hostname 0-n (was Re: [jsdl-wg] Issues for todays phone conference)

[Karl Czajkowski]

On Apr 14, Andreas Savva loaded a tape reading:
> I have a followup question on changing the hostname from 0-1 to 0-n. In 
> the spec we had said that hostname may refer to a single host or any 
> logical group of hosts. (And that logical group could be anything 
> understood by the system.)  The intention was to be able to do something 
> like
> <Resource>
>  <HostName> the-nine-muses </HostName>
>    ...
>  <ResourceCount> <exact>2.0<exact></ResourceCount>
> </Resource>
> 
> And get back, for example, resources "thalia" and "urania".
> 
> Doesn't this cover already (most of) the use case mentioned below and is 
> there really a need to change the multiplicity of this element.
> 
> Andreas
> 


A common real-world example is that I am choosing from a set of nodes
in a cluster according to an arbitrary application-specific constraint
that cannot be captured in the resource selection language otherwise.

I've seen this with some stateful "storage" clusters where one job
wrote data to a set of nodes and subsequent jobs need to process them.
It is ugly but useful.  In GRAM we have seen sites add site-specific
extensions to handle this since we did not provide it in our RSL.

karl

-- 
Karl Czajkowski
karlcz at univa.com