[HDFS-2679] Add interface to query current state to HAServiceProtocol

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: HA branch (HDFS-1623)
• Fix Version/s: HA branch (HDFS-1623)
• Component/s: ha, hdfs-client, namenode
• Target Version/s: HA branch (HDFS-1623)
• Hadoop Flags: Reviewed
• Assignee: Eli Collins
• Reporter: Eli Collins
• Created: 14/Dec/11 07:07
• Updated: 24/Jan/12 19:52
• Resolved: 19/Dec/11 05:24

Description

Let's add an interface to HAServiceProtocol to query the current state of a NameNode for use by the the CLI (HAAdmin) and Web UI (HDFS-2677). This essentially makes the names "active" and "standby" from ACTIVE_STATE and STANDBY_STATE public interfaces, which IMO seems reasonable. Unlike the other APIs we should be able to use the interface even when HA is not enabled (as by default a non-HA NN is active).