gistfile1.txt

#!/usr/bin/env ruby

# adapted for RMSR from http://gist.github.com/41713
# run every couple minutes via cron
# and output results to script_output.log
# sudo crontab -e
# then add the following:
# */2 * * * * ruby /bin/passenger_monitor_cron 2>&1 >> /var/log/script_output.log

command = '/usr/bin/passenger-memory-stats'
memory_limit = 200 # megabytes

def running?(pid)
  begin
    return Process.getpgid(pid) != -1
  rescue Errno::ESRCH
    return false
  end
end

`#{command}`.each_line do |line|
  next unless /(\d+)\s+\d+\s+(\d+\.\d+)\s+MB\s+(\d+\.\d+)\s+MB\s+Rails:/.match(line)
  all, pid, vm_size, private = $~.to_a
  if private.to_i > memory_limit
    puts "#{Time.now}: Killing #{pid}, memory usage == #{private}"
    Process.kill("SIGUSR1", pid.to_i)
    puts "Finished kill attempt. Sleeping for 20 seconds..."
    sleep 20
    if running?(pid.to_i)
      puts "Process is still running, sending term signal"
      Process.kill("KILL", pid.to_i)
    end
  # remove these two lines after everything checks out
  else
     puts "#{Time.now}: Everything ok."
  end
end

Save this file to the following location on your server and make sure it's executable:

/bin/passenger_monitor_cron

Also, set the memory usage threshold for each Passenger process on line 11. This depends on the size of the server and the number of Passenger processes specified by the PassengerPoolSize. For a 256mb server running MySQL, 50mb is a good starting point. For a 512mb server, try starting with 200 maybe.