A Checkpointing Algorithm Based Unreliable Non-FIFO Channels

Abstract

We propose a coordinated checkpointing algorithm based unreliable non-FIFO channel. In unreliable non-FIFO channel, the system can lose, duplicate, or reorder messages. The processes may not compute some messages because of message losses; the processes may compute some messages twice or more because of message duplicate; the processes may not compute messages according to their sending order because of message reordering. The above-mentioned problems make processes produce incorrect computation result, consequently, prevent processes from taking consistent global checkpoints. Our algorithm assigns each message a sequence number in order to resolve above-mentioned problems. During the establishing of the checkpoint, the consistency of checkpoint can be determined by the sequence number of sending and receiving messages. We can identify the lost messages, reordering messages and duplicate messages by checking the sequence number of sending and receiving messages. We resolve above-mentioned problems by resending the lost messages, buffering the reordering messages and dropping the duplicate messages. Our algorithm makes processes take consistent global checkpoints.