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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-4937) ReplicationMonitor can infinite-loop in BlockPlacementPolicyDefault#chooseRandom()
Date Thu, 29 Oct 2015 19:45:27 GMT

    [ https://issues.apache.org/jira/browse/HDFS-4937?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14981132#comment-14981132
] 

Kihwal Lee commented on HDFS-4937:
----------------------------------

The failed test cases pass when run locally. 
{noformat}
-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Java HotSpot(TM) 64-Bit Server VM warning: ignoring option MaxPermSize=768m; support was removed
in 8.0
Running org.apache.hadoop.hdfs.server.namenode.snapshot.TestRenameWithSnapshots
Tests run: 36, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 146.108 sec - in org.apache.hadoop.hdfs.server.namenode.snapshot.TestRenameWithSnapshots
Java HotSpot(TM) 64-Bit Server VM warning: ignoring option MaxPermSize=768m; support was removed
in 8.0
Running org.apache.hadoop.hdfs.server.namenode.snapshot.TestSnapshotBlocksMap
Tests run: 7, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 30.379 sec - in org.apache.hadoop.hdfs.server.namenode.snapshot.TestSnapshotBlocksMap
Java HotSpot(TM) 64-Bit Server VM warning: ignoring option MaxPermSize=768m; support was removed
in 8.0
Running org.apache.hadoop.hdfs.server.namenode.ha.TestEditLogTailer
Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 12.582 sec - in org.apache.hadoop.hdfs.server.namenode.ha.TestEditLogTailer
Java HotSpot(TM) 64-Bit Server VM warning: ignoring option MaxPermSize=768m; support was removed
in 8.0
Running org.apache.hadoop.hdfs.server.namenode.ha.TestStandbyCheckpoints
Tests run: 7, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 104.369 sec - in org.apache.hadoop.hdfs.server.namenode.ha.TestStandbyCheckpoints

Results :

Tests run: 54, Failures: 0, Errors: 0, Skipped: 0
{noformat}
Also, there actually is no new findbugs issue.

> 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
>         Attachments: HDFS-4937.patch, HDFS-4937.v1.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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