Kahlil Oppenheimer created HBASE-18164:
------------------------------------------
Summary: Much faster locality cost function and candidate generator
Key: HBASE-18164
URL: https://issues.apache.org/jira/browse/HBASE-18164
Project: HBase
Issue Type: Improvement
Components: Balancer
Reporter: Kahlil Oppenheimer
Assignee: Kahlil Oppenheimer
Priority: Minor
We noticed that during the stochastic load balancer was not scaling well with
cluster size. That is to say that on our smaller clusters (~17 tables, ~12
region servers, ~5k regions), the balancer considers ~100,000 cluster
configurations in 60s per balancer run, but only ~5,000 per 60s on our bigger
clusters (~82 tables, ~160 region servers, ~13k regions) .
Because of this, our bigger clusters are not able to converge on balance as
quickly for things like table skew, region load, etc. because the balancer does
not have enough time to "think".
We have re-written the locality cost function to be incremental, meaning it
only recomputes cost based on the most recent region move proposed by the
balancer, rather than recomputing the cost across all regions/servers every
iteration.
Further, we also cache the locality of every region on every server at the
beginning of the balancer's execution for both the LocalityBasedCostFunction
and the LocalityCandidateGenerator to reference. This way, they need not
collect all HDFS blocks of every region at each iteration of the balancer.
The changes have been running in all 6 of our production clusters and all 4 QA
clusters without issue. The speed improvements we noticed are massive. Our big
clusters now consider 20x more cluster configurations.
We are currently preparing a patch for submission.
--
This message was sent by Atlassian JIRA
(v6.3.15#6346)
