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From Freddi Gyara <>
Subject Re: sandbox/messaging - your feedbacks are welcome
Date Tue, 20 Jul 2004 13:29:04 GMT
>> As a matter of fact, this proto uses multicast (UDP) only for its
>>heartbeat mechanism and unicast (TCP) for all the other activities. </snip>

I think i was a bit vague. No doubt, TCP is required for all p2p
communications. However, when a server has a (sorted) list of live
servers (LeaderNode-Node1-Node2 as in your example), it automatically
knows its neighbours (Node1's nbrs are LeaderNode and Node2) and can
communicate with them over TCP.

Your idea of being able to create a bespoke topology is also good, but:
a) Users should have the choice of not having to specify one (default
topology). Otherwise the complexity of setting up the cluster could be
too onerous.

b) Un-trained users may end up creating a topology that is not
resilient to failures
eg consider a star with LeaderNode as the center and nodes N1, N2, N3
as spokes. If LeaderNode fails, which node becomes the center ? Who
decides ? Is this configurable .... etc etc etc). Ideally the system
should be able to identify topologies that have single points of

> This is a great idea. Actually, I had this thought a while back: for
> each server, one configures an ordered list of  servers. When a server
> is started, the first N available servers are considered as their
> "neighbours".
A list of "prefered neighbours" - that may be a simpler configuration
option v/s the definition of a topology

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