Coupling as a trade-off in an Enterprise Service Bus
Traditionally, integration problems between IT systems were solved by point-to-point connections. These point-to-point connections pose issues with scalability, reliability, and flexibility. To overcome these issues, companies typically invest in Enterprise Application Integration (EAI) using an Enterprise Service Bus (ESB) to integrate the IT systems through a central middleware infrastructure. EAI promises improvement of scalability, reliability, and flexibility by implementing loosely coupled integration solutions to realise loosely coupled IT systems. By wrongly implementing EAI on an ESB IT systems may still be tightly coupled and the issues with point-to-point connections could be recreated on the ESB. Currently there is no out-of-the-box solution to identify the integration solution where tight coupling causes these issues. The goal of this research is to investigate an approach to identify the coupling state in an Enterprise Service Bus and identify the integration solutions on an ESB which have a negative impact on the quality attributes due to tight coupling. The first step in the approach is applying a set of properties on the integration solutions to identify their coupling state. Manually identifying the coupling state is labour intensive, so it is automated by implementing a prototype with the Eclipse MoDisco framework. The second step in the approach is evaluating a trade-off between the risk of being in a certain coupling state and the efficiency loss of migrating to a less risky coupling state. With the outcome of the trade-off it can be ascertained whether or not it is beneficial to migrate to a different coupling state. The result of the approach is a list of integration solutions for which it would be beneficial to migrate to a different coupling state. This gives a concrete measure to be able to determine which integration solutions need to be improved to strive for the optimal balance between quality and the effort needed to realise quality. The approach was validated using the ESB implementation of a large European airport as a case study.