Introduction

PM2 or Process Manager 2, is an Open Source, production Node.js process manager helping Developers and Devops manage Node.js applications in production environment.

Installation

sudo npm install pm2 -g

Usage

We going to see how run in cluster mode the next worker with PM2:

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7 // File: app.js
const uncaughtExceptionHandler = require('./lib/error/uncaughtExceptionHandler');
const worker = require('./lib/worker');

worker.run();

process.on('uncaughtException', uncaughtExceptionHandler);

Environment Dev:

We can create js file to pm2 can read the configuration, so we won´t use parameters in the command line, only will tell to PM2 load settings from js file. See in the settings to dev we put watch to true, this is because in development environment we want PM2 restart our cluster if we modify the source code (this value should be false in production).

As well we put in environment dev the environment variables to run easily our service, in prod environment, machines should provide these environment variables with right values to execute in production.

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28 // File: dev_ecosystem.config.js
module.exports = {
  /**
   * Application configuration section
   * http://pm2.keymetrics.io/docs/usage/application-declaration/
   */
  apps : [
    {
      name      : "MyService-DEV",
      script    : "app.js",
      watch     : true,
      exec_mode : "cluster",
      instances : 4,
      max_memory_restart: "3G",
      env: {
        NODE_ENV: "dev",
        NODE_DEBUG_REQUESTER: true,
        RABBITMQ_HOST: "myRabbitHost",
        RABBITMQ_PORT: 5672,
        RABBITMQ_USER: "myUser",
        RABBITMQ_PASSWORD: "myPassword",
        RABBITMQ_VHOST: "myVhost",
        STATSD_HOST: "localhost",
        STATSD_PORT: 8125
      }
    }
  ]
}

Environment Prod:

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17 // File: prod_ecosystem.config.js
module.exports = {
  /**
   * Application configuration section
   * http://pm2.keymetrics.io/docs/usage/application-declaration/
   */
  apps : [
    {
      name      : "MyService-PROD",
      script    : "app.js",
      watch     : false,
      exec_mode : "cluster",
      instances : 8,
      max_memory_restart: "3G",
    }
  ]
}