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https://issues.apache.org/jira/browse/HDFS-10201?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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GAO Rui updated HDFS-10201:
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Attachment: HDFS-10201-demo.patch
> Implement undo log in parity datanode for hflush operations
> -----------------------------------------------------------
>
> Key: HDFS-10201
> URL: https://issues.apache.org/jira/browse/HDFS-10201
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: erasure-coding
> Reporter: Mingliang Liu
> Assignee: Mingliang Liu
> Attachments: HDFS-10201-demo.patch
>
>
> According to the current design doc for hflush support in erasure coding (see
> [HDFS-7661]), the parity datanode (DN) needs an undo log for flush
> operations. After hflush/hsync, the last cell will be overwritten when 1) the
> current strip is full, 2) the file is closed, 3) or the hflush/hsync is
> called again for the current non-full stripe. To serve new reader client and
> to tolerate failures between successful hflush/hsync and overwrite operation,
> the parity DN should preserve the old cell in the undo log before overwriting
> it.
> As parities correspond to block group (BG) length and parity data of
> different BG length may have the same block length, the undo log should also
> save the respective block group (BG) length information for the flushed data.
> This jira is to track the effort of designing and implementing an undo log in
> parity DN to support hflush/hsync operations.
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