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From "Duo Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14949) Resolve name conflict when splitting if there are duplicated WAL entries
Date Wed, 17 Feb 2016 01:49:18 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14949?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15149677#comment-15149677
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Duo Zhang commented on HBASE-14949:
-----------------------------------

{quote}
We still need the migration switch to not use new naming convention until cluster is all up
on new code? If so, lets file issue for it as blocker on 2.0.
{quote}

This patch should go first before the Async WAL. It does not break anything and could also
work if we do not have duplicated WAL entries.

And for an HBase version which has Async WAL on, we could only rolling upgrade from a version
which already has this patch, otherwise we may have data loss because the old split logic
may delete a recovered edits file incorrectly.

Thanks.

> Resolve name conflict when splitting if there are duplicated WAL entries
> ------------------------------------------------------------------------
>
>                 Key: HBASE-14949
>                 URL: https://issues.apache.org/jira/browse/HBASE-14949
>             Project: HBase
>          Issue Type: Sub-task
>            Reporter: Heng Chen
>            Assignee: Duo Zhang
>         Attachments: HBASE-14949-v3.patch, HBASE-14949-v4.patch, HBASE-14949.patch, HBASE-14949_v1.patch,
HBASE-14949_v2.patch
>
>
> The AsyncFSHLog introduced in HBASE-14790 may write same WAL entries to different WAL
files. WAL entry itself is idempotent so replay is not a problem but the intermediate file
name and final name when splitting is constructed using the lowest or highest sequence id
of the WAL entries written, so it is possible that different WAL files will have same intermediate
or final file name when splitting. In the currentm implementation, this will cause split fail
or data loss. We need to solve this.



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