Getting Started with PM2, the Node.js Process Manager

PM2, or Process Manager 2 is an incredibly versatile production process manager written in Node.js.

Uses for PM2

PM2 has a lot of uses, let’s look at a few:

• Restarting after crashes: PM2 allows us to keep processes running until the heat death of the universe, or a server failure, whichever happens first
• Monitoring and managing processes remotely: A magic-powered web portal allows you to keep an eye on remote processes and manage them
• It doesn’t just run Node apps: PM2 isn’t limited to just Node.js processes, that’s right, you can even use it to keep your Minecraft server online
• Restart-Persistance: PM2 can remember all your processes and restart them after a system restart
• And a whole lot more

Getting started

First thing we need to do is to install PM2 globally on your machine:

$ npm i -g pm2

Basic Commands

Let’s get into the basics of how to use it. To start a process under PM2, all you have to do is run pm2 start <app>. App being the name of the file you’re running. PM2 will output something like this:

[PM2] Starting C:\Users\moose\app.js in fork_mode (1 instance)
[PM2] Done.
┌──────────┬────┬
│ App name │ id │
├──────────┼────|
│ app      │ 0  │
└──────────┴────|

Reduced and simplified for brevity

Pay attention to what it says under id. If you forget just run pm2 list. If you want to add a name to the process when you start it, you can use the --name parameter (pm2 start app.js --name mycoolapp). Awesome! Your app is now running under PM2, if it crashes, PM2 will restart it.

Restarting on File Changes

Another awesome feature that PM2 has is restarting when a file in the working directory changes. To make PM2 watch our directory and restart on file changes, include the --watch flag when you start your app.

Persistence Through Restarts

PM2 also allows us to start our processes when our server (re)starts. Start whatever you want to have running all the time through pm2 start and then run pm2 save.

$ pm2 save                                                                                                
[PM2] Saving current process list...
[PM2] Successfully saved in C:\Users\moose\.pm2\dump.pm2

Now, when our system restarts, PM2 will start whatever processes we had running when we ran pm2 save.

🐊 PM2 does a lot of things, most of which are out of the scope of this brief introduction. In the future we might cover PM2’s cluster mode, remote process management and more. Thanks for reading!