[Standards-JIG] RFC 3921 Better User Presence Experience(Implementation Detail)
jd.conley at coversant.net
Thu Oct 26 18:15:39 UTC 2006
> So , if you have to mirror this at the local server , you will need to
> cache all n x m presence updates from that server and invalidate all of
> them with unavailable presence to the n local users as soon as the
> remote server goes mia - very expensive imo.
This could be cached in memory but also done in a persistent store (database, file system, etc) as it would not need to be accessed very often -- only when a server rejoins the net. And all you have to store is a list of probe requests that are last known to be active keyed by domain JID. As far as database queries go this one is pretty simple, especially if you already persist the presence of your local users to the DB.
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