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https://issues.apache.org/jira/browse/HDFS-5182?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13841685#comment-13841685
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Todd Lipcon commented on HDFS-5182:
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bq. It's edge-triggered in the sense that both the DN and the client send
notifications when something changes
Hrm, so that means that the data xceiver protocol would become bidirectional
instead of a simple request/response protocol? This seems like it could get
kind of hairy.
> BlockReaderLocal must allow zero-copy reads only when the DN believes it's
> valid
> ---------------------------------------------------------------------------------
>
> Key: HDFS-5182
> URL: https://issues.apache.org/jira/browse/HDFS-5182
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: hdfs-client
> Affects Versions: 3.0.0
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
>
> BlockReaderLocal must allow zero-copy reads only when the DN believes it's
> valid. This implies adding a new field to the response to
> REQUEST_SHORT_CIRCUIT_FDS. We also need some kind of heartbeat from the
> client to the DN, so that the DN can inform the client when the mapped region
> is no longer locked into memory.
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