@Override
  public void processMarker() {
    if (!processedMarker) {
      handleMarker();
      processedMarker = true;
    } else {
      if (logger.isDebugEnabled()) {
        logger.debug("{}: extra marker received", this);
      }
    }
  }
This will store the ThreadId to latest received sequence Id

Keys are instances of {@link ThreadIdentifier} Values are instances of
{@link SequenceIdAndExpirationObject}
geode-core/src/main/java/org/apache/geode/cache/client/internal/QueueStateImpl.java