容错技术在分布式多层应用系统中的实现

在分布式多层应用系统中，把应用程序服务器分布在两台或更多的计算机中执行，根据负载平衡的原理，客户端应用程序连接到其中一台计算机的应用程序服务器要求服务。如果客户端应用程序当前连接的应用程序服务器计算机发生故障而无法继续执行，在Agent的帮助下，他可以动态连接到其他机器中的应用程序服务器继续要求新的应用程序服务器为其提供服务。如果运行应用服务器的所有机器都发生故障，仍可以在客户端保存更新的资料，待应用程序服务器的机器恢复功能后，再自动把原先保存的资料更新回远程数据库服务器中，使得分布式多层应用系统的容错性能得到极大的提高。

Realization of Fault-tolerant Technique in Distributed Multi-layer System

In distributed multilayer system, we distribute application server in two or more computers, according to load balancing, client application can connect with one of application servers and ask for services If the application server fails and can't keep providing services Under the help of Agent, client application can link to other application server running in other computers and ask for services If all the computers running application servers fail, client application can save updating data, when the computers failed come back to normal states, client application write the saved data back to the remote database automatically, so the fault tolerance of distributed multilayer application system is improved greatly.