address review comments for #27622 (#27659)

test/cpp/qps/json_run_localhost_scenario_gen.py

@@ -17,7 +17,7 @@
 import os
 import sys
 
-script_dir = os.path.dirname(sys.argv[0])
+script_dir = os.path.dirname(os.path.abspath(__file__))
 sys.path.append(script_dir)
 
 import scenario_generator_helper as gen

test/cpp/qps/qps_json_driver_scenario_gen.py

@@ -17,7 +17,7 @@
 import os
 import sys
 
-script_dir = os.path.dirname(sys.argv[0])
+script_dir = os.path.dirname(os.path.abspath(__file__))
 sys.path.append(script_dir)
 
 import scenario_generator_helper as gen

test/cpp/qps/scenario_generator_helper.py

@@ -45,6 +45,7 @@ _COPYRIGHT = """# Copyright 2021 The gRPC Authors
 
 
 def _mutate_scenario(scenario_json):
+    """Modifies vanilla benchmark scenario config to make it more suitable for running as a unit test."""
     # tweak parameters to get fast test times
     scenario_json = dict(scenario_json)
     scenario_json['warmup_seconds'] = 0
@@ -53,11 +54,11 @@ def _mutate_scenario(scenario_json):
     if scenario_json['client_config'][
             'client_type'] == 'SYNC_CLIENT' or scenario_json['server_config'][
                 'server_type'] == 'SYNC_SERVER':
+        # reduce the number of threads needed for scenarios that use synchronous API
         outstanding_rpcs_divisor = 10
     scenario_json['client_config']['outstanding_rpcs_per_channel'] = max(
-        1,
-        int(scenario_json['client_config']['outstanding_rpcs_per_channel'] /
-            outstanding_rpcs_divisor))
+        1, scenario_json['client_config']['outstanding_rpcs_per_channel'] //
+        outstanding_rpcs_divisor)
     return scenario_config.remove_nonproto_fields(scenario_json)