Consensus on Transaction Commit

TL;DR

This paper introduces Paxos Commit, a fault-tolerant consensus-based transaction commit protocol that avoids blocking and improves reliability over the classic Two-Phase Commit by using Paxos consensus.

Contribution

It presents a novel Paxos-based transaction commit protocol that generalizes Two-Phase Commit and ensures progress with fault tolerance.

Findings

Requires 2F + 1 coordinators for fault tolerance

Makes progress if at least F + 1 coordinators are operational

In the fault-free case, has the same delay as Two-Phase Commit

Abstract

The distributed transaction commit problem requires reaching agreement on whether a transaction is committed or aborted. The classic Two-Phase Commit protocol blocks if the coordinator fails. Fault-tolerant consensus algorithms also reach agreement, but do not block whenever any majority of the processes are working. Running a Paxos consensus algorithm on the commit/abort decision of each participant yields a transaction commit protocol that uses 2F +1 coordinators and makes progress if at least F +1 of them are working. In the fault-free case, this algorithm requires one extra message delay but has the same stable-storage write delay as Two-Phase Commit. The classic Two-Phase Commit algorithm is obtained as the special F = 0 case of the general Paxos Commit algorithm.