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https://issues.apache.org/jira/browse/HADOOP-14872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16192015#comment-16192015
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John Zhuge edited comment on HADOOP-14872 at 10/4/17 8:53 PM:
--------------------------------------------------------------

Patch 008
* Keep both constant strings and enums
* Fix checkstye in 007
* Constant string names have extra prefix "CAP_" over enum names. If constant 
string names are the same as enum, DFSOutputStream.java will not compile due to 
name conflicts.

Some of the test timeouts for Patch 007 are puzzling.


was (Author: jzhuge):
Patch 008
* Keep both constant strings and enums
* Constant string names have extra prefix "CAP_" over enum names. If constant 
string names are the same as enum, DFSOutputStream.java will not compile due to 
name conflicts.

Some of the test timeouts for Patch 007 are puzzling.

> CryptoInputStream should implement unbuffer
> -------------------------------------------
>
>                 Key: HADOOP-14872
>                 URL: https://issues.apache.org/jira/browse/HADOOP-14872
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: fs
>    Affects Versions: 2.6.4
>            Reporter: John Zhuge
>            Assignee: John Zhuge
>         Attachments: HADOOP-14872.001.patch, HADOOP-14872.002.patch, 
> HADOOP-14872.003.patch, HADOOP-14872.004.patch, HADOOP-14872.005.patch, 
> HADOOP-14872.006.patch, HADOOP-14872.007.patch, HADOOP-14872.008.patch
>
>
> Discovered in IMPALA-5909.
> Opening an encrypted HDFS file returns a chain of wrapped input streams:
> {noformat}
> HdfsDataInputStream
>   CryptoInputStream
>     DFSInputStream
> {noformat}
> If an application such as Impala or HBase calls HdfsDataInputStream#unbuffer, 
> FSDataInputStream#unbuffer will be called:
> {code:java}
>     try {
>       ((CanUnbuffer)in).unbuffer();
>     } catch (ClassCastException e) {
>       throw new UnsupportedOperationException("this stream does not " +
>           "support unbuffering.");
>     }
> {code}
> If the {{in}} class does not implement CanUnbuffer, UOE will be thrown. If 
> the application is not careful, tons of UOEs will show up in logs.
> In comparison, opening an non-encrypted HDFS file returns this chain:
> {noformat}
> HdfsDataInputStream
>   DFSInputStream
> {noformat}
> DFSInputStream implements CanUnbuffer.
> It is good for CryptoInputStream to implement CanUnbuffer for 2 reasons:
> * Release buffer, cache, or any other resource when instructed
> * Able to call its wrapped DFSInputStream unbuffer
> * Avoid the UOE described above. Applications may not handle the UOE very 
> well.



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