public Mpack getMpack(Long mpackId) {
    if (mpackManager.getMpackMap() != null && mpackManager.getMpackMap().containsKey(mpackId)) {
      return mpackManager.getMpackMap().get(mpackId);
    }
    return null;
  }
Fetch a particular mpack based on mpackid
@return a single mpack
ambari-server/src/main/java/org/apache/ambari/server/api/services/AmbariMetaInfo.java