Forum OpenACS Q&A: Response to Building a high-capacity, high-availability OpenACS solution...

The ACS has some (presumably primitive) hooks in it for load balancing, I doubt if anyone here's tried them out and I believe aD themselves have only used them on a handful of sites.

Jim Davidson of AOL gave a talk at a Tcl meeting a few months ago on the Digital City solution.  It is run with a surprisingly small number  of servers (when you consider the bazillions needed to run microsoft.com).  They've put a lot of energy into the design, figuring  out what database queries can be cached rather than executed each time, etc.  I think that's the kind of thing you'll need to be looking  at when your site gets busy, because the single database server is probably going to be the bottleneck.  The presentation may be up on the AOLserver site, I'm not sure - if not, Jim's registered at the site so you should be able to find his e-mail address and ask him where it exists.  This is the single most useful thing I can think of, because it goes  into the architecture of Digital City in decent detail.

Postgres 7.1 will have the ability to cache query plans, and if you do  so you'll be able to avoid the overhead of parsing and optimizing queries.  Since newer versions of the ACS will name queries, it should  be possible for us to make use of this feature, though it will be a memory hog.  Along with query caching, there's good potential for increasing the scalability of PG-backed websites down the road.