From: Ilmari Heikkinen <kig@...>
Date: 2004-12-12T02:41:40+09:00
Subject: Re: Bridging DRb UNIX socket services on two hosts

Eric, Masatoshi, thank you for the tips.

> > You can use GWIdConv to link process (Gateway id Converter)
> >
> > http://segment7.net/projects/ruby/drb/idconv.html
> 
> and Japanese version is here.
> 
> * http://www.druby.org/ilikeruby/drbssh.html
> 

It seems that the gateway approach would need extra work (translating
DRbObject uris) to pass DRbObjects through it? 

As an example:

# ...
# Set up gateway on remote host from unix socket to tcp socket.
#
# def remote_object.hello(x); "Hello, " + x.to_s; end
# def remote_object.self; self; end
# ...

#local:
 DRb.start_service('drbunix:/tmp/local')
 ro = DRbObject.new_with_uri(remote_uri)
 ro[:unix].hello "Foo"  #=> "Hello, Foo"

 a = Object.new
 a.extend DRbUndumped
 def a.to_s; "Bar"; end

 ro.hello a  #=> DRb::DRbConnError: drbunix:/tmp/local -
                 #<Errno::ENOENT: No such file or directory -
                   /tmp/local>

# Which is fixed by switching to a TCP socket instead of the UNIX socket
# for the local service.

 DRb.stop_service
 DRb.start_service
 ro.hello a #=> "Hello, Bar"

# But:

 ro.self.hello "Foo" #=> DRb::DRbConnError: drbunix:/tmp/gw_c -
                         #<Errno::ENOENT: No such file or directory -
                          /tmp/gw_c>


Or am I missing something?



I got it somewhat working by using socat with ssh to tunnel between two
unix sockets. It doesn't need extra TCP sockets for communication, but
would require writing some connection handling code to automatically set
up the tunnels.

Using the objects from above:


First, start services on both hosts:
------------------------------------
#remote:
 DRb.start_service('drbunix:/tmp/remote', remote_object)

#local:
 DRb.start_service('drbunix:/tmp/local')


Next, set up tunnels:
---------------------
# Connect remote /tmp/remote to local /tmp/remote
local$ socat UNIX-LISTEN:/tmp/remote \
             EXEC:'ssh remote socat STDIO UNIX-CONNECT:/tmp/remote'

# Connect local /tmp/local to remote /tmp/local
remote$ socat UNIX-LISTEN:/tmp/local \
              EXEC:'ssh local socat STDIO UNIX-CONNECT:/tmp/local'


Ready to go:
------------
#local:
 ro = DRbObject.new_with_uri('drbunix:/tmp/remote')
 ro.hello "Foo"  #=> "Hello, Foo"
 ro.hello a      #=> "Hello, Bar"
 ro.self.hello a #=> "Hello, Bar"

# But, this doesn't work:
 ro.hello ro  #=> DRb::DRbConnError: drbunix:/tmp/remote - 
                  #<Errno::ECONNREFUSED: Connection refused - 
                    /tmp/remote>