Cache requests for user's devices from federation (#15675)

This should mitigate the issue where lots of different servers requests
the same user's devices all at once.

1 files changed, 4 insertions, 0 deletions

diff --git a/synapse/storage/databases/main/devices.py b/synapse/storage/databases/main/devices.py

index a67fdb3c22..f677d048aa 100644
--- a/synapse/storage/databases/main/devices.py
+++ b/synapse/storage/databases/main/devices.py
@@ -1941,6 +1941,10 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
             user_id,
             stream_ids[-1],
         )
+        txn.call_after(
+            self._get_e2e_device_keys_for_federation_query_inner.invalidate,
+            (user_id,),
+        )
 
         min_stream_id = stream_ids[0]