[jboss-jira] [JBoss JIRA] Commented: (JGRP-1009) Prevent merging during JOIN/LEAVE processing

[Bela Ban (JIRA)]

    [ https://jira.jboss.org/jira/browse/JGRP-1009?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12481601#action_12481601 ] 

Bela Ban commented on JGRP-1009:
--------------------------------

Merging and join/leaves should be separate and can never overlap. 

When a merge is in progress:
- Join and leave requests should get discarded (or queued ?)

When a join or leave is processed:
- MERGE events should be discarded
- MERGE-REQ requests received from other partitions should be *rejected*



> Prevent merging during JOIN/LEAVE processing
> --------------------------------------------
>
>                 Key: JGRP-1009
>                 URL: https://jira.jboss.org/jira/browse/JGRP-1009
>             Project: JGroups
>          Issue Type: Task
>            Reporter: Bela Ban
>            Assignee: Bela Ban
>             Fix For: 2.9
>
>
> - Say we have V1={A,B,C} and D joins
> - A multicasts the new view V2={A,B,C,D} to {A,B,C} and sends a it via unicast to D
> - At time T1, A and C have V2, but B might still have V1
> - At timeT3 B will also have V2
> - HOWEVER, *before* T3 (at T2), A's MERGE functionality gets the current views and discovers the discrepancy
> - A will now initiate a merge. This is superfluous because B would have received V2 at T3 (maybe a few ms later) !
> This is not incorrect, but we still want to prevent spurious merges.
> SOLUTION:
> - Turn off merging during view change processing
> - This can be done via discarding of MERGE events at GMS during view processing, or by disabling merging directly in MERGE2, MERGE3, MERGEFAST. The first option looks more promising, as it requires only 1 hange in GMS

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