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https://issues.apache.org/jira/browse/HDFS-14655?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16885850#comment-16885850
 ] 

Ayush Saxena commented on HDFS-14655:
-------------------------------------

For Observer read, The edit log tail period is set to 0, 
(dfs.ha.tail-edits.period)
There are three Journal nodes, the tailing process succeeds if it is able to 
fetch the response from majority of the JN's and then moves out. i.e succeeds 
and returns if it gets response from 2 JN. The thread for the third JN keeps on 
trying 10 times on ConnectException. But since the tailing period is quite low, 
By the time one stuck thread completes. Similar retrying stuck threads, Piles 
up. Leading to OOM

> SBN : Namenode crashes if one of The jN is down
> -----------------------------------------------
>
>                 Key: HDFS-14655
>                 URL: https://issues.apache.org/jira/browse/HDFS-14655
>             Project: Hadoop HDFS
>          Issue Type: Bug
>            Reporter: Harshakiran Reddy
>            Priority: Major
>
> {noformat}
> 2019-07-04 17:35:54,064 | INFO  | Logger channel (from parallel executor) to 
> XXXXXXX/XXXXXXX | Retrying connect to server: XXXXXXX/XXXXXXX. Already tried 
> 9 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, 
> sleepTime=1000 MILLISECONDS) | Client.java:975
> 2019-07-04 17:35:54,087 | FATAL | Edit log tailer | Unknown error encountered 
> while tailing edits. Shutting down standby NN. | EditLogTailer.java:474
> java.lang.OutOfMemoryError: unable to create new native thread
>       at java.lang.Thread.start0(Native Method)
>       at java.lang.Thread.start(Thread.java:717)
>       at 
> java.util.concurrent.ThreadPoolExecutor.addWorker(ThreadPoolExecutor.java:957)
>       at 
> java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1378)
>       at 
> com.google.common.util.concurrent.MoreExecutors$ListeningDecorator.execute(MoreExecutors.java:440)
>       at 
> com.google.common.util.concurrent.AbstractListeningExecutorService.submit(AbstractListeningExecutorService.java:56)
>       at 
> org.apache.hadoop.hdfs.qjournal.client.IPCLoggerChannel.getJournaledEdits(IPCLoggerChannel.java:565)
>       at 
> org.apache.hadoop.hdfs.qjournal.client.AsyncLoggerSet.getJournaledEdits(AsyncLoggerSet.java:272)
>       at 
> org.apache.hadoop.hdfs.qjournal.client.QuorumJournalManager.selectRpcInputStreams(QuorumJournalManager.java:533)
>       at 
> org.apache.hadoop.hdfs.qjournal.client.QuorumJournalManager.selectInputStreams(QuorumJournalManager.java:508)
>       at 
> org.apache.hadoop.hdfs.server.namenode.JournalSet.selectInputStreams(JournalSet.java:275)
>       at 
> org.apache.hadoop.hdfs.server.namenode.FSEditLog.selectInputStreams(FSEditLog.java:1681)
>       at 
> org.apache.hadoop.hdfs.server.namenode.FSEditLog.selectInputStreams(FSEditLog.java:1714)
>       at 
> org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer.doTailEdits(EditLogTailer.java:307)
>       at 
> org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer$EditLogTailerThread.doWork(EditLogTailer.java:460)
>       at 
> org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer$EditLogTailerThread.access$300(EditLogTailer.java:410)
>       at 
> org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer$EditLogTailerThread$1.run(EditLogTailer.java:427)
>       at java.security.AccessController.doPrivileged(Native Method)
>       at javax.security.auth.Subject.doAs(Subject.java:360)
>       at 
> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1709)
>       at 
> org.apache.hadoop.security.SecurityUtil.doAsLoginUserOrFatal(SecurityUtil.java:483)
>       at 
> org.apache.hadoop.hdfs.server.namenode.ha.EditLogTailer$EditLogTailerThread.run(EditLogTailer.java:423)
> 2019-07-04 17:35:54,112 | INFO  | Edit log tailer | Exiting with status 1: 
> java.lang.OutOfMemoryError: unable to create new native thread | 
> ExitUtil.java:210
> {noformat}



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