71 lines
2.3 KiB
Markdown
71 lines
2.3 KiB
Markdown
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# A synchronous and simple Maelstrom crate
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`nebkor-maelstreom` is a lean and simple synchronous library for writing
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[Maelstrom](https://github.com/jepsen-io/maelstrom/tree/0186f398f96564a0453dda97c07daeac67c3d8d7)-compatible
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distributed actors. It has three dependencies:
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- serde
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- serde_json
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- serde_repr
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For a simple example, see the [gg-echo](https://git.kittencollective.com/nebkor/chatty-catties/src/branch/main/gg-echo/src/main.rs) program:
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``` rust
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use std::sync::{Arc, Mutex};
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use nebkor_maelstrom::{Body, Message, Node, Runner};
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struct Echo;
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impl Node for Echo {
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fn handle(&mut self, runner: &Runner, msg: Message) {
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let typ = &msg.body.typ;
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if typ.as_str() == "echo" {
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let body = Body::from_type("echo_ok").with_payload(msg.body.payload.clone());
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runner.reply(&msg, body);
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}
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}
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}
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fn main() {
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let node = Echo;
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let node = Arc::new(Mutex::new(node));
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let runner = Runner::new(node);
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runner.run(None);
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}
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```
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## How to use
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Create a struct and implement `nebkor_maelstrom::Node` for it, which involves a single method,
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`handle(&mut self, &Runner, Message)`. This method is passed a `Runner` which contains methods like
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`send`, `reply`, and `rpc`.
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In your main function, instantiate that struct and wrap it in an `Arc<Mutex<>>`, then pass that into
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`Runner::new()` to get a Runner. The `run()` method takes an optional closure that will be run when
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the `init` Message is received; see the
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[broadcast](https://git.kittencollective.com/nebkor/chatty-catties/src/commit/fff7fdc2d52f7d4c2d4d9c581ea16cdf0e1e3f30/gg-broadcast/src/main.rs#L18-L33)
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program for an example of that, where it spawns a thread to send periodic messages to the node.
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## Design considerations
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I wanted the client code to be as simple as possible, with the least amount of boilerplate. Using
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`&mut self` as the receiver for the `handle()` method lets you easily mutate state in your node if
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you need to, without the ceremony of `Rc<Mutex<>>` and the like. Eschewing `async` results in an
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order of magnitude fewer dependencies, and the entire workspace (crate and clients) can be compiled
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in a couple seconds.
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## Acknowledgments
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I straight-up stole the design of the IO/network system from
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[Maelbreaker](https://github.com/rafibayer/maelbreaker/), which allowed me to get a working RPC
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call. Thanks!
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## TODO
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- add error handling.
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