2 files changed, 30 insertions, 7 deletions
diff --git a/synapse/rest/admin/federation.py b/synapse/rest/admin/federation.py
index 50d88c9109..8cd3fa189e 100644
--- a/synapse/rest/admin/federation.py
+++ b/synapse/rest/admin/federation.py
@@ -111,25 +111,37 @@ class DestinationsRestServlet(RestServlet):
     ) -> Tuple[int, JsonDict]:
         await assert_requester_is_admin(self._auth, request)
 
+        if not await self._store.is_destination_known(destination):
+            raise NotFoundError("Unknown destination")
+
         destination_retry_timings = await self._store.get_destination_retry_timings(
             destination
         )
 
-        if not destination_retry_timings:
-            raise NotFoundError("Unknown destination")
-
         last_successful_stream_ordering = (
             await self._store.get_destination_last_successful_stream_ordering(
                 destination
             )
         )
 
-        response = {
+        response: JsonDict = {
             "destination": destination,
-            "failure_ts": destination_retry_timings.failure_ts,
-            "retry_last_ts": destination_retry_timings.retry_last_ts,
-            "retry_interval": destination_retry_timings.retry_interval,
             "last_successful_stream_ordering": last_successful_stream_ordering,
         }
 
+        if destination_retry_timings:
+            response = {
+                **response,
+                "failure_ts": destination_retry_timings.failure_ts,
+                "retry_last_ts": destination_retry_timings.retry_last_ts,
+                "retry_interval": destination_retry_timings.retry_interval,
+            }
+        else:
+            response = {
+                **response,
+                "failure_ts": None,
+                "retry_last_ts": 0,
+                "retry_interval": 0,
+            }
+
         return HTTPStatus.OK, response
diff --git a/synapse/storage/databases/main/transactions.py b/synapse/storage/databases/main/transactions.py
index 6c299cafa5..4b78b4d098 100644
--- a/synapse/storage/databases/main/transactions.py
+++ b/synapse/storage/databases/main/transactions.py
@@ -560,3 +560,14 @@ class TransactionWorkerStore(CacheInvalidationWorkerStore):
         return await self.db_pool.runInteraction(
             "get_destinations_paginate_txn", get_destinations_paginate_txn
         )
+
+    async def is_destination_known(self, destination: str) -> bool:
+        """Check if a destination is known to the server."""
+        result = await self.db_pool.simple_select_one_onecol(
+            table="destinations",
+            keyvalues={"destination": destination},
+            retcol="1",
+            allow_none=True,
+            desc="is_destination_known",
+        )
+        return bool(result)