Generic distributed replication protocol implementations, written in Rust.
Distributed protocols, be it distributed register, state-machine replication, etc. are notoriously hard to get right. However, they are still re-implemented multiple times, mainly because it seems a difficult solution to generalize. This repository contains generic implementations of common distributed protocols, along with examples (written in Rust with gRPC as the communication protocol).
There are several protocols which are modelled in literature as a set of nodes doing operations on a state machine --- aka State Machine Replication. The crate state-machine offers a generic abstraction over these, with the discriminating read-only operations, as those can be sped-up, in certain scenarios.
The ABD (Attiya, Bar-Noy, Dolev) protocol models a distributed register x, to which one can set a value or get the current value. This protocol is linearizable, and can be used to build key-value stores.
The generic implementation requires servers to implement an abd::store::LocalStore, while clients need to implement a abd::Conn, which models the connection to each server.
- implement asymmetric quorums
There are other interesting protocols to implement:
- permissioned ABD (ABD with permissions: this requires the servers to check a permission based on the client id, shifting the onus of coordinating the protocol to a server)
- Paxos
- Raft
Moreover, BFT services are also important:
- PBFT
- Byzantine Quorums