nats-micro

NATS Microservice Library

A convenient microservice library based on NATS and compatible with nats-go microservices

Description

This is a typescript-first library that provides a convinient (in 10 lines of code or less!) way to write microservises with out of the box auto discovery, observability and load balancing.

Full interoperability with to-be-released nastcli v0.0.36 that adds nats micro info, nats micro stats and nats micro ping commands

It also support service schema discovery which is not (yet?) supported by nats micro

Limitations / TODO

1. No multi-reply support yet.

When you send a message you will be getting exactly one response (or a timeout error)

1. No load balancing yet

Usage

It is extremely simple:

Functional

const broker = await new Broker('echo' + process.pid).connect();

await Microservice.create(
  broker,
  {
    name: 'echo',
    description: 'Simple echo microservice',
    version: '0.0.1',
    methods: {
      say: {
        handler: (text) => text,
        // subject is autogenerated according to nats micro protocol
      },
      'config-change-event': {
        handler: console.log,
        // subject is manually specified which allows for broadcast
        // event bus
        subject: '$EVT.config.change',
      },
    },
  }
);

Declarative way

class EchoMicroservice {
  public get config(): MicroserviceConfig {
    return {
      name: 'echo',
      description: 'Simple echo microservice',
      version: '0.0.1',
      methods: {
        say: { handler: this.say },
        'config-change-event': { handler: this.onConfigChange },
      },
    };
  }

  private say(text: string): string {
    return text;
  }

  private onConfigChange(change: unknown): void {
    console.log(change);
  }
}

const echoMicroservice = new EchoMicroservice();

const broker = await new Broker('echo' + process.pid).connect();
await Microservice.create(broker, echoMicroservice.config);

Decorators

@microservice({ name: 'echo', description: 'Decorated service' })
// @microservice() // as simple as this 
export default class EchoMicroservice {

  // name is manual, subject is autodetected
  @method({name: 'say'}) 
  private reply(text: string): string {
    return text;
  }
  
  // name is autodetected as 'config-change-event', subject is manual
  @method({ subject: '$EVT.config.change' }) 
  private configChangeEvent(change: unknown): void {
    console.log(change);
  }
}

const echoMicroservice = new EchoMicroservice();

const broker = await new Broker('echo' + process.pid).connect();
await Microservice.createFromClass(broker, echoMicroservice);