[horde] Horde 3.1, memcache sessionhandler, sidebar, and flock()

[Chris Stromsoe]

I'm seeing some weird issues with a recent upgrade to Horde 3.1. I'm using 
memcache for session management.  Imp isset as the default application. 
The sidebar always displays for authenticated users.

Several of my users log in successfully, but are experiencing browser 
hangs while the sidebar tries to load.  The sidebar eventually times out 
when PHP kills the process for taking too much CPU time. All of the 
reports have come from individuals that have inboxes that take a few 
seconds to open.

It looks like the memcache session handler added flock() handling to 
serialize session access in between 3.0 and 3.1.  I'm looking at the 
locking as one area that could be problematic.

Right now, the code is structured to always obtain an exclusive lock 
(LOCK_EX).  Is that necessary?  Is there any reason that read() doesn't 
obtain a shared lock (LOCK_SH) instead?



-Chris