Causal Distributed Breakpoints

A causal distributed breakpoint is initiated by a sequential breakpoint in one process of a distributed computation, and restores each process in the computation to its earliest state that reflects all events that "happened before" the breakpoint. A causal distributed breakpoint is the natural extension for distributed programs of the conventional notion of a breakpoint in a sequential program. We present an algorithm for finding the causal distributed breakpoint given a sequential breakpoint in one of the processes. Approximately consistent checkpoint sets are used for efficiently restoring each process to its state in a causal distributed breakpoint. Causal distributed breakpoints assume deterministic processes that communicate solely by messages. The dependencies that arise from communication between processes are logged. Dependency logging and approximately consistent checkpoints sets have been implemented on a network of SUN workstations running the V-System. Overhead on the mess..