RiteRaft - A raft framework, for regular people
This is an attempt to create a layer on top of tikv/raft-rs, that is easier to use and implement. This is not supposed to be the most featureful raft, but instead a convenient interface to get started quickly, and have a working raft in no time.
The interface is strongly inspired by the one used by canonical/raft.
Getting started
In order to "raft" storage, we need to implement the Storage trait for it.
Bellow is an example with HashStore, which is a thread-safe wrapper around an
HashMap:
/// convienient data structure to pass Message in the raft
#[derive(Serialize, Deserialize)]
pub enum Message {
Insert { key: u64, value: String },
}
#[derive(Clone)]
struct HashStore(Arc<RwLock<HashMap<u64, String>>>);
impl Store for HashStore {
type Error = RaftError;
fn apply(&mut self, message: &[u8]) -> Result<Vec<u8>, Self::Error> {
let message: Message = deserialize(message).unwrap();
let message: Vec<u8> = match message {
Message::Insert { key, value } => {
let mut db = self.0.write().unwrap();
db.insert(key, value.clone());
serialize(&value).unwrap()
}
};
Ok(message)
}
fn snapshot(&self) -> Vec<u8> {
serialize(&self.0.read().unwrap().clone()).unwrap()
}
fn restore(&mut self, snapshot: &[u8]) -> Result<(), Self::Error> {
let new: HashMap<u64, String> = deserialize(snapshot).unwrap();
let mut db = self.0.write().unwrap();
let _ = std::mem::replace(&mut *db, new);
Ok(())
}
}Only 3 methods need to be implemented for the Store:
Store::apply: applies a commited entry to the store.Store::snapshot: returns snapshot data for the store.Store::apply: applies the snapshot passed as argument.
running the raft
#[tokio::main]
fn main() {
let store = HashStore::new();
let raft = Raft::new(options.raft_addr, store.clone());
let mailbox = Arc::new(raft.mailbox());
let (raft_handle, mailbox) = match options.peer_addr {
Some(addr) => {
info!("running in follower mode");
let handle = tokio::spawn(raft.join(addr));
(handle, mailbox)
}
None => {
info!("running in leader mode");
let handle = tokio::spawn(raft.lead());
(handle, mailbox)
}
};
tokio::join!(raft);
}The mailbox gives you a way to interact with the raft, for sending a message, or leaving the cluster for example.