pm2

Modern CLI process manager for Node apps with a builtin load-balancer

npm install pm2
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PM2

pm2 is a process manager for Node apps with a built-in load balancer.

Tech notes

pm2 is perfect when you need to spread your stateless Node.js code accross all CPUs available on a server, to keep all processes alive forever and to 0s reload them.

Main features

  • Built-in load balancer (using the native cluster module)
  • Script daemonization
  • 0s downtime reload for Node apps
  • Generate SystemV/SystemD startup scripts (Ubuntu, Centos...)
  • Pause unstable process (avoid infinite loop)
  • Restart on file change with --watch
  • Monitoring in console

Tested with Node v0.11, v0.10 (https://travis-ci.org/Unitech/pm2).

The recommended Node.js version is v0.11.10

Compatible with CoffeeScript. Works on Linux & MacOS.

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NPM

Build Status

Master: Build Status

Development: Build Status

Monitoring dashboard

Dashboard

We're going to release a very nice product, a dashboard to monitor every part of your Node.js applications. Here are some links:

Thanks in advance and we hope that you like pm2!


Table of contents

Quick start

Features

Specific

Knowledge

More


Quick start

Installation

The prefered Node version to run PM2, is the 0.11.10

The latest stable version can always be installed via NPM:

$ npm install pm2@latest -g

If the above fails:

$ npm install git://github.com/Unitech/pm2#master -g

Common problems on installation:

  • node-gyp permission problem: Setup a new user on your server or add the --unsafe-perm to the npm command
  • if Make/GCC or other are missing sudo apt-get install build-essential on Ubuntu

Usage

Hello world:

$ pm2 start app.js

Examples

Raw examples:

$ pm2 start app.js --name my-api # Name process

$ pm2 start app.js -i max        # Will start maximum processes with LB depending on available CPUs

# Listing

$ pm2 list               # Display all processes status
$ pm2 jlist              # Print process list in raw JSON
$ pm2 prettylist         # Print process list in beautified JSON

$ pm2 describe 0         # Display all informations about a specific process

$ pm2 monit              # Monitor all processes

# Logs

$ pm2 logs               # Display all processes logs in streaming
$ pm2 flush              # Empty all log file
$ pm2 reloadLogs         # Reload all logs

# Actions

$ pm2 stop all           # Stop all processes
$ pm2 restart all        # Restart all processes

$ pm2 reload all         # Will 0s downtime reload (for NETWORKED apps)
$ pm2 gracefulReload all # Send exit message then reload (for networked apps)

$ pm2 stop 0             # Stop specific process id
$ pm2 restart 0          # Restart specific process id

$ pm2 delete 0           # Will remove process from pm2 list
$ pm2 delete all         # Will remove all processes from pm2 list

# Misc

$ pm2 ping               # Ensure pm2 dameon has been launched

Different ways to launch a process

$ pm2 start app.js -i max  # Will start maximum processes depending on available CPUs

$ pm2 start app.js -i 3    # Will start 3 processes

$ pm2 start app.js --node-args="--debug=7001 --trace-deprecation" # --node-args command line option to pass options to node

$ pm2 start app.js -x            # Start app.js in fork mode instead of cluster
$ pm2 start app.js -x -- -a 23   # Start app.js in fork mode and pass arguments (-a 23)

$ pm2 start app.js --name serverone # Start a process an name it as server one
                                    # you can now stop the process by doing
                                    # pm2 stop serverone

$ pm2 start app.json                # Start processes with options declared in app.json
                                    # Go to chapter Multi process JSON declaration for more

$ pm2 start app.js -i max -- -a 23  # Pass arguments after -- to app.js

$ pm2 start app.js -i max -e err.log -o out.log  # Will start and generate a configuration file

For scripts in other languages:

$ pm2 start echo.coffee
$ pm2 start echo.php
$ pm2 start echo.py
$ pm2 start echo.sh
$ pm2 start echo.rb
$ pm2 start echo.pl

Options

Options:

    -h, --help                   output usage information
    -V, --version                output the version number
    -v --verbose                 verbose level
    -s --silent                  hide all messages
    -m --mini-list               display a compacted list without formatting
    -f --force                   force actions
    -n --name <name>             set a <name> for script
    -i --instances <number>      launch [number] (load balanced) instances (for networked app)
    -o --output <path>           specify out log file
    -e --error <path>            specify error log file
    -p --pid <pid>               specify pid file
    -x --execute-command         execute a program using fork system
    -u --user <username>         define user when generating startup script
    -c --cron <cron_pattern>     restart a running process based on a cron pattern
    -w --write                   write configuration in local folder
    --interpreter <interpreter>  the interpreter pm2 should use for executing app (bash, python...)
    --no-daemon                  run pm2 daemon in the foreground if it doesn't exist already
    --merge-logs                 merge logs
    --watch                      watch application folder for changes
    --node-args <node_args>      space-delimited arguments to pass to node in cluster mode - e.g. --node-args="--debug=7001 --trace-deprecation"

Features

Transitional state of apps (important)

PM2 is a process manager, as said, pm2 can start, stop, restart and delete processes.

Start a process:

$ pm2 start app.js --name "my-api"
$ pm2 start web.js --name "web-interface"

Now let's say I need to stop the web-interface:

$ pm2 stop web-interface

As you can see the process hasn't disapeared. It is still there but now in stopped status.

To restart it just do:

$ pm2 restart web-interface

Now I want to delete the app from the pm2 process list. To do that:

$ pm2 delete web-interface

Process listing

Monit

To list all running processes:

$ pm2 list
# Or
$ pm2 [list|ls|l|status]

To get more details about a specific process:

$ pm2 describe 0

Monitoring CPU/Memory usage

Monit

Monitor all processes launched:

$ pm2 monit

Logs management

Displaying logs in realtime

Monit

Displaying logs of specified process or all processes in realtime:

$ pm2 logs
$ pm2 logs big-api
$ pm2 flush # Clear all the logs

Reloading all logs (SIGUSR2/Logrotate)

To reload all logs, you can send SIGUSR2 to the pm2 process.

You can also reload all logs via the command line with:

$ pm2 reloadLogs

Options

--merge-logs : merge logs from different instances but keep error and out separated

Clustering

Launch max instances (max depending on the number of CPUs available) and set the load balancer to balance queries among process:

$ pm2 start app.js --name "API" -i max

If your app is well-designed (stateless) you'll be able to process many more queries.

Important concepts to make a Node.js app stateless:

Reloading without downtime

This special feature has been added to PM2 a while ago.

Warning It only works for apps in cluster mode (the default mode), that uses HTTP/HTTPS/Socket connections.

Reloading an app:

$ pm2 reload api

If the reload system hasn't managed to reload gracefully, a timeout will simply kill the process and will restart it.

Graceful reload

Sometimes you can experience a very long reload, or a reload that doesn't work (fallback to restart).

It means that your app still has open connections on exit.

To work around this problem you have to use the graceful reload. Graceful reload is a mechanism that will send a shutdown message to your process before reloading it.

Example:

process.on('message', function(msg) {
  if (msg == 'shutdown') {
    // Your process is going to be reloaded
    // You have to close all database/socket.io/* connections

    console.log('Closing all connections...');

    // You will have 4000ms to close all connections before
    // the reload mechanism will try to do its job

    setTimeout(function() {
      console.log('Finished closing connections');
      // This timeout means that all connections have been closed
      // Now we can exit to let the reload mechanism do its job
      process.exit(0);
    }, 1500);
  }
});

Then use the command:

$ pm2 gracefulReload [all|name]

Startup script

PM2 has the amazing ability to generate startup scripts and configure it. PM2 is also smart enough to save all your process list and to bring back all your processes on restart.

$ pm2 startup [ubuntu|centos|systemd]

Warning It's tricky to make this feature work generically, so once PM2 has setup your startup script, reboot your server to make sure that PM2 has launched your apps!

More information

Two types of startup scripts are available:

  • SystemV init script (with the option ubuntu or centos)
  • SystemD init script (with the systemd option)

The startup options are using:

  • ubuntu will use updaterc.d and the script lib/scripts/pm2-init.sh
  • centos will use chkconfig and the script lib/scripts/pm2-init-centos.sh
  • systemd will use systemctl and the script lib/scripts/pm2.service

User permissions

Let's say you want the startup script to be executed under another user.

Just use the -u <username> option !

$ pm2 startup ubuntu -u www

Derivated commands

Dump all processes status and environment managed by pm2:

$ pm2 dump

It populates the file ~/.pm2/dump.pm2 by default.

To bring back the latest dump:

$ pm2 resurrect

Watch & Restart

pm2 can automatically restart your app when a file changes in the current directory or its subdirectories:

$ pm2 start app.js --watch

JSON app declaration

You can define parameters for your apps in processes.json:

[{
  "name"      : "echo",
  "script"    : "./examples/args.js",
  "args"      : "['--toto=heya coco', '-d', '1']",
  "env": {
      "NODE_ENV": "production",
      "AWESOME_SERVICE_API_TOKEN": "xxx"
  }
}, {
  "name"       : "api",
  "script"     : "./examples/child.js",
  "instances"  : "4",
  "error_file" : "./examples/child-err.log",
  "out_file"   : "./examples/child-out.log",
  "pid_file"   : "./examples/child.pid",
  "exec_mode"  : "cluster_mode",
  "port"       : 9005
}, {
  "name"       : "auto-kill",
  "script"     : "./examples/killfast.js"
  "min_uptime" : "100",
  "exec_mode"  : "fork_mode",
}]

Then run:

$ pm2 start processes.json
$ pm2 stop processes.json
$ pm2 delete processes.json
$ pm2 restart processes.json

Miscellaneous

Launching PM2 without daemonizing itself:

$ pm2 start app.js --no-daemon

Sending a system signal to a process:

$ pm2 sendSignal SIGUSR2 my-app

Configuration file

You can specifiy the following options by editing the file ~/.pm2/custom_options.sh:

PM2_RPC_PORT
PM2_PUB_PORT
PM2_BIND_ADDR
PM2_API_PORT
PM2_GRACEFUL_TIMEOUT
PM2_MODIFY_REQUIRE
PM2_NODE_OPTIONS

API health endpoint

$ pm2 web

Enabling Harmony ES6

Enable by default for all processes

You can enable Harmony ES6 by setting PM2_NODE_OPTIONS='--harmony' environment variable option when you start pm2 (pm2 should not be already daemonized).

To pass this option by default, you can edit ~/.pm2/custom_options.sh and add:

export PM2_NODE_OPTIONS='--harmony'

Then:

$ pm2 dump
$ pm2 exit
$ pm2 resurrect

If ES6 has been enabled you should see this message at the beggining of each pm2 command:

● ES6 mode

Enable for specific processes

$ pm2 start my_app.js --node-args="--harmony"

CoffeeScript

$ pm2 start my_app.coffee

That's all!

Knowledge

Statless apps

We recommend (and you must) write stateless NodeJS apps. Apps that don't retain any form of local variables or local instances or whatever local. Every data, states, websocket session, session data, must be shared via any kind of database.

We recommend using Redis for sharing session data, websocket.

We recommend following the 12 factor convention : http://12factor.net/

Setup PM2 on a server

How To Use PM2 to Setup a Node.js Production Environment On An Ubuntu VPS

Log and PID files

By default, logs (error and output), pid files, dumps, and pm2 logs are located in ~/.pm2/:

.pm2/
├── dump.pm2
├── custom_options.sh
├── pm2.log
├── pm2.pid
├── logs
└── pids

Execute any script: What is fork mode?

The default mode of PM2 consists of wrapping the code of your node application into the Node Cluster module. It's called the cluster mode.

There is also a more classical way to execute your app, like node-forever does, called the fork mode.

In fork mode almost all options are the same as the cluster mode. But there is no reload or gracefulReload command.

By using the fork mode you will lose core features of PM2 like the automatic clusterization of your code over all CPUs available and the 0s reload.

So use it if you only need a forever-like behaviour.

Here is how to start your app within a fork:

$ pm2 start app.js -x   # Will start your app.js in fork mode
$ pm2 list              # You will see that on the row "mode" it's written "fork"

You can also exec scripts written in other languages:

$ pm2 start my-bash-script.sh -x --interpreter bash

$ pm2 start my-python-script.py -x --interpreter python

JSON app configuration via pipe from stdout

Pull-requests:

#!/bin/bash

read -d '' my_json <<_EOF_
[{
    "name"       : "app1",
    "script"     : "/home/projects/pm2_nodetest/app.js",
    "instances"  : "4",
    "error_file" : "./logz/child-err.log",
    "out_file"   : "./logz/child-out.log",
    "pid_file"   : "./logz/child.pid",
    "exec_mode"  : "cluster_mode",
    "port"       : 4200
}]
_EOF_

echo $my_json | pm2 start -

Is my production server ready for PM2?

Just try the tests before using PM2 on your production server

$ git clone https://github.com/Unitech/pm2.git
$ cd pm2
$ npm install  # Or do NODE_ENV=development npm install if some packages are missing
$ npm test

If a test is broken please report us issues here Also make sure you have all dependencies needed. For Ubuntu:

$ sudo apt-get install build-essential
# nvm is a Node.js version manager - https://github.com/creationix/nvm
$ wget -qO- https://raw.github.com/creationix/nvm/master/install.sh | sh
$ nvm install v0.11.10
$ nvm use v0.11.10
$ nvm alias default v0.11.10

Contributing/Development mode

To hack PM2, it's pretty simple:

$ pm2 kill   # kill the current pm2
$ git clone my_pm2_fork.git
$ cd pm2/
$ DEBUG=* PM2_DEBUG=true ./bin/pm2 --no-daemon

Each time you edit the code, be sure to kill and restart pm2 to make changes taking effect.

Install pm2 development

$ npm install git://github.com/Unitech/pm2#development -g

Known bugs and workarounds

First, install the lastest pm2 version:

$ npm install -g pm2@latest

Node 0.10.x doesn't free the script port when stopped. It's due to the Node.js cluster module.

So if you feel that this problem is important for your use case, use the fork mode instead. By using the fork mode you will lose core features of PM2 like the automatic clusterization of your code over all CPUs available and the 0s reload.

$ pm2 start index.js -x  # start my app in fork mode

For more information about this, see issue #74.

Cannot read property 'getsockname' of undefined

When using the cluster mode (by default) you can't use ports from 0 to 1024. If you really need to exec in this range use the fork mode with the -x parameter. By using the fork mode you will lose core features of PM2 like the automatic clusterization of your code over all CPUs available and the 0s reload.

External resources and articles

Contributors

   195  tknew2
   184  Alexandre Strzelewicz
    20  Alex Kocharin
     8  soyuka
     6  sailxjx
     5  Bret Copeland
     4  AS
     4  Ville Walveranta
     4  achingbrain
     3  Ben Postlethwaite
     3  Evan You
     2  Frederico Silva
     2  Ivan Seidel
     2  MATSUU Takuto
     2  Oleg
     2  Willian
     2  Yani Iliev
     1  Almog Melamed
     1  Brent Burgoyne
     1  Daniel Pihlstrom
     1  Ed Hubbell
     1  Eugene Lucash
     1  Gil Pedersen
     1  Hao-kang Den
     1  John Hurliman
     1  Jose V. Trigueros
     1  Josh Skidmore
     1  Juozas Valenčius
     1  Kevin Gao
     1  Loïc Mahieu
     1  Mark Evans
     1  Nathan Peck
     1  TruongSinh Tran-Nguyen
     1  Wes Mason
     1  Zihua Li
     1  perfectworks
     1  subeeshcbabu

Sponsors

Thanks to Devo.ps and Wiredcraft for their knowledge and expertise.

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License

Files in lib/ are made available under the terms of the GNU Affero General Public License (AGPL). pm2-interface is made under the terms of the Apache V2 license.

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