[Templates] Caching Output of Components

[Jonathan Rockway]

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I have a similar problem with my blogging software.  Most of the content
is static, and it's kind of a waste to regenerate everything every time
someone views the page.  My solution to this problem is to use a a
Cache::FastMmap object to store the formatted HTML content of each post,
keyed on the source material's MD5sum (and filetype, for reasons not
relevant to this discussion :)

This results in a nice speedup, since certain HTML filters are slow
(OO.org document -> HTML, for example).

I also cache full pages, after they've been assembled by TT, keyed on
the md5sum of each included article and some metadata (comment count,
tags, etc.)  The end result is a 5-20x speed up.  With Catalyst's
embedded server, I can do about 5 requests per second without cache, but
it goes up to about 40-50 requests/second with the cache.  So obviously
a speedup.  (And I'm still not doing a very good job, this was just a 20
minute hack!)

For the gory details, check out the code here:

http://www.jrock.us/trac/blog_software/browser/lib/Blog/Controller/Root.p=
m#L105
(page cache)

and:
http://www.jrock.us/trac/blog_software/browser/lib/Blog/Model/Filesystem/=
Item.pm#L355
(object cache)


Another caching strategy is to set dynamic pages to be cachable for say,
10 seconds, and then letting Apache's mod_cache (experimental in 2.2.3,
but it works for me) do the hard work.  Your application gets hit once
every ten seconds to refresh Apache's cache, but all the end-user
requests are handled by serving from Apache's memory cache.  With
mpm_worker, it's *super fast*, and a 10 second update delay isn't bad.

If your application is really slow, this will let you increase your
slashdot resistance factor (as I call it) enormously.  A quick ab
against some cached content gave me a requests/per second rate of
1638... much better than whatever your app would do by itself.

And you don't really lose much by taking this approach, other than a 10
second delay with your articles going live... but 10 seconds is nothing
if you're getting 1500 requests per second and handling it with an old
PIII :)

If this info is useful to anyone else, let me know (off-list) and I'll
write up a more detailed article about it :)

Regards,
Jonathan Rockway


> Thank you, you raise a good point that I had not fully considered.  My
> goal is to display a dynamically generated page, but where most of the
> "dynamic" content is actually static for a period amount of time.  (Tak=
e
> a news page, for example, where the list of news stories updates once a=
n
> hour.)
>
> Having thought about the problem a bit more, I can likely simulate what=

> I'm looking for by using a template that INSERTs the "dynamic" content
> that was generated by a cronjob periodically.  This would move the heav=
y
> DB processing offline relative to the page view.
>
> Randal, thank you for your insight!
>
> Have a great night.
>     -- Robert
>
>  =20



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