# Passenger apps

Passenger is an embedded server that assists in securely managing Node, Python, and Ruby apps. Passenger may launch directly from Apache, proxy through to a separate Nginx server, or proxy through to itself in standalone mode.

# Configuration

An .htaccess (opens new window) file instructs Apache how to map this request. Passenger applications must be explicitly defined

A few directives are used. All directives below are prefixed with Passenger. Values specified as this are to be taken literally.

Directive Values Description
Enabled on Enable Passenger support
AppRoot path Required when StartupFile is not located in .htaccess directory.
StartupFile path Entry script relative to app root
AppType node, python, or ruby Application type
Nodejs optional full path to node executable Used when AppType is node
Python optional full path to python executable Used when AppType is python
Ruby optional full path to ruby executable Used when AppType is ruby
FriendlyErrorPages default is on, off hides errors Shows errors in browser. Set to off for production.

Integrating these facts above let's install Nodejs 12.16.3, on a subdomain whose document root (opens new window) is /var/www/hq/public. The application resides in /var/www/hq and its entry script (startup file) is /var/www/hq/current/index.js.

First, determine which Node, Python, or Ruby interpreter you'd like to use.

# Install Nodejs v12.16.3
nvm install 12.16.3
# Get the path to this file
nvm which 12.16.3
# Returns "/home/myadmin/.nvm/versions/node/v12.16.3/bin/node"

Lastly, create a .htaccess file in /var/www/hq/public with the following lines:

PassengerEnabled on
PassengerStartupFile current/index.js
PassengerAppType node
PassengerAppRoot /var/www/hq
PassengerNodejs /home/myadmin/.nvm/versions/node/v12.16.3/bin/node

# Restarting

Create a directory named tmp within the application root. touch either file to restart one time or before every request:

File Purpose
restart.txt Restart once
always_restart.txt Restart before each request
cd /var/www/ghost
mkdir tmp
touch tmp/restart.txt

Passenger will restart automatically once the timer has elapsed (~2 minutes).

# Idle shutdowns

All apps spindown processes if no activity is received after a fixed time (5 minutes). This behavior is consistent with PHP-FPM pool management. Unlike PHP however, there is no warm cache to resume code from making initialization sometimes expensive.

Global idle shutdown may be modified by overriding PassengerPoolIdleTime in /etc/httpd/conf/httpd-custom.conf (see Apache.md).

# Disable idle shutdowns
PassengerPoolIdleTime 0

# See also