@Override
  public void debugDump(StringBuilder sb) {
    sb.append("Clusters=[ ");
    boolean first = true;
    for (Cluster c : getClustersByName().values()) {
      if (!first) {
        sb.append(" , ");
      }
      first = false;
      sb.append("\n  ");
      c.debugDump(sb);
      sb.append(" ");
    }
    sb.append(" ]");
  }
Attempts to map the host to the cluster via clusterhostmapping table if not already present, and add a host_version
record for the cluster's currently applied (stack, version) if not already present.
@param hostname Host name
@param clusterName Cluster name
@throws AmbariException May throw a DuplicateResourceException.
ambari-server/src/main/java/org/apache/ambari/server/state/cluster/ClustersImpl.java