[ogsa-wg] effective use of resource lifetimes in grid infrastructure

[Steve Loughran]

Ian Foster wrote:
>   Steve:
> 
> A variety of semantics and connections are possible between a 
> "WS-Resource" and an "entity that the WS-Resource repesents", including 
> both your (a) and (b) below. I don't believe that the implied resource 
> pattern implies that one particular approach be adopted.
> 
> The following are some rough notes on how we have chosen to handle 
> things in the GT4 GRAM service. This may perhaps be relevant to your 
> problem.
> 
> The approach that we take in GT4 GRAM is as follows:
> 
> 1) A GRAM ManagedJobFactory defines a "create job" operation that:
> 
> a) creates a job, and also
> 
> b) creates a ManagedJob WS-Resource, which represents the resource 
> manager's view of the job.
> 
> 2) The ManagedJob WS-Resource and the job are then linked as follows:
> 
> a) Destroying the ManagedJob WS-Resource kills the job
> 
> b) State changes in the job are reflected in the ManagedJob WS-Resource
> 
> c) Termination of the job also destroys the ManagedJob WS-Resource, but 
> not immediately: we find that you typically want to leave the managedjob 
> state around for "a while" after the job terminates to allow clients to 
> figure out what happened to the job after the fact
> 
> Regards -- Ian.

Ian,

What is your fault tolerance strategy here?

Is every ManagedJob WS-Resource hosted on the same host (and perhaps, 
same process) as the job itself?

This would mean that there is no way for the managedjob EPR to fail 
without the job itself failing, but would require the entire set of job 
hosts to be visible for inbound SOAP messages. And prevent you moving a 
job from one node to another without some difficultly (the classic CORBA 
object-moved problem, I believe, though HTTP 304 responses would work if 
only SOAP stacks processed them reliably)

I am trying to do a design which would enable (though would not require) 
only a subset of nodes -call them portal nodes- to be visible to outside 
callers, with the rest of the nodes only accessible to the portal 
itself. Once I assume this architecture, modelling the resources gets 
complex, as EPRs contain routing info that may become invalid if a 
portal node fails.

-steve