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https://issues.apache.org/jira/browse/HDFS-15120?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17044404#comment-17044404
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Jinglun commented on HDFS-15120:
--------------------------------
Hi [~ayushtkn], thanks your comments. Agree with you, the
BlockPlacementPolicies.getPolicy() is in many hot paths and we should try to
avoid the lock cost ! We can make the placementPolicies variable volatile and
refresh it directly. There can only be one thread updating the reference so it
should be thread-safe. Upload v07.
> Refresh BlockPlacementPolicy at runtime.
> ----------------------------------------
>
> Key: HDFS-15120
> URL: https://issues.apache.org/jira/browse/HDFS-15120
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Jinglun
> Assignee: Jinglun
> Priority: Major
> Attachments: HDFS-15120.001.patch, HDFS-15120.002.patch,
> HDFS-15120.003.patch, HDFS-15120.004.patch, HDFS-15120.005.patch,
> HDFS-15120.006.patch
>
>
> Now if we want to switch BlockPlacementPolicies we need to restart the
> NameNode. It would be convenient if we can switch it at runtime. For example
> we can switch between AvailableSpaceBlockPlacementPolicy and
> BlockPlacementPolicyDefault as needed.
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