Engined

A micro framework for application in Node.js. it aims to provide a way to manage your services inside instance.

Requirements

Engined widely uses async/await in ES6+ so Node.js v7.4+ is required and v7.6 is prefered. If you are working on Node.js v7.6, you have to run Node.js with --harmony-async-await options.

Installation

You can just install module via NPM:

npm install engined

Get Started

Here is an example to use engined to manange services:

const { Manager, Service } = require('engined');
 
class MyService extends Service {
 
    constructor(context) {
        super(context);
 
        this.counter = 0;
    }
 
    delay(interval) {
        return new Promise((resolve) => {
            setTimeout(resolve, interval);
        });
    }
 
    async start() {
 
        // Getting global counter from context
        this.counter = this.getContext().get('global_counter') || 0;
 
        for (let index = 0; index < 10; index++) {
            this.counter++;
            console.log(this.counter);
            await this.delay(100);
        }
 
        this.getContext().set('global_counter', this.counter);
    }
 
    async stop() {
 
        // Getting global counter from context
        this.counter = this.getContext().get('global_counter') || 0;
 
        for (let index = 0; index < 10; index++) {
            this.counter--;
            console.log(this.counter);
            await this.delay(100);
        }
 
        this.getContext().set('global_counter', this.counter);
    }
}
 
const main = async () => {
 
    // Create manager
    let serviceManager = new Manager({ verbose: true });
 
    // Adding services to manager
    serviceManager.add('MyService1', MyService);
    serviceManager.add('MyService2', MyService);
 
    // Start all services and stop
    await serviceManager.startAll();
    await serviceManager.stopAll();
 
    console.log('exit');
};
 
main();

Usage

engined.Manager class provides serveral methods for service management.

Load modules at once

There is a way to load multiple modules with loadServices method at once.

await serviceManager.loadServices({
    MyService1: MyService,
    MyService2: MyService
});

Add and remove specific service

Add and remove specific service with add and remove method.

serviceManager.add('MyService1', MyService);
serviceManager.remove('MyService1');

Note that remove will stop service if service is running.

Start and stop specific service

It can start and stop specific service with start and stop method.

await serviceManager.start('MyService1');
await serviceManager.stop('MyService1');

Accessing Context

Sharing data among services is allowed, just save it in the context object. engined.Manager and engined.Service classes provide a method for accessing the context object.

Get context via service manager

engined.Manager provide getContext method to get current Context instance:

let context = serviceManager.getContext();

Get context from inside the service

engined.Service provide getContext method to get current Context instance:

let context = this.getContext();

Store data in context object

Store custom key/value pairs by calling set method.

context.set('mykey', 'test');

Get data from context object

Get key/value pairs by calling get method.

let mykey = context.get('mykey');

Agent Manager

engined.AgentManager was designed in order to manage multiple agents. We usually expose agent manager to other services via context object.

Manager service can be implmeneted like below:

class fooManagerService extends Service {
 
    constructor(context) {
        super(context);
 
        this.agentManager = null;
    }
 
 
    async start() {
        this.agentManager = new AgentManager();
        this.getContext().set('foo', agentManager);
    }
 
    async stop() {
 
        if (this.agentManager === null)
            return;
 
        this.getContext().remove('foo');
        this.agentManager = null;
 
    }
 

Then we can implement agent service and register agent in above manager service:

class fooAgentService extends Service {
 
    constructor(context) {
        super(context);
 
        this.agent = null;
    }
 
 
    async start() {
        this.agent = {
            data: 'Hello'
        };
        this.getContext().get('foo').register('AgentA', this.agent);
    }
 
    async stop() {
 
        if (this.agent === null)
            return;
 
        this.getContext().get('foo').unregister('AgentA');
        this.agent = null;
 
    }

In other services, getAgent() is the way to accessing specific agent of manager.

let agent = this.getContext().get('foo').getAgent('AgentA');
 
console.log(agent.data);

Easy way to assert agent manager in context

There is a way to create agent manager then register on context faster.

this.getContext().assert('foo');

License

Licensed under the MIT License

Authors

Copyright(c) 2017 Fred Chien（錢逢祥） <[e-mail]>