From: Jonathan Paisley <jp-www@...>
Date: 2006-03-23T21:34:51+09:00
Subject: Re: drb over pipes

On Thu, 23 Mar 2006 18:42:49 +0900, Reto Schuettel wrote:


> I'd like to establish a drb connection over ssh, preferably over the
> stdin/stdout channels which are provided by ssh itself. Is there a
> drb protocol which uses pipes?  If not, is it easy to implement?
> 
> I've seen that the tcpprotocol uses two connections, this could be
> problem, as pipes/stdin/stdout only provide one stream.
> 
> At the end of the day I'd like to do something like that:
>   # ruby client.rb | ssh host 'ruby agent.rb'

I implemented a quick hack to do this. Hopefully the code below will help.
It's a bit of a mess, but allows you to use a DRb scheme like
'drbfd://0,1' which means uses file descriptors 0 and 1 (stdin/stdout) for
communication.

module DRb
  class DRbFDSocket
    def self.parse_uri(uri)
      if /^drbfd:\/\/(\d+),(\d+)(?:\?(.*))?$/ =~ uri
        [$1.to_i,$2.to_i, $3]
      else
        raise DRbBadScheme,uri unless uri =~ /^drbfd:/
        raise DRbBadURI, "can't parse uri: " + uri
      end
    end
  
    def self.uri_option(uri,config)
      infd,outfd, option = parse_uri(uri)
      return ["drbfd://#{infd},#{outfd}", option]
    end
  
    def self.open(uri,config)
      opts = parse_uri(uri)
      self.new(uri,opts,config)
    end 
  
    def self.open_server(uri,config)
      opts = parse_uri(uri)
      self.new(uri,opts,config)
    end
  
    def initialize(uri,fds,config)
      @uri = uri
      @in_fp = IO.new(fds[0],"r")
      @out_fp = IO.new(fds[1],"w")
      @out_fp.sync = true
      
      @msg = DRbMessage.new(config)
    end
  
    attr_reader :uri
  
    def send_request(ref, msg_id, arg, b)
      begin
        result = @msg.send_request(@out_fp, ref, msg_id, arg, b)
      rescue DRb::DRbConnError
        Kernel.exit! 0
      end
      result
    end
  
    def recv_request
      begin
        result = @msg.recv_request(@in_fp)      
      rescue DRb::DRbConnError
        Kernel.exit! 0
      end
      result
    end
  
    def send_reply(succ, result)
      begin
        result = @msg.send_reply(@out_fp, succ, result)
      rescue DRb::DRbConnError
        Kernel.exit! 0
      end
      result
    end
  
    def recv_reply
      begin
        @msg.recv_reply(@in_fp)
      rescue DRb::DRbConnError
        Kernel.exit! 0
      end
    end

    def alive?
      true
    end
  
    def close
      @in_fp.close
      @out_fp.close
    end
    
    def accept
      if @accepted then
        sleep 60 while true
      else
        @accepted = true
        self
      end
    end
     
  end
  DRbProtocol.add_protocol(DRbFDSocket)
end