Last night I implemented a custom SessionManager that uses memcached as
its backend. (memcached is a super-high-performance distributed cache
server.) One thing I discovered was that for each request, I was doing
three cache fetches from memcached and one update, when I sort of
expected to do just one fetch and one update.
The reason turns out to be pretty simple, but it's a potential
efficiency issue that anyone implementing a SessionManager should be
aware of, with or without my refactoring. For a page that just extends
identified.xml, the session manager's isSessionValid() method is called,
then, if that's successful, its getSessionUserId() and its
continueSession(). If you are fetching your session data from a backing
store on each of those calls, you will do three fetches per logged-in
request.
Absent any way for my SessionManager to get at a request-scoped object
to set an attribute on, I am now keeping a WeakHashMap to cache my data
for a very brief time (100ms, which is probably total overkill) and with
that in place, I now do one fetch and one update against memcached per
page request, as desired. The WeakHashMap entry for a given authId gets
cleared out explicitly whenever there's a write operation.
By the way, if you want to see the session manager, I posted it to
http://rifers.org/paste/show/1726 and http://rifers.org/paste/show/1727
-- it works, but plugging it in will be a bit of an ordeal for you until
my still-in-progress refactoring of RIFE's authentication system hits
the official source base. (See the devel list for details about that;
basically I'm making it much easier to plug in custom authentication
backends.) It depends on the Java memcached client from
http://www.whalin.com/memcached/ . At some point, after my refactoring
is done and integrated, I will probably try to convince Geert to include
some variant of this session manager in RIFE, but one thing at a time!
-Steve
_______________________________________________
Rife-users mailing list
Rife-users@uwyn.com
http://lists.uwyn.com/mailman/listinfo/rife-users
