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From "John Zhuge (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-14872) CryptoInputStream should implement unbuffer
Date Thu, 19 Oct 2017 17:11:00 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-14872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16211366#comment-16211366
] 

John Zhuge commented on HADOOP-14872:
-------------------------------------

The changes can be divided into 2 independent groups:

Enhance StreamCapabilities and add it to input streams
* FSDataInputStream.java
* StreamCapabilities.java
* filesystem.md
* DFSInputStream.java
* DFSOutputStream.java
* BlockBlobAppendStream.java

CryptoInputStream to support unbuffer
* CryptoInputStream.java
* CryptoStreamsTestBase.java
* TestCryptoStreams.java
* TestCryptoStreamsForLocalFS.java
* TestCryptoStreamsNormal.java

If CryptoInputStream unbuffer change has to be reverted for any reason, we will still have
StreamCapabilities enhancements.

> 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, HADOOP-14872.009.patch, HADOOP-14872.010.patch, HADOOP-14872.011.patch,
HADOOP-14872.012.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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