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https://issues.apache.org/jira/browse/HDFS-8277?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14536124#comment-14536124
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Arpit Agarwal commented on HDFS-8277:
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Hi [~brahmareddy], you are right and that is part of the fix. It does not
address the main issue that the administrator's intention is not preserved
across failover and restart. Even a successful command guarantees nothing since
failover just a few seconds later could put the filesystem back in read-write
mode.
>From a brief offline chat with [~sanjay.radia] and [~cnauroth] - the agreement
>was that manual safe mode transitions must be logged in NN persistent storage.
>We'll need edit log entries for manual safe mode transitions and a flag in the
>FsImage. [~surendrasingh], do you want to take a crack at fixing it as part of
>this jira? I'd be happy to help if you get stuck.
> 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
> 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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