Patterns of Distributed Systems

Chapter 21

Two-Phase Commit

Update resources on multiple nodes in one atomic operation.

Problem

When data needs to be atomically stored on multiple cluster nodes, nodes cannot make the data accessible to clients until the decision of other cluster nodes is known. Each node needs to know if other nodes successfully stored the data or if they failed.

Solution

Comparison with Paxos and Replicated Log

Paxos and Replicated Log implementations also have two phases of execution. But the key difference is that those consensus algorithms are used when all the cluster nodes involved store the same values.

Two-phase commit works across cluster nodes storing different values—for example, across different partitions of a database. Each partition can ...