An Event-based Approach on Automatic Synchronous-to-Asynchronous Transformation of Web Service Invocations

One of the approaches to increase the performance of Distributed Systems, such as Service Oriented Systems, is the asynchronous invocation of the services. This is applicable because in many cases the clients do not need the result immediately and need not be blocked after the invocation. Without this mechanism, a developer should use a set of complex techniques to gain the mentioned performance. However, this procedure is both error-prone and cumbersome for the developers. Also, the state-of-the-art tools and languages which provide asynchronous mechanisms, involve the developers with the details of these invocations, as the mechanism is not transparent in these languages. In this paper, a new approach is proposed which generates an event-based middleware based on the candidate invocations available in the source/initial code. The approach also modifies the initial code to adapt with the middleware. This middleware plays the role of an interface between clients and web services. Using this approach, the invocations are transparent for the developers. This means that the synchronous and asynchronous invocations of web services are done in the same manner from the developer perspective. This is realized by automatic transformation of synchronous invocations to asynchronous ones via the generated middleware. The experimental evaluations show that the approach transforms the invocations successfully. Also, the results show that the performance of the asynchronous invocations are by far better than the synchronous ones.

I. Introduction

Calling the services in an asynchronous way in distributed system can increase the performance of the system. This asynchrony is possible if the client does not need the result of the invocation immediately. In this way, the client can continue running in parallel with the service, until the result is returned. This parallelism improves the performance and responsiveness [1], [2]. This general approach can be very useful in service oriented systems, such as web services.