The Raft Consensus Algorithm
Diego Ongaro and John Ousterhout
Stanford University
May 2015
Paxos Protocol
- Leslie Lamport, 1989
- Nearly synonymous with consensus
“The dirty little secret of the NSDI community is that at most five people really, truly understand every part of Paxos ;-).”
—NSDI reviewer
“There are significant gaps between the description of the Paxos algorithm and the needs of a real-world system...the final system will be based on an unproven protocol.”
—Chubby authors
Raft's Design for Understandability
We wanted an algorithm optimized for building real systems
- Must be correct, complete, and perform well
- Must also be understandable
“What would be easier to understand or explain?”
- Fundamentally different decomposition than Paxos
- Less complexity in state space
- Less mechanism
How Is Consensus Used?
Top-level system configuration
Replicate entire database state
Raft User Study
Raft Implementations
| Name | Primary Authors | Language | License |
|---|---|---|---|
| etcd/raft | Blake Mizerany, Xiang Li and Yicheng Qin (CoreOS) | Go | Apache 2.0 |
| go-raft | Ben Johnson (Sky) and Xiang Li (CMU, CoreOS) | Go | MIT |
| hashicorp/raft | Armon Dadgar (hashicorp) | Go | MPL-2.0 |
| copycat | Jordan Halterman | Java | Apache2 |
| LogCabin | Diego Ongaro (Stanford, Scale Computing) | C++ | ISC |
| akka-raft | Konrad Malawski | Scala | Apache2 |
| kanaka/raft.js | Joel Martin | Javascript | MPL-2.0 |
| rafter | Andrew Stone (Basho) | Erlang | Apache2 |
| OpenDaylight | Moiz Raja, Kamal Rameshan, Robert Varga (Cisco), Tom Pantelis (Brocade) | Java | Eclipse |
| liferaft | Arnout Kazemier | Javascript | MIT |
| skiff | Pedro Teixeira | Javascript | ISC |
| ckite | Pablo Medina | Scala | Apache2 |
| willemt/raft | Willem-Hendrik Thiart | C | BSD |
Copied from Raft website, probably stale.
LogCabin
- C++, permissive license
- Started as research platform for Raft at Stanford
- Working with Scale Computing to make production-ready
- 1.0 released last week
- Rolling upgrades
- Looking for more users!
