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https://issues.apache.org/jira/browse/HDFS-4937?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14983924#comment-14983924
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Hudson commented on HDFS-4937:
------------------------------
FAILURE: Integrated in Hadoop-Mapreduce-trunk-Java8 #612 (See
[https://builds.apache.org/job/Hadoop-Mapreduce-trunk-Java8/612/])
Revert "HDFS-4937. ReplicationMonitor can infinite-loop in (yliu: rev
7fd6416759cbb202ed21b47d28c1587e04a5cdc6)
* hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
*
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockPlacementPolicyDefault.java
> ReplicationMonitor can infinite-loop in
> BlockPlacementPolicyDefault#chooseRandom()
> ----------------------------------------------------------------------------------
>
> Key: HDFS-4937
> URL: https://issues.apache.org/jira/browse/HDFS-4937
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 2.0.4-alpha, 0.23.8
> Reporter: Kihwal Lee
> Assignee: Kihwal Lee
> Labels: BB2015-05-TBR
> Fix For: 3.0.0, 2.7.2
>
> Attachments: HDFS-4937.patch, HDFS-4937.v1.patch, HDFS-4937.v2.patch
>
>
> When a large number of nodes are removed by refreshing node lists, the
> network topology is updated. If the refresh happens at the right moment, the
> replication monitor thread may stuck in the while loop of {{chooseRandom()}}.
> This is because the cached cluster size is used in the terminal condition
> check of the loop. This usually happens when a block with a high replication
> factor is being processed. Since replicas/rack is also calculated beforehand,
> no node choice may satisfy the goodness criteria if refreshing removed racks.
> All nodes will end up in the excluded list, but the size will still be less
> than the cached cluster size, so it will loop infinitely. This was observed
> in a production environment.
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