Correctly implementing distributed algorithms such as the Paxos and Raft consensus protocols is notoriously difficult due to the presence of nondeterminism, whereby nodes lack perfectly synchronized clocks and the network reorders and drops messages. Stateright is a library and tool for designing, implementing, and verifying the correctness of distributed systems by leveraging a technique called model checking. Unlike with traditional model checkers, systems implemented using Stateright can also be run on a real network without being reimplemented in a different language. It also features a web browser UI that can be used to interactively explore how a system behaves, which is useful for both learning and debugging.

A typical workflow might involve:

```sh

1. Interactively explore reachable states in a web browser.

cargo run --release --example paxos explore 2 localhost:3000

2. Then model check to ensure all edge cases are addressed.

cargo run --release --example paxos check 3

3. Finally, run the service on a real network, with JSON messages over UDP...

cargo run --release --example paxos spawn

... and send it commands.

nc -u 0 3000 {"Put":{"value":"X"}} "Get" ```

Examples

Stateright includes a variety of examples, such as an actor based Single Decree Paxos cluster and an abstract two phase commit model.

To model check, run:

sh cargo run --release --example 2pc check 3 # 2 phase commit, 3 resource managers cargo run --release --example paxos check 2 # paxos, 2 clients cargo run --release --example wor check 3 # write-once register, 3 clients

To interactively explore a model's state space in a web browser UI, run:

sh cargo run --release --example 2pc explore cargo run --release --example paxos explore cargo run --release --example wor explore

Stateright also includes a simple runtime for executing an actor mapping messages to JSON over UDP:

sh cargo run --release --example paxos spawn cargo run --release --example wor spawn

Performance

To benchmark model checking speed, run with larger state spaces:

sh cargo run --release --example 2pc check 8 cargo run --release --example paxos check 4 cargo run --release --example wor check 6

Contributing

1. Clone the repository: sh git clone https://github.com/stateright/stateright.git cd stateright
2. Install the latest version of rust: sh rustup update || (curl https://sh.rustup.rs -sSf | sh)
3. Run the tests: sh cargo test && cargo test --examples
4. Review the docs: sh cargo doc --open
5. Explore the code: sh $EDITOR src/ # src/lib.rs is a good place to start
6. If you would like to share improvements, please fork the library, push changes to your fork, and send a pull request.

License

Stateright is copyright 2018 Jonathan Nadal and other contributors. It is made available under the MIT License.

To avoid the need for a Javascript package manager, the Stateright repository includes code for the following Javascript dependencies used by Stateright Explorer:

• KnockoutJS is copyright 2010 Steven Sanderson, the Knockout.js team, and other contributors. It is made available under the MIT License.