Software Fault-Tolerance based on Observation and Control of Distributed Programs

为了降低与软件故障相关的风险，研究重点是基于前瞻受控执行的容错方法。 在这种方法中，程序以先行模式运行，而不影响外部环境。在前瞻过程中，会跟踪足够的信息，以便分析故障。 如果执行分析表明没有错误，则将提交前瞻执行，并且其效果对环境可见。 否则，前瞻执行的结果将被丢弃，并且系统以受控模式运行。在这种模式下，系统通过引入额外的同步或改变消息的顺序来进行控制，以避免在前瞻期间发生故障。该项目由三个主要部分组成：软件故障检测算法、自动控制算法（例如基于前瞻的控制消息插入和消息重新排序）以及支持前瞻受控执行的系统。 为了检测软件故障，先前的算法将被扩展以适用于出现故障时更通用的计算模型。对于自动控制，该项目将重点关注并发程序中的同步错误。最后，将开发一个支持前瞻受控执行的Java系统。

To reduce the risks associated with software faults, the research focuses on a fault tolerance method based on controlled execution with lookahead. In this approach, a program is run in a lookahead mode without affecting the external environment. During lookahead, sufficient information is traced so that it can be analyzed for faults. If the analysis of the execution shows that there are no faults, then the lookahead execution is committed and its effects are visible to the environment. Otherwise, the results from the lookahead execution are discarded, and the system is run in a controlled mode. In this mode, the system exercises control by introducing additional synchronization or by changing the order of messages to avoid the fault that occurred during lookahead.There are three main components of the project - algorithms fordetection of software faults, algorithms for automaticcontrol such as insertion of control messages and reordering ofmessages based on lookahead, and a system which supports controlledexecution with lookahead. For detection of software faults, previous algorithms will be extended to work for more general model ofcomputation in the presence of failures. For automatic control, the project will focus on synchronization faults in concurrent programs.Finally, a system in Java that supports controlledexecution with lookahead will be developed.