many Marshaler instances promote to old gen

[huange7]

Now, TraceRequestMarshaler is added to a Future/Callback when exporting traces.

However, in web services, Young GC occurs very frequently. As a result, many TraceRequestMarshaler objects are likely to be promoted to the Old Generation. This leads to a large number of TraceRequestMarshaler objects that won't be collected in Young GC, causing the Old Generation to store unnecessary objects.

Is it necessary to set the ResourceSpansMarshalers in the request to null after sending the trace is complete to assist the program in better GC?

We make the following changes in the exporter:

  public void send(T request, Runnable onSuccess, BiConsumer<GrpcResponse, Throwable> onError) {
    MarshalerServiceStub<T, ?, ?> stub = this.stub;
    if (timeoutNanos > 0) {
      stub = stub.withDeadlineAfter(timeoutNanos, TimeUnit.NANOSECONDS);
    }
    Futures.addCallback(
        stub.export(request),
        new FutureCallback<Object>() {
          @Override
          public void onSuccess(@Nullable Object unused) {
            // set null 
            request.clear();
            onSuccess.run();
          }

          @Override
          public void onFailure(Throwable t) {
            request.clear();
            Status status = Status.fromThrowable(t);
            onError.accept(
                GrpcResponse.create(status.getCode().value(), status.getDescription()), t);
          }
        },
        MoreExecutors.directExecutor());
  }

add clear method to Marshaler

public final class TraceRequestMarshaler extends MarshalerWithSize {

  private ResourceSpansMarshaler[] resourceSpansMarshalers;

  @Override
  @SuppressWarnings("NullAway")
  public void clear() {
    this.resourceSpansMarshalers = null;
  }
}

Thank you for any response! 😊

[jack-berg]

For a while I've been thinking about refactoring the protobuf marshalers to remove state. It should be possible but I haven't had enough time to go investigate it. I opened this issue to track it: #5727

I'll likely get to it at some point, but you're welcome to take a crack at it if you have an urgent need 🙂

[huange7]

I'd love to investigate the solutions here. Could you please share some valuable suggestions?