[jira] [Commented] (HBASE-21767) findRegionsToForceFlush could be improved

["Duo Zhang (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-21767?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16750584#comment-16750584 ] 

Duo Zhang commented on HBASE-21767:
-----------------------------------

Agree.

IIRC for now we only consider the oldest file, maybe we should check all the files over the limit to find out regions to flush?

> findRegionsToForceFlush could be improved
> -----------------------------------------
>
>                 Key: HBASE-21767
>                 URL: https://issues.apache.org/jira/browse/HBASE-21767
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Sergey Shelukhin
>            Priority: Minor
>         Attachments: image-2019-01-23-16-07-42-166.png
>
>
> We see Too many WALs message logged a lot, and it seems like it usually fails to bring the WAL count back down for a long time, sometimes hours. This results in large steady state WAL volume on some region servers, and slower recovery.
> Based on the functionality in HBASE-21626, it should be possible to add an option to be aggressive in this method, and to determine the minimum set of regions that will actually bring WAL count close to a limit in one operation.
> An example of too-many-WALs log statements reporting WAL count over ~2.5 hours, with a limit of 79. You can see when the count is coming down; it often doesn't come anywhere close to the limit so another flush is requested, etc. for a long time.
>  !image-2019-01-23-16-07-42-166.png! 



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