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Process management

PM2 is a process kept in the background, a daemon, that takes care of all your running processes.

We’ll learn how to manage process with PM2 and discover a key concept : the process list.

The process list

The process list is where all running applications are registered.

Manage your process list in a few commands:

# start and add a process to your list
pm2 start app.js

# show your list
pm2 ls

# stop and delete a process from the list
pm2 delete app

When you use pm2 start app.js, two actions are performed:

  • the app is registered in the process list of pm2
  • the app is started in the background.

Default name in the process list is the name of the script without his extension. Use --nameor -n to change.

Routine

Once setup your process list, every actions are done with the process name.

# kill the process but keep it in the process list
pm2 stop app

# start the process again
pm2 start app

# both stop and start
pm2 restart app

Multiple app can be specified at once:

pm2 restart app1 app2 app3

Or, shorter with a regexp:

pm2 restart /app/

Save your process list

You can save and resurrect your process list with:

# save your list in hard disk memory
pm2 save

# resurrect your list previously saved
pm2 resurrect

Your process list is saved into $HOME/.pm2/dump.pm2.

You can then setup a startup hook, to automatically start your process list through machine restarts.

Manage any application type

pm2 is compatible with other programming languages, using this equivalence:

{
  ".sh": "bash",
  ".py": "python",
  ".rb": "ruby",
  ".coffee": "coffee",
  ".php": "php",
  ".pl": "perl",
  ".js": "node"
}

Without extension, the app is started as a binary file.

To start a script in python for example, use:

pm2 start echo.py

If you want to specify the path of an interpreter, specify it in your ecosystem file:

module.exports = {
  "apps" : [{
    name: "script",
    script: "./script.py",
    interpreter: "/usr/bin/python",
  }]
}

Local Monitoring

pm2 local monitoring

The local monitoring tool get you insight about CPU usage, memory usage, loop delay or request/min for each process:

pm2 monit

Monitor your app on a web dashboard, with PM2 Plus

Next Steps

Log Management