PassengerMonit

This plugin provides means for monitoring Rails application which run under Passenger with Monit.

The pid file name (hardcoded) is /var/tmp/rack.X.pid, where X denotes the instance number.

Installation

Add this line to your Gemfile:

gem 'passenger_monit', :group => :production

Example Monit configuration


check process instance1 with pidfile /var/tmp/rack.1.pid
    group web
    start program = "/bin/true" with timeout 30 seconds
    stop program = "/bin/sh -c 'kill `cat /var/tmp/rack.1.pid`'"
    if totalmem > 120.0 MB for 5 cycles then restart
    if changed pid 2 times within 2 cycles then alert
    if changed ppid 2 times within 2 cycles then alert

Bugs and missing features

Only tested with nginx
The pid file location is hardcoded
Sometimes there are more passenger instances in the air than anticipated, so when one goes down, there might be first pid file missing, e.g.: from [rack.1.pid, rack.2.pid] to [rack.1.pid, rack.2.pid, rack.3.pid] to [rack.2.pid, rack.3.pid] - monit will complain that the first instance is missing.