[jboss-dev-forums] [Design of Clustering on JBoss (Clusters/JBoss)] - Re: Handling cluster state when network partitions occur

[bela@jboss.com]

"manik.surtani at jboss.com" wrote : I inherently don't like using a static cluster size configuration.  With larger clusters, nodes joining and leaving the cluster should be seen as "normal" and it should be able to scale up or down without reconfiguration.
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This is not a static configuration, e.g. {A,B,C,D,E}. The only thing that's static is the primary partition size.

anonymous wrote : 
  | Correct me if I am wrong, but if you have {A, B, C} on switch S1 and {D, E} on switch S2, and if S2 fails, does JGroups deliver 2 view changes to {A, B, C} (one without D and one without both D and E) or just a single view change, without D and E?  Assuming FD_SOCK is used for immediate switch failure detection?
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Depends. usually you get 2 view changes, sometimes 1. Remember that if a switch goes down, the TCP connection in FD_SOCK will *not* be closed, so we'd have to rely on FD here.

anonymous wrote : 
  | If this is the case, can't a split brain threshold be used?  I.e., if a view change is received in which more than N% of members are removed, assume a split brain as opposed to normal drop-offs?

No, because you can't rely on JGroups excluding all 'dead' members in *1* view. This depends on the failure detection and group membership protocol impl, and they might all be different.

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