Thoughts

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10
Feb

Solr, Jetty, and daemons: debugging jetty.sh

I recently added a Solr-powered search feature to this site (using django-haystack). Rather than go to the trouble (and server resources drain) of deploying Solr via Tomcat, I decided instead to deploy it via Jetty. There's a wiki page with detailed instructions for deploying Solr with Jetty, and the wiki page also includes a link to the jetty.sh startup script.

The instructions seem simple enough. However, I ran into some serious problems when trying to get the startup script to work. The standard java -jar start.jar was working fine for me. But after following the instructions to the letter, and after double-checking everything, a call to:

sudo /etc/init.d/jetty start

still resulted in my getting the (incredibly unhelpful) error message:

Starting Jetty: FAILED

My server is running Ubuntu Jaunty (9.04), and from my experience, the start-stop-daemon command in jetty.sh doesn't work on that platform. Let me know if you've experienced the same or similar issues on other *nix flavours or on other Ubuntu versions. Your mileage may vary.

31
Jan

Jimmy Page: site-wide Django page caching made simple

For some time, I've been using the per-site cache feature that comes included with Django. This site's caching needs are very modest: small personal site, updated infrequently, with two simple blog-like sections and a handful of static pages. Plus, it runs fast enough even without any caching. A simple "brute force" solution like Django's per-site cache is more than adequate.

However, I grew tired of the fact that whenever I published new content, nothing was invalidated in the cache. I began to develop a routine of first writing and publishing the content in the Django admin, and then SSHing in to my box and restarting memcached. Not a good regime! But then again, I also couldn't bring myself to make the effort of writing custom invalidation routines for my cached pages. Considering my modest needs, it just wasn't worth it. What I needed was a solution that takes the same "brute force" page caching approach that Django's per-site cache already provided for me, but that also includes a similarly "brute force" approach to invalidation. Enter Jimmy Page.

23
Jan

On and off

English is a language bursting with ambiguity and double meanings. But the words "on" and "off" would have to be two of the worst offenders. I was thinking about words that foreign-language speakers would surely find particularly hard to master, when learning to speak English. And I couldn't go past these two. From the most basic meaning of the words, which relates to position — e.g. "the book is on the table", and "the plane is off the ground" — "on" and "off" have been overloaded more thoroughly than an Indian freight train.

09
Jan

The Art of Sport

Soccer (or football) is the most popular sport in the world today; likewise, with over 700 million viewers, the 4-yearly FIFA World Cup is the most watched event in human history. Why is this so? Is it mere chance — a matter of circumstance — that soccer has so clearly and definitively wooed more devotees than any other sport? I think not. Team sports are an approximation of military battle. All such sports endeavour to foster the same strategies that can be used effectively in traditional warfare. Soccer, in my opinion, fosters those strategies better than any other sport; this is because, in tactical terms, it is the most pure sport in the modern world.

30
Aug

The English Language and The Celtic Question

According to most linguistic / historical sources, the English language as we know it today is a West Germanic language (the other two languages in this family being German and Dutch). Modern English is the descendant of Old English, and Old English was essentially born when the Anglo-Saxons migrated to the isle of Great Britain in the 5th c. C.E., from their traditional homeland in the north-west of modern Germany. Prior to this time, it's believed that the inhabitants of all parts of the British Isles were predominantly Celtic speakers, with a small Latin influence resulting from the Roman occupation of Britain.

Of the languages that have influenced the development of English over the years, there are three whose effect can be overwhelmingly observed in modern English: French ("Old Norman"), Latin, and Germanic (i.e. "Old English"). But what about Celtic? It's believed that the majority of England's pre-Anglo-Saxon population spoke Brythonic (i.e. British Celtic). It's also been recently asserted that the majority of England's population today is genetically pre-Anglo-Saxon Briton stock. How, then — if those statements are both true — how can it be that the Celtic languages have left next to no legacy on modern English?

25
Aug

Boycott GPS

In the developed world, with its developed mapping providers and its developed satellite coverage, GPS is becoming ever more popular amongst automobile drivers. This is happening to the extent that I often wonder if the whole world is now running on autopilot. "In two hundred metres, take the second exit at the roundabout, then take the third left." Call me a luddite and a dinosaur if you must, all ye GPS faithful… but I refuse to use a GPS. I really can't stand the things. They're annoying to listen to. I can usually find a route just fine without them. And using them makes you navigationally illiterate. Join me in boycotting GPS!

06
Jun

An inline image Django template filter

Adding image fields to a Django model is easy, thanks to the built-in ImageField class. Auto-resizing uploaded images is also a breeze, courtesy of sorl-thumbnail and its forks/variants. But what about embedding resized images inline within text content? This is a very common use case for bloggers, and it's a final step that seems to be missing in Django at the moment.

Having recently migrated this site over from Drupal, my old blog posts had inline images embedded using image assist. Images could be inserted into an arbitrary spot within a text field by entering a token, with a syntax of [img_assist nid=123 ... ]. I wanted to be able to continue embedding images in roughly the same fashion, using a syntax as closely matching the old one as possible.

So, I've written a simple template filter that parses a text block for tokens with a syntax of [thumbnail image-identifier], and that replaces every such token with the image matching the given identifier, resized according to a pre-determined width and height (by sorl-thumbnail), and formatted as an image tag with a caption underneath. The code for the filter is below.

30
May

An autop Django template filter

autop is a script that was first written for WordPress by Matt Mullenweg (the WordPress founder). All WordPress blog posts are filtered using wpautop() (unless you install an additional plug-in to disable the filter). The function was also ported to Drupal, and it's enabled by default when entering body text into Drupal nodes. As far as I'm aware, autop has never been ported to a language other than PHP. Until now.

In the process of migrating this site from Drupal to Django, I was surprised to discover that not only Django, but also Python in general, lacks any linebreak filtering function (official or otherwise) that's anywhere near as intelligent as autop. The built-in Django linebreaks filter converts all single newlines to <br /> tags, and all double newlines to <p> tags, completely irrespective of HTML block elements such as <code> and <script>. This was a fairly major problem for me, as I was migrating a lot of old content over from Drupal, and that content was all formatted in autop style. Plus, I'm used to writing content in that way, and I'd like to continue writing content in that way, whether I'm in a PHP environment or not.

Therefore, I've ported Drupal's _filter_autop() function to Python, and implemented it as a Django template filter. From the limited testing I've done, the function appears to be working just as well in Django as it does in Drupal. You can find the function below.

25
May

Introducing GreenAsh 4

It's that time again. GreenAsh makeover time!

What can I say? It's been a while. I was bored. The old site and the old server were getting crusty. And my technology preferences have shifted rather dramatically of late. Hence, it is with great pride that I present to you the splendiferously jaw-dropping 4th edition of GreenAsh, my personal and professional web site all rolled into one (oh yes, I love to mix business and pleasure).

15
May

Non-Shelbyville Sydney map

A work colleague of mine recently made a colourful remark to someone. "You live in [boring outer suburb]?", she gasped. "That's so Shelbyville!" Interesting term, "Shelbyville". Otherwise known as "the 'burbs", or "not where the hip-hop folks live". Got me thinking. Where in Sydney is a trendy place for young 20-somethings to live, and where is Shelbyville?

I've lived in Sydney all my life. I've almost always lived quite squarely in Shelbyville myself. However, since the age of 18, I've gotten to know most of the popular nightlife haunts pretty well. And since entering the world of student share-houses, I've also become pretty familiar with the city's accommodation hotspots. So, having this background, and being a fan of online mapping funkiness, I decided to sit down and make a map of the trendiest spots in Sydney to live and play.

Map of non-Shelbyville Sydney

Map of non-Shelbyville Sydney

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