Implement the SHHS complexity API (#5216)

synapse/storage/events_worker.py

@@ -13,6 +13,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from __future__ import division
+
 import itertools
 import logging
 from collections import namedtuple
@@ -614,7 +616,7 @@ class EventsWorkerStore(SQLBaseStore):
 
     def _get_total_state_event_counts_txn(self, txn, room_id):
         """
-        See get_state_event_counts.
+        See get_total_state_event_counts.
         """
         sql = "SELECT COUNT(*) FROM state_events WHERE room_id=?"
         txn.execute(sql, (room_id,))
@@ -635,3 +637,49 @@ class EventsWorkerStore(SQLBaseStore):
             "get_total_state_event_counts",
             self._get_total_state_event_counts_txn, room_id
         )
+
+    def _get_current_state_event_counts_txn(self, txn, room_id):
+        """
+        See get_current_state_event_counts.
+        """
+        sql = "SELECT COUNT(*) FROM current_state_events WHERE room_id=?"
+        txn.execute(sql, (room_id,))
+        row = txn.fetchone()
+        return row[0] if row else 0
+
+    def get_current_state_event_counts(self, room_id):
+        """
+        Gets the current number of state events in a room.
+
+        Args:
+            room_id (str)
+
+        Returns:
+            Deferred[int]
+        """
+        return self.runInteraction(
+            "get_current_state_event_counts",
+            self._get_current_state_event_counts_txn, room_id
+        )
+
+    @defer.inlineCallbacks
+    def get_room_complexity(self, room_id):
+        """
+        Get a rough approximation of the complexity of the room. This is used by
+        remote servers to decide whether they wish to join the room or not.
+        Higher complexity value indicates that being in the room will consume
+        more resources.
+
+        Args:
+            room_id (str)
+
+        Returns:
+            Deferred[dict[str:int]] of complexity version to complexity.
+        """
+        state_events = yield self.get_current_state_event_counts(room_id)
+
+        # Call this one "v1", so we can introduce new ones as we want to develop
+        # it.
+        complexity_v1 = round(state_events / 500, 2)
+
+        defer.returnValue({"v1": complexity_v1})