[Building Sakai] Displaying Users Present (or not)

[Stephen Marquard]

The 2.7 presence service also has support for expiring presence more aggressively if not renewed to handle cases such as where users close the browser (currently the presence for such a user would only go away when his/her session ended).

However this conflicts to some extent with the portal-generated presence events because the presence would 'ping pong' (get expired and set again on page navigation). The portal-generated presence should really have a longer timeout (e.g. valid for 15 minutes or something) if presence is not being disabled.

As some of the reason why sites disabled presence is to reduce server load (especially for large sites where you might expected 400+ concurrent users in a site for assessment scenarios), I'm not sure if leaving the courier calls but not displaying the user list would really be a popular option.

There is also the privacy service which lets individuals opt out of their presence being shown.

Regards
Stephen

>>> Matthew Buckett <matthew.buckett at oucs.ox.ac.uk> 5/7/2010 2:45 PM >>>
Ok, currently in our production installation we have all sites
displaying the list of users present. We are looking at switching this
off and relying on the portal to generate events so that we can still
track accesses to sites.

I had a quick look at this and it seems that the PresenceService
stashes a Presence object into a presence tool session. This is
normally done as part of the setPresence() call. setPresence() also
looks through all the presence locations for expired presence status.

If setPresence() isn't called for a short while for a particular user
then none of the existing presences get expired.

If it was only the portal that called setPresence() and we weren't
displaying users present then being and end events for a site would
tie up, but other tools (eg chat) also make calls to setPresence()
which can result in your presence in the site getting timed out but
in-fact you are still in the site. Then when you do reload the portal
it will show you as having entered the site again, when infact you
never left.

Is this an issue?

Does site stats cope with this?

Is it worth changing the presence so it's active but can be set to not
display the users present in a site? This way the status of someone's
presence in a site remains accurate without the privacy concerns.

-- 
  Matthew Buckett
  VLE Developer, LTG, Oxford University Computing Services
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