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https://issues.apache.org/jira/browse/HDFS-8277?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14518968#comment-14518968
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surendra singh lilhore commented on HDFS-8277:
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In {{DFSAdmin.java}} class {{setSafeMode()}} API will iterate on NN proxy list
and one by one set NN in safe mode.
If first namenode connection is failed then it will come out from loop.
{code}
for (ProxyAndInfo<ClientProtocol> proxy : proxies) {
ClientProtocol haNn = proxy.getProxy();
boolean inSafeMode = haNn.setSafeMode(action, false);
if (waitExitSafe) {
inSafeMode = waitExitSafeMode(haNn, inSafeMode);
}
System.out.println("Safe mode is " + (inSafeMode ? "ON" : "OFF")
+ " in " + proxy.getAddress());
}
{code}
Here we should catch the connection exception and continue for next NN.
> 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: Improvement
> 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 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.
> Hari Sekhon
> http://www.linkedin.com/in/harisekhon
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