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https://issues.apache.org/jira/browse/YARN-3222?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14329136#comment-14329136
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Rohith commented on YARN-3222:
------------------------------

I see there are 2 ways of fixing the issue.
# Always send NODE_RESOURCE_UPDATE event to scheduler via 
RMNodeEventType.RESOURCE_UPDATE of RMnode
# When NODE_ADDED event is sent to scheduler, again sending 
NODE_RESOURCE_UPDATE event to same node ReconnectedNodeTransition is duplicate 
update request because scheduler has already been updated resources with newly 
added node i.e NODE_REMOVED->NODE_ADDED-->NODE_RESOURCE_UPDATE-->. So if NO 
applications are  running in the node, then it is not required to send 
node_resource_update request.

I would prefer for 2nd option because here one duplicate resource update can be 
optimized. 

> RMNodeImpl#ReconnectNodeTransition should send scheduler events in sequential 
> order
> -----------------------------------------------------------------------------------
>
>                 Key: YARN-3222
>                 URL: https://issues.apache.org/jira/browse/YARN-3222
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: resourcemanager
>    Affects Versions: 2.6.0
>            Reporter: Rohith
>            Assignee: Rohith
>            Priority: Critical
>
> When a node is reconnected,RMNodeImpl#ReconnectNodeTransition notifies the 
> scheduler in a events node_added,node_removed or node_resource_update. These 
> events should be notified in an sequential order i.e node_added event and 
> next node_resource_update events.
> But if the node is reconnected with different http port, the oder of 
> scheduler events are node_removed --> node_resource_update --> node_added 
> which causes scheduler does not find the node and throw NPE and RM exit.
> Node_Resource_update event should be always should be triggered via 
> RMNodeEventType.RESOURCE_UPDATE



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