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https://issues.apache.org/jira/browse/HDFS-6840?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14140539#comment-14140539
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Hudson commented on HDFS-6840:
------------------------------
FAILURE: Integrated in Hadoop-Mapreduce-trunk #1901 (See
[https://builds.apache.org/job/Hadoop-Mapreduce-trunk/1901/])
HDFS-6840. Clients are always sent to the same datanode when read is off rack.
(wang) (wang: rev 8e73084491c9f317bc8cc3590f93ca67a63687a8)
* hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml
*
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java
*
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/NetworkTopology.java
* hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
*
hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/net/TestNetworkTopologyWithNodeGroup.java
*
hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/net/TestNetworkTopology.java
*
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeManager.java
*
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java
*
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/NetworkTopologyWithNodeGroup.java
> 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
> Fix For: 2.6.0
>
> Attachments: hdfs-6840.001.patch, hdfs-6840.002.patch,
> hdfs-6840.003.patch, hdfs-6840.branch-2.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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