npm package discovery and stats viewer.

Discover Tips

  • General search

    [free text search, go nuts!]

  • Package details

    pkg:[package-name]

  • User packages

    @[username]

Sponsor

Optimize Toolset

I’ve always been into building performant and accessible sites, but lately I’ve been taking it extremely seriously. So much so that I’ve been building a tool to help me optimize and monitor the sites that I build to make sure that I’m making an attempt to offer the best experience to those who visit them. If you’re into performant, accessible and SEO friendly sites, you might like it too! You can check it out at Optimize Toolset.

About

Hi, 👋, I’m Ryan Hefner  and I built this site for me, and you! The goal of this site was to provide an easy way for me to check the stats on my npm packages, both for prioritizing issues and updates, and to give me a little kick in the pants to keep up on stuff.

As I was building it, I realized that I was actually using the tool to build the tool, and figured I might as well put this out there and hopefully others will find it to be a fast and useful way to search and browse npm packages as I have.

If you’re interested in other things I’m working on, follow me on Twitter or check out the open source projects I’ve been publishing on GitHub.

I am also working on a Twitter bot for this site to tweet the most popular, newest, random packages from npm. Please follow that account now and it will start sending out packages soon–ish.

Open Software & Tools

This site wouldn’t be possible without the immense generosity and tireless efforts from the people who make contributions to the world and share their work via open source initiatives. Thank you 🙏

© 2024 – Pkg Stats / Ryan Hefner

distributed-eventemitter

v1.2.1

Published

The ultra fast, distributed (multi process and multi server), STOMP based event emitter for Node.js!

Downloads

17

Readme

Why?

The library solve the need of a multi process and multi server oriented messaging API in Node.js. Using the known EventEmitter API, listeners registration and events emitting is super simple. A new 'emitToOne' method allows one-to-one events notification, intended for request/response flows on clustered services. The classic 'emit' method broadcast custom events to local and distributed listeners.

For non-distributed usage of this API (browser, single node process or development) developers can use: process-eventemitter

Donate to support the evolution of this project:
Donate

Quick Start

  1. Mailer server (A.js):
var EventEmitter = require('distributed-eventemitter');
var events = new EventEmitter(); // host: localhost, port: 61613
events.connect().then(() => {
  events.on('email.send', (message, resolve, reject) => {
    console.log('sending email...');
    //... send email
    // ...

    resolve('sent');
  });
});
  1. Run mailer server as a cluster with PM2:
pm2 start A.js -i 4 --node-args="--harmony"
  1. Mailer client (B.js):
var EventEmitter = require('distributed-eventemitter');
var events = new EventEmitter(); // host: localhost, port: 61613
events.connect().then(() => {
  events.emitToOne('email.send', {
    to: '[email protected]',
    subject: 'Hello Node.js',
    body: 'Introducing easy distributed messaging for Node.js...'
  }, 3000).then((response) => {
    if ('sent' === response) {
      console.log('email was sent!');
    }
  }).catch(console.log.bind());
});
  1. Run mailer client:
node --harmony B.js

Example using ES6 generators

"use strict";

const EventEmitter = require('distributed-eventemitter');
const co = require('co');
const events = new EventEmitter(); // host: localhost, port: 61613

co(function* () {
    try {
        yield events.connect();
        let response = yield events.emitToOne('email.send', {
            to: '[email protected]',
            subject: 'Hello Node.js',
            body: 'Introducing easy distributed messaging for Node.js...'
        }, 3000);

        if ('sent' === response) {
            console.log('email was sent!');
        }
        yield events.disconnect();
    } catch (error) {
        console.log('error: ' + error);
    }
});

Requirements

  • Running STOMP compliant server instance. Default client destinations are:

    1. /topic/distributed-eventemitter: Used for events broadcast (emit)
    • /queue/distributed-eventemitter: Used for one-to-one events (emitToOne)

      If the server require clients to be authenticated, you can use:

    {
      'host': 'localhost',
      'connectHeaders': {
        'heart-beat': '5000,5000',
        'host': '',
        'login': 'username',
        'passcode': 'password'
      }
    }

Installation

$ npm install distributed-eventemitter

Features

  • Extends eventemitter2. (wildcards are enabled).
  • ECMA6 Promise based API.
  • Request/Response communication intended for service clusters (emitToOne). Uncaught exceptions automatically invoke 'reject(error.message)'
  • Events broadcast to local and distributed listeners (emit)
  • Works with any STOMP compliant server (ie. ActiveMQ, RabbitMQ, ...).
  • Uses stompit as STOMP client. (automated server reconnection is supported)

Config params

var config = {};
config.destination = 'distributed-eventemitter'; // server topic and queue destinations
config.excludedEvents = []; // events that are not distributed
config.servers = [{
  'host': 'localhost',
  'port': 61613,
  'connectHeaders': {
    'heart-beat': '5000,5000',
    'host': '',
    'login': '',
    'passcode': ''
  }
}];
config.reconnectOpts = {
  maxReconnects: 10;
}

var events = new EventEmitter(config);

For more details about 'servers' and 'reconnectOpts' params please check: http://gdaws.github.io/node-stomp/api/connect-failover/

Internal events

events.on('connected', (emitterId) => {
    // triggered when the emitter has been connected to the network (STOMP server)
});

events.on('disconnected', (emitterId) => {
    // triggered when the emitter has been disconnected from the network (STOMP server)
});

events.on('error', (error) => {
   // triggered when an error occurs in the connection channel. 
}):

events.on('connecting', (connector) => {
   // triggered when the STOMP client is trying to connect to a server.
}):

events.on('request', (event, request, raw) => {
   // triggered before invoke a listener using emitToOne feature
   
   // request data filtering and modification is allowed
   // example:
   request.data = ('string' === typeof request.data) ? request.data.toUpperCase() : request.data
}):

events.on('response', (event, response, raw) => {
   // triggered after invoke a listener using emitToOne feature
   
   // response data filtering and modification is allowed
   // example:
   if (response.ok)
     response.data = ('string' === typeof response.data) ? response.data.toUpperCase() : response.data
   else 
     console.log('error ocurred: ' + response.data.message);
}):

API

getId: Get the emitter instance unique id.

events.getId(); // UUID v4 value

connect: Connect the emitter to the server. Emit the 'connected' event.

events.connect().then(()=> {
  console.log('connected');
});

disconnect: Disconnect the emitter from the server. Emit the 'disconnected' event.

events.disconnect().then(()=> {
  console.log('disconnected');
});

emitToOne: Notify a custom event to only one target listener (locally or in the network). The method accept only one argument as event data.

events.on('my.event', (data, resolve, reject) => {
  if ('hello' === data){
    resolve('world');
  } else {
    reject('invalid args');
  }
});

// calling without timeout
events.emitToOne('my.event', 'hello').then((response) => {
  console.log('world' === response);
});

// calling with timeout (ms)
events.emitToOne('my.event', {data: 'hello'}, 100).catch((error) => {
  console.log('invalid args' === error);
});

Roadmap

  1. Express integration.

Known limitations

  • The feature 'emitAsync' from the EventEmitter2, only work locally(not distributed).

Tests

$ npm install
$ npm test

History changes

1.1.x

  • From version 1.1.0+ we use Stompit as STOMP client because Stompjs does not support server reconnections and is also unmaintained.
  • No API changes from 1.0 version except the configuration params, since now we consider a list of STOMP servers to connect/reconnect.

1.1.1

  • Supporting request/request events intended for pre invocation content filtering and modification.

1.1.2

  • Fixing dependencies declaration (due to automatic modification from 'npm update --save').

1.1.3

  • Fixing issue on distributed events broadcast(emit) that caused repeated broadcasts.

1.1.4

  • Updating dependencies and adding generators example to docs.

1.1.5

  • Updating dependencies and docs.

1.1.6

  • Improving unexpected error handling when data can't be transmited because the STOMP connection is closed. Produced exceptions are notified as an 'error' event on the emitter.

1.2.0

  • Supporting jWebSocket EventBus. JVM based applications using the jWebSocket EventBus component, can communicate with nodejs services through this module.

1.2.1

  • Minor source code refactorization.
  • Package updates.