final void validate(Cluster cluster, Direction direction, UpgradeType type,
        UpgradePack upgradePack, Map<String, Object> requestMap) throws AmbariException {

      // run this instance's check
      check(cluster, direction, type, upgradePack, requestMap);

      // pass along to the next
      if (null != m_nextValidator) {
        m_nextValidator.validate(cluster, direction, type, upgradePack, requestMap);
      }
    }
Validates the upgrade request from this point in the chain.

@param cluster
@param direction
@param type
@param upgradePack
@param requestMap
@throws AmbariException
ambari-server/src/main/java/org/apache/ambari/server/stack/upgrade/orchestrate/UpgradeContext.java