DRb object mutation issues

Ruby
1

file 1

require ‘drb/drb’
require ‘thread’
DRb.start_service(“druby://:1234”, Hash.new.extend(DRbUndumped))
DRb.thread.join

EOF

file 2

require ‘drb/drb’
d = DRbObject.new_with_uri(“druby://:1234”)
d[0] = ‘zero’
d[0] #=> “zero”
d[0].slice!(0, 1)
d[0] #=> “zero”

file 3

h = Hash.new
h[0] = ‘zero’
h[0].slice!(0, 1)
h[0] #=> “ero”

how can I change the state of the distributed hash’s values?

2

Nwallins wrote:

d = DRbObject.new_with_uri(“druby://:1234”)

how can I change the state of the distributed hash’s values?

Some options:

  1. make the values DRbUndumped, too.

  2. use non-destructive methods on the values:

    d[0] = d[0].slice(0, 1)

  3. define a method on your front object that handles everything at
    server side, so the client says this:

    idx = 0
    d.slice_at_index(idx,0,1)

3

On Jul 11, 3:02 pm, Joel VanderWerf [email protected] wrote:

d = DRbObject.new_with_uri(“druby://:1234”)

  1. define a method on your front object that handles everything at
    server side, so the client says this:

    idx = 0
    d.slice_at_index(idx,0,1)

–
vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

Joel,

thanks for the response.

(1) is not viable, as you cannot make objects or classes undumpable
from the client
(2) does not address the issue – to mutate the value
(3) is interesting, but violates the architecture that my simplified
example is distilled from

I’m still wondering if the demonstrated behavior is a bug or a
feature. I’m leaning towards the former :wink:

  • Rick
4

On Jul 12, 1:50 pm, Nwallins [email protected] wrote:

DRb.start_service(“druby://:1234”, Hash.new.extend(DRbUndumped))

  1. make the values DRbUndumped, too.

(3) is interesting, but violates the architecture that my simplified
require ‘drb/drb’
d = DRbObject.new_with_uri(“druby://:1234”)
d[0] = ‘zero’.extend(DRbUndumped)

DRb::DRbConnError: DRb::DRbServerNotFound

from /usr/lib/ruby/1.8/drb/drb.rb:1650:in `current_server’

  • Rick

There is also this approach, but it still fails:

d[0].extend(DRbUndumped)
=> “zero”
d[0].slice!(0,1)
=> “z”
d[0]
=> “zero”

  • Rick
5

On Jul 12, 1:46 pm, Nwallins [email protected] wrote:

EOF

h = Hash.new

  1. use non-destructive methods on the values:
    vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

I’m still wondering if the demonstrated behavior is a bug or a
feature. I’m leaning towards the former :wink:

  • Rick

Regarding my comment for (1), I presume you mean something like this:

file 2

require ‘drb/drb’
d = DRbObject.new_with_uri(“druby://:1234”)
d[0] = ‘zero’.extend(DRbUndumped)

DRb::DRbConnError: DRb::DRbServerNotFound

from /usr/lib/ruby/1.8/drb/drb.rb:1650:in `current_server’

  • Rick
6

Nwallins wrote:

  1. make the values DRbUndumped, too.
    …
    (1) is not viable, as you cannot make objects or classes undumpable
    from the client

What about extend-ing the hash to make its values undumped as soon as
they are assigned? (Or subclass Hash to do this.)

7

On Jul 11, 2007, at 12:15 PM, Nwallins wrote:

d = DRbObject.new_with_uri(“druby://:1234”)

how can I change the state of the distributed hash’s values?

cfp:~ > ruby a.rb server &
[1] 2778

cfp:~ > ruby a.rb client
316250
“druby://8-159.boulder.noaa.gov:1234”
zero
#DRb::DRbObject:0x986ac
ero
#DRb::DRbObject:0x96014

cfp:~ > cat a.rb
#! /usr/bin/env ruby
require ‘drb/drb’
require ‘thread’

class Table
def initialize
extend DRbUndumped
@table = {}
end
def [] k
@table[k.to_s]
end
def []= k, v
v.extend DRbUndumped
@table[k.to_s] = v
end
class ::Object
def Table(*a, &b) Table.new(*a, &b) end
end
end

mode = ARGV.shift || ‘server’
case mode
when ‘server’
DRb.start_service “druby://:1234”, Table()
DRb.thread.join

when ‘client’
d = DRbObject.new_with_uri “druby://:1234”

 # this marshals data across the wire to server, never to come

back as
# anything other that a remote object
d[0] = ‘zero’

 # the repercusions are that you can only call remote methods on the
 # object, including to_s, inspect, etc which all act as a drb

object
p d[0].__drbref
p d[0].__drburi
puts d[0].downcase
puts d[0]

 # on the other hand the client may detruct object on the server
 d[0].slice!(0, 1)
 puts d[0].downcase
 puts d[0]

end

-a