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

[Bela Ban (JIRA)]

Prevent merging during JOIN/LEAVE processing
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                 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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