[jira] [Updated] (ZOOKEEPER-1209) LeaderElection recipe doesn't handle the split-brain issue, n/w disconnection can bring both the client nodes to be in ELECTED

["Michael Han (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ZOOKEEPER-1209?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Michael Han updated ZOOKEEPER-1209:
-----------------------------------
    Fix Version/s:     (was: 3.5.3)
                   3.5.4

> LeaderElection recipe doesn't handle the split-brain issue, n/w disconnection can bring both the client nodes to be in ELECTED
> ------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: ZOOKEEPER-1209
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1209
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: recipes
>    Affects Versions: 3.3.3
>            Reporter: Rakesh R
>            Assignee: Rakesh R
>             Fix For: 3.5.4, 3.6.0
>
>         Attachments: ZOOKEEPER-1209.patch
>
>
> *Case1-* N/w disconnection can bring both the client nodes to be in ELECTED state. Current LeaderElectionSupport(LES) f/w handles only 'NodeDeletion'.
>  
> Consider the scenario where ELECTED and READY nodes are running. Say ELECTED node's n/w got failed and is "Disconnected" from ZooKeeper. But it will behave as ELECTED as it is not getting any events from the LeaderElectionSupport(LES) framework.
> After sessiontimeout, node in READY state will be notified by 'NodeDeleted' event and will go to ELECTED state.
> *Problem:* 
> Both the node becomes ELECTED and finally the user sees two Master (ELECTED) node and cause inconsistencies.
> *Case2-* Also in this case, Let's say if user has started only one client node and becomes ELECTED. After sometime n/w has disconnected with the ZooKeeper server and the session got expired. 
> *Problem:*
> Still the client node will be in the ELECTED state. After sometime if user has started the second client node. Again both the nodes becomes ELECTED.



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