--- title: PM2 date: 2022-11-25 18:10:00 background: bg-[#230769] tags: - process categories: - Linux Command intro: | [PM2] is a daemon process manager that will help you manage and keep your application online. Getting started with PM2 is straightforward, it is offered as a simple and intuitive CLI. plugins: - copyCode --- ## Getting Started ### Install The latest PM2 version is installable with NPM or Yarn ```shell script $ npm install pm2@latest -g ``` OR ```shell script $ yarn global add pm2 ``` ### Start an app The simplest way to start, daemonize and monitor your application is by using this command line ```shell script $ pm2 start app.js ``` Or start any other application easily ```shell script $ pm2 start bashscript.sh $ pm2 start python-app.py --watch $ pm2 start binary-file -- --port 1520 ``` ### Some options you can pass to the CLI {.row-span-3} Specify an app name ```shell script --name ``` Watch and Restart app when files change ```shell script --watch ``` Set memory threshold for app reload ```shell script --max-memory-restart <200MB> ``` Specify log file ```shell script --log ``` Pass extra arguments to the script ```shell script -- arg1 arg2 arg3 ``` Delay between automatic restarts ```shell script --restart-delay ``` Prefix logs with time ```shell script --time ``` Do not auto restart app ```shell script --no-autorestart ``` Specify cron for forced restart ```shell script --cron ``` Attach to application log ```shell script --no-daemon ``` ### Managing processes Managing application state is simple here are the commands ```shell script $ pm2 restart app_name $ pm2 reload app_name $ pm2 stop app_name $ pm2 delete app_name ``` #### Instead of app_name you can pass - `all` to act on all processes - `id` to act on a specific process id ### Check status, logs, metrics {.row-span-2} Now that you have started this application, you can check its status, logs, metrics and even get the online dashboard with [pm2.io](https://pm2.io/). List the status of all application managed by PM2 ```shell script $ pm2 [list|ls|status] ``` To display logs in realtime ```shell script $ pm2 logs ``` To dig in older logs ```shell script $ pm2 logs --lines 200 ``` Here is a realtime dashboard that fits directly into your terminal ```shell script $ pm2 monit ``` Web based dashboard, cross servers with diagnostic system ```shell script $ pm2 plus ``` ### Cluster mode For Node.js applications, PM2 includes an automatic load balancer that will share all HTTP[s]/Websocket/TCP/UDP connections between each spawned processes. To start an application in Cluster mode ```shell script $ pm2 start app.js -i max ``` Read more about cluster mode [here](https://pm2.keymetrics.io/docs/usage/quick-start/). ### Ecosystem File {.row-span-2} You can also create a configuration file, called Ecosystem File, to manage multiple applications. To generate an Ecosystem file ```shell script $ pm2 ecosystem ``` This will generate an ecosystem.config.js file ``` module.exports = { apps : [{ name: "app", script: "./app.js", env: { NODE_ENV: "development", }, env_production: { NODE_ENV: "production", } }, { name: 'worker', script: 'worker.js' }] } ``` And start it easily ```shell script $ pm2 start ecosystem.config.js ``` Read more about application declaration [here](https://pm2.keymetrics.io/docs/usage/application-declaration/) ### Setup startup script Restarting PM2 with the processes you manage on server boot/reboot is critical. To solve this, just run this command to generate an active startup script ```shell script $ pm2 save ``` Read more about startup script generator [here](https://pm2.keymetrics.io/docs/usage/startup/) ### Restart application on changes It’s pretty easy with the `--watch` option ``` $ cd /path/to/my/app $ pm2 start env.js --watch --ignore-watch="node_modules" ``` This will watch & restart the app on any file change from the current directory + all subfolders and it will ignore any changes in the node_modules folder `--ignore-watch="node_modules"`. You can then use `pm2 logs` to check for restarted app logs. --- ### CheatSheet {.row-span-2 .col-span-2} Here are some commands that are worth knowing. Just try them with a sample application or with your current web application on your development machine Fork mode ```shell script $ pm2 start app.js --name my-api # Name process ``` Cluster mode ```shell script $ pm2 start app.js -i 0 # Will start maximum processes with LB depending on available CPUs $ pm2 start app.js -i max # Same as above, but deprecated. $ pm2 scale app +3 # Scales `app` up by 3 workers $ pm2 scale app 2 # Scales `app` up or down to 2 workers total ``` Listing ```shell script $ 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 information about a specific process $ pm2 monit # Monitor all processes ``` Logs ```shell script $ pm2 logs [--raw] # Display all processes logs in streaming $ pm2 flush # Empty all log files $ pm2 reloadLogs # Reload all logs ``` Actions ```shell script $ pm2 stop all # Stop all processes $ pm2 restart all # Restart all processes $ pm2 reload all # Will 0s downtime 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 ```shell script $ pm2 reset # Reset meta data (restarted time...) $ pm2 updatePM2 # Update in memory pm2 $ pm2 ping # Ensure pm2 daemon has been launched $ pm2 sendSignal SIGUSR2 my-app # Send system signal to script $ pm2 start app.js --no-daemon $ pm2 start app.js --no-vizion $ pm2 start app.js --no-autorestart ``` ### Updating PM2 We made it simple, there is no breaking change between releases and the procedure is straightforward ```shell script $ npm install pm2@latest -g ``` Then update the in-memory PM2 ```shell script $ pm2 update ``` ## Also see - [QUICK START](https://pm2.keymetrics.io/docs/usage/quick-start/) _(pm2.keymetrics.io)_