jepsen-io/maelstrom is a workbench for testing toy implementations of distributed systems.
This crate abstracts away the boilerplate of setting up the stdin/stdout for a node in a distributed system, and provides a few useful utilities for writing handlers.
Note: This crate is inspired from and primarily written for the Fly.io Distributed Systems challenge.
TLDR; Your node is an actor in the system that communicates with Maelstrom using enveloped messages.
You'll need to implement the Actor trait. This trait has two associated types, InboundMessage and OutboundMessage. These types are used to define the types of messages that your actor can receive and send, respectively.
Write a handle_message that processes the requests coming in from clients and return the response appropriately.
A solution to the first challenge.
use maelstrom_common::{
Actor,
Envelope,
run
};
use serde::{Serialize, Deserialize};
#[derive(Debug, Serialize, Deserialize, Clone)]
#[serde(tag = "type")]
pub enum Request {
#[serde(rename = "init")]
Init {
msg_id: usize,
node_id: String,
},
#[serde(rename = "echo")]
Echo {
echo: String,
msg_id: usize
}
}
#[derive(Debug, Serialize, Deserialize, Clone)]
#[serde(tag = "type")]
pub enum Response {
#[serde(rename = "init_ok")]
InitOk {
in_reply_to: usize,
},
#[serde(rename = "echo_ok")]
EchoOk {
echo: String,
in_reply_to: usize
}
}
#[derive(Debug, Default)]
pub struct Echo {
// Store our ID when a client initializes us.
node_id: Option<String>
}
impl Actor for Echo {
type InboundMessage = Request;
type OutboundMessage = Response;
fn handle_message(&mut self, msg: Envelope<Self::InboundMessage>) -> Option<Envelope<Self::OutboundMessage>> {
Some(match msg.body {
Request::Init { msg_id, node_id } => {
self.node_id = Some(node_id.clone());
eprintln!("[INIT] Initialized node: {}", node_id);
Envelope {
body: Response::InitOk { in_reply_to: msg_id },
src: msg.dest,
dest: msg.src
}
},
Request::Echo { echo, msg_id } => {
eprintln!("[ECHO] Echoing back: {}, in reply to: {}", echo, msg_id);
Envelope {
src: msg.dest,
dest: msg.src,
body: Response::EchoOk { echo, in_reply_to: msg_id }
}
},
})
}
}
pub fn main() -> Result<(), Box<dyn std::error::Error>> {
run(Echo::default())?;
Ok(())
}