boolean isClusterPropertyCached(String propertyName) {
    return m_clusterPropertyCache.containsKey(propertyName);
  }
Gets whether the specified cluster property is already cached.

@param propertyName
         the property to check.
@return {@code true} if the property is cached.
ambari-server/src/main/java/org/apache/ambari/server/state/cluster/ClusterImpl.java