Comprehensive Low-overhead Process Recovery Based on Quasi-synchronous Checkpointing

In this paper, we propose a low-overhead recovery algorithm based on a quasi-synchronous checkpointing algorithm. The checkpointing algorithm preserves process autonomy by allowing them to take checkpoints asynchronously and uses communication-induced checkpoint coordination for the progression of the recovery line which helps bound rollback propagation during a recovery. Thus, it has the easeness and low overhead of asynchronous checkpointing and the recovery time advantages of synchronous checkpointing. There is no extra message overhead involved during checkpointing and the additional checkpointing overhead is nominal. The checkpointing algorithm ensures the existence of a recovery line consistent with the latest checkpoint of any process all the time. The recovery algorithm exploits this feature to restore the system to a state consistent with the latest checkpoint of a failed process, in the event of a failure. The recovery algorithm has no domino eeect and a failed process needs only to rollback to its latest checkpoint and request the other processes to roll back to a consistent checkpoint. It uses selective pessimistic message logging at the receiver end to handle the messages lost due to rollback. Neither the recovery algorithm nor the checkpointing algorithm requires the channels to be FIFO. We do not use vector timestamps for determining dependency between checkpoints which result in high message overhead during failure-free operation if the number of processes is large.