[jira] Commented: (HBASE-2021) Add compaction details to master UI

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    [ https://issues.apache.org/jira/browse/HBASE-2021?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12796053#action_12796053 ] 

stack commented on HBASE-2021:
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Patch looks great Lars.   It applies cleanly and all builds.  I like that you only check FS every two minutes (Doing it on every metrics interval would be too much methinks).  I'll commit this tomorrow, but if you have a second between here and then, perhaps change the two minutes to be a configuration... it doesn't have to have an entry in hbase-default.xml.. just be something someone could discover configurable if they took the trouble to read the source.  Good stuff.

> Add compaction details to master UI
> -----------------------------------
>
>                 Key: HBASE-2021
>                 URL: https://issues.apache.org/jira/browse/HBASE-2021
>             Project: Hadoop HBase
>          Issue Type: Improvement
>            Reporter: Lars George
>            Assignee: Lars George
>            Priority: Minor
>             Fix For: 0.20.3, 0.21.0
>
>         Attachments: HBASE-2021-0.20-v2.patch, HBASE-2021-0.20.patch, HBASE-2021.patch
>
>
> There are two issues with this, first to detect that there is a compaction needed. You can currently use the little helper util that checks if a table has at least one colfam with more than one store file. I though about scanning all tables and all colfams in each and then compute the "fragmentation" ratio as a percentage of colfams with more than one store to the total number of colfams. That gives a "Table xyz is 33% fragmented" output. While minor percentage are normal under insert operations it is still important to know how bad the fragmentation is overall.
> Another idea is to weigh the number of files per store too, so that if you have two per colfam it is considered "low" and if you have more, for example 6-8 it is considered "high". Not sure how that can be done yet but noting the idea down here.
> Of course seeing the .META. fragmentation is useful to quickly debug performance issues (as JD told me on IRC).
> The other issue is that when you have started a compaction you have no idea how far it is and if it is still in progress. One indication of course is the above value. If it is 0% then all is done. But if you are at say 23%, is it still compacting? We could have a simple status that compactions are still in progress.

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