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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-11109) flush region sequence id may not be larger than all edits flushed
Date Sat, 03 May 2014 01:11:15 GMT

    [ https://issues.apache.org/jira/browse/HBASE-11109?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13988504#comment-13988504
] 

stack commented on HBASE-11109:
-------------------------------

[~jeffreyz] Thank you for pushing back.  Thinking on it, there may be a less burdensome soln.,
one that will not require us sync in the majority of cases using facility @nkeywal made us
restore.   Let me play.

On revisit after uniting seqid and mvcc, yes, it will change the lay of the land.  Lets revisit
after this patch goes in ('correct' but likely with some small cost) and after your grand
unification gets committed.  Thanks for review.

> flush region sequence id may not be larger than all edits flushed
> -----------------------------------------------------------------
>
>                 Key: HBASE-11109
>                 URL: https://issues.apache.org/jira/browse/HBASE-11109
>             Project: HBase
>          Issue Type: Sub-task
>          Components: wal
>    Affects Versions: 0.99.0
>            Reporter: stack
>            Assignee: stack
>            Priority: Critical
>             Fix For: 0.99.0
>
>         Attachments: 11109.txt, 11109v2.txt
>
>
> This was found by [~jeffreyz]  See parent issue.  We have this issue since we put the
ring buffer/disrupter into the WAL (HBASE-10156).
> An edits region sequence id is set only after the edit has traversed the ring buffer.
 Flushing, we just up whatever the current region sequence id is.  Crossing the ring buffer
may take some time and is done by background threads.  The flusher may be taking the region
sequence id though edits have not yet made it across the ringbuffer: i.e. edits that are actually
scoped by the flush may have region sequence ids in excess of that of the flush sequence id
reported.
> The consequences are not exactly clear.  Would rather not have to find out so lets fix
this here.



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