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https://issues.apache.org/jira/browse/HDFS-7369?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14357981#comment-14357981
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Kai Zheng commented on HDFS-7369:
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I looked at the patch, and have some comments or questions.
1. What is the case we're targeting for, is it the block recovering in
stripping ec case ? If so, we need to make the title clearer, since we also
have other cases for erased block recovering in pure ec form.
2. Related to [~jingzhao]'s above comment in #1, is it possible to explicitly
assemble all the necessary information in a {{BlockGroup}} and pass around to
construct a {{ErasureCodingRecoveryWork}}, then in any way ensure the block
group object to be transferred to DataNode or client, where the recovery
command or task gets performed. I'm not very sure about this in this phase, but
sure we can achieve this in follow up.
3. I don't see {missingBlockIdx}} is actually used.
4. It's ok to have hard-coded logic regarding how many blocks are erased and to
be recovered now, in follow up we need to leverage codec specific constructs to
tell if any erased data/parity blocks, if so then any recoverable blocks, and
etc., and only when we have recoverable ones, we need to consider the recovery
work.
5. Looks like there're some minor coding formats.
> Erasure coding: distribute block recovery work to DataNode
> ----------------------------------------------------------
>
> Key: HDFS-7369
> URL: https://issues.apache.org/jira/browse/HDFS-7369
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Zhe Zhang
> Assignee: Zhe Zhang
> Attachments: HDFS-7369-000-part1.patch, HDFS-7369-000-part2.patch,
> HDFS-7369-001.patch
>
>
> This JIRA updates NameNode to handle background / offline recovery of erasure
> coded blocks. It includes 2 parts:
> # Extend {{UnderReplicatedBlocks}} to recognize EC blocks and insert them to
> appropriate priority levels.
> # Update {{ReplicationMonitor}} to distinguish block codec tasks and send a
> new DataNode command.
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