[test] Allow set request/response size in interop soak test

test/cpp/interop/observability_client.cc

@@ -116,6 +116,14 @@ ABSL_FLAG(int32_t, soak_overall_timeout_seconds, 0,
 ABSL_FLAG(int32_t, soak_min_time_ms_between_rpcs, 0,
           "The minimum time in milliseconds between consecutive RPCs in a "
           "soak test (rpc_soak or channel_soak), useful for limiting QPS");
+ABSL_FLAG(
+    int32_t, soak_request_size, 271828,
+    "The request size in a soak RPC. "
+    "The default value is set based on the interop large unary test case.");
+ABSL_FLAG(
+    int32_t, soak_response_size, 314159,
+    "The response size in a soak RPC. "
+    "The default value is set based on the interop large unary test case.");
 ABSL_FLAG(int32_t, iteration_interval, 10,
           "The interval in seconds between rpcs. This is used by "
           "long_connection test");
@@ -319,14 +327,18 @@ int main(int argc, char** argv) {
       absl::GetFlag(FLAGS_soak_max_failures),
       absl::GetFlag(FLAGS_soak_per_iteration_max_acceptable_latency_ms),
       absl::GetFlag(FLAGS_soak_min_time_ms_between_rpcs),
-      absl::GetFlag(FLAGS_soak_overall_timeout_seconds));
+      absl::GetFlag(FLAGS_soak_overall_timeout_seconds),
+      absl::GetFlag(FLAGS_soak_request_size),
+      absl::GetFlag(FLAGS_soak_response_size));
   actions["rpc_soak"] = std::bind(
       &grpc::testing::InteropClient::DoRpcSoakTest, &client,
       absl::GetFlag(FLAGS_server_host), absl::GetFlag(FLAGS_soak_iterations),
       absl::GetFlag(FLAGS_soak_max_failures),
       absl::GetFlag(FLAGS_soak_per_iteration_max_acceptable_latency_ms),
       absl::GetFlag(FLAGS_soak_min_time_ms_between_rpcs),
-      absl::GetFlag(FLAGS_soak_overall_timeout_seconds));
+      absl::GetFlag(FLAGS_soak_overall_timeout_seconds),
+      absl::GetFlag(FLAGS_soak_request_size),
+      absl::GetFlag(FLAGS_soak_response_size));
   actions["long_lived_channel"] =
       std::bind(&grpc::testing::InteropClient::DoLongLivedChannelTest, &client,
                 absl::GetFlag(FLAGS_soak_iterations),