[horde] usage tracking w/ the memcache session handler?

[liamr@umich.edu]

Hey guys -

When were running the mysql session handler, I tracked my usage by 
querying horde_sessionhandler, and requesting a count of any 
session_lastmodified fields that fell inside a 30 minute window.  I'd 
run this every half hour out of cron, and it worked pretty well.  We 
gathered usage statistics this way for three years for our webmail 
service.

We switched to memcached last summer as our mysql servers couldn't 
handle the increased session size when we upgraded to Horde 3.x.  I 
know I can query memcached for statistics, but I don't think any of 
them translate as cleanly into "how many users are using my service 
right now" as my session_lastmodified query did.

Is anyone else using memcache doing usage tracking?  Anyone have 
suggestions as to how I might get the data I'm looking for w/o trying 
to parse transfer logs?

Liam