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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:
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Status: Patch Available (was: Open)
> 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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