Gunnar Wolf

I think I should follow up on Victor's lament. Yes, we have a Rails application which works fine most of the time... But quite often, throws out a segmentation fault I just have been unable to pin-point. It might be related to rmagick, the only non-pure-Ruby component I am using (and I'm tempted to try minimagick instead, even if I prefer in-memory operations than on-disk, piping an image and slurping it again).
Victor came up with an easy script to check the server - but to reduce the impact it has (I was running a single Mongrel instance, which meant, whenever it dies the whole system becomes inaccessible for everybody; I replaced it with a mongrel_cluster of five processes, plus pound as a easy-to-use balancer which looks quite nice), the very simplistic and to-the-point script did no longer work.
Anyway... Ruby rocks ;-) I'm sharing this with you mostly because I am sure some readers will find more than one useful construct, not because it is precisely beautiful code. And besides, we should work on fixing the cause, not the consequence, of the bug! :)

#!/usr/bin/ruby
require 'yaml'
confdir = '/etc/mongrel-cluster/sites-enabled'
restart_cmd = '/etc/init.d/mongrel-cluster restart'
needs_restart = false
 
(Dir.open(confdir).entries - ['.', '..']).each do |site|
  conf = YAML.load_file "#{confdir}/#{site}"
  pid_location = [conf['cwd'], conf['pid_file']].join('/').gsub(/\.pid$/, '*.pid')
  pid_files = Dir.glob(pid_location)
 
  pid_files.each do |pidf|
    pid = File.read(pidf)
    begin
      Process.getpgid(pid.to_i)
    rescue Errno::ESRCH
      warn "Process #{pid} (cluster #{site}) is dead!"
      File.unlink pidf
      needs_restart = true
    end
  end
end
 
system(restart_cmd) if needs_restart