From: Madan Manoharan <madan.manoharan@...>
Date: 2006-05-18T12:03:24+09:00
Subject: Asynchronous calls in DRb

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Hello:

I am thinking about writing a distributed application in Ruby where the
application would process all computationally intensive activities in a
'dedicated' server. As I was digging thro' drb/drb.rb, I found the
following:

   def send_message(ref, msg_id, arg, block)  # :nodoc:
      @protocol.send_request(ref, msg_id, arg, block)
      @protocol.recv_reply
<----------- of interest
    end

in the class DRbConn; and


   def main_loop
      Thread.start(@protocol.accept) do |client|
    @grp.add Thread.current
    Thread.current['DRb'] =3D { 'client' =3D> client ,
                              'server' =3D> self }
    loop do
      begin
        succ =3D false
        invoke_method =3D InvokeMethod.new(self, client)
        succ, result =3D invoke_method.perform
        if !succ && verbose
          p result
          result.backtrace.each do |x|
        puts x
          end
        end
        client.send_reply(succ, result) rescue nil
<----------- of interest
      ensure
        unless succ
          client.close
          break
        end
      end
    end
      end
    end
  end

in the class DRbServer.

Clearly, DRb is synchronous. This would mean that my 'client' cannot hand
off the job to the 'server' and do other things when the 'server' is doing
the computationally intensive job (parallel execution of the 'client' and
'server' is not possible as the 'client' will be blocked waiting for reply
from the 'server').

My questions are:
(1) Is there a way for me to make asynchronous calls in DRb; in other words=
,
am I overlooking that functionality?
(2) If there is no asynchronous call capabilities in DRb, why was that not
added when it could have been easily done (not call client.send_reply and
recv_reply)? Is there a technical reason for it?

Any help will be greatly appreciated.

Thanks,
Madan.

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