Today, most of the SOA efforts are keen on implementing synchronous request-response interaction patterns to connect different and distributed processes. This approach works well for highly centralized environments and creates a kind of loose coupling for distributed software components at the IT infrastructure level. However, SOA leads to the tight coupling of application functions due to the synchronous communication. This being said, increasingly enterprise environments are tending towards being dynamic and real-time in their interactions, decision-enablement, and actuation. The SOA patterns may find it difficult in ensuring the overwhelmingly pronounced requirements of next-generation enterprise IT.
SOA is a good option if the requirement is just to send requests and receive responses synchronously. But SOA is not good enough to handle real-time events asynchronously. That is why the new pattern of event-driven SOA, which intrinsically combines the proven SOA's request-response and the EDA's event publish-subscribe paradigms, is acquiring a lot of attention and attraction these days. That is, in order to fulfil the newly incorporated requirements, there is a need for such a composite pattern. This is being touted as the new-generation SOA (alternatively touted as SOA 2.0). It is based on the asynchronous message-driven communication model to propagate information across all sorts of enterprise-grade applications throughout an enterprise. Services are activated by differently sourced events and the resulting event messages pass through the right services to accomplish the predestined business operation. Precisely speaking, the participating and contributing services are fully decoupled and joined through event messages. All kinds of dependencies get simply eliminated in this new model.
Applications are being designed, developed, and deployed in such a way to be extremely yet elegantly sensitive and responsive. With enterprise applications and big data mandating the distributed computing model, undoubtedly the event-driven SOA pattern is the way forward. The goals of dynamism, autonomy, and real-time interactions can be achieved through this new pattern. This new event-driven SOA pattern allows system architects and designers to process both event messages and service requests (RPC/RMI). This enables a closer affinity and association between business needs and the respective IT solutions. This invariably results in business agility, adaptivity, autonomy, and affordability.
The following diagram illustrates the traditional request-and-response SOA style. The SOA pattern generally prescribes the synchronous and pull-based approach:
The following diagram depicts the message-oriented, event-driven, asynchronous, and non-blocking process architecture:
