cnauroth commented on pull request #3463:
URL: https://github.com/apache/hadoop/pull/3463#issuecomment-928096868


   One other consideration is the behavior as it stands now for HDFS clusters 
that have disabled xattrs with `dfs.namenode.xattrs.enabled=false`.  (The 
default for this property is `true` in recent versions, and with a lot of 
people wanting at-rest encryption, it's become less common to set to `false`.)
   
   In current behavior, the NameNode will throw an `IOException` (not a more 
specific subclass) that propagates to the client.  DistCp will catch that and 
throw its own `XAttrsNotSupportedException`.
   
   With this patch, the NameNode still throws `IOException`, but now DistCp 
propagates that straight to the caller instead of throwing 
`XAttrsNotSupportedException`.  There is a risk that this could cause subtle 
behavioral differences for higher-layer tooling (Oozie? Airflow?) that 
coordinates DistCp jobs.
   
   I'm not certain there is a problem, but I agree with @steveloughran that 
there is reason to be cautious.  It's also difficult to anticipate if custom 
`FileSystem` implementers have overridden and thrown a different exception, 
despite the base class providing `UnsupportedOperationException` out of the box.


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