Reliability and group communications

Werner responds. I don’t think we’re that out of synch, but I maintain that from what I’ve read of the techniques he’s talking about, they are not suited for Internet scale use. And by that, I mean a few orders of magnitude larger than the 10K/100K numbers he quotes. More like 10^8-10^11.

I know that Werner is anti-transparency, as am I. It was really interesting to watch the evolution of GCS research and tools in this regard. Sometime during this transition, “group communications” stopped being referred to as such, perhaps due to the reduced degree of coupling between members of a group; a result of the movement away from transparency (or perhaps because of the bad rep that it got due to the early highly-transparent commercial toolkits being quite brittle 8-). I guess I never bought into that terminology switchover though, as I always considered “group communications” to refer to any multi-party state-alignment based approach to concensus problems, which I’d say that even Werner’s groups more recent work falls under. Hopefully that explains my seemingly outdated view of the work of his group.

Anyhow, to see what a RESTful “GCS” might look like, I point to KnowNow and their mod_pubsub project. The principle means of managing reliability is via the stateless approach that’s part of REST, that KnowNow reused. That is, the client maintains application state, and so is responsible for dealing with partial failures and getting up-to-state (using GET, of course).

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