Rast

~~F~~ast. R~~u~~st. Ra~~f~~t.

Rast is a toy implementation of the [raft consistency protocol] with a focus on steady-state speed.

This is a proof of concept and not ready for production use.

Features

• Fully pipelined. The raft logic is non-blocking and can continue to respond to incoming rpcs and clock ticks during disk IO.
• [Not yet implemented] Zero-copy serde. One thing that [Kafka] got right was making the network format and the disk format the same. This allowed for use of the Linux [zero-copy] optimization that copies the incoming network traffic straight to disk for persistance. There's no reason a Raft log implemenation couldn't work the same way and io_uring makes this even easier.
• [Not yet implemented] Zero-alloc, lazy serde. The Raft logic in the steady state hot-path only looks at a couple fields of each incoming message, but popular serde implementations (like the [Protocol Buffers] of GRPC) require that an entire message be deserialized and allocate while doing so. Alternative wire formats like [Cap’n Proto] and [FlatBuffers] avoid this.

v0.1.0-alpha.0

• [x] Replace printlns with log crate
• [x] Resolve all WIP comments
• [x] Audit all TODO comments
• [x] Resolve all ignored tests
• [x] External documentation
• [x] Small cleanups
  • [x] Make currenttime an Option
  • [x] Structs for {Persist,ReadStateMachine}{Req,Res}
  • [x] Clear maxoutstandingreadid when applicable

v0.1.0-alpha.1

• [ ] Handle node restarts
  • [ ] Persist hard state
• [ ] Zero-copy message serialization
• [ ] More extensive nemesis testing
• [ ] Initial benchmarking
• [ ] Message idempotency
• [ ] Read-write requests (cput)
• [ ] Handle panics in state machine
• [ ] Audit public interface
• [x] Make logging an optional dependency
• [ ] Clean up log messages
• [ ] Internal documentation
• [ ] Idiomatic rustdoc

v0.1.0

• [ ] Test with [maelstrom]
• [ ] Failure testing
• [ ] Harden public interface
• [ ] Membership changes

After v0.1.0

• [ ] Snapshots