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https://issues.apache.org/jira/browse/HDFS-9391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15802316#comment-15802316
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Manoj Govindassamy commented on HDFS-9391:
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Case 1: One replica is decommissioning and two replicas of the same block are 
entering maintenance

{quote} the code will still increment maintenanceOnlyReplicas when processing 
the decommissioning node, because NumberReplicas includes all replicas stats.
{quote}

* I don't think so. In the current upstream trunk code, a node can only be in 
one state and {{NumberReplicas}} accounting for _Decommission_ and 
_Maintenance_ are exclusive. If the replica is Decommissioning, it cannot be in 
any of Maintenance states, and vice versa. 

* In the current upstream trunk code, {{outOfServiceReplicas}} is defined as a 
sum of both decommission and maintenance

* Patch v02 in this jira, just makes use of already accounted numbers in 
{{NumberReplicas}} in different variables namely -- decommissionOnlyReplicas 
and maintenanceOnlyReplicas

So in the above example, with the patch v02 we will get following numbers 
-- decommissionOnlyReplicas = 1
-- maintenanceOnlyReplicas = 2
-- outOfServiceReplicas = 3 

Hence, 
-- Entering Maintenance page will only show 2 maintenance replica nodes
-- Decommissioning page will only show 1 decommissioning replica node


Case 2: All replicas are decommissioning

{quote}EnteringMaintenance page will have nothing to show to begin with given 
no nodes are entering maintenance.{quote}

* Thats right. When all replicas are decommissioning, {{NumberReplicas}} will 
only have decommissionedAndDecommissioning nodes.
* Entering Maintenance page will be empty
* Decommissioning page will show all these decommissioning nodes
 

[~mingma],
* Do the above cases and results match your expectation ?

* Also, lets make sure we are targeting the same goals w.r.t Decommissioing and 
EnteringMaintenance Page. Based on the discussions we had earlier (refer 
comments 1 - 4), I assumed we want the following 
** Entering Maintenance Page to show the nodes that are Entering Maintenance / 
In Maintenance Only.
** Decommissioning Page to show the nodes that are Decommissioning / 
Decommissioned Only.

* Please correct me if my understanding from the current upstream trunk code is 
wrong or if we want different goals for the pages.



> Update webUI/JMX to display maintenance state info
> --------------------------------------------------
>
>                 Key: HDFS-9391
>                 URL: https://issues.apache.org/jira/browse/HDFS-9391
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>    Affects Versions: 3.0.0-alpha1
>            Reporter: Ming Ma
>            Assignee: Manoj Govindassamy
>         Attachments: HDFS-9391-MaintenanceMode-WebUI.pdf, HDFS-9391.01.patch, 
> HDFS-9391.02.patch, Maintenance webUI.png
>
>




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