Bug #4409

DRb: discrepency between and DRb.uri leads to failure to dereference a DrbObject

Added by nbondoux (Nicolas Bondoux) almost 10 years ago. Updated about 9 years ago.

Target version:
ruby -v:
ruby 1.9.2p0 (2010-08-18 revision 29036) [i486-linux]


When a reference on a local object is sent back by a client to a server, it may not be recognised as a local object during marshalling:
An object instance being sent as a reference is wrapped in a DRbObject built by make_proxy with; the DRbObject's uri will be the uri returned by DRb::uri.
When this reference is sent back, DRbObject::_load checks if it matches uri of current server with DRb::here? method.

The problem is that checks that a DRbObject uri is the same as the uri which was used by current DRbServer at his creation, while DRb.uri will return an uri created from the local socket from current thread's connection.

So, when a DRbObject it sent back, it may not be recognized as referencing a local object

Fixing so that it compares with the uri returned by DRb.uri should be enough to quick fix this problem, and seems safe to me.
(I call it a quick fix because I am sure that even with this change, it is possible to build some less realistics cases with the same kind of problem, due to the fact that a same reference may be valid or not depending which client sent it back ...)

Here is a very simple proof of concept:
The server:

require 'drb'
class A
include DRb::DRbUndumped

class TheServer
include DRb::DRbUndumped
def initialize
@a =

def get_a

def is_a(iA)
puts "inside is_a: current DRb.uri:#{DRb.uri}; iA.class = #{iA.class} #{iA.__drburi if DRb::DRbObject === iA}"
@a.eql? iA

def getToken
retVal = @@token.clone
return retVal


theServer =
puts "DRb.uri just after start_service: #{DRb.uri}"

The client:

require 'drb'

theServer =,ARGV.shift)

a = theServer.get_a
puts "a.drburi == #{a.drburi}"
puts "theServer.is_a(a) == #{theServer.is_a(a)}"

the outputs:
server side:
DRb.uri just after start_service: druby://Venus:60106
inside is_a: current DRb.uri:druby://; iA.class = DRb::DRbObject druby://

client side:
a.__drburi == druby://
theServer.is_a(a) == false




Updated by naruse (Yui NARUSE) over 9 years ago

  • Status changed from Open to Assigned
  • Assignee set to seki (Masatoshi Seki)

Updated by nahi (Hiroshi Nakamura) over 9 years ago

  • Target version set to 1.9.3

Updated by seki (Masatoshi Seki) over 9 years ago

  • Status changed from Assigned to Closed
  • % Done changed from 0 to 100

This issue was solved with changeset r32254.
Nicolas, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.

fix [Bug #4409]. add DRbServer#here?

Updated by iamcory (Cory Banks) about 9 years ago

Nicolas, thank you for reporting this issue -

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