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https://issues.apache.org/jira/browse/HDFS-8137?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14521460#comment-14521460
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Kai Zheng commented on HDFS-8137:
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Hi Uma,
bq.We supposed to get schema values from ECSchemaManager, but right now I don't
see a better way to get from ECScheaManeger, so I added an API to get from
BlockCollection itself like isStriped API in it.
{{ECSchemaManager}} might not be supposed to get a schema associated with a
zone, dir/file, but {{ErasureCodingZoneManager}} may do. We could query the
schema info from a zone using ErasureCodingZoneManager. I thought it's good to
add the method {{getECSchema}} along with the existing method {{isStriped}}, as
it's essential to erasure coded files.
A quick look at the patch found it might need to align with some latest
changes, regarding how to get schema from a zone/dir/xAttr, would you double
check? Thanks.
> Sends the EC schema to DataNode as well in EC encoding/recovering command
> -------------------------------------------------------------------------
>
> Key: HDFS-8137
> URL: https://issues.apache.org/jira/browse/HDFS-8137
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Kai Zheng
> Assignee: Uma Maheswara Rao G
> Attachments: HDFS-8137-0.patch
>
>
> Discussed with [~umamaheswararao] and [~vinayrpet], we should also send the
> EC schema to DataNode as well contained in the EC encoding/recovering
> command. The target DataNode will use it to guide the executing of the task.
> Another way would be, DataNode would just request schema actively thru a
> separate RPC call, and as an optimization consideration, DataNode may cache
> schemas to avoid repeatedly asking for the same schema twice.
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