Keeping Node.js Server Run Permanently Using Process Managers

A. Through the command line interface

1. To install forever, use this command:

[sudo] npm install -g forever

2. Then start your application using:

forever app.js

Or as a service:

forever start app.js

Replace app.js with the name of the file that is your app’s main entry point.

You will see an output like this:

$ forever start app.js
warn: --minUptime not set. Defaulting to: 1000ms
warn: --spinSleepTime not set. Your script will exit if it does not stay up for at least 1000ms
info: Forever processing file: app.js

It’s safe to ignore the warnings but if you want to explicitly set them, you can refer to the forever –help command. Here’s a sample command to set up the minUptime and spinSleepTime:

forever start --minUptime 1000 --spinSleepTime 1000 app.js

3. To check all processes listed up which are registered with forever, enter this command:

forever list

You will see an output like this:

$ forever list
info: Forever processes running
data: uid command 
script forever pid id logfile uptime
data: [0] BQL5 /home/dh_df4zyr/.nvm/versions/node/v12.18.3/bin/node app.js 10 818 14388 /home/dh_df4zyr/.forever/BQL5.log 0:0:0:1.642

4. To make sure that the application will automatically restart itself when the server reboots, we will need to create an auto-start script using crontab. It is a file which contains the schedule of cron entries to be run and at specified times.

Use this command to edit your crontab file:

crontab -e

Then add this line to the bottom of the file and save it:

@reboot forever start /home/node/app/app.js

Just replace app.js with the name of your file. By adding this, crontab will run the forever start command after the system reboots.

B. Using it programmatically

You can use forever inside your own Node.js code using forever-monitor.

1. Embed this code to your app.js file and save it:

var forever = require('forever-monitor'); 
var child = new(forever.Monitor)('app.js', { 
max: 3, silent: true, options: [] }); 
child.on('exit', function() { 
console.log('app.js has exited after 3 restarts'); }); 
child.start();

2. Install forever-monitor

$ npm install forever-monitor

Here are some options available when using Forever programmatically which most of this configuration is just optional.

  {

    //

    // Basic configuration options

    //

    'silent': false,            // Silences the output from stdout and stderr in the parent process

    'uid': 'your-UID',          // Custom uid for this forever process. (default: autogen)

    'pidFile': 'path/to/a.pid', // Path to put pid information for the process(es) started

    'max': 10,                  // Sets the maximum number of times a given script should run

    'killTree': true,           // Kills the entire child process tree on `exit`

 

    //

    // These options control how quickly forever restarts a child process

    // as well as when to kill a "spinning" process

    //

    'minUptime': 2000,     // Minimum time a child process has to be up. Forever will 'exit' otherwise.

    'spinSleepTime': 1000, // Interval between restarts if a child is spinning (i.e. alive < minUptime).

 

    //

    // Command to spawn as well as options and other vars

    // (env, cwd, etc) to pass along

    //

    'command': 'perl',         // Binary to run (default: 'node')

    'args':    ['foo','bar'],  // Additional arguments to pass to the script,

    'sourceDir': 'script/path',// Directory that the source script is in

 

    //

    // Options for restarting on watched files.

    //

    'watch': true,               // Value indicating if we should watch files.

    'watchIgnoreDotFiles': null, // Whether to ignore file starting with a '.'

    'watchIgnorePatterns': null, // Ignore patterns to use when watching files.

    'watchDirectory': null,      // Top-level directory to watch from. You can provide multiple watchDirectory options to watch multiple directories (e.g. for cli: forever start -w='app' -w='some_other_directory' app\index.js)

    //

    // All or nothing options passed along to `child_process.spawn`.

    //

    'spawnWith': {

      customFds: [-1, -1, -1], // that forever spawns.

      setsid: false,

      uid: 0,      // Custom UID

      gid: 0,      // Custom GID

      shell: false // Windows only - makes forever spawn in a shell

    },

    //

    // More specific options to pass along to `child_process.spawn` which

    // will override anything passed to the `spawnWith` option

    //

    'env': { 'ADDITIONAL': 'CHILD ENV VARS' },

    'cwd': '/path/to/child/working/directory',

 

    //

    // Log files and associated logging options for this instance

    //

    'logFile': 'path/to/file', // Path to log output from forever process (when daemonized)

    'outFile': 'path/to/file', // Path to log output from child stdout

    'errFile': 'path/to/file', // Path to log output from child stderr

 

    //

    // ### function parseCommand (command, args)

    // #### @command {String} Command string to parse

    // #### @args    {Array}  Additional default arguments

    //

    // Returns the `command` and the `args` parsed from

    // any command. Use this to modify the default parsing

    // done by 'forever-monitor' around spaces.

    //

    'parser': function (command, args) {

      return {

        command: command,

        args:    args

      };

    }

  }

Managing Processes

Here are some useful forever commands to manage your node application. You can view these using this command:

$ forever --help