Fix stuck invites

If rejecting a remote invite fails with an error response don't fail
the entire request; instead mark the invite as locally rejected.

This fixes the bug where users can get stuck invites which they can
neither accept nor reject.

2 files changed, 21 insertions, 1 deletions

diff --git a/synapse/storage/__init__.py b/synapse/storage/__init__.py

index 57863bba4d..07916b292d 100644
--- a/synapse/storage/__init__.py
+++ b/synapse/storage/__init__.py
@@ -94,7 +94,8 @@ class DataStore(RoomMemberStore, RoomStore,
         )
 
         self._stream_id_gen = StreamIdGenerator(
-            db_conn, "events", "stream_ordering"
+            db_conn, "events", "stream_ordering",
+            extra_tables=[("local_invites", "stream_id")]
         )
         self._backfill_id_gen = StreamIdGenerator(
             db_conn, "events", "stream_ordering", step=-1
diff --git a/synapse/storage/roommember.py b/synapse/storage/roommember.py

index 36456a75fc..66e7a40e3c 100644
--- a/synapse/storage/roommember.py
+++ b/synapse/storage/roommember.py
@@ -102,6 +102,25 @@ class RoomMemberStore(SQLBaseStore):
                         event.state_key,
                     ))
 
+    @defer.inlineCallbacks
+    def locally_reject_invite(self, user_id, room_id):
+        sql = (
+            "UPDATE local_invites SET stream_id = ?, locally_rejected = ? WHERE"
+            " room_id = ? AND invitee = ? AND locally_rejected is NULL"
+            " AND replaced_by is NULL"
+        )
+
+        def f(txn, stream_ordering):
+            txn.execute(sql, (
+                stream_ordering,
+                True,
+                room_id,
+                user_id,
+            ))
+
+        with self._stream_id_gen.get_next() as stream_ordering:
+            yield self.runInteraction("locally_reject_invite", f, stream_ordering)
+
     def get_room_member(self, user_id, room_id):
         """Retrieve the current state of a room member.