@Override
    public void childEvent(final CuratorFramework client, final PathChildrenCacheEvent event) {
      Preconditions.checkArgument(client != null
          && client.getState() == CuratorFrameworkState.STARTED, "client is not started");

      synchronized (this) {
        ChildData childData = event.getData();
        if (childData == null) return;
        String nodeName = extractNodeName(childData);
        if (nodeName.equals(workerNodePrefix)) {
          LOG.warn("Invalid LLAP worker node name: {} was {}", childData.getPath(), event.getType());
        }
        if (!isLlapWorker(nodeName, workerNodePrefix)) return;
        LOG.info("{} for zknode {}", event.getType(), childData.getPath());
        InstanceType instance = extractServiceInstance(event, childData);
        if (instance != null) {
          int ephSeqVersion = extractSeqNum(nodeName);
          switch (event.getType()) {
            case CHILD_ADDED:
              addToCache(childData.getPath(), instance.getHost(), instance);
              for (ServiceInstanceStateChangeListener<InstanceType> listener : stateChangeListeners) {
                listener.onCreate(instance, ephSeqVersion);
              }
              break;
            case CHILD_UPDATED:
              addToCache(childData.getPath(), instance.getHost(), instance);
              for (ServiceInstanceStateChangeListener<InstanceType> listener : stateChangeListeners) {
                listener.onUpdate(instance, ephSeqVersion);
              }
              break;
            case CHILD_REMOVED:
              removeFromCache(childData.getPath(), instance.getHost());
              for (ServiceInstanceStateChangeListener<InstanceType> listener : stateChangeListeners) {
                listener.onRemove(instance, ephSeqVersion);
              }
              break;
            default:
              // Ignore all the other events; logged above.
          }
        } else {
          LOG.info("instance is null for event: {} childData: {}", event.getType(), childData);
        }
      }
    }
Get the ensemble server addresses from the configuration. The format is: host1:port,
host2:port..

@param conf configuration
llap-client/src/java/org/apache/hadoop/hive/registry/impl/ZkRegistryBase.java