[HBASE-23054] Remove synchronization block from MetaTableMetrics and fix LossyCounting algorithm

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.1.5
• Fix Version/s: 3.0.0-alpha-1, 2.3.0, 2.1.7, 2.2.2
• Component/s: metrics
• Hadoop Flags: Reviewed
• Assignee: Ankit Singhal
• Reporter: Ankit Singhal
• Created: 19/Sep/19 20:27
• Updated: 08/Oct/19 21:05
• Resolved: 02/Oct/19 12:02

Description

While trying to use LossyCounting for HBASE-15519 , found following bugs in current implementation
– Remove synchronization block from MetaTableMetrics to avoid congestion at the code 

– Fix license format

– Fix LossyCounting algorithm as per http://www.vldb.org/conf/2002/S10P03.pdf 

– Avoid doing sweep on every insert in LossyCounting

– Remove extra redundant data structures from MetaTableMetrics.

Issue Links

• is related to: HBASE-19722 Meta query statistics metrics source
• is related to: HBASE-21991 Fix MetaMetrics issues - [Race condition, Faulty remove logic], few improvements