PM2 can be used programmatically, meaning that you can embed a process manager directly in your code, spawn processes, keep them alive even if the main script is exited.
It’s also useful when you deploy a Node.js application in any kind of Cloud Provider / PaaS.
This example shows you how to start app.js with some configuration attributes. Elements passed to start are the same than those you can declare in a JS/JSON configuration file:
NB: If your script does not exit by itself, make sure you called pm2.disconnect() at the end.
npm install pm2 --save
var pm2 = require('pm2');
pm2.connect(function(err) {
if (err) {
console.error(err);
process.exit(2);
}
pm2.start({
script : 'app.js', // Script to be run
exec_mode : 'cluster', // Allows your app to be clustered
instances : 4, // Optional: Scales your app by 4
max_memory_restart : '100M' // Optional: Restarts your app if it reaches 100Mo
}, function(err, apps) {
pm2.disconnect(); // Disconnects from PM2
if (err) throw err
});
});
npm install pm2 --save
pm2.connect(errback) - Either connects to a running pm2 daemon (“God”) or launches and daemonizes one. Once launched, the pm2 process will keep running after the script exits.
pm2.connect(noDaemonMode, errback)
noDaemonMode - (Default: false) If true is passed for the first argument, pm2 will not be run as a daemon and will die when the related script exits. By default, pm2 stays alive after your script exits. If pm2 is already running, your script will link to the existing daemon but will die once your process exits.errback(error) - Called when finished connecting to or launching the pm2 daemon process.pm2.start(options, errback) - Starts a script that will be managed by pm2.
pm2.start(jsonConfigFile, errback)
pm2.start(script, errback)
pm2.start(script, options, errback)
pm2.start(script, jsonConfigFile, errback)
script - The path of the script to run.jsonConfigFile - The path to a JSON file that can contain the same options as the options parameter.errback(err,proc) - An errback called when the script has been started. The proc parameter will be a pm2 process object.options - An object with the following options (additional descriptions of these options are here):
name - An arbitrary name that can be used to interact with (e.g. restart) the process later in other commands. Defaults to the script name without its extension (eg "testScript" for "testScript.js").script - The path of the script to run.args - A string or array of strings composed of arguments to pass to the script.interpreterArgs - A string or array of strings composed of arguments to call the interpreter process with. Eg “–harmony” or [”–harmony”,”–debug”]. Only applies if interpreter is something other than “none” (its “node” by default).cwd - The working directory to start the process with.output - (Default: "~/.pm2/logs/app_name-out.log") The path to a file to append stdout output to. Can be the same file as error.error - (Default: "~/.pm2/logs/app_name-error.err") The path to a file to append stderr output to. Can be the same file as output.logDateFormat - The display format for log timestamps (eg “YYYY-MM-DD HH:mm Z”). The format is a moment display format.pid - (Default: "~/.pm2/pids/app_name-id.pid") The path to a file to write the pid of the started process. The file will be overwritten. Note that the file is not used in any way by pm2 and so the user is free to manipulate or remove that file at any time. The file will be deleted when the process is stopped or the daemon killed.minUptime - The minimum uptime of the script before it’s considered successfully started.maxRestarts - The maximum number of times in a row a script will be restarted if it exits in less than min_uptime.maxMemoryRestart - If sets and script’s memory usage goes about the configured number, pm2 restarts the script. Uses human-friendly suffixes: ‘K’ for kilobytes, ‘M’ for megabytes, ‘G’ for gigabytes’, etc. Eg “150M”.killTimeout - (Default: 1600) The number of milliseconds to wait after a stop or restart command issues a SIGINT signal to kill the script forceably with a SIGKILL signal.restartDelay - (Default: 0) Number of millseconds to wait before restarting a script that has exited.interpreter - (Default: 'node') The interpreter for your script (eg “python”, “ruby”, “bash”, etc). The value “none” will execute the ‘script’ as a binary executable.execMode - (Default: 'fork') If sets to ‘cluster’, will enable clustering (running multiple instances of the script). See here for more details.instances - (Default: 1) How many instances of script to create. Only relevant in exec_mode ‘cluster’.mergeLogs - (Default: false) If true, merges the log files for all instances of script into one stderr log and one stdout log. Only applies in ‘cluster’ mode. For example, if you have 4 instances of ‘test.js’ started via pm2, normally you would have 4 stdout log files and 4 stderr log files, but with this option set to true you would only have one stdout file and one stderr file.watch - If set to true, the application will be restarted on change of the script file.force (Default: false) By default, pm2 will only start a script if that script isn’t already running (a script is a path to an application, not the name of an application already running). If force is set to true, pm2 will start a new instance of that script.autorestart (Default true). If false, pm2 will not attempt to restart it following successful completion or process failure.cronexecuteCommandwritesourceMapSupportdisableSourceMapSupportpm2.disconnect() - Disconnects from the pm2 daemon.
pm2.stop(process, errback) - Stops a process but leaves the process meta-data in pm2’s list. See here for how pm2 stops a process
pm2.restart(process, errback) - Stops and restarts the process.
pm2.delete(process, errback) - Stops the process and removes it from pm2’s list. The process will no longer be accessible by its name.
pm2.reload(process, errback) - Zero-downtime rolling restart. At least one process will be kept running at all times as each instance is restarted individually. Only works for scripts started in cluster mode. See here for more details.
pm2.gracefulReload(process, options, errback) - Sends the process a shutdown message before initiating reload. See here for more details.
process - Can either be the name as given in the pm2.start options, a process id, or the string “all” to indicate that all scripts should be restarted.options - (Optional) An object with the following options:
updateEnv - (Default: false) If true is passed in, pm2 will reload it’s environment from process.env before reloading your process.errback(err, proc)pm2.killDaemon(errback) - Kills the pm2 daemon (same as pm2 kill). Note that when the daemon is killed, all its processes are also killed. Also note that you still have to explicitly disconnect from the daemon even after you kill it.
pm2.describe(process,errback) - Returns various information about a process: eg what stdout/stderr and pid files are used.
errback(err, processDescription)processDescription - An object with information about the process. Contains the properties:
name - The name given in the original start command.pid - The pid of the process.pm_id - The pid for the pm2 God daemon process.monit - An object containing:
memory - The number of bytes the process is using.cpu - The percent of CPU being used by the process at the moment.pm2_env - The list of path variables in the process’s environment. These variables include:
pm_cwd - The working directory of the process.pm_out_log_path - The stdout log file path.pm_err_log_path - The stderr log file path.exec_interpreter - The interpreter used.pm_uptime - The uptime of the process.unstable_restarts - The number of unstable restarts the process has been through.restart_timestatus - “online”, “stopping”, “stopped”, “launching”, “errored”, or “one-launch-status”instances - The number of running instances.pm_exec_path - The path of the script being run in this process.pm2.list(errback) - Gets the list of running processes being managed by pm2.
errback(err, processDescriptionList) - The processDescriptionList parameter will contain a list of processDescription objects as defined under pm2.describe.pm2.dump(errback) - Writes the process list to a json file at the path in the DUMP_FILE_PATH environment variable (“~/.pm2/dump.pm2” by default).
errback(err, result)pm2.flush(process,errback) - Flushes the logs.
errback(err, result)pm2.dump(errback)
errback(err, result)pm2.reloadLogs(errback) - Rotates the log files. The new log file will have a higher number in it (the default format being ${process.name}-${out|err}-${number}.log).
errback(err, result)pm2.launchBus(errback) - Opens a message bus.
errback(err, bus) - The bus will be an Axon Sub Emitter object used to listen to and send events.pm2.sendSignalToProcessName(signal, process, errback)
errback(err, result)pm2.startup(platform, errback) - Registers the script as a process that will start on machine boot. Platform can currently be: “ubuntu”, “centos”, “redhat”, “gentoo”, “systemd”, “darwin”, or “amazon”. The current process list will be dumped and saved for resurrection on reboot.
errback(err, result)Available in PM2 0.15.11>
pm2-call.js:
pm2.connect(function() {
pm2.sendDataToProcessId({
type : 'process:msg',
data : {
some : 'data',
hello : true
},
id : 0, // id of procces from "pm2 list" command or from pm2.list(errback) method
topic: 'some topic'
}, function(err, res) {
});
});
pm2.launchBus(function(err, bus) {
pm2_bus.on('process:msg', function(packet) {
packet.data.success.should.eql(true);
packet.process.pm_id.should.eql(proc1.pm2_env.pm_id);
done();
});
});
pm2-app.js:
process.on('message', function(packet) {
process.send({
type : 'process:msg',
data : {
success : true
}
});
});