LoggingTransaction accepts None for callback lists.

Its a bit disingenuousto give LoggingTransaction lists to append
callbacks to if we're not going to run the callbacks.

synapse/storage/_base.py

@@ -86,7 +86,21 @@ _CURRENT_STATE_CACHE_NAME = "cs_cache_fake"
 class LoggingTransaction(object):
     """An object that almost-transparently proxies for the 'txn' object
     passed to the constructor. Adds logging and metrics to the .execute()
-    method."""
+    method.
+
+    Args:
+        txn: The database transcation object to wrap.
+        name (str): The name of this transactions for logging.
+        database_engine (Sqlite3Engine|PostgresEngine)
+        after_callbacks(list|None): A list that callbacks will be appended to
+            that have been added by `call_after` which should be run on
+            successful completion of the transaction. None indicates that no
+            callbacks should be allowed to be scheduled to run.
+        exception_callbacks(list|None): A list that callbacks will be appended
+            to that have been added by `call_on_exception` which should be run
+            if transaction ends with an error. None indicates that no callbacks
+            should be allowed to be scheduled to run.
+    """
 
     __slots__ = [
         "txn",
@@ -97,7 +111,7 @@ class LoggingTransaction(object):
     ]
 
     def __init__(
-        self, txn, name, database_engine, after_callbacks, exception_callbacks
+        self, txn, name, database_engine, after_callbacks=None, exception_callbacks=None
     ):
         object.__setattr__(self, "txn", txn)
         object.__setattr__(self, "name", name)

synapse/storage/event_push_actions.py

@@ -79,8 +79,6 @@ class EventPushActionsWorkerStore(SQLBaseStore):
             db_conn.cursor(),
             name="_find_stream_orderings_for_times_txn",
             database_engine=self.database_engine,
-            after_callbacks=[],
-            exception_callbacks=[],
         )
         self._find_stream_orderings_for_times_txn(cur)
         cur.close()

synapse/storage/roommember.py

@@ -70,8 +70,6 @@ class RoomMemberWorkerStore(EventsWorkerStore):
             db_conn.cursor(),
             name="_check_safe_current_state_events_membership_updated",
             database_engine=self.database_engine,
-            after_callbacks=[],
-            exception_callbacks=[],
         )
         self._check_safe_current_state_events_membership_updated_txn(txn)
         txn.close()