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At MindCamp 2.0 I was asked about how you would replicate a TupleSpace. I whipped up the following implementation:

class Rinda::TupleSpaceReplicator

  attr_accessor :debug

  attr_reader :local_tuplespace, :remote_tuplespace

  def initialize(remote_tuplespace, templates)
    @local_tuplespace = Rinda::TupleSpace.new
    @remote_tuplespace = remote_tuplespace
    @templates = templates

    @debug = false

    @replicators = ThreadGroup.new
  end

  def replicate
    @templates.each do |template|
      %w[write take].each do |type|
        make_replicator type, template
      end
    end
  end

  def make_replicator(event_type, template)
    thread = Thread.start do
      observer = @remote_tuplespace.notify event_type, template
      observer.each do |event, tuple|
        break if event == 'close'
        @local_tuplespace.send event, tuple
        $stderr.puts "master #{event}: #{tuple.inspect}" if @debug
      end
    end

    @replicators.add thread
  end

end

The core of this is the make_replicator method. It replicates tuples of the specified template from the remote tuplespace to the local tuplespace.

Here it is in operation:

# master.rb
require 'rinda/tuplespace'

here = 'druby://127.0.0.1:10000'
ts = Rinda::TupleSpace.new

DRb.start_service here, ts
DRb.thread.join

# slave.rb
require 'rinda/tuplespace'
require 'tuplespace_replicator'

here = 'druby://127.0.0.1:10001'
there = 'druby://127.0.0.1:10000'

rts = DRbObject.new_with_uri there
repl = Rinda::TupleSpaceReplicator.new rts, [[nil]]

DRb.start_service here, repl.local_tuplespace
repl.replicate
DRb.thread.join

# test.rb
require 'drb'

ts1 = DRbObject.new_with_uri 'druby://127.0.0.1:10000'
ts2 = DRbObject.new_with_uri 'druby://127.0.0.1:10001'

ts1.write [0]
ts1.write [1]
ts1.write [2]

p ts2.read_all([nil])

ts1.take [0]
ts1.take [1]
ts1.take [2]

p ts2.read_all([nil])

And then we run it!

$ ruby master.rb &
[1] 18289
$ ruby slave.rb &
[2] 18290
$ ruby test.rb
[[0], [1], [2]]
[]
$