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<feedxmlns="http://www.w3.org/2005/Atom"><title>Content Considered Harmful Atom Feed</title><id>http://blog.jrock.us/</id><linkhref="http://blog.jrock.us/feeds/category/Catalyst/xml"rel="self"/><linkhref="http://blog.jrock.us/"/><subtitletype="html">This is Jonathan Rockway's Blog, quite possibily the best blog ever.
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Or something.
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</subtitle><generatoruri="http://www.jrock.us/"version="0.01_01">AngerWhale</generator><updated>2006-08-10T02:43:00Z</updated><entry><title>Catalyst + Cache</title><author><name>Jonathan T. Rockway</name><email>[email protected]</email></author><id>urn:guid:8D9B9CBE-27DB-11DB-B6C2-F007B8516AA5</id><linkhref="http://blog.jrock.us/articles/Catalyst%20+%20Cache.pod"/><categoryterm="Catalyst"scheme="http://blog.jrock.us/categories/"/><updated>2006-08-09T19:07:58Z</updated><contenttype="xhtml"><divxmlns="http://www.w3.org/1999/xhtml"><divclass="pod">
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<p>I recently posted this to the <cite>Template::Toolkit</cite> mailing list, but
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the moderator rejected it for some reason. (Probably because <code><jon-perl-list-templates AT jrock.us></code> is the address that's
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subscribed, not <code><jon AT jrock.us></code>.)</p>
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<p>Anyway, here it is. I will expand on this further with actual
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measurements, but this will have to do for now.</p>
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<h4id="Original_Message">Original Message</h4>
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<divid="Original_Message_CONTENT">
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<p><i>Thank you, you raise a good point that I had not fully considered. My
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goal is to display a dynamically generated page, but where most of the
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"dynamic" content is actually static for a period amount of time.
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(Take a news page, for example, where the list of news stories updates
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once an hour.)</i></p>
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</div>
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<h4id="My_Reply">My Reply</h4>
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<divid="My_Reply_CONTENT">
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<p>I have a similar problem with my blogging software. Most of the content
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is static, and it's kind of a waste to regenerate everything every time
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someone views the page. My solution to this problem is to use a
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<cite>Cache::FastMmap</cite> object to store the formatted HTML content of each post,
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keyed on the source material's MD5sum (and filetype, for reasons not
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relevant to this discussion :) </p>
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<p>This results in a nice speedup, since certain HTML filters are slow
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(OO.org document -> HTML, for example).</p>
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<p>I also cache full pages, after they've been assembled by TT, keyed on
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the md5sum of each included article and some metadata (comment count,
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tags, etc.) The end result is a 5-20x speed up. With Catalyst's
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embedded server, I can do about 5 requests per second without cache, but
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it goes up to about 40-50 requests/second with the cache. So obviously
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a speedup. (And I'm still not doing a very good job, this was just a 20
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minute hack!)</p>
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<p>For the gory details, check out the code here:</p>
<p>Another caching strategy is to set dynamic pages to be cachable for say,
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10 seconds, and then letting Apache's mod_cache (experimental in 2.2.3,
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but it works for me) do the hard work. Your application gets hit once
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every ten seconds to refresh Apache's cache, but all the end-user
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requests are handled by serving from Apache's memory cache. With
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mpm_worker, it's *super fast*, and a 10 second update delay isn't bad.</p>
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<p>If your application is really slow, this will let you increase your
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slashdot resistance factor (as I call it) enormously. A quick ab
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against some cached content gave me a requests/per second rate of
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1638... much better than whatever your app would do by itself.</p>
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<p>And you don't really lose much by taking this approach, other than a 10
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second delay with your articles going live... but 10 seconds is nothing
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if you're getting 1500 requests per second and handling it with an old
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PIII :) </p>
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<p>If this info is useful to anyone else, let me know (off-list) and I'll
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write up a more detailed article about it :) </p>
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</div>
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</div></div></content></entry><entry><title>Quantum Physics and the Template Toolkit</title><author><name>Jonathan T. Rockway</name><email>[email protected]</email></author><id>urn:guid:BB054AF0-2601-11DB-9738-946FBD312859</id><linkhref="http://blog.jrock.us/articles/Quantum%20Physics%20and%20the%20Template%20Toolkit.pod"/><categoryterm="Catalyst"scheme="http://blog.jrock.us/categories/"/><categoryterm="Programming"scheme="http://blog.jrock.us/categories/"/><updated>2006-08-07T10:44:20Z</updated><contenttype="xhtml"><divxmlns="http://www.w3.org/1999/xhtml"><divclass="pod">
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<p>As a programmer, you probably don't spend a lot of time thinking about
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the similarities between programming and quantum physics. Fortunately
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for us Perl users, some people <i>do</i> spend a lot of time thinking
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about physics, and they even wrap up the results in
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<ahref="http://search.cpan.org">CPAN</a> modules for us!</p>
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<p>One such module is <cite>Quantum::Superpositions</cite>, which let me easily add
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some nice functionality to my <ahref="http://www.jrock.us/trac/blog_software">blog software</a> the other day. </p>
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<p>As you can see (if you're looking at this article on my blog, not in
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an RSS reader), I have a list of tags to the left of my main content.
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If you click one, it shows you a list of articles that have been
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tagged with that tag. If you select more than one tag, you get this
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intersection of the two sets (tag1 AND tag2).</p>
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<p>That's nice, but I like to use the left navigation bar to show the
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user where he is <i>in addition to</i> letting him move somewhere else.
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To do this, I bold the current location, and remove the link. That
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way, the user won't try to visit the page he's already looking at.
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This is pretty simple to implement for things like the "home page" or
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the "archives". You just check the current page, and if the link
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you're about to print out matches, make it bold instead. That logic
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looks something like this:</p>
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<pre> [% FOREACH category = categories %]
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[% IF category == current_category %]
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<b>[% category %]</b>
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[% ELSE %]
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[% category %]
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[% END %]
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[% END %]
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</pre>
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<p>Simple, and it provides excellent visual cues as to what the user is
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looking at.</p>
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<p>The problem with tags, though, is that an article can have lots of
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them. The technique above doesn't work there; you need to do a search
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for each tag. Not a show stopper, but do you really want to do array
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searches inside the Template Toolkit? No!</p>
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<p>And this is where <cite>Quantum::Superpositions</cite> comes to the rescue. In
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quantum physics, almost nothing is "certain" -- you can't tell with
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100% certainty both where a particle is and what its velocity is.
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The state of an individual particle is in sort of a flux until you
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observe, and when you observe, a tangible state comes into existence.</p>
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<p>How does this help with tags? By thinking of the set of all tags as a
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cloud of particles, we can apply the same principle. We don't care
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what all the tags are until we look at them.</p>
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<p>So how do we do this in perl? Let's see an example:</p>
<p>Then inside my <ahref="http://www.jrock.us/trac/blog_software/browser/root/navbox.tt#L40">Template Toolkit View</a>, I "observe" the state as
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necessary (with the <code>==</code> operator):</p>
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<pre> [% FOREACH tag = all_tags %]
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[% IF tag == article_tags %]
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<b>[% tag %]</b>
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[% ELSE %]
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[% tag %]
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[% END %]
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[% END %]
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</pre>
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<p>As you can see, this is exactly the same as what we did when we only
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had one possible value. If you think about it, it's really the same
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thing. You just needed to think more about physics :)</p>
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