Di Li commented on AMBARI-19289:

pushed to trunk as 

> HDFS Service check fails if previous active NN is down
> ------------------------------------------------------
>                 Key: AMBARI-19289
>                 URL: https://issues.apache.org/jira/browse/AMBARI-19289
>             Project: Ambari
>          Issue Type: Bug
>          Components: ambari-server
>    Affects Versions: 2.4.2
>            Reporter: Weiwei Yang
>            Assignee: Weiwei Yang
>             Fix For: trunk
>         Attachments: AMBARI-19289_branch-2.5.01.patch, 
> AMBARI-19289_trunk.01.patch, AMBARI-19289_trunk.02.patch
> *Reproduce steps*
> # Enable namenode HA
> # Shutdown the active namenode, standby takes over
> # Run HDFS service check
> hdfs service check script uses
> {{hdfs dfsadmin -fs hdfs://mycluster -safemode get | grep OFF}}
> to check if namenode is out of safemode. However this command will fail if 
> 1st NN is down without checking the state of 2nd NN. This is likely a HDFS 
> bug similar to HDFS-8277.
> *Proposal*
> There are several approaches to fix this
> # Loop each namenode address and get safemode with {{hdfs dfsadmin -fs 
> hdfs://nn_host:8020 -safemode get | grep OFF}}, as long as there is one NN 
> returns OFF, consider DFS is not in safemode and continue the rest of check. 
> However is it really necessary to add such complexity for service check?
> # Remove the safemode check code, if HDFS is in safemode, read/write 
> operations will fail anyway so service check won't pass
> I am preferring to #2 because it makes script simpler and work in all cases. 
> Note this is service check, it should pass as long as HDFS is in working 
> state. It is not namenode check.

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