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https://issues.apache.org/jira/browse/HBASE-8370?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13694433#comment-13694433
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Varun Sharma commented on HBASE-8370:
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Also, coming back to the point about the metrics being actionable.
RE:If your bloom block cache hit count goes down you can do....... Not much.
Not worth counting if you can't take action on it.
I disagree that its not actionable. I would go fix the block cache in this
case. It means there is something seriously wrong with our implementation of
the block cache if we are evicting bloom blocks - maybe its just me but I feel
we should not be evicting bloom blocks.
- If the cache hit rate is too low on Data Blocks, the action item is to
increase Block Cache amount.
I would agree that index block metrics are not needed or actionable if it is
indeed the case that we pin index blocks forever.
> Report data block cache hit rates apart from aggregate cache hit rates
> ----------------------------------------------------------------------
>
> Key: HBASE-8370
> URL: https://issues.apache.org/jira/browse/HBASE-8370
> Project: HBase
> Issue Type: Improvement
> Components: metrics
> Reporter: Varun Sharma
> Assignee: Varun Sharma
> Priority: Minor
>
> Attaching from mail to [email protected]
> I am wondering whether the HBase cachingHitRatio metrics that the region
> server UI shows, can get me a break down by data blocks. I always see this
> number to be very high and that could be exagerated by the fact that each
> lookup hits the index blocks and bloom filter blocks in the block cache
> before retrieving the data block. This could be artificially bloating up the
> cache hit ratio.
> Assuming the above is correct, do we already have a cache hit ratio for data
> blocks alone which is more obscure ? If not, my sense is that it would be
> pretty valuable to add one.
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