code: public CountDownLatch broadcastOperation(final BroadcastOpFactory of,
      final Collection<MemcachedNode> nodes) {
      final CountDownLatch latch = new CountDownLatch(nodes.size());
  
      for (MemcachedNode node : nodes) {
        getLogger().debug("broadcast Operation: node = " + node);
        Operation op = of.newOp(node, latch);
        op.initialize();
        node.addOp(op);
        op.setHandlingNode(node);
        addedQueue.offer(node);
        metrics.markMeter(OVERALL_REQUEST_METRIC);
      }
  
      Selector s = selector.wakeup();
      assert s == selector : "Wakeup returned the wrong selector.";
      return latch;
    }
docs: Broadcast an operation to a collection of nodes.
  
  @return a {@link CountDownLatch} that will be counted down when the
  operations are complete.