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https://issues.apache.org/jira/browse/HADOOP-15928?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16687009#comment-16687009
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Pranay Singh edited comment on HADOOP-15928 at 11/14/18 7:16 PM:
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Did some investigation around libhdfs tests, currently none of those tests use 
DummyFileSystem, so it will involve creating a setup for DummyFileSystem, 
wouldn't  manual testing be sufficient to test this fix.


was (Author: pranay_singh):
Did some investigation around libhdfs tests, currently none of those tests use 
DummyFileSystem, so it will involve creating a setup for DummyFileSystem, 
wouldn't a manual testing be sufficient to test this fix.

> libhdfs logs errors when opened FS doesn't support ByteBufferReadable
> ---------------------------------------------------------------------
>
>                 Key: HADOOP-15928
>                 URL: https://issues.apache.org/jira/browse/HADOOP-15928
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: hdfs-client
>            Reporter: Pranay Singh
>            Assignee: Pranay Singh
>            Priority: Major
>              Labels: libhdfs
>             Fix For: 3.0.3
>
>         Attachments: HADOOP-15928.001.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:
> --------------------------------------------------------------------------------------------------
> 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)
> 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.
> 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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