From: Phil Tomson <rubyfan@...>
Date: 2006-08-31T03:31:11+09:00
Subject: Drb and mystery ports (and Queue question)

I'm trying to make a simple message queue. Messages can be added to
the queue by drb clients and the main queue class just sits in a
different thread and goes through the queue trying to send them out.
I figured I'd use the Queue class from Thread.

Here's the server:

#server
require 'thread'
require 'drb'

class Message
  @@num = 0
  def initialize message = "Time is now: #{Time.now}",&b
    @num = @@num
    @message = message
    if b
      @block = b
    else
      @block = lambda{rand > 0.5}
    end
    @@num +=1
  end

  def try_send
    @block.call
  end

  def to_s
    "#{self.class} number: #{@num} message: #{@message}"
  end
end

class MsgQueue
  include DRb::DRbUndumped
  attr_reader :thread
  def initialize sleeptime = rand
    @queue = Queue.new
    @sleeptime = sleeptime
  end

  def method_missing methid, *args, &b
    @queue.send(methid, *args, &b)
  end

  def start
    @thread = Thread.new {
      loop do
        if @queue.size != 0
          msg = @queue.shift
          if msg.try_send
            puts "sending of message: #{msg} succeeded!"
          else
            puts "sending failed...."
            @queue << msg #put it back in queue
          end
        else
          puts "...queue empty..."
        end
        sleep @sleeptime
      end
    }
  end

  def start_works
    @thread = Thread.new {
      loop do
        puts "queue size is now: #{@queue.size}"
        sleep 0.1
      end
    }
  end
end

if __FILE__ == $0
  mq = MsgQueue.new 0.5
  DRb.start_service('druby://localhost:9759', mq)
  mq.start

  mq.thread.join
  DRb.thread.join

end # server


And here's the client:

#client:
require 'msgqueue'
require 'drb'

DRb.start_service()
mq = DRbObject.new(nil, 'druby://localhost:9759')
20.times do
  puts "send message..."
  mq << Message.new( "message from client...")
  sleep 0.1
end #client


When I run the server and then the client I usually end up with something like:
  $> ruby msgqueue.rb
  ...queue empty...
  ...queue empty...
  sending failed....
  sending of message: Message number: 1 message: message from
client...     succeeded!
sending of message: Message number: 2 message: message from client... succeeded!
sending failed....
/usr/local/lib/ruby/1.8/drb/drb.rb:733:in `open':
druby://phpe-dev-10.hf.intel.com:33135 - #<Errno::ECONNREFUSED:
Connection refused - connect
                      ^^^^^^^
(2)> (DRb::DRbConnError)
        from msgqueue.rb:73:in `join'
        from msgqueue.rb:73


So what's with the port number 33135?  It's not a port I'm using.

also, is Queue (the one that comes in with require 'thread' ) good for
this kind of use?  It's advertised as being safe for multiple thread
access, but in this case there are also multiple processes involved as
well.

Phil