Fix message duplication if something goes wrong after persisting the event (#8476)

Should fix #3365.

1 files changed, 5 insertions, 1 deletions

diff --git a/synapse/storage/databases/main/registration.py b/synapse/storage/databases/main/registration.py
index 236d3cdbe3..9a003e30f9 100644
--- a/synapse/storage/databases/main/registration.py
+++ b/synapse/storage/databases/main/registration.py
@@ -1003,7 +1003,7 @@ class RegistrationStore(RegistrationBackgroundUpdateStore):
         token: str,
         device_id: Optional[str],
         valid_until_ms: Optional[int],
-    ) -> None:
+    ) -> int:
         """Adds an access token for the given user.
 
         Args:
@@ -1013,6 +1013,8 @@ class RegistrationStore(RegistrationBackgroundUpdateStore):
             valid_until_ms: when the token is valid until. None for no expiry.
         Raises:
             StoreError if there was a problem adding this.
+        Returns:
+            The token ID
         """
         next_id = self._access_tokens_id_gen.get_next()
 
@@ -1028,6 +1030,8 @@ class RegistrationStore(RegistrationBackgroundUpdateStore):
             desc="add_access_token_to_user",
         )
 
+        return next_id
+
     def _set_device_for_access_token_txn(self, txn, token: str, device_id: str) -> str:
         old_device_id = self.db_pool.simple_select_one_onecol_txn(
             txn, "access_tokens", {"token": token}, "device_id"