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https://issues.apache.org/jira/browse/HDFS-8277?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14535144#comment-14535144
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surendra singh lilhore commented on HDFS-8277:
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Thanks [~arpitagarwal] for looking in to this issue.

bq.  if the other NN comes back and there is a failover for any reason.

Same problem will come if both NN in safe mode and one namenode got restarted.

I think restart case we should handle in new Jira, but here safe mode command 
should not fail if one NN is down.

> Safemode enter fails when Standby NameNode is down
> --------------------------------------------------
>
>                 Key: HDFS-8277
>                 URL: https://issues.apache.org/jira/browse/HDFS-8277
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: ha, HDFS, namenode
>    Affects Versions: 2.6.0
>         Environment: HDP 2.2.0
>            Reporter: Hari Sekhon
>            Assignee: surendra singh lilhore
>            Priority: Minor
>              Labels: BB2015-05-RFC
>         Attachments: HDFS-8277.patch, HDFS-8277_1.patch, HDFS-8277_2.patch, 
> HDFS-8277_3.patch, HDFS-8277_4.patch
>
>
> HDFS fails to enter safemode when the Standby NameNode is down (eg. due to 
> AMBARI-10536).
> {code}hdfs dfsadmin -safemode enter
> safemode: Call From nn2/x.x.x.x to nn1:8020 failed on connection exception: 
> java.net.ConnectException: Connection refused; For more details see:  
> http://wiki.apache.org/hadoop/ConnectionRefused{code}
> This appears to be a bug in that it's not trying both NameNodes like the 
> standard hdfs client code does, and is instead stopping after getting a 
> connection refused from nn1 which is down. I verified normal hadoop fs writes 
> and reads via cli did work at this time, using nn2. I happened to run this 
> command as the hdfs user on nn2 which was the surviving Active NameNode.
> After I re-bootstrapped the Standby NN to fix it the command worked as 
> expected again.



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