From: Ara.T.Howard@...
Date: 2004-09-23T11:04:35+09:00
Subject: Re: DrbUndumped and GC

On Thu, 23 Sep 2004, Masatoshi SEKI wrote:

> How about TimerIdConv?
>
>   require 'drb/timeridconv'
>
>   ....
>
>   DRb.install_id_conv(DRb::TimerIdConv.new)
>   DRb.start_service(....)
>
>
> I like the following simple approach.
>
>   class Server
>     def initialize
>       @proxy = Proxy.new
>     end
>     def method
>       @proxy
>     end
>   end

in my case the code is

   require 'drb'
   require 'detach'
   class JobRunner
   #{{{
     include DRbUndumped
     attr :job
     attr :jid
     attr :cid
     alias pid cid
     attr :shell
     attr :command
     attr :status
     def initialize job
   #{{{
       @status = nil
       @job = job
       @jid = job['jid']
       @command = job['command']
       @shell = job['shell'] || 'bash'
       @r,@w = IO.pipe
       @cid =
         #Util::fork do
         fork do
           @w.close
           STDIN.reopen @r
           if File::basename(@shell) == 'bash' || File::basename(@shell) == 'sh'
             exec [@shell, "__rq_job__#{ @jid }__#{ File.basename(@shell) }__"], '--login'
           else
             exec [@shell, "__rq_job__#{ @jid }__#{ File.basename(@shell) }__"], '-l'
           end
         end
       @r.close
   #}}}
     end
     def run
   #{{{
       @w.puts @command
       @w.close
   #}}}
     end
     def wait2 flags = 0
   #{{{
       pid, status = Process::waitpid2 @cid, flags
       @status = status
       [pid, status]
   #}}}
     end
     def wait flags = 0
   #{{{
       wait2(flags).last
   #}}}
     end
   #}}}
   end
   class JobRunnerDaemon
   #{{{
     class << self
   #{{{
       def new(*a,&b)
   #{{{
         super(*a,&b).detach(:background=>false)
   #}}}
       end
   #}}}
     end
     def runner(*a,&b)
   #{{{
       JobRunner::new(*a,&b)
   #}}}
     end
     alias new_runner runner
     alias runner_new runner
     %w( wait wait2 waitpid waitpid2 ).each do |m|
       eval "def #{ m }(*a,&b);Process::#{ m }(*a,&b);end"
     end
   #}}}
   end
   JobRunD = JobRunnerDaemon

i need an object that can fork for me in another process.  i can't fork in the
current process due to some compilcations with sqlite and open files carried
across forks.  so i'm creating potentially dozens of these JobRunner objects
and using

   jrd.wait

to do a blocking wait on their completion (also some non-blocking waits but
that's an impl detail).

it works great now, i was just worrying about the GC - now i know i should be.
because i should always do some sort of wait on the JobRunner's i can probably
hook something into the 'def runner' method that registers the objects in a
class datastructure (preventing gc) and hook something into the wait* methods
that does the wait and removes them from this structure.

i'll check out DRb::TimerIdConv tomorrow and get back to you.

btw.  thanks VERY much for the speedy reply!  this mailing list is amazing!

cheers.

-a
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