[Gllug] Single IP, HTTP accelerator fronting multiple webservers

[Daniel P. Berrange]

On Thu, Feb 23, 2006 at 06:38:52PM +0000, Richard Jones wrote:
> > The only scenario I can think of where it would help is if you're
> > dynamically generating static content. In that case, why not just
> > pregenerate static pages once a day from cron or something, and serve
> > them up as regular static content, which would give you the same
> > performance improvement
>
> Much of our normal content is generated on the fly from a database,
> and I can't see us changing that, for example every page on
> http://merjis.com is generated on the fly.  On the other hand,
> fronting a dynamic site with a caching HTTP accelerator is exactly the
> same as pregenerating static content, because the HTTP accelerator
> caches pages into files for you.  The application doesn't need to
> worry about this, and there is a clearer logical separation of layers.

Its much more managable to use a HTTP proxy as a content accelrator
then to script something to dump files to disk periodically, because
the dynamic content publishing backend can control the cache lifetime 
of individual pages, via the HTTP cache control headers. Since you 
can have arbitrary caching proxies between your server & the end
user, you have to get the cache control headers correct anyway, so
you might as well take advantage of this by adding SQUID in front of
your own servers.

> > without the need for an extra component to
> > get in the way (and potentially fail)?
> 
> This is a worry, but I'm pretty happy with Squid - never seen it fall
> over.  Has anyone had reliability problems with it?

It works very well - every single APLAWS+ site is running SQUID in
front of the Apache+Java Appserver layer to provide acceleration.
If you want redundancy you can setup multiple SQUID servers in all
sorts of peering arrangements.

Regards
Dan.
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