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From "Hari Mankude (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-8247) Auto-HA: add a config to enable auto-HA, which disables manual FC
Date Mon, 09 Apr 2012 23:31:18 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-8247?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13250296#comment-13250296
] 

Hari Mankude commented on HADOOP-8247:
--------------------------------------

bq.Hi Hari. That's specifically the point of the FORCEMANUAL flag. It is not safe to use it
with automatic failover. So, the user has to accept the warning and acknowledge they're about
to do something dumb, that will break auto failover if the ZKFCs are running.

If there is such a significant element of danger in using FORCEMANUAL with unforseen consequences
and possibilities such as data corruption and even worse HA state, is this command option
useful? There are always admins who disregard these warnings. Instead, wouldn't it be better
to come up with a set of procedures to unwedge the cluster, starting with setting auto-failover
key to false, resetting NNs and using manual failover?
                
> 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
>
>
> 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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