# Do i have to use DRbUndumped?

**URL:** <https://www.ruby-forum.com/t/do-i-have-to-use-drbundumped/57396>\
**Category:** Ruby\
**Created:** [April 10, 2006, 5:26pm UTC](https://www.ruby-forum.com/t/do-i-have-to-use-drbundumped/57396 "2006-04-10T17:26:06Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![holy\_sinner](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/9d8465/32.png) [@holy\_sinner](https://www.ruby-forum.com/u/holy_sinner)\
**Post date:** [April 10, 2006, 5:26pm UTC](https://www.ruby-forum.com/t/do-i-have-to-use-drbundumped/57396/1 "2006-04-10T17:26:06Z")

</div>

i am currently using Ruby 1.8.4 and DRb 2.0.4, and i am stuck with some  
marshalling problem  
related to tuplespace. this is my hello world code using tuplespace

* * *

#HelloWorld.rb  
require “rinda/ring”

class HelloWorld

# include DRbUndumped

```
def initialize(str)
	@str = str
end
def _dump(dumpDepth)
	@str
end
def HelloWorld._load(srcString)
	HelloWorld.new(srcString)
end
def to_s
	@str
end

```

end

DRb.start\_service

ringServer = Rinda::RingFinger.primary  
tupleSpace = ringServer.read([:name, :TupleSpace, nil, nil])[2]  
tupleSpace = Rinda::TupleSpaceProxy.new tupleSpace

tupleSpace.write([“helloWorldObject”, HelloWorld.new(“Hello World!”)])

aHelloWorldObject = tupleSpace.take([“helloWorldObject”, nil])  
puts aHelloWorldObject[1]

#DRb.thread.join

* * *

my problem is that \_dump doesn’t work, because the HelloWorld object  
gets converted into  
DRb::DRbUnknown, which can not be converted into tuple to be inserted  
into the tuplespace. it does  
not occur if i use DRb::DRbUndumped, but i think using DRb::DRbUndumped  
is rather unsecure if i  
try using read instead of take to get the object out of the tuplespace.  
the question is:

- what’s wrong with my \_dump (and \_load) ? do i have to use  
DRb::DRbUndumped ?
- do i have to use Rinda::Ring to work with Rinda::TupleSpace ?

---

<div class="post-metadata">

**Author:** ![holy\_sinner](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/9d8465/32.png) [@holy\_sinner](https://www.ruby-forum.com/u/holy_sinner)\
**Post date:** [April 10, 2006, 5:44pm UTC](https://www.ruby-forum.com/t/do-i-have-to-use-drbundumped/57396/2 "2006-04-10T17:44:44Z")

</div>

yn Tue, 11 Apr 2006, holy sinner wrote:

> - what’s wrong with my \_dump (and \_load) ? do i have to use DRb::DRbUndumped ?

harp:~ \> cat a.rb  
require ‘rinda/ring’

class HelloWorld  
def initialize(str) @str = str end  
def \_dump(\*a, &b) Marshal.dump(@str, \*a, &b) end  
def HelloWorld.\_load(\*a, &b) new(Marshal.load(\*a, &b)) end  
def to\_s() @str end  
end

hello\_world = HelloWorld.new ‘hello world’

puts(Marshal.load(Marshal.dump(hello\_world)))

harp:~ \> ruby a.rb  
hello world

-a

---

<div class="post-metadata">

**Author:** ![holy\_sinner](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/9d8465/32.png) [@holy\_sinner](https://www.ruby-forum.com/u/holy_sinner)\
**Post date:** [April 10, 2006, 8:12pm UTC](https://www.ruby-forum.com/t/do-i-have-to-use-drbundumped/57396/3 "2006-04-10T20:12:18Z")

</div>

On Apr 10, 2006, at 8:23 AM, holy sinner wrote:

> def initialize(str)  
> end  
> aHelloWorldObject = tupleSpace.take([“helloWorldObject”, nil])  
> DRb::DRbUndumped is rather unsecure if i try using read instead of  
> take to get the object out of the tuplespace.

Unsecure? Why?

If you’re worried about losing the object due to the taking process  
dying use a TupleSpaceProxy. It ensures that the object won’t get lost.

> the question is:
> 
> - what’s wrong with my \_dump (and \_load) ? do i have to use  
> DRb::DRbUndumped ?

You should really use marshal\_load and marshal\_dump.  
DRb::DRbUndumped must be used on objects that don’t have their class  
present on all ruby processes in the system.

> - do i have to use Rinda::Ring to work with Rinda::TupleSpace ?

No. Rinda::Ring lets you find DRb services easily. It is zeroconf  
for DRb.

–  
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)

---

<div class="post-metadata">

**Author:** ![holy\_sinner](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/9d8465/32.png) [@holy\_sinner](https://www.ruby-forum.com/u/holy_sinner)\
**Post date:** [April 11, 2006, 9:29am UTC](https://www.ruby-forum.com/t/do-i-have-to-use-drbundumped/57396/4 "2006-04-11T09:29:30Z")

</div>

thanx, it indeed can replace DRbUndumped, but with the same consequence:  
it is still a pass-by-reference thing, which is rather dangerous to be  
used when working with tuplespace’s read operation.

consider this, what if two clients read the same object written by some  
server, and one of the client modifies the object (hoping it would only  
change his “copy of object”). using DRbUndumped or this alternative  
marshalling is a bad method, since the object would still appear changed  
on both clients.

what i really need is a pass-by-value marshalling so that the one  
written into the space is actually the copy of the real object, and not  
the reference to it. can anyone help me? i believe the drawback of  
having the client to own physical copy of the object’s class (i.e. the  
object’s source code) is not something to be worried about. or is there  
any other disadvantage of using pass-by-value compared to using  
pass-by-reference, maybe speed / execution time?

i currently combine Rinda::TupleSpace and Rinda::Ring instead of putting  
the tuplespace as a DRbServer’s front object, trying to make the whole  
thing works like jini

---

<div class="post-metadata">

**Author:** ![holy\_sinner](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/9d8465/32.png) [@holy\_sinner](https://www.ruby-forum.com/u/holy_sinner)\
**Post date:** [April 11, 2006, 7:50pm UTC](https://www.ruby-forum.com/t/do-i-have-to-use-drbundumped/57396/5 "2006-04-11T19:50:01Z")

</div>

Not quoting past messages is very bad form. Please quote relevant  
parts of the message you are replying to.

On Apr 11, 2006, at 12:29 AM, xaea alvein wrote:

> thanx, it indeed can replace DRbUndumped, but with the same  
> consequence:  
> it is still a pass-by-reference thing, which is rather dangerous to be  
> used when working with tuplespace’s read operation.

#read is not dangerous. #take can lose the object if the taking node  
quits before receiving the object, so you should use a  
TupleSpaceProxy whenever you take tuples.

> consider this, what if two clients read the same object written by  
> some  
> server, and one of the client modifies the object (hoping it would  
> only  
> change his “copy of object”). using DRbUndumped or this alternative  
> marshalling is a bad method, since the object would still appear  
> changed  
> on both clients.

That is as intended. It is called Distributed Ruby after all.

It sounds like you really want some kind of access control or locking  
mechanism.

> what i really need is a pass-by-value marshalling so that the one  
> written into the space is actually the copy of the real object, and  
> not  
> the reference to it. can anyone help me? i believe the drawback of  
> having the client to own physical copy of the object’s class (i.e. the  
> object’s source code) is not something to be worried about. or is  
> there  
> any other disadvantage of using pass-by-value compared to using  
> pass-by-reference, maybe speed / execution time?

Your problem seems to be an implementation detail. It seems you want  
an object usable by only one node at a time.

You should either use take to remove the object from the TupleSpace  
or provide locking via the TupleSpace to prevent other nodes from  
fiddling with your object while one node is working on it.

Pass by reference allows a transparent object space. Pass by value  
is going to complicate your design much more than building atop of  
the primitive operations TupleSpace provides.

> i currently combine Rinda::TupleSpace and Rinda::Ring instead of  
> putting  
> the tuplespace as a DRbServer’s front object, trying to make the whole  
> thing works like jini

I don’t understand what this means.

–  
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)

---

<div class="post-metadata">

**Author:** ![holy\_sinner](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/9d8465/32.png) [@holy\_sinner](https://www.ruby-forum.com/u/holy_sinner)\
**Post date:** [April 12, 2006, 9:48am UTC](https://www.ruby-forum.com/t/do-i-have-to-use-drbundumped/57396/6 "2006-04-12T09:48:49Z")

</div>

Eric H. wrote:

> Not quoting past messages is very bad form. Please quote relevant  
> parts of the message you are replying to.

i am very sorry

i guess i better give an example:

a master/server M has an object A that he want to put into tuplespace  
(using write).  
a worker/client C1 wants to have a copy of the object A for himself to  
work with (by using read, instead of take).  
a worker/client C2 also wants copy of object A (also using read).

the problem is, i currently only know that M have to use  
DRb::DRbUndumped (or use the alternative dumping as listed in the first  
reply of this topic by -a) if A is to be put into tuplespace, which is a  
pass-by-reference, meaning that the copy of A that each client C1 and C2  
has is actually the very same object currently residing in master M  
(since the one put into the tuplespace is none other than DRbObject  
reference to the object A)

what i need is that M to put exactly a copy of object A into the  
tuplespace instead just a reference to the object A, and C1 and C2 to  
each have the copy of the copy of object A that was previously inserted  
into the tuplespace, so that if C1 or C2 each modifies the copy (of copy  
of A, if that matters), it only appears to himself. this is what i  
believe is a pass-by-value

> …
> 
> #read is not dangerous. #take can lose the object if the taking node  
> quits before receiving the object, so you should use a  
> TupleSpaceProxy whenever you take tuples.

i am using tuplespaceproxy, thank you

> That is as intended. It is called Distributed Ruby after all.
> 
> It sounds like you really want some kind of access control or locking  
> mechanism.
> 
> …
> 
> Your problem seems to be an implementation detail. It seems you want  
> an object usable by only one node at a time.
> 
> You should either use take to remove the object from the TupleSpace  
> or provide locking via the TupleSpace to prevent other nodes from  
> fiddling with your object while one node is working on it.
> 
> Pass by reference allows a transparent object space. Pass by value  
> is going to complicate your design much more than building atop of  
> the primitive operations TupleSpace provides.
> 
> > i currently combine Rinda::TupleSpace and Rinda::Ring instead of  
> > putting  
> > the tuplespace as a DRbServer’s front object, trying to make the whole  
> > thing works like jini
> 
> I don’t understand what this means.

javaspace is a service to jini. for further reference, please use  
[http://www.jini.org](http://www.jini.org)

i am using Rinda::TupleSpace and Rinda::Ring based on your example, Mr.  
Eric, and i prefer using it compared to serving a TupleSpace instance as  
a DRbServer’s front object, since the Ring API works somehow like jini’s  
lookup service

---

<div class="post-metadata">

**Author:** ![holy\_sinner](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/9d8465/32.png) [@holy\_sinner](https://www.ruby-forum.com/u/holy_sinner)\
**Post date:** [April 13, 2006, 7:20pm UTC](https://www.ruby-forum.com/t/do-i-have-to-use-drbundumped/57396/7 "2006-04-13T19:20:26Z")

</div>

maybe some code could illustrate better:

[assuming there is a TupleSpace-based name server and TupleSpace  
provider, like the one given in Mr. Eric H.'s Ring example in his  
Segment7 site]

* * *

#HelloWorld.rb

class HelloWorld  
attr\_writer :str

# you can use DRbUndumped or the following.

# either results in the same

```
def initialize(str)
	@str = str
end
def _dump(*args, &block)
	Marshall.dump(@str, *args, &block)
end
def HelloWorld._load(*args, &block)
	HelloWorld.new(Marshall.load(*args, &block))
end
def to_s
	@str
end

```

end

* * *

#Master.rb

require “rinda/ring”  
require “HelloWorld”

DRb.start\_service

ringServer = Rinda::RingFinger.primary  
tupleSpace = ringServer.read([:name, :TupleSpace, nil, nil])[2]  
tupleSpace = Rinda::TupleSpaceProxy.new tupleSpace

tupleSpace.write([“helloWorldObject”, HelloWorld.new(“Hello World!”)])

DRb.thread.join

* * *

#Client1.rb

require “rinda/ring”  
#require “HelloWorld”

DRb.start\_service

ringServer = Rinda::RingFinger.primary  
tupleSpace = ringServer.read([:name, :TupleSpace, nil, nil])[2]  
tupleSpace = Rinda::TupleSpaceProxy.new tupleSpace

loop {  
aHelloWorldObject = tupleSpace.read([“helloWorldObject”, nil])  
puts aHelloWorldObject[1]  
}

* * *

#Client2.rb

require “rinda/ring”  
#require “HelloWorld”

DRb.start\_service

ringServer = Rinda::RingFinger.primary  
tupleSpace = ringServer.read([:name, :TupleSpace, nil, nil])[2]  
tupleSpace = Rinda::TupleSpaceProxy.new tupleSpace

aHelloWorldObject = tupleSpace.read([“helloWorldObject”, nil])  
aHelloWorldObject[1].str = “Goodbye!”

* * *

anyone can help me with HelloWorld’s dumping alternative, or do i have o  
use DRbUndumped / pass-by-reference? i am expecting that each client  
gets a fresh copy of HelloWorld object, not a reference to it

xaea alvein wrote:

> i guess i better give an example:
> 
> a master/server M has an object A that he want to put into tuplespace  
> (using write).  
> a worker/client C1 wants to have a copy of the object A for himself to  
> work with (by using read, instead of take).  
> a worker/client C2 also wants copy of object A (also using read).
> 
> the problem is, i currently only know that M have to use  
> DRb::DRbUndumped (or use the alternative dumping as listed in the first  
> reply of this topic by -a) if A is to be put into tuplespace, which is a  
> pass-by-reference, meaning that the copy of A that each client C1 and C2  
> has is actually the very same object currently residing in master M  
> (since the one put into the tuplespace is none other than DRbObject  
> reference to the object A)
> 
> what i need is that M to put exactly a copy of object A into the  
> tuplespace instead just a reference to the object A, and C1 and C2 to  
> each have the copy of the copy of object A that was previously inserted  
> into the tuplespace, so that if C1 or C2 each modifies the copy (of copy  
> of A, if that matters), it only appears to himself. this is what i  
> believe is a pass-by-value