Wednesday, February 25, 2009

Standards vs. Upgrade pains

In Standards Based vs. Standardized Neal Ford develops a very interesting rhetoric that is mainly focused on what he sees being "wrong with SOA (Service Oriented Architecture) in the way that it's being sold by vendors", but really touches a vast subject that has many thought provoking ramifications.

While considering the application upgrades I am involved in or that occur around me, it is clear that applications deployed on standardized platforms have easier upgrade paths. Or have they?

Let me consider the whole spectrum of applications I am involved with and discuss the related upgrade pains, how standards play a role there and if they are worth the effort. I won't discuss the necessity of upgrading application platforms: I reckon everybody feels the same itch when they see an application running on a platform that is many releases behind its current revision.

Non-standardized

Neal mentions ESBs as canonical non-standardized platforms, so I will start with them and consider my experience with following Mule versions. Many aspects of Mule are standards-based, from its protocol stacks to the zillions of libraries it is built upon (which I consider as being industry standards). Even its configuration mechanism piggybacks on Spring's schema driven configuration. What is not standardized are Mule's API and configuration syntax. Therefore they tend to evolve quickly, and sometimes drastically, as Mule expands and refines its feature base. Consequently, following Mule versions is not a small feat: it requires a pretty advanced knowledge of the platform to be performed right (and the assistance of extensive unit and integration tests, but everyone has this already, right?). Why would anyone willingly accept to jump through such hoops? Because it is worth it: being exposed to Mule's non-standard aspects is rewarded by a full access to its complete feature set and its full power.

Standardized

At the other end of the spectrum lies web applications that fully pack their dependencies and can be deployed on pretty much any container that understands their standardized configuration. A typical example is a Spring/Hibernate application deployed on JEE web container, like Tomcat or Jetty. It is to be noted that, even if this kind of applications can have very complex needs, their reliance on the JEE standard is actually quite small: a few entries in web.xml that hook some basic application entry points to the container and that is pretty much it. The rest is not standardized but fully resides in the realm of what the application controls (Spring and Hibernate configurations for example). Hence migrating between different versions or even different implementations of the JEE container is usually a no-brainer.

Somewhat standardized

Finally, in the middle of the spectrum, we find the applications deployed on platforms where standards fall short of allowing them to easily follow releases. Consider a full fledged JEE application, say deployed on JBoss. In this case, two forces act against the standard. The first one is the limitation in scope of this standard: anything that has been left to the interpretation of the implementor will likely differ enough between major releases to cause troubles. The second force is the fact that the standard itself is a keyhole applied against the full range of features of the platform itself: these features are there, accessible, often compelling, and it requires a lot of willpower to refuse to use them directly (by shielding them behind a custom facade) or not at all (by using extra dependencies to get these needed features). These two forces combined usually lead to full-range JEE applications that do not evolve gracefully when their underlying standardized platform is upgraded.

So, there is a clear trade off between having full access to a platform and being isolated from the disruptive aspects of its evolution over time. It is also true that standards with more teeth are probably needed (OSGi is an interesting one in this matter).

But everybody knew this already.

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