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Date: Mon, 2 Jul 2012 18:51:20 +0000 (UTC)
From: "Uma Maheswara Rao G (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HDFS-3561) ZKFC retries for 45 times to connect
 to other NN during fencing when network between NNs broken and standby Nn
 will not take over as active
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    [ https://issues.apache.org/jira/browse/HDFS-3561?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13405238#comment-13405238 ] 

Uma Maheswara Rao G commented on HDFS-3561:
-------------------------------------------

Thanks Aaron :-)

{quote}
Regardless, note that I don't object to the main point of this JIRA, i.e. that we should lower the number of retries when attempting to gracefully fence an NN. If someone wants to supply a patch for that, I'll be happy to review/commit it.
{quote}
Sure. I will ask Vinay to upload the patch what we have.
                
> ZKFC retries for 45 times to connect to other NN during fencing when network between NNs broken and standby Nn will not take over as active 
> --------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-3561
>                 URL: https://issues.apache.org/jira/browse/HDFS-3561
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: auto-failover
>            Reporter: suja s
>            Assignee: Vinay
>
> Scenario:
> Active NN on machine1
> Standby NN on machine2
> Machine1 is isolated from the network (machine1 network cable unplugged)
> After zk session timeout ZKFC at machine2 side gets notification that NN1 is not there.
> ZKFC tries to failover NN2 as active.
> As part of this during fencing it tries to connect to machine1 and kill NN1. (sshfence technique configured)
> This connection retry happens for 45 times( as it takes  ipc.client.connect.max.socket.retries)
> Also after that standby NN is not able to take over as active (because of fencing failure).
> Suggestion: If ZKFC is not able to reach other NN for specified time/no of retries it can consider that NN as dead and instruct the other NN to take over as active as there is no chance of the other NN (NN1) retaining its state as active after zk session timeout when its isolated from network
> From ZKFC log:
> {noformat}
> 2012-06-21 17:46:14,378 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: HOST-xx-xx-xx-102/xx.xx.xx.102:65110. Already tried 22 time(s).
> 2012-06-21 17:46:35,378 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: HOST-xx-xx-xx-102/xx.xx.xx.102:65110. Already tried 23 time(s).
> 2012-06-21 17:46:56,378 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: HOST-xx-xx-xx-102/xx.xx.xx.102:65110. Already tried 24 time(s).
> 2012-06-21 17:47:17,378 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: HOST-xx-xx-xx-102/xx.xx.xx.102:65110. Already tried 25 time(s).
> 2012-06-21 17:47:38,382 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: HOST-xx-xx-xx-102/xx.xx.xx.102:65110. Already tried 26 time(s).
> 2012-06-21 17:47:59,382 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: HOST-xx-xx-xx-102/xx.xx.xx.102:65110. Already tried 27 time(s).
> 2012-06-21 17:48:20,386 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: HOST-xx-xx-xx-102/xx.xx.xx.102:65110. Already tried 28 time(s).
> 2012-06-21 17:48:41,386 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: HOST-xx-xx-xx-102/xx.xx.xx.102:65110. Already tried 29 time(s).
> 2012-06-21 17:49:02,386 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: HOST-xx-xx-xx-102/xx.xx.xx.102:65110. Already tried 30 time(s).
> 2012-06-21 17:49:23,386 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: HOST-xx-xx-xx-102/xx.xx.xx.102:65110. Already tried 31 time(s).
> {noformat}
>  

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