[jira] [Commented] (MAPREDUCE-4233) NPE can happen in RMNMNodeInfo.

["Bikas Saha (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MAPREDUCE-4233?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13270634#comment-13270634 ] 

Bikas Saha commented on MAPREDUCE-4233:
---------------------------------------

Does this happen because a node got added back (say because it became healthy) and the nodes list in RMContext got updated before the nodes list in Scheduler? Then the solution to check for null would be valid because its a temporary synch issue.

Any chance that the above was due to a bug which caused RMcontext nodes list and Scheduler nodes list to become permanently out of sync?
                
> NPE can happen in RMNMNodeInfo.
> -------------------------------
>
>                 Key: MAPREDUCE-4233
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4233
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>    Affects Versions: 0.23.3
>            Reporter: Robert Joseph Evans
>            Assignee: Robert Joseph Evans
>            Priority: Critical
>
> {noformat}
> Caused by: java.lang.NullPointerException
>         at org.apache.hadoop.yarn.server.resourcemanager.RMNMInfo.getLiveNodeManagers(RMNMInfo.java:96)
>         at sun.reflect.GeneratedMethodAccessor50.invoke(Unknown Source)
>         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
>         at java.lang.reflect.Method.invoke(Method.java:597)
>         at com.sun.jmx.mbeanserver.StandardMBeanIntrospector.invokeM2(StandardMBeanIntrospector.java:93)
>         at com.sun.jmx.mbeanserver.StandardMBeanIntrospector.invokeM2(StandardMBeanIntrospector.java:27)
>         at com.sun.jmx.mbeanserver.MBeanIntrospector.invokeM(MBeanIntrospector.java:208)
>         at com.sun.jmx.mbeanserver.PerInterface.getAttribute(PerInterface.java:65)
>         at com.sun.jmx.mbeanserver.MBeanSupport.getAttribute(MBeanSupport.java:216)
>         at javax.management.StandardMBean.getAttribute(StandardMBean.java:358)
>         at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.getAttribute(DefaultMBeanServerInterceptor.java:666)
> {noformat}
> Looks like rmcontext.getRMNodes() is not kept in sync with scheduler.getNodeReport(), so that the report can be null even though the context still knowns about the node.
> The simple fix is to add in a null check.

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