Maintaining a legacy application An interview conducted with David, one of the founders of TenTwentyFour1024
What is Flowey CMD?
Flowey CMD is a PHP-based project for L.C.I. Flowey S.A., one of the largest producers for car-wash products in Europe, that was begun in the
1990s and has since seen its fair share of developers "fiddling" with its code-base.
In 2014, the current developer was no longer available to look after the project and thus the company that had until then be maintaining the application was looking for experienced PHP developers to take on the job.
In their eyes it was very important that the next developer of the application be more than just your standard eight-to-five developer, instead bringing passion and a solid programming experience into play.
In fact, since the 1990s, the code had never really been refactored or
brought up to speed, which means in essence it was, and largely still
The project also didn't have any namespaces of course, no classes, except
where – rarely, external libraries were used – and almost no functions either. Most of the code flow used to be linear with conditional statements throughout the files, often thousands of lines long, determining which code to execute, what to print, etc.
What is TenTwentyFour1024's task on this project?
TenTwentyFour1024's job in this project is two-fold: First,
maintaining the application, upgrading those parts that need urgent
replacement (e.g. replacing the php-mysql database driver with php-mysql-nd and MySQLi or PDO), fixing bugs and adding new functionality.
New functionality however, is added by using a Silex-based application
completely rewritten from scratch.
The second job is to gradually migrate the legacy code to new, PHP5.6/PHP7
based code using the same silex application as a backend, and relying on REST
APIs wherever possible, to integrate the new parts with the existing legacy code.
Faced with this "spaghetti code" nightmare, how did you proceed to make it more manageable?
The first steps that TenTwentyFour1024 took were to
bring the entire project under version control, add code-style and mess
detection checks and add additional software metrics, such as coupling,
stability, cyclometic complexity… to get an initial understanding of how problematic the code was and how much effort would be required to tame it.
Using the Behat BDD tool, TenTwentyFour1024 gradually started covering most functionality of the application, first and foremost the parts that needed to be refactored, extended or otherwise improved.
Having the support of these tools, TenTwentyFour1024 could finally start to modify the code's application without fear of inadvertedly breaking existing functionality.
More than 216 scenarios and 3530 steps currently cover the application,
all of them passing with flying colors in Jenkins, our continuous integration tool.
Whereas the application was previously developed in a separate folder
structure on the production server, TenTwentyFour1024 has introduced a reproducible build process including database migrations using ant and flyway. We are developing the application locally using a docker ecosystem and deploy a new revision continuously
using capistrano in a matter of just seconds.
What problems arose during development and how did you solve them?
Due to the structure of the project, it is extremely difficult to grasp
the entire control flow and keep it in one's mind during development.
Parts of the application were sometimes only working due to errors that
had the desired side-effects. The HTML througout the application was
generally broken, so was its encoding.
TenTwentyFour1024's concern was to introduce a proper MVC
pattern to separate the various concerns and quickly understand
what is going on.
The functional tests we keep adding help us stay sane while moving around the code, gradually replacing parts of it and fixing really old bugs.
PHP is a popular general-purpose scripting language that is especially suited to web development. Fast, flexible and pragmatic, PHP powers everything from your blog to the most popular websites in the world.
Behat is an open source behavior-driven development framework for PHP 5.3 and 5.4 that was inspired by Ruby's Cucumber project, especially its Gherkin syntax. Behat drives the functional tests on this project.
Silex is a php micro-framework based on Symfony2 components. Comparable to flask for python or express.js for node, silex is powerful, yet free of the usual bloat and it gives you complete freedom over your application's structure.
phpspec is a php toolset to drive emergent design by specification. Offering a more fluent interface and a better integration with mocking frameworks, phpspec has replaced PHPUnit in our newer projects.
MySQL is a relational database management system being used for persisting and manipulating application data. It is one of the most widely used database system for PHP applications, if not the most.
gulp is a toolkit that helps you automate painful or time-consuming tasks in your development workflow. It uses streaming file transformations and in contrast to grunt, gulp allows to define tasks, rather than configurations.