[HBASE-12102] Duplicate keys in HBase.RegionServer metrics JSON

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.0.0, 0.98.10, 2.0.0
• Fix Version/s: 1.0.1, 1.1.0, 0.98.11, 2.0.0
• Hadoop Flags: Reviewed
• Assignee: Ravi Kishore Valeti
• Reporter: Andrew Kyle Purtell
• Created: 26/Sep/14 16:42
• Updated: 28/Apr/15 19:18
• Resolved: 18/Feb/15 17:28

Description

The JSON returned by /jmx on the RegionServer contains duplicate 'tag.Context' keys for various HBase.RegionServer metrics.

Regions:

{
    "name" : "Hadoop:service=HBase,name=RegionServer,sub=Regions",
    "modelerType" : "RegionServer,sub=Regions",
    "tag.Context" : "regionserver",
    "tag.Context" : "regionserver",
    "tag.Hostname" : "some.host.name",
    ...
}

Server:

"name" : "Hadoop:service=HBase,name=RegionServer,sub=Server",
    "modelerType" : "RegionServer,sub=Server",
    "tag.Context" : "regionserver",
    "tag.zookeeperQuorum" : "some.zookeeper.quorum.peers",
    "tag.serverName" : "some.server.name",
    "tag.clusterId" : "88c186ea-2308-4713-8b5f-5a3e829cbb10",
    "tag.Context" : "regionserver",
    ...
}

IPC:

{
    "name" : "Hadoop:service=HBase,name=IPC,sub=IPC",
    "modelerType" : "IPC,sub=IPC",
    "tag.Context" : "ipc",
    "tag.Context" : "ipc",
    "tag.Hostname" : "some.host.name",
    ...
}

This can cause issues with some JSON parsers. We should avoid emitting duplicate keys if it is under our control.