[jira] [Commented] (HDFS-5579) Under construction files make DataNode decommission take very long hours

["Vinay (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDFS-5579?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13834600#comment-13834600 ] 

Vinay commented on HDFS-5579:
-----------------------------

Thanks [~zhaoyunjiong] for filing Jira.

I think your fix would work and decommission datanode quickly.
Here is little comments about your patch.

1. try-catch not required. no statement inside try block will throw exception.

2. {code}block.getBlockId() == bc.getLastBlock().getBlockId(){code}
Better to use block.equals(bc.getLastBlock())

3. {code}if (block.getBlockId() == bc.getLastBlock().getBlockId() && curReplicas > 1) {
+              continue;
+            }{code}
Instead of 1 use minReplication

4. {code}+          underReplicatedInOpenFiles++;{code}
This should be incremented only if enough replicas are not there.

> Under construction files make DataNode decommission take very long hours
> ------------------------------------------------------------------------
>
>                 Key: HDFS-5579
>                 URL: https://issues.apache.org/jira/browse/HDFS-5579
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 1.2.0, 2.2.0
>            Reporter: zhaoyunjiong
>            Assignee: zhaoyunjiong
>         Attachments: HDFS-5579-branch-1.2.patch, HDFS-5579.patch
>
>
> We noticed that some times decommission DataNodes takes very long time, even exceeds 100 hours.
> After check the code, I found that in BlockManager:computeReplicationWorkForBlocks(List<List<Block>> blocksToReplicate) it won't replicate blocks which belongs to under construction files, however in BlockManager:isReplicationInProgress(DatanodeDescriptor srcNode), if there  is block need replicate no matter whether it belongs to under construction or not, the decommission progress will continue running.
> That's the reason some time the decommission takes very long time.



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