[HBASE-11229] Change block cache percentage metrics to be doubles rather than ints

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.99.0
• Component/s: metrics
• Hadoop Flags: Incompatible change, Reviewed

Release Note

Renames metric "blockCountHitPercent" as "blockCacheCountHitPercent". Changes this metrics type from int to double.

Small changes in this metric can have significant impact serving. While this metric may show 99.xx percent, most of the cache hits are because we are fetching index and bloom blocks. A significant percentage of data block evictions may only register as a small change in this metric. Keep an eye on evictions as well changes (even if small) in this metric.

• Assignee: Michael Stack
• Reporter: Michael Stack
• Created: 21/May/14 22:05
• Updated: 21/Feb/15 23:32
• Resolved: 22/May/14 18:44

Description

See parent issue. Small changes in the hit percentage can have large implications, even when movement is inside a single percent: i.e. going from 99.11 to 99.87 percent. As is, percents are ints. Make them doubles.