From: Joel VanderWerf <vjoel@...>
Date: 2008-10-14T04:19:35+09:00
Subject: Re: Accessing Ruby Object in Memory

Thomas B. wrote:
> Bryan Richardson wrote:
>> Hello all,
>>
>> I have a long running Ruby simulation in which data is stored to Ruby
>> hashes throughout the simulation.  I'd like to be able to access the
>> hashes in memory from another Ruby script while the simulation is still
>> running to see what the progress of the simulation is (rather than
>> printing to the screen, using log4r, etc.  Is this possible?  If so, any
>> suggestions how to do so?
> 
> Hello. I guess this is not possible, and even if it is, it is not a good 
> idea to do this. Probably a much better idea would be to start a TCP 
> server in the daemon, and connect to it from the other program, and 
> communicate using some simple protocol. Another idea could be to write 
> some progress info into a file, and open the file from the other 
> process, but then you'll have to handle some concurrency problems (not 
> very hard, I guess, it will be enough to wait a moment and retry on file 
> opening failure). But still I think the server is a better and more 
> standard way to do this. Have a look at TCPServer and TCPSocket in 
> 'socket', it is not hard.

DRb is the canonical way of doing this if both processes are ruby 
programs. For example:

== server.rb ==
require 'drb'

uri = "drbunix:/tmp/my-simulation.sock" # use "localhost:4444" on win
h = {1=>2, 3=>4}
DRb.start_service(uri, h)
DRb.thread.join

== client.rb ==
require 'drb'

uri = "drbunix:/tmp/my-simulation.sock" # use "localhost:4444" on win
DRb.start_service(nil, nil)
server_object = DRbObject.new(nil, uri)

p server_object.keys
server_object.each do |k, v|
   p [k, v]
end

================
Output:

[1, 3]
[1, 2]
[3, 4]

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