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https://issues.apache.org/jira/browse/HDFS-15495?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17167526#comment-17167526
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Siyao Meng edited comment on HDFS-15495 at 7/29/20, 10:20 PM:
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Awesome! Thanks [~sodonnell] for the writeup and unit test.
I tried your UT and it works - I mean it failed because the decom is hung. So 
we can confirm this is still the case on trunk.


was (Author: smeng):
Awesome! Thanks [~sodonnell] for the writeup and unit test.
I tried your UT and it works - I mean it failed because the decom is hang. So 
we can confirm this is still the case on trunk.

> Decommissioning a DataNode with corrupted EC files should not be blocked 
> indefinitely
> -------------------------------------------------------------------------------------
>
>                 Key: HDFS-15495
>                 URL: https://issues.apache.org/jira/browse/HDFS-15495
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: block placement, ec
>    Affects Versions: 3.0.0
>            Reporter: Siyao Meng
>            Assignee: Siyao Meng
>            Priority: Major
>
> Originally discovered in patched CDH 6.2.1 (with a bunch of EC fixes: 
> HDFS-14699, HDFS-14849, HDFS-14847, HDFS-14920, HDFS-14768, HDFS-14946, 
> HDFS-15186).
> When there's an EC file marked as corrupted on NN, if the admin tries to 
> decommission a DataNode having one of the remaining blocks of the corrupted 
> EC file, *the decom will never finish* unless the file is recovered by 
> putting the missing blocks back in:
> {code:title=The endless DatanodeAdminManager check loop, every 30s}
> 2020-07-23 16:36:12,805 TRACE blockmanagement.DatanodeAdminManager: Processed 
> 0 blocks so far this tick
> 2020-07-23 16:36:12,806 DEBUG blockmanagement.DatanodeAdminManager: 
> Processing Decommission In Progress node 127.0.1.7:5007
> 2020-07-23 16:36:12,806 TRACE blockmanagement.DatanodeAdminManager: Block 
> blk_-9223372036854775728_1013 numExpected=9, numLive=4
> 2020-07-23 16:36:12,806 INFO BlockStateChange: Block: 
> blk_-9223372036854775728_1013, Expected Replicas: 9, live replicas: 4, 
> corrupt replicas: 0, decommissioned replicas: 0, decommissioning replicas: 1, 
> maintenance replicas: 0, live entering maintenance replicas: 0, excess 
> replicas: 0, Is Open File: false, Datanodes having this block: 
> 127.0.1.12:5012 127.0.1.10:5010 127.0.1.8:5008 127.0.1.11:5011 127.0.1.7:5007 
> , Current Datanode: 127.0.1.7:5007, Is current datanode decommissioning: 
> true, Is current datanode entering maintenance: false
> 2020-07-23 16:36:12,806 DEBUG blockmanagement.DatanodeAdminManager: Node 
> 127.0.1.7:5007 still has 1 blocks to replicate before it is a candidate to 
> finish Decommission In Progress.
> 2020-07-23 16:36:12,806 INFO blockmanagement.DatanodeAdminManager: Checked 1 
> blocks and 1 nodes this tick
> {code}
> "Corrupted" file here meaning the EC file doesn't have enough EC blocks in 
> the block group to be reconstructed. e.g. for {{RS-6-3-1024k}}, when there 
> are less than 6 blocks for an EC file, the file can no longer be retrieved 
> correctly.



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