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https://issues.apache.org/jira/browse/HDFS-15120?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17043268#comment-17043268
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Ayush Saxena commented on HDFS-15120:
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Thanx [~LiJinglun] . Had a quick look. Couldn't check in full.
But can we avoid taking lock and stuff, this would be part of normal write
flow, I am not sure, how much impact, but there would be some in taking read
lock, though trivial, and BPP changing in runtime would be a very rare
scenario. I don't think we should put its cost to any other basic process. Can
we get rid of it. I think we can handle some latency in updating of BPP, when
we reconfigure it at runtime.
Secondly, Can we directly just change the {{placementPolicies}} variable with a
new one in {{BlockManager}} rather than changing it internally?
> 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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