add a new flag for Spanner tests

PiperOrigin-RevId: 829592447

Author: ScottLinnn

perfkitbenchmarker/providers/gcp/gcp_spanner.py

@@ -576,6 +576,8 @@ def GetResourceMetadata(self) -> Dict[Any, Any]:
       })
     else:
       metadata['gcp_spanner_node_count'] = self.nodes
+    if _MAX_COMMIT_DELAY.value:
+      metadata['gcp_spanner_max_commit_delay'] = _MAX_COMMIT_DELAY.value
     return metadata
 
   def GetAverageCpuUsage(

perfkitbenchmarker/sql_engine_utils.py

@@ -378,8 +378,15 @@ def Connect(
       sessions_arg = (
           f'-r "minSessions={sessions};'
           f'maxSessions={_PGADAPTER_MAX_SESSIONS};'
-          f'numChannels={int(_PGADAPTER_MAX_SESSIONS/100)}"'
+          f'numChannels={int(_PGADAPTER_MAX_SESSIONS/100)}'
       )
+      if FLAGS.cloud_spanner_max_commit_delay is not None:
+        sessions_arg = (
+            sessions_arg
+            + f';maxCommitDelay={FLAGS.cloud_spanner_max_commit_delay}'
+        )
+      sessions_arg = sessions_arg + '"'
+
     properties = self.connection_properties
     database_name = database_name or properties.database_name
     command = (