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https://issues.apache.org/jira/browse/HDFS-8432?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Chris Nauroth updated HDFS-8432:
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Attachment: HDFS-8432.002.patch
[~arpitagarwal] pointed out to me that I had set some wrong values for the
minimum compatible layout versions. {{TRUNCATE}} was added in Apache Hadoop
2.7.0 as layout version -61. We need to set its minimum compatible layout
version to -61. (Setting it to itself means it is not downgradeable to any
prior versions.) By extension, we also need to set {{APPEND_NEW_BLOCK}} and
{{QUOTA_BY_STORAGE_TYPE}} to minimum compatible layout version -61. Those
features also shipped in Apache Hadoop 2.7.0, so it wouldn't make sense to
claim those features are downgradeable to any pre-truncate version.
Thank you for the review, Arpit. Here is patch v002. I also addressed the
Jenkins feedback from the last run.
> Introduce a minimum compatible layout version to allow downgrade in more
> rolling upgrade use cases.
> ---------------------------------------------------------------------------------------------------
>
> Key: HDFS-8432
> URL: https://issues.apache.org/jira/browse/HDFS-8432
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode, rolling upgrades
> Reporter: Chris Nauroth
> Assignee: Chris Nauroth
> Attachments: HDFS-8432-HDFS-Downgrade-Extended-Support.pdf,
> HDFS-8432.001.patch, HDFS-8432.002.patch
>
>
> Maintain the prior layout version during the upgrade window and reject
> attempts to use new features until after the upgrade has been finalized.
> This guarantees that the prior software version can read the fsimage and edit
> logs if the administrator decides to downgrade. This will make downgrade
> usable for the majority of NameNode layout version changes, which just
> involve introduction of new edit log operations.
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