From: ara.t.howard@...
Date: 2005-12-06T08:35:17+09:00
Subject: Re: Problem with method that starts process, yields pid then yields return code

On Tue, 6 Dec 2005, x1 wrote:

> What we have so far works, however ideally, printing the pid should not rely
> on the completion of the job. The only thing that should rely on the
> completion of the job would be outputting the exitstatus.

but that is the exactly the case? example:

   harp:~ > ruby servant.rb server &
   [2] 31570


   harp:~ > ruby servant.rb client
   ---
   start: "2005-12-05T16:29:21-07:00"
   ---
   pid: 31572
   ---
   after getting pid...: "2005-12-05T16:29:21-07:00"
   ---
   exitstatus: 43
   ---
   finish: "2005-12-05T16:29:24-07:00"


note the times.  __only__ getting the exitstatus relies on job completion (by
definition) and is a blocking operation.

before i read more of your post make sure you understand the above.  the code
again:

   harp:~ > cat servant.rb
   #! /usr/bin/env ruby
   %w( thread drb socket time yaml ).each{|lib| require lib}
   class Execute
     %w( cmd queue pipe pid thread exitstatus alive ).each{|a| attr_accessor a}
     def initialize(cmd)
       @cmd = cmd
       @queue = Queue.new
       @thread = Thread.new(queue) do |q|
         pipe = IO.popen(cmd)
         q.push pipe
         q.push pipe.pid
         begin
           loop{ stdout = pipe.gets or break }
           pipe.close
           q.push $?.exitstatus
         rescue => e
           q.push e
         end
       end
       @pipe = queue.pop
       @pid = queue.pop
       @exitstatus = nil
     end
     def wait
       @exitstatus = @queue.pop
     end
   end
   class Executioner
     def execute cmd
       Execute::new cmd
     end
   end

   mode, hostname, port = ARGV.shift, Socket.gethostname, 4501

   case mode
     when %r/server/i
       DRb.start_service "druby://#{ hostname }:#{ port }", Executioner.new
       DRb.thread.join

     when %r/client/i
       DRb.start_service
       executioner = DRbObject.new nil, "druby://#{ hostname }:#{ port }"
       sleep = executioner.execute "ruby -e' sleep 3 and exit 43 '"
       y "start" => Time::now.iso8601
       y "pid" => sleep.pid
       y "after getting pid..." => Time::now.iso8601
       y "exitstatus" => sleep.wait
       y "finish" => Time::now.iso8601
   end


regarding your questions about 'initialize' and 'new' - ruby is object
orientied.  everything is an object constructed from a class.  the method new,
when called on a class returns an object which was created an initialized
using it's initialize method.  check out the 'pickaxe' and the 'ruby way' for
deep insight into ruby - you can't code without them.

kind regards.

-a
-- 
===============================================================================
| ara [dot] t [dot] howard [at] noaa [dot] gov
| all happiness comes from the desire for others to be happy.  all misery
| comes from the desire for oneself to be happy.
| -- bodhicaryavatara
===============================================================================


cat a.rb