Merge 0e0ddda877 into b09d90cac9

scripts-dev/complement.sh

@@ -65,4 +65,4 @@ if [[ -n "$1" ]]; then
 fi
 
 # Run the tests!
-go test -v -tags synapse_blacklist,msc2946,msc3083,msc2403,msc2716 -count=1 "${EXTRA_COMPLEMENT_ARGS[@]}" ./tests/...
+go test -v -tags synapse_blacklist,msc2946,msc3083,msc2403,msc2716,msc3030 -count=1 "${EXTRA_COMPLEMENT_ARGS[@]}" ./tests/...

synapse/rest/client/room.py

@@ -1070,6 +1070,32 @@ def register_txn_path(
         )
 
 
+class TimestampLookupRestServlet(RestServlet):
+    PATTERNS = client_patterns("/rooms/(?P<room_id>[^/]*)/timestamp_to_event$")
+
+    def __init__(self, hs: "HomeServer"):
+        super().__init__()
+        self._auth = hs.get_auth()
+        self._store = hs.get_datastore()
+
+    async def on_GET(
+        self, request: SynapseRequest, room_id: str
+    ) -> Tuple[int, JsonDict]:
+        requester = await self._auth.get_user_by_req(request)
+        await self._auth.check_user_in_room(room_id, requester.user.to_string())
+
+        timestamp = parse_integer(request, "ts")
+
+        event_id = await self._store.get_event_for_timestamp(
+            room_id,
+            timestamp,
+        )
+
+        return 200, {
+            "event_id": event_id,
+        }
+
+
 class RoomSpaceSummaryRestServlet(RestServlet):
     PATTERNS = (
         re.compile(
@@ -1239,6 +1265,7 @@ def register_servlets(
     RoomAliasListServlet(hs).register(http_server)
     SearchRestServlet(hs).register(http_server)
     RoomCreateRestServlet(hs).register(http_server)
+    TimestampLookupRestServlet(hs).register(http_server)
 
     # Some servlets only get registered for the main process.
     if not is_worker:

synapse/storage/databases/main/events_worker.py

@@ -1626,3 +1626,45 @@ class EventsWorkerStore(SQLBaseStore):
             "_cleanup_old_transaction_ids",
             _cleanup_old_transaction_ids_txn,
         )
+
+    async def get_event_for_timestamp(self, room_id, timestamp):
+        sql_template = """
+            SELECT event_id, origin_server_ts FROM events
+            WHERE
+                origin_server_ts %s ?
+                AND room_id = ?
+            ORDER BY origin_server_ts
+            LIMIT 1;
+        """
+
+        def get_event_for_timestamp_txn(txn):
+            txn.execute(sql_template % ("<=",), (timestamp, room_id))
+            row = txn.fetchone()
+            if row:
+                event_id_before, ts_before = row
+            else:
+                event_id_before, ts_before = None, None
+
+            txn.execute(sql_template % (">=",), (timestamp, room_id))
+            row = txn.fetchone()
+            if row:
+                event_id_after, ts_after = row
+            else:
+                event_id_after, ts_after = None, None
+
+            if event_id_before and event_id_after:
+                # Return the closest
+                if (timestamp - ts_before) < (ts_after - timestamp):
+                    return event_id_before
+                else:
+                    return event_id_after
+
+            if event_id_before:
+                return event_id_before
+
+            return event_id_after
+
+        return await self.db_pool.runInteraction(
+            "get_event_for_timestamp_txn",
+            get_event_for_timestamp_txn,
+        )