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https://issues.apache.org/jira/browse/HDFS-9607?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15146636#comment-15146636
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Dinesh S. Atreya commented on HDFS-9607:
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Konstantin,
Agree with your statement:
{quote}
Dinesh, this is an application-level logic.
{quote}
It will be good to indicate at the API level that HDFS will carry out
{{canWrite}} checks with the information it has or it has been provided with.
For example in the initial implementation we can use {{canWrite}} checks to
disallow updating information more than a HDFS block length, certainly beyond
the end of a file (even beyond the end of a block). Higher levels, for example
applications then can override this method to carry out additional checks. (_I
will log JIRAS for other projects so that they can provide inputs/perspectives
including additional requirements_).
In future {{blockWrite}} API may be introduced for updating info spanning
multiple blocks as needed. (*_Separately I need to create another JIRA for
block level leases in addition to file level leases that is prevalent now._*)
> Advance Hadoop Architecture (AHA) - HDFS Update (write-in-place)
> ----------------------------------------------------------------
>
> 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.
> Currently following are supported.
> # Sequential writes
> # Append (HADOOP-1700, HDFS-265)
> # Snapshots (HDFS-2802)
> # Truncate (HDFS-3107)
> This JIRA is for random updates (write-in-place).
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