[jboss-jira] [JBoss JIRA] Commented: (JGRP-1061) FLUSH: asymmetric merge fails

[Bela Ban (JIRA)]

    [ https://jira.jboss.org/jira/browse/JGRP-1061?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12488181#action_12488181 ] 

Bela Ban commented on JGRP-1061:
--------------------------------

The solution was to *prevent* overlapping flushes in the way the merge algorithm works: in the case of
A: BAC
B: BC
C: BC

The merge coordinator was B and the participants B and A. The total members were {A,B,C}. In the first step, all members associated with a coordinator are removed from the total members:
B: BC and members={A}

In the second step, we create individual members lists for the (non-coord) merge participants:
A: {A}

In this case, we have 
B: {B,C} and A: {A}, so the flushes won't overlap.

Another example: 
A: AB
B: AB
C: CD
D: CD

If we get responses from A and D, then the merge participants and associated members are
A: {A,B}
C: {C}
D: {D}

The reason that we didn't flush {C,D} as a sub-partition is that we didn't get a response from C itself, but from D !

> FLUSH: asymmetric merge fails
> -----------------------------
>
>                 Key: JGRP-1061
>                 URL: https://jira.jboss.org/jira/browse/JGRP-1061
>             Project: JGroups
>          Issue Type: Bug
>            Reporter: Bela Ban
>            Assignee: Bela Ban
>             Fix For: 2.8
>
>
> A: {B,A,C}
> B: {B,C}
> C: {B,C}
> B and C have the same view, but A has a different (older) view which still includes B and C
> The new merge now determines that the partition coordinators for the merge are B and A.
> When FLUSH is enabled, before handling the merge request A tries to flush {A,B,C} and B tries to flush {B,C}. The latter works, but the former fails as A cannot communicate with B and C !
> SOLUTION: the partition for A needs to be {A} and not {B,A,C}. 
> Is this possible in all cases, or can we NOT prevent merging of overlapping partitions ? (Then flush would always fail !)

-- 
This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators: https://jira.jboss.org/jira/secure/Administrators.jspa
-
For more information on JIRA, see: http://www.atlassian.com/software/jira