As the complexity of your IT architecture grows, it becomes increasingly difficult to implement a change by changing a single system. The dependencies may even grow so strong, that a single request requires changes in multiple interdependent systems. To make sure that individual changes on different systems will work correctly together, you need to test all new versions of the systems working together in an integrated acceptance environment. After an extensive test period, you need to release all new versions of the systems to production at the same time. The integrated acceptance environment become a bottleneck for the individual teams, as each team wants to to test there changes in isolation. It is clear that the complexity of the IT landscape reduces the time to market of changes.
How did this turn out this way and how can this be avoided?
Service oriented architecture increases complexity
The compelling argument of Service Oriented Architecture was to reduce cost by leveraging reusability of systems. Unfortunately with the introduction of each reusable service, a new dependency is created between two systems. Over time, a complex web of interdependent systems is created. In this architecture the consuming systems are dependent on the quality and stability of the system providing the service. Errors ripple through the IT landscape and finding the cause of the error is time consuming. A rigorous acceptance testing period is introduced to avoid errors and a quarterly release calendar is used to minimising the number of changes to achieve "continuity".
Maximize autonomy of systems
The key to speeding up the delivery of new releases is to create autonomous systems that can be released and deployed independently of the other systems in the IT landscape. Instead of maximizing reusability, you should focus on maximizing autonomy of the systems. Although complete autonomy of a system is seldom, striving for autonomy will simplify your IT architecture and speed up the delivery of new releases and increase both stability and quality.
This post is part of a series on Continuous Delivery. Please see our tag Continuous Delivery for more posts on this subject. Or check our Continuous Delivery website to learn how Xebia can help you improve your time to market, reduce costs and improve quality using Continuous Delivery best practices.