Move outlier out of InternalMetadata._dict

Ultimately, this will allow us to stop writing it to the database. For now, we
have to grandfather it back in so as to maintain compatibility with older
versions of Synapse.

synapse/events/__init__.py

@@ -98,7 +98,7 @@ def __get__(self, instance, owner=None):
 
 
 class _EventInternalMetadata:
-    __slots__ = ["_dict", "stream_ordering"]
+    __slots__ = ["_dict", "stream_ordering", "outlier"]
 
     def __init__(self, internal_metadata_dict: JsonDict):
         # we have to copy the dict, because it turns out that the same dict is
@@ -108,7 +108,10 @@ def __init__(self, internal_metadata_dict: JsonDict):
         # the stream ordering of this event. None, until it has been persisted.
         self.stream_ordering = None  # type: Optional[int]
 
-    outlier = DictProperty("outlier")  # type: bool
+        # whether this event is an outlier (ie, whether we have the state at that point
+        # in the DAG)
+        self.outlier = False
+
     out_of_band_membership = DictProperty("out_of_band_membership")  # type: bool
     send_on_behalf_of = DictProperty("send_on_behalf_of")  # type: str
     recheck_redaction = DictProperty("recheck_redaction")  # type: bool
@@ -129,7 +132,7 @@ def get_dict(self) -> JsonDict:
         return dict(self._dict)
 
     def is_outlier(self) -> bool:
-        return self._dict.get("outlier", False)
+        return self.outlier
 
     def is_out_of_band_membership(self) -> bool:
         """Whether this is an out of band membership, like an invite or an invite

synapse/events/utils.py

@@ -54,6 +54,8 @@ def prune_event(event: EventBase) -> EventBase:
         event.internal_metadata.stream_ordering
     )
 
+    pruned_event.internal_metadata.outlier = event.internal_metadata.outlier
+
     # Mark the event as redacted
     pruned_event.internal_metadata.redacted = True
 

synapse/replication/http/federation.py

@@ -40,6 +40,7 @@ class ReplicationFederationSendEventsRestServlet(ReplicationEndpoint):
                                     // containing the event
                 "event_format_version": .., // 1,2,3 etc: the event format version
                 "internal_metadata": { .. serialized internal_metadata .. },
+                "outlier": true|false,
                 "rejected_reason": ..,   // The event.rejected_reason field
                 "context": { .. serialized event context .. },
             }],
@@ -84,6 +85,7 @@ async def _serialize_payload(store, room_id, event_and_contexts, backfilled):
                     "room_version": event.room_version.identifier,
                     "event_format_version": event.format_version,
                     "internal_metadata": event.internal_metadata.get_dict(),
+                    "outlier": event.internal_metadata.is_outlier(),
                     "rejected_reason": event.rejected_reason,
                     "context": serialized_context,
                 }
@@ -116,6 +118,7 @@ async def _handle_request(self, request):
                 event = make_event_from_dict(
                     event_dict, room_ver, internal_metadata, rejected_reason
                 )
+                event.internal_metadata.outlier = event_payload["outlier"]
 
                 context = EventContext.deserialize(
                     self.storage, event_payload["context"]

synapse/replication/http/send_event.py

@@ -80,6 +80,10 @@ async def _serialize_payload(
             extra_users (list(UserID)): Any extra users to notify about event
         """
 
+        # we only expect this interface to be used for local events, so they shouldn't
+        # be outliers.
+        assert not event.internal_metadata.is_outlier()
+
         serialized_context = await context.serialize(event, store)
 
         payload = {

synapse/storage/databases/main/events.py

@@ -1270,8 +1270,10 @@ def _update_outliers_txn(self, txn, events_and_contexts):
                     logger.exception("")
                     raise
 
+                # update the stored internal_metadata to update the "outlier" flag.
+                # TODO: This is unused as of Synapse 1.30. Remove it once we are happy
+                #  to drop backwards-compatibility with 1.29.
                 metadata_json = json_encoder.encode(event.internal_metadata.get_dict())
-
                 sql = "UPDATE event_json SET internal_metadata = ? WHERE event_id = ?"
                 txn.execute(sql, (metadata_json, event.event_id))
 
@@ -1319,6 +1321,19 @@ def event_dict(event):
             d.pop("redacted_because", None)
             return d
 
+        def get_internal_metadata(event):
+            im = event.internal_metadata.get_dict()
+
+            # temporary hack for database compatibility with Synapse 1.29 and earlier:
+            # store the `outlier` flag inside the internal_metadata json as well as in
+            # the `events` table, so that if anyone rolls back to an older Synapse,
+            # things keep working. This can be removed once we are happy to drop support
+            # for that
+            if event.internal_metadata.is_outlier():
+                im["outlier"] = True
+
+            return im
+
         self.db_pool.simple_insert_many_txn(
             txn,
             table="event_json",
@@ -1327,7 +1342,7 @@ def event_dict(event):
                     "event_id": event.event_id,
                     "room_id": event.room_id,
                     "internal_metadata": json_encoder.encode(
-                        event.internal_metadata.get_dict()
+                        get_internal_metadata(event)
                     ),
                     "json": json_encoder.encode(event_dict(event)),
                     "format_version": event.format_version,