private DistributedMember getTransactionalNode() {
    if (cache.getTxManager().getTXState() != null) {
      return cache.getTxManager().getTXState().getTarget();
    }
    return null;
  }
@return the node which a transaction is already is progress, null otherwise
geode-core/src/main/java/org/apache/geode/internal/cache/DistributedRegion.java