private void invalidateRecoveryTimestamp(String clusterName, String hostname) {
    if (StringUtils.isNotEmpty(clusterName)) {
      ConcurrentHashMap<String, Long> hostTimestamp = timestampMap.get(clusterName);
      if (hostTimestamp != null) {
        if (StringUtils.isNotEmpty(hostname)) {
          // Clear the time stamp for the specified host in this cluster
          hostTimestamp.put(hostname, 0L);
        }
        else {
          // Clear the time stamp for all hosts in this cluster
          for(Map.Entry<String, Long> hostEntry : hostTimestamp.entrySet()) {
            hostEntry.setValue(0L);
          }
        }
      }
    }
  }
Cluster-env configuration changed.
@param event
ambari-server/src/main/java/org/apache/ambari/server/agent/RecoveryConfigHelper.java