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Date: Wed, 11 Apr 2012 00:07:20 +0000 (UTC)
From: "Todd Lipcon (Updated) (JIRA)" <jira@apache.org>
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Subject: [jira] [Updated] (HADOOP-8247) Auto-HA: add a config to enable
 auto-HA, which disables manual FC
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     [ https://issues.apache.org/jira/browse/HADOOP-8247?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Todd Lipcon updated HADOOP-8247:
--------------------------------

    Attachment: hadoop-8247.txt

Attached patch implements the above. Here is a transcript of its usage:
$ ./bin/hdfs haadmin -transitionToStandby nn1 -forcemanual
You have specified the forcemanual flag. This flag is dangerous, as it can induce a split-brain scenario that WILL CORRUPT your HDFS namespace, possibly irrecoverably.

It is recommended not to use this flag, but instead to shut down the cluster and disable automatic failover if you prefer to manually manage your HA state.

You may abort safely by answering 'n' or hitting ^C now.

Are you sure you want to continue? (Y or N) n
12/04/10 17:05:53 FATAL ha.HAAdmin: Aborted


todd@todd-w510:~/git/hadoop-common/hadoop-dist/target/hadoop-3.0.0-SNAPSHOT$ ./bemanual haadmin -transitionToStandby nn1 -force
You have specified the forcemanual flag. This flag is dangerous, as it can induce a split-brain scenario that WILL CORRUPT your HDFS namespace, possibly irrecoverably.

It is recommended not to use this flag, but instead to shut down the cluster and disable automatic failover if you prefer to manually manage your HA state.

You may abort safely by answering 'n' or hitting ^C now.

Are you sure you want to continue? (Y or N) y
12/04/10 17:02:05 WARN ha.HAAdmin: Proceeding with manual HA state management even though
automatic failover is enabled for NameNode at todd-w510/127.0.0.1:8021

                
> Auto-HA: add a config to enable auto-HA, which disables manual FC
> -----------------------------------------------------------------
>
>                 Key: HADOOP-8247
>                 URL: https://issues.apache.org/jira/browse/HADOOP-8247
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: auto-failover, ha
>    Affects Versions: Auto Failover (HDFS-3042)
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>         Attachments: hadoop-8247.txt, hadoop-8247.txt, hadoop-8247.txt, hadoop-8247.txt, hadoop-8247.txt
>
>
> Currently, if automatic failover is set up and running, and the user uses the "haadmin -failover" command, he or she can end up putting the system in an inconsistent state, where the state in ZK disagrees with the actual state of the world. To fix this, we should add a config flag which is used to enable auto-HA. When this flag is set, we should disallow use of the haadmin command to initiate failovers. We should refuse to run ZKFCs when the flag is not set. Of course, this flag should be scoped by nameservice.

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