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https://issues.apache.org/jira/browse/HDFS-16333?focusedWorklogId=690836&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-690836
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ASF GitHub Bot logged work on HDFS-16333:
-----------------------------------------

                Author: ASF GitHub Bot
            Created on: 06/Dec/21 08:59
            Start Date: 06/Dec/21 08:59
    Worklog Time Spent: 10m 
      Work Description: liubingxing edited a comment on pull request #3679:
URL: https://github.com/apache/hadoop/pull/3679#issuecomment-986568780


   @tasanuma Thank you for your review and comments. 
   
   I run the UT `doTestBalancerWithStripedFile` in current trunk branch and 
sometimes the errors occur .
   
![企业微信截图_fa59a4ad-e149-4259-b587-31468bb77e69](https://user-images.githubusercontent.com/2844826/144813625-e15c5bea-ec9f-48e9-8aff-c0d14449ffe1.png)
   
   Therefore, it is not good to use `assertEquals(0, 
nnc.getBlocksFailed().get())` to check the result in this new UT.
   I will redesign a UT to test this scenario as soon as possible.
   If you have any suggestions, please let me know, thank you.


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Issue Time Tracking
-------------------

    Worklog Id:     (was: 690836)
    Time Spent: 1h 50m  (was: 1h 40m)

> fix balancer bug when transfer an EC block
> ------------------------------------------
>
>                 Key: HDFS-16333
>                 URL: https://issues.apache.org/jira/browse/HDFS-16333
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: balancer & mover
>            Reporter: qinyuren
>            Assignee: qinyuren
>            Priority: Major
>              Labels: pull-request-available
>         Attachments: image-2021-11-18-17-25-13-089.png, 
> image-2021-11-18-17-25-50-556.png, image-2021-11-18-17-28-03-155.png
>
>          Time Spent: 1h 50m
>  Remaining Estimate: 0h
>
> We set the EC policy to (6+3) and we also have nodes that were 
> decommissioning when we executed balancer.
> With the balancer running, we find many error logs as follow.
> !image-2021-11-18-17-25-13-089.png|width=858,height=135!
> Node A wants to transfer an EC block to node B, but we found that the block 
> is not on node A. The FSCK command to show the block status as follow
> !image-2021-11-18-17-25-50-556.png|width=607,height=189!
> In the dispatcher. getBlockList function
> !image-2021-11-18-17-28-03-155.png!
>  
> Assume that the location of the an EC block in storageGroupMap look like this
> indices:[0, 1, 2, 3, 4, 5, 6, 7, 8]
> node:[a, b, c, d, e, f, g, h, i]
> after decommission operation, the internal block on indices[1] were 
> decommission to another node.
> indices:[0, 1, 2, 3, 4, 5, 6, 7, 8]
> node:[a, {color:#FF0000}j{color}, c, d, e, f, g, h, i]
> the location of indices[1] change from node {color:#FF0000}b{color} to node 
> {color:#FF0000}j{color}.
>  
> When the balancer get the block location and check it with the location in 
> storageGroupMap.
> If a node is not found in storageGroupMap, it will not be add to block 
> locations.
> In this case, node {color:#FF0000}j {color}will not be added to the block 
> locations, while the indices is not updated.
> Finally, the block location may look like this, 
> indices:[0, 1, 2, 3, 4, 5, 6, 7, 8]
> {color:#FF0000}block.location:[a, c, d, e, f, g, h, i]{color}
> the location of the nodes does not match their indices
>  
> Solution:
> we should update the indices and match with the nodes
> {color:#FF0000}indices:[0, 2, 3, 4, 5, 6, 7, 8]{color}
> {color:#FF0000}block.location:[a, c, d, e, f, g, h, i]{color}



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