Clara Xiong created HBASE-25697:
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Summary: StochasticBalancer improvement for large scale clusters
Key: HBASE-25697
URL: https://issues.apache.org/jira/browse/HBASE-25697
Project: HBase
Issue Type: Improvement
Components: Balancer, master, UI
Reporter: Clara Xiong
h2. Findings on a large scale cluster (100,000 regions on 300 nodes)
* Balancer starts and stops before getting a plan
* Adding new racks doesn’t trigger balancer
* Balancer stops leaving some racks at 50% lower region counts
* Regions for large tables don’t get evenly distributed
* Observability is poor
* Too many knobs makes tuning empirical and takes many experiments
h2. Improvements made and bing made
* Cost function enhancement to capture outliers especially table skew.
https://issues.apache.org/jira/browse/HBASE-25625?filter=-2
* Explain why balancer stops https://issues.apache.org/jira/browse/HBASE-25666
will back port too https://issues.apache.org/jira/browse/HBASE-24528
h2. More proposals
* minCostNeedBalance for each cost function instead of weights. We want to
trigger balancing if any factor is out of balancer instead of trying to combine
the factors in arbitrary weights. This makes operation and configuration much
easier.
* Simulated annealing to lower minCostNeedBalance periodically to unstuck the
balancer from sub-optimum then gradually increase to keep the system stable.
Also add cost of move as a counter measure for the decision
[https://opensourcelibs.com/lib/tempest]
* Orchestrated scheduling of compaction, normalizer and balancer
* PID approach [https://www.amazon.com/dp/1449361692/ref=rdr_ext_tmb]
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