protected final Set<InstanceType> getByHostInternal(String host) {
    Set<InstanceType> byHost = nodeToInstanceCache.get(host);
    byHost = (byHost == null) ? Sets.newHashSet() : byHost;
    if (LOG.isDebugEnabled()) {
      LOG.debug("Returning " + byHost.size() + " hosts for locality allocation on " + host);
    }
    return byHost;
  }
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