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https://issues.apache.org/jira/browse/HBASE-14949?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15136811#comment-15136811
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Duo Zhang commented on HBASE-14949:
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{quote}
It will be better if we use a switch which store in System Table, after upgrade
finished, we can switch on manually to use new WAL logic.
{quote}
This is a good idea but how do we know upgrade is finished? For HDFS, there is
a rolling upgrade state. We call "hdfs dfsadmin -rollingUpgrade prepare" when
starting and call "hdfs dfsadmin -rollingUpgrade finalize" when done. Is there
a similar tool in HBase? I think our rolling upgrade is just kill the old
server and restart it with the new code...
Thanks.
> Skip duplicate entries when replay WAL.
> ---------------------------------------
>
> Key: HBASE-14949
> URL: https://issues.apache.org/jira/browse/HBASE-14949
> Project: HBase
> Issue Type: Sub-task
> Reporter: Heng Chen
> Attachments: HBASE-14949.patch, HBASE-14949_v1.patch,
> HBASE-14949_v2.patch
>
>
> As HBASE-14004 design, there will be duplicate entries in different WAL. It
> happens when one hflush failed, we will close old WAL with 'acked hflushed'
> length, then open a new WAL and write the unacked hlushed entries into it.
> So there maybe some overlap between old WAL and new WAL.
> We should skip the duplicate entries when replay. I think it has no harm to
> current logic, maybe we do it first.
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