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https://issues.apache.org/jira/browse/HDFS-9607?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15080678#comment-15080678
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Dinesh S. Atreya commented on HDFS-9607:
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A few checks that should be implemented by the method checkWriteInPlace (or
alternatively checkUpdtInPlace) are as follows:
* The maximum length of either readLength or writeBuffer should be less than
the blocksize
** Multiple updates can be chained with separate method call with each update
less than equal to the blocksize.
* readLength should be equal to writeBuffer.length
** if it is not then the check fails.
* desiredWritePos + readLength (and desiredWritePos + writeBuffer.length)
cannot extend beyond the block boundary.
* It is presumed that any updates should not extend beyond the end of file.
Hence desiredWritePos + readLength (and desiredWritePos + writeBuffer.length)
should be less than equal to the length of the file. This will ensure that EOF
is not compromised.
Please indicate other checks should be implemented.
*Since we are talking about HDFS, data integrity is very _critical_. The checks
should ensure that data does not get corrupted.*
> Advance Hadoop Architecture (AHA) - HDFS
> ----------------------------------------
>
> Key: HDFS-9607
> URL: https://issues.apache.org/jira/browse/HDFS-9607
> Project: Hadoop HDFS
> Issue Type: New Feature
> Reporter: Dinesh S. Atreya
>
> Link to Umbrella JIRA
> https://issues.apache.org/jira/browse/HADOOP-12620
> Provide capability to carry out in-place writes/updates. Only writes in-place
> are supported where the existing length does not change.
> For example, "Hello World" can be replaced by "Hello HDFS!"
> See
> https://issues.apache.org/jira/browse/HADOOP-12620?focusedCommentId=15046300&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15046300
> for more details.
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