Another issue I'm facing :
I need my module to be able to detect changes in the database and report
it to the connected users if necessary. (Use case : the person adds a
friend with something else than a XMPP client, like a web page interface
or a webservice API, while she's connected).
The way I choose to do that is :
- the session manager looks for a syncro='out_of_sync' field in the database
- set syncro to 'syncing' for some rows
- then change the memory roster items and push packets to the user's
sessions with selected changes
- then set syncro to 'ok'.
(In order to make this case simpler, I will do as if there were no row
deletions, but there are ^_^)
I'm wondering when is the best way to call this function :
- I can make a per-user function, looking only for changes in rows
concerning a specific user, and call it at the beginning of the
mod->in_sess and mod->pkt_user functions.
- I can call it on a regular interval (something like 5 seconds) and
look for changes for any user. Then, if the user is loaded, apply
changes, and if the user has at least one opened session, send the packets.
For now, I've implemented the first solution. But my feeling is that the
2nd solution would be better performance-wise (too many requests with
the 1st). I'm only stopped by the "regular interval" thing.
My question : *Should I add a "timetick" chain to the SM (called every
second for example), and add my module to this chain (with a rate_t
check) ?* I'm not thrilled by this solution, because for now, I haven't
changed any code from jabberd2 except from the new module, which make it
easier to test or get in production. *Is there another, better way ?*
Thanks for reading, and I'm grateful in advance for any useful insight. :)
On a side note : the 5s interval could lead to some race conditions, but
I think we can avoid any inconststencies (by using "INSERT ... ON
DUPLICATE KEY UPDATE ..." instead of "UPDATE ..." for one). The behavior
being undetermined if a user issues 2 conflicting commands at the same
time through differents means is not an issue, if the resulting state is
the result of one of the user's commands.
--
Sylvain "Gugli" Guglielmi
Gamedev@Nadeo@Ubisoft
