[HBASE-13376] Improvements to Stochastic load balancer

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.0.0, 0.98.12
• Fix Version/s: 1.2.0, 1.3.0, 2.0.0
• Component/s: Balancer
• Hadoop Flags: Reviewed
• Assignee: Vandana Ayyalasomayajula
• Reporter: Vandana Ayyalasomayajula
• Created: 01/Apr/15 10:22
• Updated: 24/Jun/22 18:07
• Resolved: 04/Feb/16 20:16

Description

There are two things this jira tries to address:

1. The locality picker in the stochastic balancer does not pick regions with least locality as candidates for swap/move. So when any user configures locality cost in the configs, the balancer does not always seems to move regions with bad locality.

2. When a cluster has equal number of loaded regions, it always picks the first one. It should pick a random region on one of the equally loaded servers. This improves a chance of finding a good candidate, when load picker is invoked several times.