Using DRbObservable

[Andre Nathan]

Hi

I'm trying to find out how to use the DRbObservable module. This is
what I have so far:

--[ Server ]--
require 'drb/drb'
require 'drb/observer'

class Foo
include DRb:RbObservable
def run
changed
puts 'Notifying observer'
notify_observers('foo message')
end
end

DRb::start_service("druby://localhost:8888", Foo.new)
DRb::thread.join

--[ Client ]--
require 'drb/drb'
require 'drb/observer'

class Warner
def initialize(obj)
obj.add_observer(self)
end
def update(msg)
puts "Update message: #{msg}"
end
end

DRb.start_service
obj = DRbObject.new(nil, 'druby://localhost:8888')
Warner.new(obj)
obj.run


This is the error I get when I run the client after starting the
server:

$ ruby client.rb
(druby://localhost:8888) /usr/local/lib/ruby/1.8/observer.rb:126:in
`add_observer': observer needs to respond to `update' (NoMethodError)
from b.rb:6:in `initialize'
from b.rb:15:in `new'
from b.rb:15

I don't understand it, since I've defined an 'update' method... can
anyone help me on that?

Thanks
Andre

 

[Eric Hodel]

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Hi
=20
I'm trying to find out how to use the DRbObservable module. This is
what I have so far:
=20
--[ Server ]--
require 'drb/drb'
require 'drb/observer'
=20
class Foo
include DRb:RbObservable
def run
changed
puts 'Notifying observer'
notify_observers('foo message')
end
end
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DRb::start_service("druby://localhost:8888", Foo.new)
DRb::thread.join
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--[ Client ]--
require 'drb/drb'
require 'drb/observer'
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class Warner

include DRb:RbUndumped # I added this

def initialize(obj)
obj.add_observer(self)
end
def update(msg)
puts "Update message: #{msg}"
end
end
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DRb.start_service
obj =3D DRbObject.new(nil, 'druby://localhost:8888')
Warner.new(obj)
obj.run
=20
=20
This is the error I get when I run the client after starting the
server:
=20
$ ruby client.rb
(druby://localhost:8888) /usr/local/lib/ruby/1.8/observer.rb:126:in
`add_observer': observer needs to respond to `update' (NoMethodError)
from b.rb:6:in `initialize'
from b.rb:15:in `new'
from b.rb:15
=20
I don't understand it, since I've defined an 'update' method... can
anyone help me on that?

Other than the line I added above, it worked out-of-the box for me using:

ruby 1.8.1 (2003-10-31) [i386-freebsd4]

--=20
Eric Hodel - (e-mail address removed) - http://segment7.net
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[Andre Nathan]

include DRb:RbUndumped # I added this

Other than the line I added above, it worked out-of-the box for me using:

It works! How do I know when I need to include DRb:RbUndumped? I read
the comments on drb.rb, but I'm afraid I don't fully understand them...

Thanks,
Andre

 

[Eric Hodel]

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g:
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It works! How do I know when I need to include DRb:RbUndumped? I read
the comments on drb.rb, but I'm afraid I don't fully understand them...

When you include DRb:RbUndumped in a class, its objects stay on the
host they were created on, and never get passed over the network.
Instead a proxy object (of class DRbObject) gets passed, and operations
on the proxy are sent across the object.

In order to send an object to the other side of the DRb connection, both
sides need to know the class definition for the object, so class Foo
would have to exist on both sides of the connection.

ruby-talk:63281 may also help you.

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Eric Hodel - (e-mail address removed) - http://segment7.net
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[Andre Nathan]

Eric Hodel said:

In order to send an object to the other side of the DRb connection, both
sides need to know the class definition for the object, so class Foo
would have to exist on both sides of the connection.

ruby-talk:63281 may also help you.

Thanks a lot, Eric.

Andre