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https://issues.apache.org/jira/browse/HBASE-8370?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14005310#comment-14005310
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stack commented on HBASE-8370:
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In trunk we do not have per block type metrics.
In trunk we do not show the cache hit rates in the UI apart from what can be
found in the metrics listing under /jmx
So I could close this issue I suppose because the pivot around which the above
discussion turns no longer exists in trunk.
But the discussion above is good around making it more plain when problematic
evictions are happening in your online serving system.
I could file an issue to make it so the block cache percentage is a double
rather than an int -- the one thing the two lads agreed to above -- but I can't
help but think that most operators will not be concerned if their block cache
hit ratio goes from 99.45% to 99.41% ([~varunsharma]'s point, in synopsis, is
that significant changes in blockcache loading should be more obvious;
[[email protected]] agrees).
Let me just do this anyways. I just made a sub-jira
So, I want to add back blocktype reporting to trunk -- data blocks at least (I
went looking for such reporting because I've been messing with block cache and
have been wanting to know what is going on inside, a recurring theme if you
search JIRA) -- but while our [~eclark] starts out at an extreme (conflating
block type reporting with the heavyweight per-columnfamily/table/region
SchemaMetrics system since purged), his argument that we should only expose
"actionable" metrics has merit. For example, in my case, excepting
DoubleBlockCache (slabcache), caches are tiered with meta (index/blooms) in the
LRCBC and the everything else in the L2; in this case reporting on data block
metrics is redundant (On other hand, most run with just one BC
implementation...)
While we could probably resolve, let me leave this issue open. We still need a
'fix'. I'll be back.
> 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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