Mailing-List: contact common-issues-help@hadoop.apache.org; run by ezmlm
Precedence: bulk
Reply-To: common-issues@hadoop.apache.org
Date: Sat, 31 Mar 2012 00:09:27 +0000 (UTC)
From: "Bikas Saha (Commented) (JIRA)" <jira@apache.org>
To: common-issues@hadoop.apache.org
Message-ID: 
 <985978469.40789.1333152567286.JavaMail.tomcat@hel.zones.apache.org>
In-Reply-To: 
 <921246741.19972.1332800666695.JavaMail.tomcat@hel.zones.apache.org>
Subject: [jira] [Commented] (HADOOP-8217) Edge case split-brain race in
 ZK-based auto-failover
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit


    [ https://issues.apache.org/jira/browse/HADOOP-8217?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13242874#comment-13242874 ] 

Bikas Saha commented on HADOOP-8217:
------------------------------------

bq.4(failure case): if NN1.transitionToStandby() times out or fails, the non-graceful fencing is initiated (same as in existing HA code for the last several months)

Can you please point me to the existing HA code for last several months? I thought we have manual HA in which admin does fencing. 
                
> Edge case split-brain race in ZK-based auto-failover
> ----------------------------------------------------
>
>                 Key: HADOOP-8217
>                 URL: https://issues.apache.org/jira/browse/HADOOP-8217
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: auto-failover, ha
>    Affects Versions: 0.24.0
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>         Attachments: hadoop-8217-testcase.txt
>
>
> As discussed in HADOOP-8206, the current design for automatic failover has the following race:
> - ZKFC1 gets active lock
> - ZKFC1 is about to send transitionToActive() and machine freezes (eg GC pause + swapping)
> - ZKFC1 loses its ZK lock, ZKFC2 gets ZK lock
> - ZKFC2 calls transitionToStandby on NN1, and transitions NN2 to active
> - ZKFC1 wakes up from pause, calls transitionToActive(), now we have a bad situation
> This is rare, since it requires ZKFC1 to freeze longer than its ZK session timeout, but worth fixing, since the results can be disastrous.

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira