hbase-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10241) implement mvcc-consistent scanners (across recovery)
Date Fri, 27 Dec 2013 20:15:51 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10241?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13857696#comment-13857696
] 

Lars Hofhansl commented on HBASE-10241:
---------------------------------------

Nice writeup. It would be better even if it would state the failure scenario we're guarding
against.

I think we have to careful not to add any "half guarantees". Currently HBase does MVCC based
SI for rows (and serializable views for increment/append). If I understand this correctly,
this is not needed for row consistency, right?
While recovery is in progress we cannot scan, so we'd never see partial rows, right?

Then what exactly are we guarding against? (As usually, I might just miss an important point
:) )


> implement mvcc-consistent scanners (across recovery)
> ----------------------------------------------------
>
>                 Key: HBASE-10241
>                 URL: https://issues.apache.org/jira/browse/HBASE-10241
>             Project: HBase
>          Issue Type: New Feature
>          Components: HFile, regionserver, Scanners
>    Affects Versions: 0.99.0
>            Reporter: Sergey Shelukhin
>            Assignee: Sergey Shelukhin
>         Attachments: Consistent scanners.pdf
>
>
> Scanners currently use mvcc for consistency. However, mvcc is lost on server restart,
or even a region move. This JIRA is to enable the scanners to transfer mvcc (or seqId, or
some other number, see HBASE-8763) between servers. First, client scanner needs to get and
store the readpoint. Second, mvcc needs to be preserved in WAL. Third, the mvcc needs to be
stored in store files per KV and discarded when not needed.



--
This message was sent by Atlassian JIRA
(v6.1.5#6160)

Mime
View raw message