A study on dynamic adaptation of distributed systems using immune mechanism

如何使软件在动态变化的环境或使用模式中使用是一个非常有趣的问题，例如由公共或未指定系统使用的服务器。如果动态环境变化是可预测的，则可以通过将这些条件和动作作为生产规则合并到软件中来实现。另一方面，对于诸如访问模式完全不可预测的Web服务器之类的软件，如果系统具有自主适应动态环境变化的能力，那么系统开发人员将非常感激。本研究的目的是实现一种系统动态适应所必需的机制。我们利用细粒度对象、反射和元级架构作为基础技术。在第一年，我们开发了一个名为iNexus的政策协调引擎，它利用人工免疫网络作为自主动态适应环境的工具。然后，我们利用iNexus实现了OpenWebServer，并验证了OpenWebServer可以根据动态变化的访问模式来改变处理策略。第二年，我们注意到人工免疫网络对环境变化的高适应性，并开发了一种利用人工免疫网络作为控制策略决策工具的通信管理系统。在实际应用中也显示了人工免疫网络的高适用性。在分布式系统整体动态适应环境的情况下，我们实现了一种对访问过于集中的服务器的内容进行复制的机制。该机制可作为Internet中Web访问的拥塞避免工具。我们还研究了各种环境下的复制成本和通信负载，并验证了其在Web服务器的实际应用中的实用性。

It is very interesting problem that how to make a software used in dynamically changing environment or usage patterns, such as a server that is used by public or unspecified systems. If the dynamic environmental change is predictable, it can be achieved by incorporating these conditions and actions as production rules into the software. On the other hand, for the software such as Web servers where access patterns are completely unpredictable, it is highly appreciate for system developers if the system has an ability to adapt autonomously to dynamic environmental change.The purpose of this research was to implement a mechanism that is necessary for dynamic adaptation of systems. We utilize fine grained objects, reflection and meta-level architecture as base technologies. In the first year, we developed a policy coordination engine named iNexus that utilized an artificial immune network as a tool for autonomous and dynamic adaptation to the environment. And then we implemented OpenWebServer that utilized the iNexus, and verified that the OpenWebServer could change processing policies depending on dynamically changing access patterns. In the second year, we noticed high adaptability to environmental change of an artificial immune networks and developed a communication management system that used an artificial immune network as a tool for decision making of control policy. The system also showed high applicability of the artificial immune network even to the real application.In case of a distributed system as a whole dynamically adopts to its environment, we realize a mechanism that makes copy of contents of a server which has over concentrated access. This mechanism can be used for a aid of congestion avoidance tool of Web access in the Internet. We also study the cost of copy and communication load in various environments and verify its usefulness in practical application to Web servers.