From: trickyvail <7ricky@...>
Date: 2008-07-15T08:50:25+09:00
Subject: Re: open3 throws exception when preceded by fork

On Jul 14, 2:52 pm, "ara.t.howard" <ara.t.how...@gmail.com> wrote:
> require 'rubygems'
> require 'slave'  # gem install slave
>
> class Server
>    def run job
>      system job
>    end
> end
>
> slave = Slave.new{ Sever.new }
> server = slave.object
>
> server.run 'echo "this is in another process you do not have to ever
> worry about"'

Thank you for you reply. Unfortunately I am unable to utilize the
slave ruby gem (and open4 gem also) due to some rubygems package
corruption? on my Ubuntu machine. I've given up fighting with it and
come up with a different solution.

daemon:
#!/usr/bin/ruby
stop = false
Signal.trap('CLD') do
  child = Process.wait
  puts "child #{child} closed."
  stop = true
end
exec('./job.rb') if fork.nil?
while(! stop)
  puts 'not finished, do some other stuff'
  sleep 5
end
puts "finished"

job:
#!/usr/bin/ruby
require 'open3'
stdin, stdout, stderr = Open3.popen3('real_job_binary')
stderr.each do |line|
  puts line
end

This way the calls to fork and open3 are isolated in different ruby
interpreter instances where they can't interfere with each other.