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https://issues.apache.org/jira/browse/HDFS-1773?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tanping Wang updated HDFS-1773:
-------------------------------

    Attachment: HDFS-1773-2.patch

Discussed with Nicholas about the first approach by removing datanode from 
datanodeMap directly.  The concern here is that datanodeMap is a super set that 
stores the datanode -> block map. If we remove the datanode from the 
datanodeMap, we are not certain if any potential negative impact would happen 
to some other related data structures whose relationship with datanodeMap is 
not that obvious.  Plus, it seems that a dedicated function, 
wipeDatanode(DatanodeID nodeID) is being used to remove a node from 
datanodeMap.  Since this is only for 20
release, ( decommission data states will be changed in next release of HDFS), 
we decide to only remove the decommission node from the list of dead nodes for 
displaying purpose only.  That is to say, before displaying the list of dead 
node to either JSP or jmx, we check for decommissioned dead data node and 
remove them for displaying.  We also add a check 
{code}
node.isDecommissioned())
{code}
to make sure before removing the data node from dead list, it is already
decommissioned.

> Remove a datanode from cluster if include list is not empty and this datanode 
> is removed from both include and exclude lists
> ----------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-1773
>                 URL: https://issues.apache.org/jira/browse/HDFS-1773
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>    Affects Versions: 0.20.203.1
>         Environment: branch-20-security
>            Reporter: Tanping Wang
>            Assignee: Tanping Wang
>            Priority: Minor
>             Fix For: 0.20.4
>
>         Attachments: HDFS-1773-2.patch, HDFS-1773.patch
>
>
> Our service engineering team who operates the clusters on a daily basis 
> founds it is confusing that after a data node is decommissioned, there is no 
> way to make the cluster forget about this data node and it always remains in 
> the dead node list.

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