Research And Implementation Of Asynchronous Messaging Based On Distributed Object

In the 90th, with the development and marriage of distributed client/server computing technology and object oriented technology, distributed object technology has come into being, and become the mainstream technology and an important computing paradigm of application integration and system development in distributed heterogeneous environment.The communication model of distributed object technology usually is synchronous and tightly coupled, but with the appearance and development of application such as workflow, E-commerce, and mobile computing, etc, traditional communication model of distributed object technology is seriously challenged. So, establishing an asynchronous and loosed coupled communication model becomes a hot spot in distributed object study.The primary work of this thesis is mainly about asynchronous and loosely coupled communication technology based on distributed object. The main idea is to extend CORBA by preserving its interoperability, reusability and portability, to introduce the messaging and message control technology of message oriented middleware seamlessly into CORBA. Therefore, this thesis presents a new asynchronous messaging model based on distributed object, and discusses the basic communication problems in the model, which includes asynchronous invoke, store-forward, object migration, message multicast, etc. Base on this model, the thesis also studies some advanced technology problem such as message routing, reliable delivery, performance guarantee, etc, which will be met in constructing complex distributed system. The primary work of this thesis include:1. To satisfy the requirement of asynchronous and loosely coupled communication model, this thesis presents a formalize definition of asynchronous messaging model based on distributed object. This model manages remote invokes through event driving, and supports two asynchronous invoke model such as asynchronous call back and polling; the model uses router as message "store-forward" mechanism, and guarantees time independent invoke of loosely coupled application; the model extends the traditional CORBA addressing way, defines a kind of logic object address, which can support object migration of loosely coupled application and increase transparency of object location; the model also defines object group address, which supports message multicast and implements "I-to-n" communication model.2. The thesis studies a static message routing algorithm (IRP algorithm) and a dynamic message routing algorithm (L-S algorithm). In IRP algorithm, routing is based on component from Server, which is simple and practical, but cannot adapt dynamic change in distributed system environment. In L-S algorithm (Link State algorithm), routing is based on table drove, which can adapt dynamic change of distributed system environment and guarantee message routing correctly.3. During the studies of reliability of message delivery, this thesis divides the problem intotwo phases: first, clients send message reliably to target object's default router; second, target object's default router continues to send message to target object. The thesis studies store and forward mechanism and redundant routing of message in first phase, and reliability algorithm based on object group in second phase, which includes active duplication algorithm and primary backup algorithm. Moreover, from a global view, the thesis studies the message order problem caused by model and presents a reliable message order algorithm based on sequence.4. From two views, this thesis studies performance problem of distributed object asynchronous messaging model. First, the thesis constructs a object cache model based on asynchronous messaging model which can improve access efficiency of object by establishing duplicate locally for remote object, and studies a serious of key problem, and presents object duplication algorithm, object migration algorithm, duplicate consistency algorithm, etc. Second, to keep up with the dynamic changes of performa...