moleculer-rs

Inspired and compatible with Moleculer JS

You can currently do all the basics of emit, broadcast and call.

However it only works with the NATS transporter and JSON serializer/deserializer.

Getting Started

Available on crates: crates.io/moleculer

Documentation available at: docs.rs/moleculer

moleculer = "0.3.3"

Simple example showing how to receive an event, and responding to a request, for more check the examples folder

use std::error::Error;
use moleculer::{
    config::{ConfigBuilder, Transporter},
    service::{Context, Event, EventBuilder, Service},
    ServiceBroker,
};
use serde::Deserialize;

#[tokio::main]
async fn main() -> eyre::Result<()> {
    env_logger::init();
    color_eyre::install()?;

    // build config
    let config = ConfigBuilder::default().transporter(Transporter::nats("nats://localhost:4222"))
    .build();

    // create the first event
    let print_hi = EventBuilder::new("printHi").add_callback(print_hi).build();

    // create the second event
    let print_name = EventBuilder::new("printName")
        .add_callback(print_name)
        .build();

    // create math action
    let math_action = ActionBuilder::new("mathAdd").add_callback(math_add).build();

    // create a service with events and actions
    let greeter_service = Service::new("rustGreeter")
        .add_event(print_hi)
        .add_event(print_name)
        .add_action(math_action);

    // create service broker with service
    let service_broker = ServiceBroker::new(config).add_service(greeter_service);

    // start the service broker
    service_broker.start().await;

    Ok(())
}


// callback for first event, will be called whenever "printHi" event is received
fn print_hi(_ctx: Context<Event>) -> Result<(), Box<dyn Error>> {
    println!("Hello from Rust");
    Ok(())
}

// callback for second event, will be called whenever "printName" event is received
fn print_name(ctx: Context<Event>) -> Result<(), Box<dyn Error>> {
    let msg: PrintNameMessage = serde_json::from_value(ctx.params)?;

    println!("Hello to: {} from Rust", msg.name);

    Ok(())
}

// callback for math action
fn math_add(ctx: Context<Action>) -> Result<(), Box<dyn Error>> {
    // get message decode using serde
    let msg: ActionMessage = serde_json::from_value(ctx.params.clone())?;
    let answer = msg.a + msg.b;

    // serialize reply using serde and send reply
    let _ = ctx.reply(answer.into());

    Ok(())
}

#[derive(Deserialize)]
struct PrintNameMessage {
    name: String,
}

#[derive(Deserialize)]
struct ActionMessage {
    a: i32,
    b: i32,
}

Current Status

Usable but missing some options

What it does

• Is discoverable by other moleculer clients
• Only NATS transporter
• Only JSON serialization/deserialization
• Can emit and broadcast events
• Can call to send request and wait for response (#20)
• Can respond to events from other molecular clients using callbacks (see: simple event example)
• Can create actions, and respond to requests (#19)

What its missing:

• Tests #17
• Better error handling on actions #24
• Support for different serializer/deserializer #23
• Support for Bulkhead, CircuitBreaker and RetryPolicy
• Support for tracing
• Support for different transporters other than NATS
• Support for different loggers