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https://issues.apache.org/jira/browse/HADOOP-4071?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Hairong Kuang updated HADOOP-4071:
----------------------------------

      Resolution: Fixed
    Hadoop Flags: [Reviewed]
          Status: Resolved  (was: Patch Available)

The failed tests are not related to this issue. The change is too small to have 
a unit test. I've committed this!

> FSNameSystem.isReplicationInProgress should add an underReplicated block to 
> the neededReplication queue using method "add" not "update"
> ---------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-4071
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4071
>             Project: Hadoop Core
>          Issue Type: Bug
>            Reporter: Hairong Kuang
>            Assignee: Hairong Kuang
>             Fix For: 0.19.0
>
>         Attachments: decommission.patch
>
>
> We have a datanode that did not get decommission done for days. It turned out 
> that there was an under replicated block that was never placed in the 
> neededReplication queue and therefore did not get replicated. The following 
> debug line showed the problem:
> " DEBUG org.apache.hadoop.dfs.StateChange: UnderReplicationBlocks.update 
> blk_-7437651423871278837_0 curReplicas 8
> curExpectedReplicas 10 oldReplicas 9 oldExpectedReplicas  10 curPri  2 oldPri 
>  2"
> The block was not in the neededReplication queue, but the update method 
> concluded that the block was under replicated and the priority level did not 
> change, so it did not add the block to the needReplication queue.
> The solution is that in stead of using the update method, the name node 
> should use the add method to add the block to the neededReplication queue. 
> The add method guarantees success if the block is indeed under replicated.

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