code: public void sendHintParallel(Node failedNode, Version version, Slop slop) {
          List<Node> nodes = new LinkedList<Node>();
          nodes.addAll(handoffStrategy.routeHint(failedNode));
          if(logger.isDebugEnabled()) {
              List<Integer> nodeIds = new ArrayList<Integer>();
              for(Node node: nodes) {
                  nodeIds.add(node.getId());
              }
              logger.debug("Hint preference list: " + nodeIds.toString());
          }
          sendOneAsyncHint(slop.makeKey(), new Versioned<byte[]>(slopSerializer.toBytes(slop),
                                                                 version), nodes);
      }
docs: Like
  {@link #sendHintSerial(voldemort.cluster.Node, voldemort.versioning.Version, Slop)}
  , but doesn't block the pipeline. Intended for handling prolonged
  failures without incurring a performance cost.
  
  @see #sendHintSerial(voldemort.cluster.Node,
  voldemort.versioning.Version, Slop)