Checks memory usage of all paseenger child process and kill if grows too large. Additionally kill off long running passengers to prevent memory leak issues (similar to the PassengerMaxRequests config variable in apache's passenger version, but works on bo

passenger-management.rb

#!/usr/bin/env ruby

#
# Passenger management script
# By James Smith http://loopj.com
# Based heavily on a similar script by Jon Bettcher
#
# Check memory usage of all paseenger child process and kill if grows 
# too large.
#
# Also kill off long running passengers to prevent memory leak issues.
#

# Path to the passenger-status and passenger-memory-status binaries
PASSENGER_STATUS = "/usr/local/bin/passenger-status 2>/dev/null"
PASSENGER_MEMORY_STATS = "/usr/local/bin/passenger-memory-stats 2>/dev/null"

# Recycle processes after this many requests
MAX_REQUEST_COUNT = 10000

# Hangup processes which use more than this much memory (in mb)
MAX_MEMORY = 500

# Email details on failure
TO_EMAIL = "[email protected]"
FROM_EMAIL = "[email protected]"

class PassengerStatsCollection < Hash
  def expired
    self.map { |k,v| v[:processed] && v[:processed] >= MAX_REQUEST_COUNT ? k : nil }.compact
  end

  def over_memory
    self.map { |k,v| v[:resident] && v[:resident] >= MAX_MEMORY ? k : nil }.compact
  end

  def bad
    (expired + over_memory).uniq
  end

  def any_expired?
    !expired.empty?
  end

  def any_over_memory?
    !over_memory.empty?
  end

  def any_bad?
    any_over_memory? || any_expired?
  end
end

# Turns these into seconds:
# 0h 5m
# 3d 5h 3m
# 3m 5s
def parse_uptime(time)
  sec = 0
  time.strip.split(/ +/).each do |part|
    unit = part[0..-2].to_i
    case part[-1..-1]
    when 'm' :
      unit *= 60
    when 'h' :
      unit *= 3600
    when 'd' :
      unit *= (24*3600)
    end
    sec += unit
  end
  sec
end

def get_status
  pids = PassengerStatsCollection.new

  `#{PASSENGER_STATUS}`.each_line do |line|
    if line =~ /^[ \*]*PID/ then
      parts = line.strip.split(/ +/)
      pids[parts[2].to_i] = {
        :sessions => parts[4],
        :processed => parts[6].to_i,
        :uptime => parse_uptime(line.match(/Uptime:.*$/).to_s[8..-1])
      }
    end
  end

  `#{PASSENGER_MEMORY_STATS}`.each_line do |line|
    if line =~ /\d+ .*Rails/ then
      parts = line.strip.split(/ +/)
      pid = parts[0].to_i
      pids[pid] = {} if pids[pid].nil?
      pids[pid].merge!({
        :virtual => parts[1].to_f,
        :resident => parts[3].to_f
      })
    end
  end

  pids
end

def email_on_failure(reason, e)
  `echo "#{reason}\n\nException trace:\n#{e.inspect}" | mail #{TO_EMAIL} -F #{FROM_EMAIL} -s "Passenger Management Exception"`
end

def main
  puts "Passenger Status:"
  status = get_status
  status.each do |k, v|
    puts "#{k}: #{v.inspect}"
  end

  # Nothing to do
  unless status.any_bad?
    puts "All passenger processes running within operating parameters"
    return
  end

  # Tell all over memory instances to abort
  over_memory = status.over_memory
  over_memory.each do |pid|
    puts "sending -ABRT to #{pid}"
    Process.kill(:ABRT, pid)
  end

  # Tell all expired instances to shut down gracefully
  expired = status.expired
  (expired - over_memory).each do |pid|
    puts "sending -USR1 to #{pid}"
    Process.kill(:USR1, pid)
  end

  # Give them a chance to die gracefully
  sleep 30

  # Find and kill any pids which are still bad
  (status.bad & get_status.bad).each do |pid|
    puts "killing -9 #{pid}"
    begin
      Process.kill(:KILL, pid)
    rescue
      email_on_failure("Error killing process #{pid}", e)
    end
  end
rescue Exception => e
  email_on_failure("Error in main", e)
end

main

At heyzap we run this script in a cron job on our app servers which runs every minute:

# Kill misbehaving passenger child processes (every minute)
*/1 *   * * *   root    /usr/local/bin/passenger-management.rb