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From "Jeffrey Zhong (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 00:27:15 GMT

    [ https://issues.apache.org/jira/browse/HBASE-11109?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13988473#comment-13988473

Jeffrey Zhong commented on HBASE-11109:

Yeah, doesn't the comment say that? In testing, I see us doing 4 or 5 syncs a ms so when we
flush there'd be some hiccup of some portion of a millisecond for this region only
I c. +1 on your current patch. Thanks.

It's possible we can move out the sync when mvcc and seqid is combined. Because it will be
the readpoint(largest sequence number) before the WriteEntry w inserted with mvcc.beginMemstoreInsert();
when we are holding the updatesLock. 

> 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
> The consequences are not exactly clear.  Would rather not have to find out so lets fix
this here.

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