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https://issues.apache.org/jira/browse/HDFS-5920?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13904631#comment-13904631
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Jing Zhao commented on HDFS-5920:
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I've committed this.
> Support rollback of rolling upgrade in NameNode and JournalNodes
> ----------------------------------------------------------------
>
> Key: HDFS-5920
> URL: https://issues.apache.org/jira/browse/HDFS-5920
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: journal-node, namenode
> Reporter: Jing Zhao
> Assignee: Jing Zhao
> Attachments: HDFS-5920.000.patch, HDFS-5920.000.patch,
> HDFS-5920.001.patch, HDFS-5920.002.patch, HDFS-5920.003.patch
>
>
> This jira provides rollback functionality for NameNode and JournalNode in
> rolling upgrade.
> Currently the proposed rollback for rolling upgrade is:
> 1. Shutdown both NN
> 2. Start one of the NN using "-rollingUpgrade rollback" option
> 3. This NN will load the special fsimage right before the upgrade marker,
> then discard all the editlog segments after the txid of the fsimage
> 4. The NN will also send RPC requests to all the JNs to discard editlog
> segments. This call expects response from all the JNs. The NN will keep
> running if the call succeeds.
> 5. We start the other NN using bootstrapstandby rather than "-rollingUpgrade
> rollback"
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