[Standards] presences and server restarts

Robin Redeker elmex at x-paste.de
Mon Feb 9 00:26:24 UTC 2009


I've recently tripped over another really annoying ghost presence while I was
chatting with someone. He always showed up as online, while he actually wasn't,
just that I never got a 'unavailable' presence stanza and wondered whether my
client was actually broken (which it wasn't as a glance on the stanza log

It was a private server on the other end, so something that easily restarts/crashes
from time to time. So it might be one of those ghost presences.

The issue of ghost presences is of course known, and I don't know currently

I was reminded of the concept of rpc.statd by a friend: It's there to inform
other NFS server about unclean restarts.

So, in XMPP that would be: A server telling the other server that he would love
to receive a message when the other server restarts/crashed. Then the servers
that receive that notice could send presence probes again for the contacts
on the server that restarts.

That would probably be at least less overhead than re-probing again and again,
like it's suggested in rfc3921bis:

   In addition, a server MAY periodically send a presence probe to a contact if it
   has not received presence information or other traffic from the contact in some
   configurable amount of time; this can help to prevent "ghost" contacts who
   appear to be online but in fact are not. 

I don't know if this "problem" has already been solved, I couldn't find much
on a quick look over the XEPs. Just wanted to throw in another idea, just
in case...

   Robin Redeker

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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