public void addHostRackInfo(String host, String rackInfo) {
    synchronized (hostRackInfo) {
      hostRackInfo.put(host, rackInfo);
    }
  }
Registers host rack information.

@param host     the name of the host
@param rackInfo the rack information
ambari-server/src/main/java/org/apache/ambari/server/topology/HostGroupInfo.java