Notes

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PM2 ​

PM2 is a daemon process manager that will help you manage and keep your application online.

https://pm2.keymetrics.io

Installation ​

Make sure node is installed on the system.

npm install pm2@latest -g
npm install pm2@latest -g

Basics ​

https://pm2.keymetrics.io/docs/usage/quick-start/

pm2 list
pm2 show app_name 

pm2 start app_name
pm2 restart app_name
pm2 reload app_name
pm2 stop app_name
pm2 delete app_name

pm2 save
pm2 list
pm2 show app_name 

pm2 start app_name
pm2 restart app_name
pm2 reload app_name
pm2 stop app_name
pm2 delete app_name

pm2 save

app_name can either be the app or the configuration file

Starting an app ​

The simplest way to start, daemonize and monitor your application is by using this command line:

$ pm2 start app.js
$ pm2 start app.js

Or start any other application easily:

$ pm2 start bashscript.sh
$ pm2 start python-app.py --watch
$ pm2 start binary-file -- --port 1520
$ pm2 start bashscript.sh
$ pm2 start python-app.py --watch
$ pm2 start binary-file -- --port 1520

Some options you can pass to the CLI:

# Specify an app name
--name <app_name>

# Watch and Restart app when files change
--watch

# Set memory threshold for app reload
--max-memory-restart <200MB>

# Specify log file
--log <log_path>

# Pass extra arguments to the script
-- arg1 arg2 arg3

# Delay between automatic restarts
--restart-delay <delay in ms>

# Prefix logs with time
--time

# Do not auto restart app
--no-autorestart

# Specify cron for forced restart
--cron <cron_pattern>

# Attach to application log
--no-daemon
# Specify an app name
--name <app_name>

# Watch and Restart app when files change
--watch

# Set memory threshold for app reload
--max-memory-restart <200MB>

# Specify log file
--log <log_path>

# Pass extra arguments to the script
-- arg1 arg2 arg3

# Delay between automatic restarts
--restart-delay <delay in ms>

# Prefix logs with time
--time

# Do not auto restart app
--no-autorestart

# Specify cron for forced restart
--cron <cron_pattern>

# Attach to application log
--no-daemon

Rename a process ​

pm2 restart id --name newName
pm2 restart id --name newName

Configuration Files ​

.yml or .json files both work

apps:
  - script   :  runjob.py
    cwd      :  /srv/runjob
    name     : 'boilerplate_api'
    watch    : true
    exec_mode: fork
    out_file : /srv/var/log/boilerplate_api.log
    err_file : /srv/var/log/boilerplate_api.err
    combine_logs : false
apps:
  - script   :  runjob.py
    cwd      :  /srv/runjob
    name     : 'boilerplate_api'
    watch    : true
    exec_mode: fork
    out_file : /srv/var/log/boilerplate_api.log
    err_file : /srv/var/log/boilerplate_api.err
    combine_logs : false

load with the same pm2 start command

pm2 start pm2.yml
pm2 start pm2.yml

https://pm2.keymetrics.io/docs/usage/application-declaration/

(if processes with same name exist, do a pm2 delete all/process_name first)

Restart options ​

By default, pm2 will restart processes when they fail. If an api is unavailable, this may result in a surge in log messages.

Exponential backoff is useful to slow restart attempts until the API is back online:

module.exports = {
  script: 'app.js',
  exp_backoff_restart_delay: 100
}
module.exports = {
  script: 'app.js',
  exp_backoff_restart_delay: 100
}

https://pm2.keymetrics.io/docs/usage/restart-strategies/

Watching ​

In production, 'watch' is a bad idea.

System Setup ​

Once things are working as desired, be sure to save the startup with:

pm2 save
pm2 save

Then generate the systemd registration with:

pm2 startup
pm2 startup

It will generate something like:

sudo env PATH=$PATH:/usr/bin /usr/lib/node_modules/pm2/bin/pm2 startup systemd -u account --hp /home/account
sudo env PATH=$PATH:/usr/bin /usr/lib/node_modules/pm2/bin/pm2 startup systemd -u account --hp /home/account

Removing settings ​

When removing all entries, may be necessary to use

pm2 save --force
pm2 save --force

to commit the changes

Log Rotation ​

https://github.com/keymetrics/pm2-logrotate

pm2 set pm2-logrotate:compress true
pm2 set pm2-logrotate:retain 8
pm2 set pm2-logrotate:rotateInterval '0 5 * * 1'
pm2 set pm2-logrotate:compress true
pm2 set pm2-logrotate:retain 8
pm2 set pm2-logrotate:rotateInterval '0 5 * * 1'
#!/bin/bash
pm2 set pm2-logrotate:max_size 500M
pm2 set pm2-logrotate:retain 26
pm2 set pm2-logrotate:compress true
pm2 set pm2-logrotate:rotateInterval '0 0 5 * * 7'
#!/bin/bash
pm2 set pm2-logrotate:max_size 500M
pm2 set pm2-logrotate:retain 26
pm2 set pm2-logrotate:compress true
pm2 set pm2-logrotate:rotateInterval '0 0 5 * * 7'

Removing Jobs ​

If you want to remove the processes, run pm2 delete [id]

To delete all jobs: pm2 delete all

Don't forget: pm2 save to make the changes persist

Environment Variables ​

https://pm2.io/docs/runtime/best-practices/environment-variables/
PM2 - Environment Variables | Best Practices | PM2 Documentation

Node scripts ​

May need to reference the path to the script in node modules

example:

apps:
  - cwd      : /srv/boilerplate/ui
    script   : node_modules/nuxt/bin/nuxt.js
    args     : 'start'
    env: 
      NODE_ENV : "production"
      HOST     : "127.0.0.1"
      BASE_URL : 'https://example.com'
      API_URL  : 'https://example.com/api/'
    name     : 'example-ui'
    watch    : false
    exec_mode: fork
    out_file : /var/log/boilerplate_admin_ui.log
    err_file : /var/log/boilerplate_admin_ui.err
    combine_logs : false
apps:
  - cwd      : /srv/boilerplate/ui
    script   : node_modules/nuxt/bin/nuxt.js
    args     : 'start'
    env: 
      NODE_ENV : "production"
      HOST     : "127.0.0.1"
      BASE_URL : 'https://example.com'
      API_URL  : 'https://example.com/api/'
    name     : 'example-ui'
    watch    : false
    exec_mode: fork
    out_file : /var/log/boilerplate_admin_ui.log
    err_file : /var/log/boilerplate_admin_ui.err
    combine_logs : false

https://duckduckgo.com/?t=ffab&q=pm2+pm2.yml+start+command+in+package.json&ia=web
pm2 pm2.yml start command in package.json at DuckDuckGo
https://pm2.keymetrics.io/docs/usage/quick-start/
PM2 - Quick Start
https://pm2.keymetrics.io/docs/usage/application-declaration/
PM2 - Ecosystem File
https://stackoverflow.com/questions/46008665/how-to-start-a-package-json-script-in-pm2
node.js - How to start a package.json script in pm2 - Stack Overflow
https://duckduckgo.com/?t=ffab&q=pm2+yml+configuration&ia=web
pm2 yml configuration at DuckDuckGo

Python Virtual Environments ​

If you activate the virtual environment eg. source venv/Scripts/activate then start your script via pm2 eg. pm2 start main.py --name migration, it will automatically use the environment you've activated.

Alternatively, pass in the interpreter:

pm2 start ./strain_to_db --interpreter ./py3env/bin/python
pm2 start ./strain_to_db --interpreter ./py3env/bin/python

via: https://stackoverflow.com/questions/36090655/running-a-python-script-in-virtual-environment-with-node-js-pm2

Docker ​

I had difficulty getting PM2 to run under Docker. It doesn't make much sense unless you're attempting to replicate a production environment in docker.

If you need to run multiple python workers in the same container, look to supervisord

Using pm2 in a container: https://pm2.keymetrics.io/docs/usage/docker-pm2-nodejs/