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https://issues.apache.org/jira/browse/HDFS-14291?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17568499#comment-17568499
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Ayush Saxena commented on HDFS-14291:
-------------------------------------
Ahh, just bumped on this one and saw there is a question which I didn't answer
since last 2.5 years. :)
Well I now don't exactly remember all the use cases, but we then backported
this to our internal fork.
Guess, one reason was when we set the default EC policy on a file, kind of send
null for policyName in setErasureCoding policy, it then sets the default policy
on the directory.
So, some client application use case was there from some customer, so they
wanted to know what is the default EC policy, rather than first set it and then
do a get policy and if it is not the one they wanted and then change it. Well I
can think of ways to do this without this today, but very faint memory why this.
Second was some upgrade scenario, when a new client tries to connect to an old
server, which doesn't support ErasureCoding, it was something from the yarn
side, that the application tries to unset any erasure coding policy set on the
tmp or the staging directory. So, if the server doesn't support erasure coding
policy(new client-old server setup), it was giving NoSuchMethod or so. So, the
ask was to if the EC policy is null in getServerDefaults() that means server
doesn't support EC policy, so don't shoot EC clean up RPCs and fail in the
entire application flow, and assume there is no EC policy set anywhere...
> EC: GetServerDefaults To Support Default Erasure Coding Policy
> --------------------------------------------------------------
>
> Key: HDFS-14291
> URL: https://issues.apache.org/jira/browse/HDFS-14291
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Ayush Saxena
> Assignee: Ayush Saxena
> Priority: Major
> Attachments: HDFS-14291-01.patch
>
>
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