[glue-wg] Endpoints and ComputingService, relationships between services. Some thoughs

[Florido Paganelli]

On 2012-08-20 12:51, stephen.burke at stfc.ac.uk wrote:
> glue-wg-bounces at ogf.org [mailto:glue-wg-bounces at ogf.org] On
>> Behalf Of Florido Paganelli said: Suppose the same machine hosts
>> two RELATED services, that is, one needs the other one for proper
>> functionality. For example a delegation service is needed to submit
>> a job to a job execution service.
>
> This sounds to me like *one* Service with two different types of
> Endpoint. For example a VOMS server can have voms endpoints to return
> credentials and voms-admin endpoints to manage VO membership, but
> they both talk to the same database so there is only one Service.
> This is the biggest structural change from GLUE 1 to 2 - in GLUE 1
> there are only GlueService objects representing endpoints, but in
> GLUE 2 we introduced the Service concept exactly so they could be
> grouped together if they provide a shared functionality.
>
> Stephen
>

Your observations are right, however the model of service you have in 
mind is monolithic and not distributed; I am in fact speaking about 
something that was not considered during the GLUE2 "making of".

I am speaking about a service wrt the following use case:

1) the service, by design, *has* distributed endpoints, that might run 
on different hosts.
2) a client would like to gather the endpoints belonging to that 
distributed service.

You can imagine an information system, like a resource-bdii, that runs 
independenlty from the resource, maybe on a different host. How to 
relate the resource-bdii endpoint with the resources it serves?

I imagine a client collecting information from some index in which you 
only have GLUE2 endpoints and service records.

How to relate these records and infer, for example, that they're on the 
same machine and/or serve the same resource?

Parsing the EndpointURL would be a choice, but you don't need GLUE2 for 
that...

All in all we could call these "service-service" relationships.
-- 
Florido Paganelli
Lund University - Particle Physics
ARC Middleware
EMI Project