Changes for HDFS-1623 branch. This change list will be merged into the trunk CHANGES.txt when the HDFS-1623 branch is merged. ------------------------------ HADOOP-7455. HA: Introduce HA Service Protocol Interface. (suresh) HADOOP-7774. HA: Administrative CLI to control HA daemons. (todd) HADOOP-7896. HA: if both NNs are in Standby mode, client needs to try failing back and forth several times with sleeps. (atm) HADOOP-7922. Improve some logging for client IPC failovers and StandbyExceptions (todd)