Services

Running async services with dependencies in node.js

Installation

npm install kacao/services

Usage

This creates 5 services: config, db, settings, backend and frontend, calling run() will load services in this order (services will wait for dependencies to be ready before starting to run):

• config
• db
• settings
• backend and frontend (asynchronously without waiting for each other) 

const {Service, Services} = require('./index');

let services = new Services();
services.add([
  new Service('config', []),
  new Service('db', ['config']);                         // db depends on config
  new Service('settings', ['config', 'db']),             // settings depends on config and db
  new Service('backend', ['config', 'db', 'settings'])   // backend depends on config, db and settings
  new Service('frontend', ['config', 'db', 'settings'])  // frontend depends on config, db and settings
  
]);

services.run().then( () => {
  console.log('done');
});

The run() function

Services have async run() which we can override to run a service after all dependencies are ready. 

let db = new Service('db', ['config']);
services.add(db);

db.run = async (ready, fail) => {
  console.log('db service init');
  // sleep for 3s then set to ready
  (new Promise(resolve => setTimeout(resolve, 3000))).then( () => {
    console.log('db ready');
    ready();
  });
}

Calling ready() will let depending services to start running, calling fail() will cause Services to stop loading services and return an Error.