The Design And Simulation Of Message Agent Of Distributed Message Bus

Due to the structure and design, there are issues such as single point of failure and lack of scalability in traditional message-oriented middlewares. To positively respond to various opportunities and challenges brought about by changes in the market, big companies are in need of message systems which are more dynamic in structure, more flexible in architecture and swifter in answering. That’s when message bus adopting a distributed architecture came into being. It utilizes a center-free design, which means the messaging service is provided by collaboration of multiple nodes of equal status. However, such messaging systems are confronted by several challenges, including how to efficiently distribute working load among multiple nodes, how to ensure no loss of messages during the course of delivery and how to handle the failure of nodes. So systems like this are extremely hard to implement, involving large amount of reasoning and validation. Thus, the design and simulation of a partial message agent, which is the definite core component of a message bus, presents as a subject of both high research value and practical value. It will also shed some light on the implementation of a real messaging system.Based on the research and summery of existing systems, this paper comes up with a new design scheme for message agent. A simulative implementation is carried out according to the design with the help of a mature simulation system called NS2. After that, the simulated message system is tested under several sets of design scenarios. The results of these tests are the basis of analysis thereafter.Firstly, the paper analyses several existing systems and proposes the goals of the design based on the pros and cons of these systems. There are three main design goals:flexible load-balancing, guarantee of no loss of messages and high availability. According to these analysis and goals, concrete design schemes are given:the design of load-balancing consists of split of ownership of topics, reordering of messages, calculation of work load and the distributed coordination service; the guarantee of no loss of messages leverage a outer persistence service; to achieve high availability, a failover mechanism for message agent is designed.Based on the design scheme, this paper then presents the design of overall structure of the simulative messaging system and several core data structures, as well as the interface between all three modules, namely, publisher, subscriber and message agent. Detailed design is carried out for the three modules, including self-contained functions. Additionally, the input and output system is also customized according to the design. In implementation related chapters, this paper depicts the design of the core algorithms, along with a couple of code snippets from three modules. Some message process logic is explained in words as well, serving as a complement for the code.Thirdly, this paper presents the simulation results, including data and charts, under several sets of specially designed scenarios, along with analysis and some conclusion.Finally, this paper summarizes the results of the work during the course of the research subject.