[ 
https://issues.apache.org/jira/browse/HDFS-6840?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14139797#comment-14139797
 ] 

Hadoop QA commented on HDFS-6840:
---------------------------------

{color:red}-1 overall{color}.  Here are the results of testing the latest 
attachment 
  http://issues.apache.org/jira/secure/attachment/12669817/hdfs-6840.003.patch
  against trunk revision eb92cc6.

    {color:green}+1 @author{color}.  The patch does not contain any @author 
tags.

    {color:green}+1 tests included{color}.  The patch appears to include 2 new 
or modified test files.

    {color:green}+1 javac{color}.  The applied patch does not increase the 
total number of javac compiler warnings.

    {color:green}+1 javadoc{color}.  There were no new javadoc warning messages.

    {color:green}+1 eclipse:eclipse{color}.  The patch built with 
eclipse:eclipse.

    {color:green}+1 findbugs{color}.  The patch does not introduce any new 
Findbugs (version 2.0.3) warnings.

    {color:green}+1 release audit{color}.  The applied patch does not increase 
the total number of release audit warnings.

    {color:red}-1 core tests{color}.  The patch failed these unit tests in 
hadoop-common-project/hadoop-common hadoop-hdfs-project/hadoop-hdfs:

                  org.apache.hadoop.hdfs.TestEncryptionZonesWithKMS
                  org.apache.hadoop.hdfs.web.TestWebHdfsFileSystemContract
                  
org.apache.hadoop.hdfs.server.namenode.ha.TestPipelinesFailover

    {color:green}+1 contrib tests{color}.  The patch passed contrib unit tests.

Test results: 
https://builds.apache.org/job/PreCommit-HDFS-Build/8090//testReport/
Console output: https://builds.apache.org/job/PreCommit-HDFS-Build/8090//console

This message is automatically generated.

> Clients are always sent to the same datanode when read is off rack
> ------------------------------------------------------------------
>
>                 Key: HDFS-6840
>                 URL: https://issues.apache.org/jira/browse/HDFS-6840
>             Project: Hadoop HDFS
>          Issue Type: Bug
>    Affects Versions: 2.5.0
>            Reporter: Jason Lowe
>            Assignee: Andrew Wang
>            Priority: Critical
>         Attachments: hdfs-6840.001.patch, hdfs-6840.002.patch, 
> hdfs-6840.003.patch
>
>
> After HDFS-6268 the sorting order of block locations is deterministic for a 
> given block and locality level (e.g.: local, rack. off-rack), so off-rack 
> clients all see the same datanode for the same block.  This leads to very 
> poor behavior in distributed cache localization and other scenarios where 
> many clients all want the same block data at approximately the same time.  
> The one datanode is crushed by the load while the other replicas only handle 
> local and rack-local requests.



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