How can I load environment variables via command line when running a node.js app in cluster mode with PM2?

Question

When starting my application with node, I typically run:

node -r dotenv/config ./build/index.js

When using PM2 in fork mode I can start the application like so:

pm2 start --node-args="-r dotenv/config" build/index.js --name API

If I try to run the application in cluster mode though, it seems to ignore node-args and fails to load the environment variables.

pm2 start --node-args="-r dotenv/config" build/index.js -i max --name API

What would be the proper workaround to solve this issue without adding it explicitly to the application code? Should I even be doing it this way to begin with?

Update: It appears pm2 ecosystem is the correct way to inject command line args if you're looking to run apps in cluster mode. Using node_args: '-r dotenv/config' I was able to achieve the desired result. Thanks!

PS Make sure you set your environment to production or you may run into unintended issues when launching the app.

Answer 1

Can you use an ecosystem file for PM2?

Running the following will generate a basic config file.

pm2 ecosystem

The default file is included below:

module.exports = {
  apps : [{
    name: 'API',
    script: 'app.js',

    // Options reference: https://pm2.keymetrics.io/docs/usage/application-declaration/
    args: 'one two',
    instances: 1,
    autorestart: true,
    watch: false,
    max_memory_restart: '1G',
    env: {
      NODE_ENV: 'development'
    },
    env_production: {
      NODE_ENV: 'production'
    }
  }],

  deploy : {
    production : {
      user : 'node',
      host : 'localhost',
      ref  : 'origin/master',
      repo : 'git@github.com:repo.git',
      path : '/var/www/production',
      'post-deploy' : 'npm install && pm2 reload ecosystem.config.js --env production'
    }
  }
};

According to the example in the documentation, you can add an "exec_mode" to the json file. See below:

module.exports = {
  apps : [{
    name        : "worker",
    script      : "./worker.js",
    watch       : true,
    env: {
      "NODE_ENV": "development",
    },
    env_production : {
       "NODE_ENV": "production"
    }
  },{
    name       : "api-app",
    script     : "./api.js",
    instances  : 4,
    exec_mode  : "cluster"
  }]
}

Modify the file as needed and run with:

pm2 start ecosystem.config.js