picom

Introduction

Picom(pico-message) is a high performance, self-discovery(nats.io), micro services communication layer.

Inner workings

Picom uses (nats.io) to send messages between services.

Each service has a name, and exposed methods.
Services sharing the same name, are expected to expose the same methods and be the same, because they will be load balanced.

Each message is a JSON, and it's expected to be relatively small (a few kb's).

Quick start

npm install picom

Then, on device 1:

var Picom = require('picom');
var service1 = new Picom('service1');
service1.expose({
    add: function(msg) {
      return Promise.reslove({hello: 'from service 1', result: msg.a + msg.b});
    },
    returnError: function(msg) {
      return Promise.reject('something went wrong');
    }
});

On device 2:

var Picom = require('picom');
var service2 = new Picom('service2');
service2.request('service1.add', {
    a: 2,
    b: 5
}).then(function(msg) {
 
    // Prints 7
    console.log(msg.result);
});
 
myService.request('service1.returnError').
catch(function(err) {
    // err is instance of Error with message: 'something went wrong'
    console.log(err);
});

API

Picom('serviceName', [options])

Initialize a new picom service.

Parameters:

• servers ([String], default: ['127.0.0.1:4222']): Nats.io address
• ttl (Integer, default: 30): After how many seconds of no response the server is considered "failing"
• retries (Integer, default: 3): How many times try reconnect (to different hosts)
• port (Integer, default: random): Used to specify a port, if omitted, a random port will be chosen

picom.expose(methods)

Expose methods and start listening.

Usage

myService.expose({
    add: function(msg) {
      return Promise.resolve(msg.a + msg.b);
    }
});

picom.request(service, [msg], [options])

Send request to remote service

Parameters:

• service (String, mandatory): Service name + method name, like 'serviceName.methodName'
• msg (Object, optional): Will become msg in remote service
• options (Object, options): for now, you can only define request timeout

Usage

// Service 1
const Picom = require('picom');
const service1 = new Picom('service1');
service1.expose({
    add: function(msg) {
      return Promise.resolve({result: msg.a + msg.b});
    }
});

// Service 2
const Picom = require('picom');
const service2 = new Picom('service2');
service2.request('service1.add', {
    a: 2,
    b: 5
}, {
    timeout: 30 * 1000 // 30 seconds timeout
}
});

picom.publish(service, [msg])

Send request to remote service, without waiting for a reply

Parameters:

• service (String, mandatory): Service name + method name, like 'serviceName.methodName'
• msg (Object, optional): Will become msg in remote service

Usage

const Picom = require('picom');
const service1 = new Picom('service1');
 
service1.expose({
    fib: function(msg) {
        // Do heavy lifting calculations, then notify service2, using picom or other channel
    }
});

const Picom = require('picom');
const service2 = new Picom('service2');
 
service2.publish('service1.fib', {
    x: 9000
}
});

picom.close()

Inform nats.io to not send anymore requests here, and disconnect.