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https://issues.apache.org/jira/browse/HBASE-30134?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Wellington Chevreuil updated HBASE-30134:
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Summary: Improve CacheAwareLoadBalancer to consider low cache ratio when
calculating imbalance (was: Improve CacheAwareLoadBalancer to consider low
cache ratio and available cache space)
> Improve CacheAwareLoadBalancer to consider low cache ratio when calculating
> imbalance
> -------------------------------------------------------------------------------------
>
> Key: HBASE-30134
> URL: https://issues.apache.org/jira/browse/HBASE-30134
> Project: HBase
> Issue Type: Sub-task
> Reporter: Wellington Chevreuil
> Assignee: Wellington Chevreuil
> Priority: Major
>
> When enabling time based priority on CFs that are already cached on clusters
> with datasets larger than the cache capacity, once the now cold data gets
> evicted, hot data that was previously uncached due to no cache space would
> remain uncached unless:
> 1) A client read request read it from the file system and caches it;
> 2) An operator manually disables and reenables tables with hot data, so that
> the prefetch executor can run and cache those blocks.
> Both options are non optimal, leading to temporary performance impacts and/or
> requiring manual interventions.
> The CacheAwareLoadBalancer, currently, only raises the cost of moving highly
> cached regions, when calculating assignment plans, and doesn't consider cache
> ratio at all when calculating potential imbalance, only skewness. So in the
> scenario where regions are evenly distributed and there's no skewness,
> CacheAwareLoadBalancer would not trigger any moves even when there would be
> regions with low cache ratio on many servers and enough cache space to
> accommodate those regions data in region servers cache.
>
> This proposal is to include low cached ratio regions in the imbalance
> calculation, so that CacheAwareLoadBalancer can trigger the computation of
> new assignment plans.
> It also needs to recalculate cache ratio on the assignment plans, simulating
> that low cache ratio regions moved to enough cache free space servers would
> get fully cached, so that such plan scores higher then the current state.
>
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