Micro-nervous NPM

Install

npm install micro-nervous

Note: Node version 6.0.0 or higher is required.

Overview

const { Nerve, Stats, Service } = require('micro-nervous');

// 'Nerves' are simple class wrappers for Resources or Connections
class RedisNerve extends Nerve {
  init() {
    // Connection logic goes here:
    this.redis = new Redis('redis://:password@my.redis.resource:6379');

    // When our connection is ready, just fire the `ready` event
    this.redis.once('ready', () => this.fire('ready'));
  }
  exit() {
    // Disconnection logic goes here, as expected:
    redis.once('end', () => this.fire('end'));
    redis.disconnect();
  }
}

// Nerves are re-usable, so can be shared between different microservices
const nerves = [
  new RedisNerve('pub'),
  new RedisNerve('sub'),
];

// A stats instance serves healthchecks and stats over http
const stats = new Stats({ port: 3000 });

// Instance of the Service class just ties together Nerve instances and stats
const service = new Service({ nerves, stats });

// This gives you an event emitter, nothing too special
service.on('ready', () => console.log('Your service is ready!'));

// But this can be useful
service.on('end', code => process.exit(code));

// Events fired by your Nerves are prefixed with their name
service.on('pub-ready', () => console.log('Publish Nerve is ready');

// Service#poweroff shuts down your connections gracefully
process.once('SIGTERM', () => service.poweroff());

// Just like Service#connect gets your connections started
service.connect();

// You also get access to the Nerve instances
service.nerve.sub.redis.subscribe('channel', (message) => {
  // And a tasking system to prevent unwanted shutdowns
  const task = service.newTask();
  // Now Service#poweroff will wait...
  // You can do lots of stuff... async stuff...
  // And even if you get a SIGTERM, from say, kubernetes...
  // Your task be allowed to finish before your connections are dropped!
  console.log('Yay, message:', message);
  task.done();
});

// The Nerve instances are attached using the keys used in the constructor
service.nerve.pub.redis.publish('channel', 'hello world!');

Healthchecks

Once you call Service#start you can hit http://host:3000/ok (or the port of your choosing) for that 200 OK feeling! Obviously that goes away the moment something goes wrong. Or when you call Service#poweroff, I guess.

Stats

You can also hit http://host:3000/stats for some sweet, sweet json. For example:

{
  "ok": true,
  "currentTasks": 0
}

The stats json just comes from service.getStats(), which can be easily overwritten

class MyService extends Service {
  getStats() {
    return {
      ok: this.ok,
      currentTasks: this.stats.currentTasks,
      answer: askDeepThought(),
    };
  }
}

Incidentally, stats.ok is used for the healthcheck: true for 200, anything else gives you a 503.