[HBASE-18568] Correct metric of numRegions

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 3.0.0-alpha-1
• Fix Version/s: 1.4.0, 2.0.0-alpha-3, 2.0.0, 1.2.7
• Component/s: metrics
• Hadoop Flags: Reviewed
• Assignee: Shibin Zhang
• Reporter: Shibin Zhang
• Created: 11/Aug/17 06:11
• Updated: 07/Sep/18 02:01
• Resolved: 29/Aug/17 02:42

Description

i found the value of metric numReigons in Regions is not correct.
the metric can not add or remove region correctly as region close or open.
the metric as follow:

"name" : "Hadoop:service=HBase,name=RegionServer,sub=Regions",
"numRegions" : 2,

after trouble shooting ,i found the reason is in MetricsRegionSourceImpl#MetricsRegionSourceImpl

agg.register(this);
...
hashCode = regionWrapper.getRegionHashCode();

when add the MetricsRegionSource to set ,but the hashCode has not yet initialized.
So, the setFromMap can not put or remove the object correctly.
it will be better like this :

hashCode = regionWrapper.getRegionHashCode();
agg.register(this);

Issue Links

• is broken by: HBASE-14278 Fix NPE that is showing up since HBASE-14274 went in
• relates to: HBASE-18924 Backport HBASE-18568 (Correct metric of numRegions) to branch-1.2 and branch-1.3