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https://issues.apache.org/jira/browse/HDFS-14083?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16687729#comment-16687729
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Steve Loughran commented on HDFS-14083:
---------------------------------------

I've moved it to HDFS, deleted the fix version as that only goes in when the 
fix is there; "target version" is the one to put the one you want in.

w.r.t testing, the purpose of tests is not to just to show that you've fixed an 
issue, *but to make sure it nevers come back*.

Yes, coming up with a good test is hard
Yes, it often involves more code than the bit of the patch which goes into 
production
And the standards for test code are high too

But: its how we improve the codebase and keep the quality high.

My personal view is "the sole excuse for not writing a test is that its 
impossible to either replicate the situation or to verify that the solution 
actually worked", though that's where mockito comes into its own. 

> libhdfs logs errors when opened FS doesn't support ByteBufferReadable
> ---------------------------------------------------------------------
>
>                 Key: HDFS-14083
>                 URL: https://issues.apache.org/jira/browse/HDFS-14083
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: native
>    Affects Versions: 3.0.3
>            Reporter: Pranay Singh
>            Assignee: Pranay Singh
>            Priority: Minor
>         Attachments: HADOOP-15928.001.patch, HADOOP-15928.002.patch
>
>
> Problem:
> ------------
> There is excessive error logging when a file is opened by libhdfs 
> (DFSClient/HDFS) in S3 environment, this issue is caused because buffered 
> read is not supported in S3 environment, HADOOP-14603 "S3A input stream to 
> support ByteBufferReadable"  
> The following message is printed repeatedly in the error log/ to STDERR:
> {code}
> --------------------------------------------------------------------------------------------------
> UnsupportedOperationException: Byte-buffer read unsupported by input 
> streamjava.lang.UnsupportedOperationException: Byte-buffer read unsupported 
> by input stream
>         at 
> org.apache.hadoop.fs.FSDataInputStream.read(FSDataInputStream.java:150)
> {code}
> h3. Root cause
> After investigating the issue, it appears that the above exception is printed 
> because
> when a file is opened via {{hdfsOpenFileImpl()}} calls {{readDirect()}} which 
> is hitting this
> exception.
> h3. Fix:
> Since the hdfs client is not initiating the byte buffered read but is 
> happening in a implicit manner, we should not be generating the error log 
> during open of a file.



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