[
https://issues.apache.org/jira/browse/HBASE-27532?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17891078#comment-17891078
]
Palash Chauhan commented on HBASE-27532:
----------------------------------------
Hi [~bbeaudreault].
I am trying to expose this metric to the Phoenix client in
[PHOENIX-7310|https://issues.apache.org/jira/browse/PHOENIX-7310]. I had a
quick question - does this metric track block bytes read only from the disk or
does it also consider blocks which were in the block cache? Based on the
behavior I am seeing in the tests I wrote, it seems to be all blocks scanned,
irrespective of whether they were on disk or in the cache. Please let me know,
thanks!
> Add block bytes scanned metrics
> -------------------------------
>
> Key: HBASE-27532
> URL: https://issues.apache.org/jira/browse/HBASE-27532
> Project: HBase
> Issue Type: Improvement
> Reporter: Bryan Beaudreault
> Assignee: Bryan Beaudreault
> Priority: Major
> Labels: patch-available
> Fix For: 2.6.0, 3.0.0-beta-1
>
>
> Initially in HBASE-14978, but more recently improved in HBASE-27558 and
> HBASE-27570, we now track the amount of block bytes scanned by read requests.
> Random read use-cases (which might read 1 small row from a 64kb block) and
> heavily filtered scans (which might scan many blocks in order to return a
> needle in a haystack row) can unknowingly cause RegionServers to do more work
> than a user expects. Now that we have block IO accounting, we should expose
> this to the user in the form of jmx metrics and ScanMetrics.
>
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
