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

[Steve Loughran]

Hello,

I am trying to design the CDDLM deployment API in the WS-RF style, and 
am having
problems with understanding the best way to make effective use of resource
lifetimes in a fault-tolerant environment. I would like some assistance :

Scenario
========

-We are supporting automated deployment of applications to allocated 
resources.

-Applications are deployed through a deployment portal; the applications
may deployed on hosts that are not running the services necessary for direct
communication, or behind a firewall.

-The deployment portal is in a DMZ or otherwise reachable by all 
callers. All
EPRs must therefore refer to the portal.

I had originally envisaged that to destroy an application,a <wsrl:Destroy/>
call could be made.

Yet I have a problem. I want to be fault tolerant without relying on
load balancing routers, round-robin DNS or mDNS hostnames.

In the stateful resources pattern, I can have EPRs that contain policy 
on how to
renew an EPR. Presumably that would list a service group location from 
whence
any other deployment portal EPR could be found that could renew an 
invalid EPR
for us (e.g. by extracting application identification info and 
constructing a
new EPR referring to the local portal)

This all seems workable, ignoring the problem of specifying the policy of
updating EPRs. Presumably we'd have to do an app specific algorithm and 
policy.

What is causing me trouble is resource lifetimes. Once I have a world in 
which
you can have multiple EPRs all referring to the same resource, the same 
deployed
application, what does that mean for WS-ResourceLifetime?

If I have multiple, different EPRs, is it right that a <wsrl:Destroy/> 
call on
one of them should terminate the final application? What if there was 
state on
each portal related to the EPR that needed cleaning up at the end of a
conversation, and so required either that destroy call, or timeout-initiated
destruction?

I think the problem here is "what should I be modelling with the implicit
resource pattern"? . Is it:-

(a) the resource in question *is* the application. When the resource is
destroyed, so is the application.

(b) the resource in question is merely a view of the application. When the
resource is destroyed, the view goes away, but the application remains until
destroyed by some other means.

-Steve