[jboss-jira] [JBoss JIRA] (JGRP-1491) Views are created with the wrong view creator

[Bela Ban (JIRA)]

    [ https://issues.jboss.org/browse/JGRP-1491?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12715136#comment-12715136 ] 

Bela Ban commented on JGRP-1491:
--------------------------------

OK, so with your suggestion of the merge leader being the view creator, we could come up with this scenario:
- {A,B,C} and {X,Y,Z} merge
- A and X are the coordinators, we sort them and it turns out that X is the merge leader
- The sorted combined view is {B,C,X,Y,A,Z}

With the current algorithm, the MergeView will be (assuming view #21) B|21={B,C,X,Y,A,Z}. A and X install B|21 in their partitions. A and X cease to be coordinators and B becomes the new coordinator.

With your suggested change, the MergeView will be X|21={B,C,X,Y,A,Z}. A and X install X|21 in their partitions. A ceases to be coordinator and X remains coordinator.
The problem with your change is that the view creator is not necessarily the first member of the list. I think this might impact existing code, but I'd have to verify this, to be sure. IIRC there are assumptions that the view creator is the first of the view.
                
> Views are created with the wrong view creator
> ---------------------------------------------
>
>                 Key: JGRP-1491
>                 URL: https://issues.jboss.org/browse/JGRP-1491
>             Project: JGroups
>          Issue Type: Bug
>    Affects Versions: 3.1
>            Reporter: David Hotham
>            Assignee: Bela Ban
>             Fix For: 3.2
>
>
> -  At a merge, the merge leader creates a view in which the ViewId.creator is not itself.
> -  This opens the possibility that two different nodes might simultaneously be creating different views - but with the same ViewId
> -  This is bound to lead to confusion, if it happens
> This is per pull request 54, which contains further discussion and a proposed fix.
> (I'm raising this ticket just to have everything tracked in one place).

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