add service config json interop flag

interop/client/client.go

@@ -54,6 +54,7 @@ var (
 	defaultServiceAccount = flag.String("default_service_account", "", "Email of GCE default service account")
 	serverHost            = flag.String("server_host", "127.0.0.1", "The server host name")
 	serverPort            = flag.Int("server_port", 10000, "The server port number")
+	serviceConfigJson     = flag.String("service_config_json", "", "Disables service config lookups and sets the provided string as the default service config.")
 	tlsServerName         = flag.String("server_host_override", "", "The server name use to verify the hostname returned by TLS handshake if it is not empty. Otherwise, --server_host is used.")
 	testCase              = flag.String("test_case", "large_unary",
 		`Configure different test cases. Valid options are:
@@ -120,6 +121,10 @@ func main() {
 	} else {
 		opts = append(opts, grpc.WithInsecure())
 	}
+	if len(*serviceConfigJson) > 0 {
+		opts = append(opts, grpc.WithDisableServiceConfig())
+		opts = append(opts, grpc.WithDefaultServiceConfig(*serviceConfigJson))
+	}
 	conn, err := grpc.Dial(serverAddr, opts...)
 	if err != nil {
 		grpclog.Fatalf("Fail to dial: %v", err)