Munin Passenger Phusion Memory Stats.rb

#!/usr/bin/env ruby

def output_config
  puts <<-END
graph_category App
graph_title Passenger memory stats 
graph_vlabel count

memory.label memory
END
  exit 0
end

def output_values
  # passenger-memory-stats does a ps for 'Rails:'. If you
  # don't 'grep -v grep' it shows as another Rails process
  status = `/usr/local/bin/passenger-memory-stats | grep Rails: |grep -v grep`
  total_mem = 0.0
  unless $?.success?
    $stderr.puts "failed executing passenger-memory-stats"
    exit 1
  end

  status.split("\n").each do |line|
    if line=~ /Rails:/
      pid, mem, mb, wha, rails, path = line.split("\s")
      total_mem += mem.to_f
    end
  end
  puts "memory.value #{total_mem * 1024.0}"
end

if ARGV[0] == "config"
  output_config
else
  output_values
end

Instead of grep Rails: | grep -v grep you can do grep "[R]ails:".

Don't remember why, but putting the first character in square brackets prevents the grep process itself from being returned.

The regex [R] matches a character set which only has one letter, R, and the literal string "ails:". grep won't match the original regular expression string, as it also includes the square brackets and treats it as literal :)