Add concept of StatelessEventContext

synapse/events/snapshot.py

@@ -13,22 +13,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from twisted.internet import defer
 
-from frozendict import frozendict
-
-
-class EventContext(object):
+class StatelessEventContext(object):
     """
     Attributes:
-        current_state_ids (dict[(str, str), str]):
-            The current state map including the current event.
-            (type, state_key) -> event_id
-
-        prev_state_ids (dict[(str, str), str]):
-            The current state map excluding the current event.
-            (type, state_key) -> event_id
-
         state_group (int|None): state group id, if the state has been stored
             as a state group. This is usually only None if e.g. the event is
             an outlier.
@@ -40,76 +28,48 @@ class EventContext(object):
 
         prev_group (int): Previously persisted state group. ``None`` for an
             outlier.
-        delta_ids (dict[(str, str), str]): Delta from ``prev_group``.
-            (type, state_key) -> event_id. ``None`` for an outlier.
 
         prev_state_events (?): XXX: is this ever set to anything other than
             the empty list?
     """
 
     __slots__ = [
-        "current_state_ids",
-        "prev_state_ids",
         "state_group",
         "rejected",
         "prev_group",
-        "delta_ids",
         "prev_state_events",
         "app_service",
     ]
 
     def __init__(self):
-        # The current state including the current event
-        self.current_state_ids = None
-        # The current state excluding the current event
-        self.prev_state_ids = None
         self.state_group = None
 
         self.rejected = False
 
         # A previously persisted state group and a delta between that
         # and this state.
         self.prev_group = None
-        self.delta_ids = None
 
         self.prev_state_events = None
 
         self.app_service = None
 
-    def serialize(self, event):
+    def serialize(self):
         """Converts self to a type that can be serialized as JSON, and then
         deserialized by `deserialize`
 
-        Args:
-            event (FrozenEvent): The event that this context relates to
-
         Returns:
             dict
         """
-
-        # We don't serialize the full state dicts, instead they get pulled out
-        # of the DB on the other side. However, the other side can't figure out
-        # the prev_state_ids, so if we're a state event we include the event
-        # id that we replaced in the state.
-        if event.is_state():
-            prev_state_id = self.prev_state_ids.get((event.type, event.state_key))
-        else:
-            prev_state_id = None
-
         return {
-            "prev_state_id": prev_state_id,
-            "event_type": event.type,
-            "event_state_key": event.state_key if event.is_state() else None,
             "state_group": self.state_group,
             "rejected": self.rejected,
             "prev_group": self.prev_group,
-            "delta_ids": _encode_state_dict(self.delta_ids),
             "prev_state_events": self.prev_state_events,
             "app_service_id": self.app_service.id if self.app_service else None
         }
 
     @staticmethod
-    @defer.inlineCallbacks
     def deserialize(store, input):
         """Converts a dict that was produced by `serialize` back into a
         EventContext.
@@ -121,52 +81,47 @@ def deserialize(store, input):
         Returns:
             EventContext
         """
-        context = EventContext()
+        context = StatelessEventContext()
         context.state_group = input["state_group"]
         context.rejected = input["rejected"]
         context.prev_group = input["prev_group"]
-        context.delta_ids = _decode_state_dict(input["delta_ids"])
         context.prev_state_events = input["prev_state_events"]
 
-        # We use the state_group and prev_state_id stuff to pull the
-        # current_state_ids out of the DB and construct prev_state_ids.
-        prev_state_id = input["prev_state_id"]
-        event_type = input["event_type"]
-        event_state_key = input["event_state_key"]
-
-        context.current_state_ids = yield store.get_state_ids_for_group(
-            context.state_group,
-        )
-        if prev_state_id and event_state_key:
-            context.prev_state_ids = dict(context.current_state_ids)
-            context.prev_state_ids[(event_type, event_state_key)] = prev_state_id
-        else:
-            context.prev_state_ids = context.current_state_ids
-
         app_service_id = input["app_service_id"]
         if app_service_id:
             context.app_service = store.get_app_service_by_id(app_service_id)
 
-        defer.returnValue(context)
+        return context
 
 
-def _encode_state_dict(state_dict):
-    """Since dicts of (type, state_key) -> event_id cannot be serialized in
-    JSON we need to convert them to a form that can.
+class EventContext(StatelessEventContext):
     """
-    if state_dict is None:
-        return None
+    Attributes:
+        current_state_ids (dict[(str, str), str]):
+            The current state map including the current event.
+            (type, state_key) -> event_id
 
-    return [
-        (etype, state_key, v)
-        for (etype, state_key), v in state_dict.iteritems()
-    ]
+        prev_state_ids (dict[(str, str), str]):
+            The current state map excluding the current event.
+            (type, state_key) -> event_id
 
+        delta_ids (dict[(str, str), str]): Delta from ``prev_group``.
+            (type, state_key) -> event_id. ``None`` for an outlier.
 
-def _decode_state_dict(input):
-    """Decodes a state dict encoded using `_encode_state_dict` above
     """
-    if input is None:
-        return None
 
-    return frozendict({(etype, state_key,): v for etype, state_key, v in input})
+    __slots__ = [
+        "current_state_ids",
+        "prev_state_ids",
+        "delta_ids",
+    ]
+
+    def __init__(self):
+        # The current state including the current event
+        self.current_state_ids = None
+        # The current state excluding the current event
+        self.prev_state_ids = None
+
+        self.delta_ids = None
+
+        super(EventContext, self).__init__()

synapse/handlers/message.py

@@ -20,6 +20,7 @@
 from synapse.api.errors import AuthError, Codes, SynapseError
 from synapse.crypto.event_signing import add_hashes_and_signatures
 from synapse.events.utils import serialize_event
+from synapse.events.snapshot import EventContext
 from synapse.events.validator import EventValidator
 from synapse.types import (
     UserID, RoomAlias, RoomStreamToken,
@@ -665,7 +666,7 @@ def handle_new_client_event(
         Args:
             requester (Requester)
             event (FrozenEvent)
-            context (EventContext)
+            context (StatelessEventContext)
             ratelimit (bool)
             extra_users (list(UserID)): Any extra users to notify about event
         """
@@ -763,9 +764,18 @@ def is_inviter_member_event(e):
                         e.sender == event.sender
                     )
 
+                # We get the current state at the event. If we have a full
+                # EventContext, use it, otherwise we hit the DB.
+                if isinstance(context, EventContext):
+                    current_state_ids = context.current_state_ids
+                else:
+                    current_state_ids = yield self.store.get_state_ids_for_group(
+                        context.state_group,
+                    )
+
                 state_to_include_ids = [
                     e_id
-                    for k, e_id in context.current_state_ids.iteritems()
+                    for k, e_id in current_state_ids.iteritems()
                     if k[0] in self.hs.config.room_invite_state_types
                     or k == (EventTypes.Member, event.sender)
                 ]

synapse/replication/http/send_event.py

@@ -19,7 +19,7 @@
     SynapseError, MatrixCodeMessageException, CodeMessageException,
 )
 from synapse.events import FrozenEvent
-from synapse.events.snapshot import EventContext
+from synapse.events.snapshot import StatelessEventContext
 from synapse.http.servlet import RestServlet, parse_json_object_from_request
 from synapse.util.async import sleep
 from synapse.util.caches.response_cache import ResponseCache
@@ -44,7 +44,7 @@ def send_event_to_master(client, host, port, requester, event, context,
         port (int): port on master listening for HTTP replication
         requester (Requester)
         event (FrozenEvent)
-        context (EventContext)
+        context (StatelessEventContext)
         ratelimit (bool)
         extra_users (list(UserID)): Any extra users to notify about event
     """
@@ -56,7 +56,7 @@ def send_event_to_master(client, host, port, requester, event, context,
         "event": event.get_pdu_json(),
         "internal_metadata": event.internal_metadata.get_dict(),
         "rejected_reason": event.rejected_reason,
-        "context": context.serialize(event),
+        "context": context.serialize(),
         "requester": requester.serialize(),
         "ratelimit": ratelimit,
         "extra_users": [u.to_string() for u in extra_users],
@@ -140,7 +140,9 @@ def _handle_request(self, request):
             event = FrozenEvent(event_dict, internal_metadata, rejected_reason)
 
             requester = Requester.deserialize(self.store, content["requester"])
-            context = yield EventContext.deserialize(self.store, content["context"])
+            context = yield StatelessEventContext.deserialize(
+                self.store, content["context"],
+            )
 
             ratelimit = content["ratelimit"]
             extra_users = [UserID.from_string(u) for u in content["extra_users"]]

synapse/storage/events.py

@@ -19,6 +19,7 @@
 from twisted.internet import defer
 
 from synapse.events import USE_FROZEN_DICTS
+from synapse.events.snapshot import EventContext
 
 from synapse.util.async import ObservableDeferred
 from synapse.util.logcontext import (
@@ -42,7 +43,6 @@
 
 # these are only included to make the type annotations work
 from synapse.events import EventBase    # noqa: F401
-from synapse.events.snapshot import EventContext   # noqa: F401
 
 logger = logging.getLogger(__name__)
 
@@ -504,61 +504,68 @@ def _get_new_state_after_events(self, room_id, events_context, new_latest_event_
             defer.returnValue({})
 
         # map from state_group to ((type, key) -> event_id) state map
-        state_groups = {}
-        missing_event_ids = []
-        was_updated = False
+        state_groups_map = {}
+        for ev, ctx in events_context:
+            if ctx.state_group is None:
+                # I don't think this can happen, but let's double-check
+                raise Exception(
+                    "Context for new extremity event %s has no state "
+                    "group" % (ev.event_id, ),
+                )
+
+            if ctx.state_group in state_groups_map:
+                continue
+
+            if isinstance(ctx, EventContext) and ctx.current_state_ids:
+                state_groups_map[ctx.state_group] = ctx.current_state_ids
+
+        # We need to map new_latest_event_ids to their state groups. First, lets
+        # check if the event is one we're persisting and then we can pull the
+        # state group from its context.
+        # Otherwise we need to pull the state group from the database.
+        missing_event_ids = []  # List of events we need to fetch groups for
+        state_groups_to_resolve = set()  # State groups of new_latest_event_ids
         for event_id in new_latest_event_ids:
-            # First search in the list of new events we're adding,
-            # and then use the current state from that
+            # First search in the list of new events we're adding.
             for ev, ctx in events_context:
                 if event_id == ev.event_id:
-                    if ctx.current_state_ids is None:
-                        raise Exception("Unknown current state")
-
-                    if ctx.state_group is None:
-                        # I don't think this can happen, but let's double-check
-                        raise Exception(
-                            "Context for new extremity event %s has no state "
-                            "group" % (event_id, ),
-                        )
-
-                    # If we've already seen the state group don't bother adding
-                    # it to the state sets again
-                    if ctx.state_group not in state_groups:
-                        state_groups[ctx.state_group] = ctx.current_state_ids
-                        if ctx.delta_ids or hasattr(ev, "state_key"):
-                            was_updated = True
+                    state_groups_to_resolve.add(ctx.state_group)
                     break
             else:
                 # If we couldn't find it, then we'll need to pull
                 # the state from the database
-                was_updated = True
                 missing_event_ids.append(event_id)
 
-        if not was_updated:
-            return
-
         if missing_event_ids:
             # Now pull out the state for any missing events from DB
             event_to_groups = yield self._get_state_group_for_events(
                 missing_event_ids,
             )
+            state_groups_to_resolve.update(event_to_groups.itervalues())
 
-            groups = set(event_to_groups.itervalues()) - set(state_groups.iterkeys())
-
-            if groups:
-                group_to_state = yield self._get_state_for_groups(groups)
-                state_groups.update(group_to_state)
+        # Now that we have calculated state_groups_to_resolve we need to get
+        # their state so we can resolve to a single state set.
+        missing_state = state_groups_to_resolve - set(state_groups_map)
+        if missing_state:
+            group_to_state = yield self._get_state_for_groups(missing_state)
+            state_groups_map.update(group_to_state)
 
-        if len(state_groups) == 1:
+        if len(state_groups_to_resolve) == 1:
             # If there is only one state group, then we know what the current
             # state is.
-            defer.returnValue(state_groups.values()[0])
+            defer.returnValue(state_groups_map[state_groups_to_resolve.pop()])
+
+        # Ok, we need to defer to the state handler to resolve our state sets.
 
         def get_events(ev_ids):
             return self.get_events(
                 ev_ids, get_prev_content=False, check_redacted=False,
             )
+
+        state_groups = {
+            sg: state_groups_map[sg] for sg in state_groups_to_resolve
+        }
+
         events_map = {ev.event_id: ev for ev, _ in events_context}
         logger.debug("calling resolve_state_groups from preserve_events")
         res = yield self._state_resolution_handler.resolve_state_groups(