[HBASE-24138] Ensure StochasticLoadBalancer can log details of decision to not run balancer

• Type: Task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.0.0-alpha-1, 2.3.0, 1.7.0, 2.2.5
• Component/s: Balancer, Operability
• Assignee: Sean Busbey
• Reporter: Sean Busbey
• Created: 08/Apr/20 12:38
• Updated: 14/Jul/20 21:31
• Resolved: 09/Apr/20 05:54

Description

Ran into a customer case where the StochasticLoadBalancer was consistently deciding not to balance when bringing new region servers on line. Even setting the class to TRACE logging would only log a summary statement like:

2020-04-03 00:29:55,133 TRACE org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer: Skipping load balancing because balanced cluster; total cost is 25.24853189705185, sum multiplier is 602.0 min cost which need balance is 0.05

Without any details about what went into that decision it's really hard to figure out what we need to tune to get the behavior we want.

Issue Links

• links to: GitHub Pull Request #1455