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https://issues.apache.org/jira/browse/HDFS-12935?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16298591#comment-16298591
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Brahma Reddy Battula commented on HDFS-12935:
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[~jiangjianfei] thanks for reporting and patch.The apporach looks good to me.

Added you as HDFS contributor,now onwards you can assign issues yourself.Have 
look at [HowToContribute|https://wiki.apache.org/hadoop/HowToContribute] 

Removed the fixversion which will be set whil committing the patch.

Can we handle for remainging admin commands(which are not require to persist) 
as part of this jira apart from safemode(HDFS-8277)..?
hdfs dfsadmin -saveNamespace
hdfs dfsadmin -refreshNodes
hdfs dfsadmin -refreshCallQueue
and if any command I miss here.



> Get ambiguous result for DFSAdmin command in HA mode when only one namenode 
> is up
> ---------------------------------------------------------------------------------
>
>                 Key: HDFS-12935
>                 URL: https://issues.apache.org/jira/browse/HDFS-12935
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: tools
>    Affects Versions: 3.0.0-beta1
>            Reporter: Jianfei Jiang
>         Attachments: HDFS_12935.001.patch
>
>
> In HA mode, if one namenode is down, most of functions can still work. When 
> considering the following two occasions:
>  (1)nn1 up and nn2 down
>  (2)nn1 down and nn2 up
> These two occasions should be equivalent. However, some of the DFSAdmin 
> commands will have ambiguous results. The commands can be send successfully 
> to the up namenode and are always functionally useful only when nn1 is up 
> regardless of exception (IOException when connecting to the down namenode 
> nn2). If only nn2 is up, the commands have no use at all and only exception 
> to connect nn1 can be found.
> See the following command "hdfs dfsadmin setBalancerBandwidth" which aim to 
> set balancer bandwidth value for datanodes as an example. It works and all 
> the datanodes can get the setting values only when nn1 is up. If only nn2 is 
> up, the command throws exception directly and no datanode get the bandwidth 
> setting. Approximately ten DFSAdmin commands use the similar logical process 
> and may be ambiguous.
> [root@jiangjianfei01 ~]# hdfs haadmin -getServiceState nn1
> active
> [root@jiangjianfei01 ~]# hdfs dfsadmin -setBalancerBandwidth 12345
> *Balancer bandwidth is set to 12345 for jiangjianfei01/172.17.0.14:9820*
> setBalancerBandwidth: Call From jiangjianfei01/172.17.0.14 to 
> jiangjianfei02:9820 failed on connection exception: 
> java.net.ConnectException: Connection refused; For more details see:  
> http://wiki.apache.org/hadoop/ConnectionRefused
> [root@jiangjianfei01 ~]# hdfs haadmin -getServiceState nn2
> active
> [root@jiangjianfei01 ~]# hdfs dfsadmin -setBalancerBandwidth 1234
> setBalancerBandwidth: Call From jiangjianfei01/172.17.0.14 to 
> jiangjianfei01:9820 failed on connection exception: 
> java.net.ConnectException: Connection refused; For more details see:  
> http://wiki.apache.org/hadoop/ConnectionRefused
> [root@jiangjianfei01 ~]# 



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