5/09/2010

Caringorm is Architectural Poison

No one has ever accused me of shying away from sensational titles, and now's not the time to get timid. I must confess I've never been a fan of Caringorm. My first impression of Caringorm was it's over engineered. Why are there so many layers? Isn't that going to just slow you down having to develop a View, Command, Delegate, Service, etc for every round trip I make to the backend? Now that I'm working on a project that has gone horribly wrong I see how Caringorm architecture directly contributed to the problems. We've been called in to straighten out the mess and put down a more suitable architecture. After understanding what the team has done I begin to see the techniques, that Caringorm purports as best practices, create more work for yourself the longer you use them.

Software architecture should organize your work so you can work at a higher level related to your problem you are trying to solve. It does this by fostering reuse in your code. It should allow you to reuse what you did yesterday to apply to today's problem reducing the work required get work done. As your project grows the only way you can move quickly is through reuse. Without reuse the work grows exponentially to the point where value can't be delivered. How long this takes before your code base becomes unproductive? Ten releases? 10 Years? I've seen it happen in 1 release, and less than 1 year.

Key signs this has happened in your project is talks about rewriting your application or major refactoring. Other signs come in when your customer says that should be easy, and then developing it takes significantly more time than you'd expect. Bad architecture robs your team's performance to deliver value. If this goes on too long your project will get scrapped and if you're lucky you'll be allowed to start another project. Most likely you won't because the business will be putting your project in maintenance mode while they spin up the "solution". Good architecture is quite the opposite. Easy things are easy and hard things are possible. At the core of this is the level of reuse in your project.

Caringorm doesn't foster reuse. It stalks it, attacks, leaves it dead, and poisons the earth to keep it from ever fostering. At the heart of this is the age old singleton problem. Singleton's are seriously bad technique, and I wish every developer out there understood this. Using singletons to limit an instance to a single instance is not all together bad, but using it as a locator pattern is where the serious issues began to make your code single use. Unfortunately you can't limit a singleton to the good parts without accepting the very serious downsides, and this is the reasons I try and void them at all costs because the downsides are that damaging. Cargingorm has no problem using the ModelLocator (which is a singleton) in your views (mxml). And there is no amount of other techniques you can introduce to overcome the problems that come with this. I don't care if you're using Code Behind, Presentation Model, or whatever. If you use a singleton in your views you can't reuse them. Anything that directly references singletons becomes single purpose in its use as well, including anything referencing those objects, and so on and so on.

Why is that a problem? Well consider if we wrote DataGrid with the same techniques Caringorm purports as acceptable practices. Let's say DataGrid.dataProvider was hard coded to look in ModelLocator.getInstance().dataProvider. Now how can you have two instances of DataGrid in your program pointing at two different dataProviders? You can't. And this is precisely the problem that leads to serious architecture problems with Caringorm programs. Now throw in calls to getController().eventManager.addEventListener() in your views and you have a serious recipe for disaster.

You might find my example contrived so let me describe a more real world scenario. Say you have a signup process that people fill out on your site and you have a view that represents the information you want to gather. In that view you're using the ModelLocator. Now the customer wants to add a new way to sign up because their doing an email campaign, and they'd like to pre-populate that form from details like the email address and ad campaign number to track it into the view. Unfortunately, ModelLocator makes it difficult to put two different models into your view because it's hard coded to one. What would have been an easy task by instantiating another instance of your view has turned into creating another view from scratch. So let's say you need to do this fast and you copy the view and makes the changes to create two different views. Then the customer wants to add a field to both views. Now you need to update two places in your application. This is precisely what I mean when I say Caringorm creates more work for you. Over time if enough of these exist in your application your productivity will drift to zero because maintaining all of it too much work.

Now hopefully I convinced you that the patterns Caringorm suggests are not helping you. And, you decide to banish ModelLocator from the views. However, the problem of geting something from the model and bound into the view still exists. So what part of the Caringorm architecture will interact with the ModelLocator and the view? Normally this would be the Controller in a traditional MVC pattern. In Caringorm the Command is suppose to be this part, but it doesn't have access to the view. Therefore, how will it set the data properties on the view? You could do some gymnastics by passing references through the FrontController into the Commands, but at this point I'm taking some serious liberties to modify Caringorm's architecture design to make it work. If the architects of Caringorm had realized this then their examples would have shown how to do this.

I'd like to think that as an industry we're working towards a shared understanding about the dangers of singletons, and if that were true I'd expect to see a drop in the number of projects using them. I'd expect to see a reduction in the number of frameworks employing singletons as an instance locator pattern. However, it's quite the opposite. Most developers don't see a singleton and get that tingling sensation that something bad is about to happen. But, singletons have all the same problems that global variables do and by in large most developers realize global variables are poison if not very carefully used.

Caringorm is like EJB of Flex. Over engineered. Expect there to be serious changes to Caringorm in the future to save the marketing that Adobe has done with clients. Just like Sun did with EJB3 for EJB. Sun had over emphasized the benefits (if there were really ever any) to using EJB, and once the community realized EJB was over engineered and more trouble than it was worth. Sun had no choice but to hire Hibernate's creator to design EJB 3.0 and started begging for forgiveness. Adobe will have to do the same.

2 comments:

Brian Sanders said...

"Cairngorm is like EJB of Flex" The most damning title a developer can bestow on a framework. :) I agree about the over-engineering. Does this particular layer/class enhance testability or maintainability? If not, axe it. Of course, if you're stuck in a statically-typed language...

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