[Standards] Inconsistent Subscriptions in XMPP

Robin Redeker elmex at x-paste.de
Wed Feb 25 23:15:18 UTC 2009

On Tue, Feb 24, 2009 at 01:49:50AM +0100, Pavel Simerda wrote:
> There are several cases when subscription databases in XMPP are
> inconsistent.
> You may view subscription information as a global distributed database.
> Subscription state between two JIDs, for example a at A and b at B are stored
> in two places at the same time. Servers A and B maintain their own
> copies of subscription state.

The problem is not just subscription state, but any state that is
not synchronized, basic presence information comes to mind, they also
get out of sync sometimes. Maybe it's less of a problem, because a client
logging in again, can refresh that state.

Subscription information of course isn't as easily 'synchronized'.

I don't know whether servers already do this, but having a consistent
state for presence, would allow for caching the presence information
on the receiving server.

A generic synchronisation protocol would of course help any
state information that has to be shared with other servers.

I brought this topic up some weeks ago (and I think also a year ago), but I'm
not a server developer (If I was, I would probably have already implemented
some proof of concept protocol to do this). But these things don't seem to
bother the (and/or developers) users much and there doesn't seem to be much (or
enough) interest for consistent information sharing amog servers.


Robin Redeker                         | Deliantra, the free code+content MORPG
elmex at ta-sa.org / r.redeker at gmail.com | http://www.deliantra.net
http://www.ta-sa.org/                 |

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