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https://issues.apache.org/jira/browse/HDFS-11019?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15582321#comment-15582321
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Kihwal Lee commented on HDFS-11019:
-----------------------------------

[~kshukla] has debugged and worked on this quite a bit. She might have an idea.

> Inconsistent number of corrupt replicas if a corrupt replica is reported 
> multiple times
> ---------------------------------------------------------------------------------------
>
>                 Key: HDFS-11019
>                 URL: https://issues.apache.org/jira/browse/HDFS-11019
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>         Environment: CDH5.7.2 
>            Reporter: Wei-Chiu Chuang
>
> While investigating a block corruption issue, I found the following warning 
> message in the namenode log:
> {noformat}
> (a client reports a block replica is corrupt)
> 2016-10-12 10:07:37,166 INFO BlockStateChange: BLOCK 
> NameSystem.addToCorruptReplicasMap: blk_1073803461 added as corrupt on 
> 10.0.0.63:50010 by /10.0.0.62  because client machine reported it
> 2016-10-12 10:07:37,166 INFO BlockStateChange: BLOCK* invalidateBlock: 
> blk_1073803461_74513(stored=blk_1073803461_74553) on 10.0.0.63:50010
> 2016-10-12 10:07:37,166 INFO BlockStateChange: BLOCK* InvalidateBlocks: add 
> blk_1073803461_74513 to 10.0.0.63:50010
> (another client reports a block replica is corrupt)
> 2016-10-12 10:07:37,728 INFO BlockStateChange: BLOCK 
> NameSystem.addToCorruptReplicasMap: blk_1073803461 added as corrupt on 
> 10.0.0.63:50010 by /10.0.0.64  because client machine reported it
> 2016-10-12 10:07:37,728 INFO BlockStateChange: BLOCK* invalidateBlock: 
> blk_1073803461_74513(stored=blk_1073803461_74553) on 10.0.0.63:50010
> (ReplicationMonitor thread kicks in to invalidate the replica and add a new 
> one)
> 2016-10-12 10:07:37,888 INFO BlockStateChange: BLOCK* ask 10.0.0.56:50010 to 
> replicate blk_1073803461_74553 to datanode(s) 10.0.0.63:50010
> 2016-10-12 10:07:37,888 INFO BlockStateChange: BLOCK* BlockManager: ask 
> 10.0.0.63:50010 to delete [blk_1073803461_74513]
> (the two maps are inconsistent)
> 2016-10-12 10:08:00,335 WARN 
> org.apache.hadoop.hdfs.server.blockmanagement.BlockManager: Inconsistent 
> number of corrupt replicas for blk_1073803461_74553 blockMap has 0 but 
> corrupt replicas map has 1
> {noformat}
> It seems that when a corrupt block replica is reported twice, blockMap 
> corrupt and corrupt replica map becomes inconsistent.
> Looking at the log, I suspect the bug is in 
> {{BlockManager#removeStoredBlock}}. When a corrupt replica is reported, 
> BlockManager removes the block from blocksMap. If the block is already 
> removed (that is, the corrupt replica is reported twice), return; Otherwise 
> (that is, the corrupt replica is reported the first time), remove the block 
> from corruptReplicasMap (The block is added into corruptReplicasMap in 
> BlockerManager#markBlockAsCorrupt) Therefore, after the second corruption 
> report, the corrupt replica is removed from blocksMap, but the one in 
> corruptReplicasMap is not removed.
> I can’t tell what’s the impact that they are inconsistent. But I feel it's a 
> good idea to fix it.



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