[sldev] Question: Replacing current group chat with XMPP?

[Tateru Nino]

David M Chess wrote:
>
> >From: "Paul Oppenheim (Poppy Linden)" <poppy at lindenlab.com>
> >
> >David M Chess wrote:
> >> I don't really understand this scaling argument.  In my experience,
> >> neither "push everything everywhere" nor "constantly ask if there's
> >> anything new" scales; what scales is actual pub/sub.  In the case of
> >> group IM, messages get pushed by some server (or some cluster of
> >> entities acting as a logical server) to all and only those places
> where
> >> someone cares.  There's some overhead in keeping track of where there
> >> are places that someone cares, but in most use-cases I've seen it's
> the
> >> approach that scales the best.
> >
> >Do you have any references / links / copypasta / personal stories on
> this kind of architecture research? I've been
> >hungering for scalability research lately, and been surprised by much
> of what I've read. I would assume polling with
> >caching would be much faster than pub/sub because you can use much
> dumber machinery, but I've also not investigated
> >too many message queuing systems (I also don't work directly on IM).
> I can't speak for others on this list, but if
> >you cook up a scalability resource mail you've got an audience of at
> least one ;)
>
> I will look around for some references; in my experience actual
> practical stories about how stuff works get published far too rarely.  :)
>
> My most recent experience with this is in some distributed computing
> middleware (IBM WebSphere VE, nee XD).  The exact situation there is
> somewhat radically different, so the details of the solution we used
> aren't really relevant, but the basic calculation is.
>
> If you have (say) a group with 1000 members, spread across 10 ADs,
> where at a typical time 100 of those members are logged in, involving
> 6 of the ADs, with a typical peak rate of 1 message every two seconds,
> and you don't want to impose an additional latency of more than 5
> seconds, say (group IM with even just a 5-second delay would be
> unusable imho, but we'll stick that in to get a lower bound), the
> choices seem to be:
>
It's my understanding that 5 seconds group IM latency is routinely
exceeded in practice.

-- 
Tateru Nino
http://www.massively.com/