events.py
@@ -312,7 +312,9 @@ class SlavedEventStoreTestCase(BaseSlavedStoreTestCase):
         else:
             state_ids = None
 
-        context = EventContext(current_state_ids=state_ids)
+        context = EventContext()
+        context.current_state_ids = state_ids
+        context.prev_state_ids = state_ids
         context.push_actions = push_actions
 
         ordering = None
diff --git a/tests/replication/test_resource.py b/tests/replication/test_resource.py
index e70ac6f14d..b69832cc1b 100644
--- a/tests/replication/test_resource.py
+++ b/tests/replication/test_resource.py
@@ -60,8 +60,8 @@ class ReplicationResourceCase(unittest.TestCase):
         self.assertEquals(body, {})
 
     @defer.inlineCallbacks
-    def test_events_and_state(self):
-        get = self.get(events="-1", state="-1", timeout="0")
+    def test_events(self):
+        get = self.get(events="-1", timeout="0")
         yield self.hs.get_handlers().room_creation_handler.create_room(
             synapse.types.create_requester(self.user), {}
         )
@@ -70,12 +70,6 @@ class ReplicationResourceCase(unittest.TestCase):
         self.assertEquals(body["events"]["field_names"], [
             "position", "internal", "json", "state_group"
         ])
-        self.assertEquals(body["state_groups"]["field_names"], [
-            "position", "room_id", "event_id"
-        ])
-        self.assertEquals(body["state_group_state"]["field_names"], [
-            "position", "type", "state_key", "event_id"
-        ])
 
     @defer.inlineCallbacks
     def test_presence(self):
diff --git a/tests/test_state.py b/tests/test_state.py
index de2d35145a..6454f994e3 100644
--- a/tests/test_state.py
+++ b/tests/test_state.py
@@ -86,17 +86,8 @@ class StateGroupStore(object):
 
         state_events = dict(context.current_state_ids)
 
-        if event.is_state():
-            state_events[(event.type, event.state_key)] = event.event_id
-
-        state_group = context.state_group
-        if not state_group:
-            state_group = self._next_group
-            self._next_group += 1
-
-            self._group_to_state[state_group] = state_events
-
-        self._event_to_state_group[event.event_id] = state_group
+        self._group_to_state[context.state_group] = state_events
+        self._event_to_state_group[event.event_id] = context.state_group
 
     def get_events(self, event_ids, **kwargs):
         return {
@@ -151,6 +142,7 @@ class StateTestCase(unittest.TestCase):
                 "get_state_groups_ids",
                 "add_event_hashes",
                 "get_events",
+                "get_next_state_group",
             ]
         )
         hs = Mock(spec_set=[
@@ -161,6 +153,8 @@ class StateTestCase(unittest.TestCase):
         hs.get_clock.return_value = MockClock()
         hs.get_auth.return_value = Auth(hs)
 
+        self.store.get_next_state_group.side_effect = Mock
+
         self.state = StateHandler(hs)
         self.event_id = 0
 
@@ -209,7 +203,7 @@ class StateTestCase(unittest.TestCase):
             store.store_state_groups(event, context)
             context_store[event.event_id] = context
 
-        self.assertEqual(2, len(context_store["D"].current_state_ids))
+        self.assertEqual(2, len(context_store["D"].prev_state_ids))
 
     @defer.inlineCallbacks
     def test_branch_basic_conflict(self):
@@ -265,7 +259,7 @@ class StateTestCase(unittest.TestCase):
 
         self.assertSetEqual(
             {"START", "A", "C"},
-            {e_id for e_id in context_store["D"].current_state_ids.values()}
+            {e_id for e_id in context_store["D"].prev_state_ids.values()}
         )
 
     @defer.inlineCallbacks
@@ -331,7 +325,7 @@ class StateTestCase(unittest.TestCase):
 
         self.assertSetEqual(
             {"START", "A", "B", "C"},
-            {e for e in context_store["E"].current_state_ids.values()}
+            {e for e in context_store["E"].prev_state_ids.values()}
         )
 
     @defer.inlineCallbacks
@@ -414,7 +408,7 @@ class StateTestCase(unittest.TestCase):
 
         self.assertSetEqual(
             {"A1", "A2", "A3", "A5", "B"},
-            {e for e in context_store["D"].current_state_ids.values()}
+            {e for e in context_store["D"].prev_state_ids.values()}
         )
 
     def _add_depths(self, nodes, edges):
@@ -447,7 +441,7 @@ class StateTestCase(unittest.TestCase):
             set(e.event_id for e in old_state), set(context.current_state_ids.values())
         )
 
-        self.assertIsNone(context.state_group)
+        self.assertIsNotNone(context.state_group)
 
     @defer.inlineCallbacks
     def test_annotate_with_old_state(self):
@@ -464,11 +458,9 @@ class StateTestCase(unittest.TestCase):
         )
 
         self.assertEqual(
-            set(e.event_id for e in old_state), set(context.current_state_ids.values())
+            set(e.event_id for e in old_state), set(context.prev_state_ids.values())
         )
 
-        self.assertIsNone(context.state_group)
-
     @defer.inlineCallbacks
     def test_trivial_annotate_message(self):
         event = create_event(type="test_message", name="event")
@@ -514,10 +506,10 @@ class StateTestCase(unittest.TestCase):
 
         self.assertEqual(
             set([e.event_id for e in old_state]),
-            set(context.current_state_ids.values())
+            set(context.prev_state_ids.values())
         )
 
-        self.assertIsNone(context.state_group)
+        self.assertIsNotNone(context.state_group)
 
     @defer.inlineCallbacks
     def test_resolve_message_conflict(self):
@@ -550,7 +542,7 @@ class StateTestCase(unittest.TestCase):
 
         self.assertEqual(len(context.current_state_ids), 6)
 
-        self.assertIsNone(context.state_group)
+        self.assertIsNotNone(context.state_group)
 
     @defer.inlineCallbacks
     def test_resolve_state_conflict(self):
@@ -583,7 +575,7 @@ class StateTestCase(unittest.TestCase):
 
         self.assertEqual(len(context.current_state_ids), 6)
 
-        self.assertIsNone(context.state_group)
+        self.assertIsNotNone(context.state_group)
 
     @defer.inlineCallbacks
     def test_standard_depth_conflict(self):