[ruby-core:59794] Re: About unmarshallable DRb objects life-time

On 15 Jan 2014, at 11:58, Rodrigo Rosenfeld Rosas <[e-mail]> wrote:

> A while ago I created a proof-of-concept that I intended to use in my project for using Java libraries from MRI through the use of JRuby and DRb:
> 
> http://rosenfeld.herokuapp.com/en/articles/ruby-rails/2013-07-16-running-java-from-mri-ruby-through-drb
> 
> [it failed randomly]
> 
> The only explanation I could think of, and after analyzing some data I logged from the DRb server, is that that some previously objects created in the DRb server (JRuby application) were being garbage collected even if I still had a reference for them in the MRI side.

This is possible and likely for DRb services.  DRb does nothing to track which objects are converted to DRbObjects and returned to the remote side.  This leaves them eligible for garbage collection if they池e not otherwise referenced.  If you池e returning references to local objects (DRbObjects) to your peers you will need to hold on to the local objects on behalf of your peers.

DRb features pluggable id conversion (id_conv) which allows you to create an alternate way of tracking the referenced local objects and keeping them alive.  There are some examples of this in the sample/ directory.

> [Stuff about DRbUndumped]

The above matters especially so for objects that you extend with DRbUndumped.  This means you must keep the object alive where you create it or the GC will throw it away when no references remain.