[Zope-dev] How to make Zope fail nicely under high load?

[Bjorn Stabell]

Richard Jones wrote:
> On Thursday 12 February 2004 01:23, Casey Duncan wrote:
> > What kinds of requests are these? Do they all require a dynamic 
> > output? If not, then you should put better caching in front of Zope,

> > or at a minimum tweak you caching headers so that some 
> > could be served as 304s for instance.
> >
> > If they are all dynamic, how dynamic? How different is the page for 
> > one session than another? If much of the page is the same then you 
> > might benefit from an ESI approach where you cache parts of 
> > pages and assemble them in the cache, serving only small pieces from
Zope.
> >
> > I'm a bit surprised that you have not (from what I can 
> > see), used the most common Zope speedup (and often the cheapest
overall): Buy more 
> > hardware and use ZEO.
> 
> I was going to suggest these things too. And a bunch of other 
> stuff. A while ago, I wrote a page about making Zope go faster - it
might help.
> 
> http://zope.org/Members/richard/docs/zope_optimisation.html

Okay, I'd better explain our situation in more detail, then.

Richard, Casey, thanks.  Except for using ZEO, we're already doing
everything Richard and you mentions.  Zope only serves pages (no images
etc) that are dynamic, the object cache is set at 20,000 objects with
only 2 threads (otherwise we got too much deactivation of objects), and
we also use the RAM Cache Manager for static bits of dynamic pages.  We
could probably have used it more, but since it can't cache persistent
objects, it's a bit of a pain sometimes.

The point is, our template is very dynamic, and our application (a BBS)
is very dynamic as well.  We have done one round of optimization
(basically making things as cacheable as possible) and after testing the
scalability now we're going to do another round of optimization,
tweaking the algorithm and removing as many ZCatalog searches as
possible.

One of the optimization we're thinking of is storing results of ZCatalog
searches (e.g., number of replies to postings) in volatile variables so
we don't have to run the catalog search at all.  We'd like to use memory
space shared between threads for this.  Using ZEO would require us to
store this in the ZODB.

I'm sure we can make the application run faster, but we'd like to
support 500-1000 simultaneous users whereas now we can only support
20-25!  I don't know if we can scale it enough just by tweaking the
application.  Another option is to scrap Zope for the BBS part and use
one of the fully featured, and optimized, BBS applications for PHP.
That would definitely be a safer choice, but would require extra
application integration time (user database, searching).

Regards,
-- 
Bjorn