# A flaw in tuplespace implementation? **URL:** \ **Category:** Ruby\ **Created:** [April 18, 2006, 9:31am UTC](https://www.ruby-forum.com/t/a-flaw-in-tuplespace-implementation/58081 "2006-04-18T09:31:46Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![guest](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/8dc957/32.png) [@guest](https://www.ruby-forum.com/u/guest)\ **Post date:** [April 18, 2006, 9:31am UTC](https://www.ruby-forum.com/t/a-flaw-in-tuplespace-implementation/58081/1 "2006-04-18T09:31:46Z")
it seems tuplespace’s read operation is not considered important somehow. consider this: class HelloWorld # include DRbUndumped ``` attr_writer :str def initialize(str) @str = str end def _dump#(*args, &block) ``` # Marshal.dump(@str, \*args, &block) ``` end def HelloWorld._load#(*args, &block) ``` # HelloWorld.new(Marshal.load(\*args, &block)) ``` end def to_s @str end ``` end i created a simple hello world class, and released its object into the tuplespace. i then created a simple process doing indefinite loop of reading the object, and another one reading _and_ modifying the object. so what is the problem you say? i don’t want to use pass-by-reference and DRbUndumped, so that each reader process actually gets a copy of the object instead of a reference to it. to do that, i have to define my own marshalling method. after a few run, i realized that the tuplespace seems only need to see a \_dump and a \_load, instead of marshal\_dump and marshal\_load, and that the tuplespace doesn’t even bother if there is no parameter given in the \_dump and \_load or if there is no operation within (returning nil). but the result is still a pass-by-reference. try uncommenting the above class code, and something similar to this will occur: in `init_with_ary': undefined method`size’ for #DRb::DRbUnknown:0x28d21d0 (NoMethodError) any suggestion, or is tuplespace’s read operation isn’t as important as take operation? is this a flaw? ---
**Author:** ![guest](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/8dc957/32.png) [@guest](https://www.ruby-forum.com/u/guest)\ **Post date:** [April 19, 2006, 9:24pm UTC](https://www.ruby-forum.com/t/a-flaw-in-tuplespace-implementation/58081/2 "2006-04-19T21:24:28Z")
On Apr 18, 2006, at 12:31 AM, Guest wrote: > so what is the problem you say? i don’t want to use pass-by-reference > and DRbUndumped, so that each reader process actually gets a copy > of the > object instead of a reference to it. This is exactly how DRb works by default. > to do that, i have to define my own marshalling method. No you don’t. DRb takes care of this for you. You don’t need to do anything other that make sure the class exists on all processes that will hold it. > try uncommenting the above class code, and something similar to > this will > occur: > > in `init_with_ary': undefined method `size’ for > #DRb::DRbUnknown:0x28d21d0 (NoMethodError) If you ever get a DRb::DRbUnknown object you don’t have the class available on one of your remote processes. Fix that problem first. The second problem is that you seem to be passing an object that is neither an Array nor a Hash into the Tuplespace. The code you gave didn’t specify how you were adding the object to the Tuplespace, so a full example is necessary to figure out what’s gone wrong. > any suggestion, or is tuplespace’s read operation isn’t as > important as > take operation? is this a flaw? There is no flaw in Tuplespace. What you want to do works out of the box. Adding extra marshalling doesn’t do anything since ruby’s built- in Marshal does that work for you. Here’s an example that illustrates what you want. Each slave process gets a copy of the object, not a reference to it. You only need to have the class exist in every process that will hold the object: $ cat ts.rb require ‘drb’ require ‘rinda/tuplespace’ require ‘x’ ts = Rinda::TupleSpace.new DRb.start\_service nil, ts puts DRb.uri DRb.thread.join $ cat master.rb require ‘drb’ require ‘x’ DRb.start\_service ts = DRbObject.new nil, ARGV.shift x = X.new x.value = 0 ts.write [:x, x] $ cat slave.rb require ‘drb’ require ‘x’ DRb.start\_service ts = DRbObject.new nil, ARGV.shift obj = ts.read [:x, nil] p obj.last p obj.last.value obj.last.value = 100 p obj.last.value $ cat x.rb class X attr\_accessor :value end $ ruby ts.rb & druby://kaa.coop.robotcoop.com:52189 [2] 17630 $ ruby master.rb druby://kaa.coop.robotcoop.com:52189 $ ruby slave.rb druby://kaa.coop.robotcoop.com:52189 #\ 0 100 $ ruby slave.rb druby://kaa.coop.robotcoop.com:52189 #\ 0 100 – Eric H. - removed\_email\_address@domain.invalid - [http://blog.segment7.net](http://blog.segment7.net) This implementation is HODEL-HASH-9600 compliant [http://trackmap.robotcoop.com](http://trackmap.robotcoop.com) ---
**Author:** ![guest](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/8dc957/32.png) [@guest](https://www.ruby-forum.com/u/guest)\ **Post date:** [April 24, 2006, 6:37am UTC](https://www.ruby-forum.com/t/a-flaw-in-tuplespace-implementation/58081/3 "2006-04-24T06:37:12Z")
have you tried combining the tuplespace and ring API? your example indeed works when ring API is not used, simply providing a tuplespace as a DRb service instead of a Ring service. but i’d rather have some code that would enable me to automatically find a tuplespace, not manually by passing the tuplespace’s uri. i modified your code to show you the problem i faced in my first post, and added two ring files (name server and space provider, which is actually your code as listed in your segment7 site) Eric H. wrote: > $ cat ts.rb > not needed, since i am using ring API to provide the tuplespace $ cat master.rb require “rinda/ring” require ‘drb’ require ‘x’ DRb.start\_service #ts = DRbObject.new nil, ARGV.shift ringServer = Rinda::RingFinger.primary ts = ringServer.read([:name, :TupleSpace, nil, nil])[2] ts = Rinda::TupleSpaceProxy.new ts x = X.new x.value = 0 ts.write [:x, x] $ cat slave.rb require “rinda/ring” require ‘drb’ require ‘x’ DRb.start\_service #ts = DRbObject.new nil, ARGV.shift ringServer = Rinda::RingFinger.primary ts = ringServer.read([:name, :TupleSpace, nil, nil])[2] ts = Rinda::TupleSpaceProxy.new ts obj = ts.read [:x, nil] p obj.last p obj.last.value obj.last.value = 100 p obj.last.value $ cat name\_server.rb require “rinda/ring” require “rinda/tuplespace” DRb.start\_service Rinda::RingServer.new Rinda::TupleSpace.new DRb.thread.join $ cat space\_provider.rb require “rinda/ring” require “rinda/tuplespace” DRb.start\_service ts = Rinda::TupleSpace.new provider = Rinda::RingProvider.new :TupleSpace, ts, “Tuple Space” provider.provide DRb.thread.join $ ruby name\_server.rb & $ ruby space\_provider.rb & $ ruby master.rb & …[error strings] in `init_with_ary': undefined method`size’ for DRb::DRbUnknown:0x28d21d0 (NoMethodError) …[another error strings] $ ruby slave.rb ---
**Author:** ![guest](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/8dc957/32.png) [@guest](https://www.ruby-forum.com/u/guest)\ **Post date:** [April 24, 2006, 8:44pm UTC](https://www.ruby-forum.com/t/a-flaw-in-tuplespace-implementation/58081/4 "2006-04-24T20:44:19Z")
On Apr 23, 2006, at 9:37 PM, removed\_email\_address@domain.invalid wrote: > have you tried combining the tuplespace and ring API? It makes no difference if you use Rinda::Ring or not. > your example indeed works when ring API is not used, simply > providing a tuplespace as a DRb service instead of a Ring service. > but i’d rather have some code that would enable me to automatically > find a tuplespace, not manually by passing the tuplespace’s uri. So just throw in Rinda::Ring. > i modified your code to show you the problem i faced in my first > post, and added two ring files (name server and space provider, > which is actually your code as listed in your segment7 site) Since you didn’t respond to the same thread I’ve since lost that email. I suggest you subscribe to the mailing list rather than post through the forum. $ cat rs.rb require ‘rinda/ring’ require ‘rinda/tuplespace’ DRb.start\_service Rinda::RingServer.new Rinda::TupleSpace.new DRb.thread.join $ cat ts.rb require ‘drb’ require ‘rinda/tuplespace’ require ‘rinda/ring’ require ‘x’ DRb.start\_service ts = Rinda::TupleSpace.new provider = Rinda::RingProvider.new :TupleSpace, ts, ‘Tuple Space’ provider.provide DRb.thread.join $ cat master.rb require ‘drb’ require ‘rinda/ring’ require ‘x’ DRb.start\_service rs = Rinda::RingFinger.primary tuple = rs.read [:name, :TupleSpace, nil, nil] ts = tuple[2] x = X.new x.value = 0 ts.write [:x, x] $ cat slave.rb require ‘drb’ require ‘rinda/ring’ require ‘x’ DRb.start\_service rs = Rinda::RingFinger.primary tuple = rs.read [:name, :TupleSpace, nil, nil] ts = tuple[2] obj = ts.read [:x, nil] p obj.last p obj.last.value obj.last.value = 100 p obj.last.value $ cat x.rb class X attr\_accessor :value end $ ruby rs.rb & [1] 28527 $ ruby ts.rb & [2] 28528 $ ruby master.rb $ ruby slave.rb #\ 0 100 – Eric H. - removed\_email\_address@domain.invalid - [http://blog.segment7.net](http://blog.segment7.net) This implementation is HODEL-HASH-9600 compliant [http://trackmap.robotcoop.com](http://trackmap.robotcoop.com)