Combinando objetos distribuídos e arquiteturas orientadas a eventos em uma infraestrutura de comunicação para sistemas distribuídos.

Abstract

In the last decades, much work has been done in order to make the development of distributed systems as simple as the development of centralized systems. However, there are inherent characteristics of a distributed environment (e.g., partial failure and concurrency), which need to be explicited to the programmer. There are also other aspects, like partial connectivity (imposed by firewalls and NATs), which are common in communication across multiple administrative domains. Distributed Objects then appeared as a solution that is as close as possible to the centralized object oriented model. Nevertheless, distributed objects create the illusion that threads traverse the whole application, which brings all the problems related to the complex and non-deterministic thread model. Moreover, as distributed objects rely on a blocking communication model, they are not well suited for applications in which a client has other things to do besides waiting for the server response. As an alternative, there are a number of message-based solutions, which delimit scope for it’s threads, but fail on providing good integration to the programming language, a well-defined failure detection mechanism or even a good support for firewall and NAT traversal. Our thesis is that it is possible to combine distributed objects with an event-driven architecture (which is an specific type of message-based solution) in order to provide a solution that relies on a non-blocking communication model, yet providing close semantics to the object oriented paradigm, providing precise scope for the application’s threads. Then, we propose JIC (Java Internet Communication), a solution that supports our thesis, also designed to be firewall and NAT friendly and which provides an embedded failure detection mechanism simple to use and with precise semantics. An evaluation shows that JIC has performance comparable to Java RMI. A software engineering analysis also shows that, by using JIC, it is possible to focus more on the business logic of the application and build well-modularized code, exploiting parallelism without writing multi-threaded programs. This greatly avoids the inherent problems of threads.