Sessions Table HUGE, bringing down site 1.5.1

After getting disk cache going via file, our session table is growing to the point I have to truncate it every hour... with active carts going.

Not sure why it's growing, I thought 1.5+ already takes care of old sessions.

I tried a script to alleviate the strain on the server by running

mysql> DELETE FROM sessions WHERE expiry < (UNIX_TIMESTAMP() - 30 * 60);
Query OK, 0 rows affected (36.59 sec)

Although it did not clean the table up. Any suggestions?

Well, there is a function in ZC that takes an unused parameter that deletes sessions based on the current time. It appears that it uses the current time compared to the expiry time rather than a time offset like used above. In fact the 0 results provided there almost seem to indicate that the sessions ARE being deleted like they should be, but the rate of database access is out running the ability to maintain...

The function to which I refer is: _sess_gc($maxlifetime)

Pass any value as the $maxlifetime as it is not used inside the function. Not sure if upgrading would also solve your problem(s). Could also use the files instead of database.

Another question would be what kind of traffic is this database seeing? Is it shared among multiple stores? Might want to provide other server specs to try to help identify potential solutions.

You say the table is "HUGE".

Can you give some more context ... like how big is "HUGE" in your mind?
And, why do you believe you need to "truncate it every hour"? Why exactly are you doing that? What business "problem" is that attempting to solve?

ZC2.2.0alpha in production...I see that my sessions table is 660MB with 200,500+ rows!
When restored locally it's 1GB.

I've truncated that today...see what happens.