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https://issues.apache.org/jira/browse/HDFS-9607?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15081048#comment-15081048
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Steve Loughran commented on HDFS-9607:
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We have something called the Posix specification to tell us what to call
things. The {{write()}} operation is the one to consider here, simply having it
fail if an update condition cannot be met; possibly add a non-side-effecting
{{canWrite}} call which checks the conditions.
Before worrying about name details, attach your implementation design for
review, covering how you would reliably implement in-place updates, in HDFS,
including in encrypted and erasure-coded parts of the FS, and coping with
failures of 1+ node during that update process.
Once that's actually been reviewed, start a github pull-request with your
initial implementation.
Any changes to filesystem APIs need
# updates to the formal filesystem specification in hadoop-common. That's
*formal* in Computer Science terminology, though we use Python as the syntax
for broader use.
# implementations for local, rawlocal, checksumfs, alongside HDFS.
# tests.
Look at HDFS-6134 for an example. You also need to consider subscribing to the
hadoop developer lists, if you haven't already, and help review other people's
work to understand the process as well as the code..
Don't expect me to participate in your work here; I know that the core HDFS
write pipeline is one of the most critical parts of HDFS, so leave it alone. I
also fear your are even more out your depth w.r.t that pipeline than I am: that
design document is what you are going to have to present to convince the HDFS
experts that this is not the case.
> 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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