Simple rails process monitoring for passenger 3
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Simple rails process monitoring for passenger 3.


IMPORTANT: passenger_mon needs to be run as root to properly get access to Passenger's passenger-memory-stats output.

# Check for out of control processes every 10 seconds
sudo passenger_mon --interval=10

# Check every 30 seconds for processes exceeding 500mb of memory
sudo passenger_mon --interval=30 --memory=500

# Specify a pidfile
sudo passenger_mon --pid=tmp/

# Specify a logfile
sudo passenger_mon --log=log/passenger_mon.log


A primary aim of this script is to have a very tiny memory footprint itself. It is a very lightweight script that is intended to be run by root as a daemon.

It works by running in a continuous loop, sleeping for the specified interval, and parsing the output of passenger-memory-stats to find processes that have crossed the specified memory threshold (the default is 400 MB).


Currently, Passenger 3 (and previous versions) don't generate pidfiles or the application processes it spawns. This makes it very difficult to monitor these processes with tools like monit and god. Further compounding this problem is the lack of any sort of per process memory threshold for passenger.


  • Rick Bradley
  • Alex Sharp