[HBASE-14838] Clarify that SimpleRegionNormalizer does not merge empty (<1MB) regions

• Type: Bug
• Status: Closed
• Priority: Trivial
• Resolution: Fixed
• Affects Version/s: 1.2.0
• Fix Version/s: 1.2.0, 2.0.0
• Component/s: documentation, regionserver
• Assignee: Josh Elser
• Reporter: Romil Choksi
• Created: 19/Nov/15 02:45
• Updated: 16/Jun/22 01:17
• Resolved: 16/Dec/15 15:01

Description

SImpleRegionNormalizer does not merge empty region of a table

Steps to repro:

• Create an empty table with few, say 5-6 regions without any data in any of them
• Verify hbase:meta table to verify the regions for the table or check HMaster UI
• Enable normalizer switch and normalization for this table
• Run normalizer, by 'normalize' command from hbase shell
• Verify the regions for table by scanning hbase:meta table or checking HMaster web UI

The empty regions are not merged on running the region normalizer. This seems to be an edge case with completely empty regions since the Normalizer checks for: smallestRegion (in this case 0 size) + smallestNeighborOfSmallestRegion (in this case 0 size) > avg region size (in this case 0 size)
thanks to elserj for verifying this from the source code side

Issue Links

• relates to: HBASE-13103 [ergonomics] add region size balancing as a feature of master