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https://issues.apache.org/jira/browse/HDFS-7159?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14151931#comment-14151931
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Arpit Agarwal commented on HDFS-7159:
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Thanks for taking a look Nicholas.
You are right that we should handle it with a more user-friendly exception
instead of throwing NPE. I'll post an updated patch.
bq. Storage policies are configurable. The current code expects that the
LAZY_PERSIST poicy exists. Otherwise, there are NPE. Should we support the case
that the LAZY_PERSIST policy is not configurated?
What do you think of making it a system policy that cannot be overridden since
a feature depends on it? It may be unexpected for administrators that
reconfiguring storage policies could affect the feature. So when we add ability
to reconfigure storage policies, in {{BlockStoragePolicySuite}} we throw an
exception if there is an attempt to redefine the LAZY_PERSIST storage policy.
> Use block storage policy to set lazy persist preference
> -------------------------------------------------------
>
> Key: HDFS-7159
> URL: https://issues.apache.org/jira/browse/HDFS-7159
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: namenode
> Reporter: Arpit Agarwal
> Assignee: Arpit Agarwal
> Attachments: HDFS-7159.01.patch
>
>
> Now that HDFS-6584 feature is ready and supports block storage policies on
> both files and directories, we can make use of Storage Policies to store the
> LAZY_PERSIST preference.
> This only affects how the preference is persisted in the FsImage/Edit logs.
> There is no change to the client API or to NN-DN interaction.
> An additional advantage is that can support setting the lazy persist
> preference on a directory and it will take effect for all new files.
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