Up until a few months ago, Simple-Talk ran on a pure .NET stack, with IIS as the web server and SQL Server as the database. Unfortunately, the platform for the site hadn’t quite gotten the love and attention it deserved. On the one hand, in the words of our esteemed editor Tony “I’d consider the current platform to be a “success”; it cost $10K, has lasted for 6 years, was finished, end to end in 6 months, and although we moan about it has got us quite a long way.” On the other hand, it was becoming increasingly clear that it needed some serious work. Among other issues, we had authors that wouldn’t blog because our current blogging platform, Community Server, was too painful for them to use.
Forgetting about Simple-Talk for a moment, if you ask somebody what blogging platform they’d choose, the odds are they’d say WordPress. Regardless of its technical merits, it’s probably the most popular blogging platform, and it certainly seemed easier to use than Community Server. The issue was that WordPress is normally hosted on a Linux stack running PHP, Apache and MySQL — quite a difference from our Microsoft technology stack. We certainly didn’t want to rewrite the entire site — we just wanted a better blogging platform, with the rest of the existing, legacy site left as is.
At a very high level, Simple-Talk’s technical design was originally very straightforward: when your browser sends an HTTP request to Simple-Talk, IIS (the web server) takes the request, does some work, and sends back a response.
In order to keep the legacy site running, except with WordPress running the blogs, a different design is called for. We now use nginx as a reverse-proxy, which can then delegate requests to the appropriate application:
So, when your browser sends a request to Simple-Talk, nginx takes that request and checks which part of the site you’re trying to access. Most of the time, it just passes the request along to IIS, which can then respond in much the same way it always has. However, if your request is for the blogs, then nginx delegates the request to WordPress.
Unfortunately, as simple as that diagram looks, it hides an awful lot of complexity. In particular, the legacy site running on IIS was made up of four .NET applications. I’ve already mentioned one of these applications, Community Server, which handled the old blogs as well as managing membership and the forums. We have a couple of other applications to manage both our newsletters and our articles, and our own custom application to do some of the rendering on the site, such as the front page and the articles. When I say that it was made up of four .NET applications, this might conjure up an image in your mind of how they fit together:
You might imagine four .NET applications, each with their own database, communicating over well-defined APIs. Sadly, reality was a little disappointing:
We had four .NET applications that all ran on the same database. Worse still, there were many queries that happily joined across tables from multiple applications, meaning that each application was heavily dependent on the exact data schema that each other application used. Add to this that many of the queries were at least dozens of lines long, and practically identical to other queries except in a few key spots, and we can see that attempting to replace one component of the system would be more than a little tricky.
However, the problems with the old system do give us a good place to start thinking about desirable qualities from any changes to the platform. Specifically:
Maintainability — the tight coupling between each .NET application made it difficult to update any one application without also having to make changes elsewhere
Replaceability — the tight coupling also meant that replacing one component wouldn’t be straightforward, especially if it wasn’t on a similar Microsoft stack. We’d like to be able to replace different parts without having to modify the existing codebase extensively
Reusability — we’d like to be able to combine the different pieces of the system in different ways for different sites
Repeatable deployments — rather than having to deploy the site manually with a long list of instructions, we should be able to deploy the entire site with a single command, allowing you to create a new instance of the site easily whether on production, staging servers, test servers or your own local machine
Testability — if we can deploy the site with a single command, and each part of the site is no longer dependent on the specifics of how every other part of the site works, we can begin to run automated tests against the site, and against individual parts, both to prevent regressions and to do a little test-driven development
In the next part, I’ll describe the high-level architecture we now have that hopefully brings us a little closer to these five traits.
