Archive for the ‘Tech’ Category

If you’re using Propel ORM, you may want to select a range of primary keys. According to the documentation, you should be able to do this using code similar to the following.

BookQuery::create()->filterById(array('min' => 1, 'max' => 100));

However, what you find you get is that will return books with the ID of 1 and 100, but nothing else.

That is because Propel does not support ranges on IDs. This has been noted on the Propel GitHub issue tracker and will be resolved at some point in the future, but until then you have two possibilities.

Firstly, if you’re only looking to specify one value in the range, you can pass a criteria constant to filter by that.

BookQuery::create()->filterById(30, \Criteria::GREATER_THAN)->find();

You can also use LESS_THAN in the same way. Or, if you need a range with both ends specified, you can resort to the where() method.

BookQuery::create()->where('id BETWEEN 1 AND 100')->find();

Though that method requires you to use the database column names, rather than the PHP names used in Propel (yours may be the same, but I often rename mine for legacy reasons).

We recently launched Village Chief, a Facebook game in which you take on the role of a local village chief with the aim of growing your community into a thriving settlement.

The project was designed from the ground up to be highly scalable – Facebook cames can go viral very quickly so you need a system which can scale up very quickly if your game suddenly becomes very popular, or you risk losing out on huge amounts of market capitalisation.

First off, it’s written in Ruby. Ruby is a cool scripting language that is similar to Python and it’s popular web framework Ruby on Rails has received a lot of praise being the framework that Twitter and 37signal’s suite (Basecamp, Highrise, etc) are written in. It’s a very forgiving language, even compared to PHP, so if you like your static typing consider Scala instead, but for rapid web development, Ruby is a gem.

Despite the popularity of the Rails framework, I was looking for something a little more lightweight, so Village Chief is built using Sinatra. The documentation is a little underdeveloped but is never the less sufficient to get buy and lets you get a web application up and running nice and fast.

Ruby also includes a great module system called Ruby Gems (spot the earlier pun now 😉 ), a system similar to PHP’s PECL. The game makes heavy use of these – for example, using Koala to interact with Facebook and Dalli to handle our caching.

For a data source, it made sense to use a NoSQL solution. I originally settled on Apache Cassandra. It doesn’t have the flexibility or functionally of Mongo but it terms of raw speed it’s hard to beat and scales onto multiple servers with eventual consistency beautifully.

When it came to deployment, I decided to go with Amazon AWS’s DynamoDB instead. I’ll discuss more about why this was later but this meant rewriting the database interaction. This was easy to do thanks to our database abstraction layer and allowed us to continue using Cassandra for our testing systems while rolling out the production environment on DynamoDB.

Some data was also rolled out using SQLite. This was used for data such as the product catalogue which doesn’t contain user data – just things you can buy. Keeping it in an SQLite database allows us get quick access while still being able to query against the records – and importantly, allows us to version control our product catalogue.

To keep the database load down, some of the sorting was moved into the web server layer instead. On top of this we built a caching system using Memcache to save a lot of the data in memory, thus making things much faster.

When it came to deployment, I decided that Amazon’s EC2 cloud. You can start up a new server in under a minute, which is fantastic for scalability. Thanks to Amazon’s Elastic IPs, you can maintain a set of public IPs and map them to any one of your EC2 servers.

The servers are based on the latest Ubuntu release and to make sure that they are delivering content at top speed, I choose to go with the nginx web server rather than Apache, which works in conjunction with Passenger to provide the platform.

One limitation of EC2 is that you either have to allocate EBS (Elastic Block Storage) which adds additional cost, or use the ephemeral storage which you lose every time you turn the box off. The solution? Put everything into an external database so that we can switch boxes on and off without a problem – hence the decision to use DynamoDB rather than running Cassandra on the servers.

Code is then deployed using Capistrano which goes onto each of the boxes and performs a structed deployment that you can easily roll back, pulling the code direct from our Git repository.

That is a whistle-stop tour of the technologies used in Village Chief. If you have any questions about any of them, feel free to post a comment.

If you have made the mistake I did of doing a fairly minimal install on Debian, you might have noticed it is missing a few fairly basic features – such as JPEG support! Luckily it’s fairly easy to install it.

wget ftp://ftp.uu.net/graphics/jpeg/jpegsrc.v6b.tar.gz
tar -zxvf jpegsrc.v6b.tar.gz
cd jpeg-6b
./configure --enable-shared
make
make install

I’m currently consulting at a small software house in Leeds city centre and we’re making continuous integration a big thing.

Initially, we started off using CruiseControl which integrates nicely with phpUnderControl. Unfortunately, phpUC is now seriously showing its age – many of the components simply didn’t work anymore and it still uses phpDocumentor, a project that was abandoned years ago to the point where it is now unusable with modern code (though I’m glad to see the project has recently been rescued and a 2.0 version is being developed).

As a result, we’ve now switched to Jenkins and it’s really working out well. it seamlessly integrates with Subversion and using the Ant build script we’re able to integrate PHPUnit, PHP CodeSniffer, PHP Copy & Paste Detector and PHP Mess Detector, all of which provide great feedback on the standard of code which is being written.

You can then varying the log level and what classes as a failed build, so if you want to ensure everything is absolutely perfect, you can have Jenkins email you every time someone doesn’t quite space their code out right, or adds a local variable that they never use. Then again, you can just have that stuff running in the background and check it when you have time.

One issue you might run into when first integrating such tools is that builds can take a long time to run – CodeSniffer and Mess Detector can take up to 10 minutes each even on a small code, when there are lots of issues to resolve. However, once you have resolved most of these issues you will find that they run quickly again and should be able to get your build time down to a couple of minutes on even a large codebase.

If you want to change your timezone on Debian, use the following command.

dpkg-reconfigure tzdata

Introducing Village Chief, a fun strategy game that allows you to come the Chief of a village and grow it into a flourishing community.

We’re very pleased to announce this first beta version. You start the game with some villages, gold and buildings to get you started. You can then expand your village by buying more houses, farms and even a bank. As you grow, your villagers will procreate and pay you taxes too – money you can use to expand your village!

Awstats is updated by cPanel once per day, but if you want to force a manual update, you can do so with the following command.

/usr/bin/perl /usr/local/cpanel/3rdparty/bin/awstats.pl -config=example.com -update

If you’re like me, which seems unlikely as statistically you’re probably far more sensible, you’ll get really annoyed when the white spacing or indentation isn’t consistent within a file.

Because of this, I recently wrote a little Ruby script which would automatically clean up my CSS files and make them all nice and pretty. It’s now publicly available on Github if you want a copy.

At some point in the future I’m intending to do similar scripts for other file types – the SocietasPro codebase already has a similar system for PHP, though that only flags inconsistencies, it doesn’t correct them.

If you want to change your SSH port to something a little less obvious, it’s easy to do. It’s debatable how much security it actually gives you, but it will certainly make you feel safer, and that is probably the most important thing.

pico /etc/ssh/sshd_config

I’m using pico in this example, but vim will work just as well. You should find a line which is commented out, specifying that the port is 22. This doesn’t need to be uncommented normally, as it defaults to port 22.

#Port 22

Just uncomment this and put a new port number in.

Port 8473

Now save the file and exit. Finally, restart SSH for it to take affect.

/etc/rc.d/init.d/sshd restart

Don’t forget, next time you SSH in you will need to use the new port number!

ssh -p 8473 hostname

If you are luckily enough to work in a Web 2.0 start up, you probably won’t have to deal with too much legacy code. But for the rest of us, we can often find ourselves working with code which can be even decades out of date.

One of the big issues in PHP has been the deprecation of register globals. Of course, this happened quite a long time ago, because the idea of register globals was just plain stupid, but recent versions of PHP (5.3 onwards), will now throw a deprecation error.

So, we need to find a way to turn register globals off.

The end solution is of course to refactor the code so it doesn’t use register globals at all. Anything short of this is going to be a security nightmare, it’s like a ticking time bomb sitting on your server. But until then, there is a way you can emulate it in your PHP code while you work to get rid of it, allowing you to turn the register global settings off.

All you need is something like this in your code.

foreach ($_REQUEST as $key => $val) {
	$$key = $val;
}