UWS POST PHASE=RUN

[Patrick Dowler]

UWS allows for the client to specify parameters and the service to 
advertise some limits (max execution time) and predictions (quote). Yes, 
they are notoriously hard to implement :-) There is some negotiation 
that can be performed, but part of that might be that the client could 
change some aspect of the job in order to negotiate a satisfactory outcome.

For example, say I create a job with MAXREC=1e6 and the server responds 
with OK, but destruction is only 1200 (seconds in the future). The the 
client modifies the job to MAXREC=1e5 and the server now sets 
destruction to 3 days in the future. Nothing says the service has to 
adjust limits, but in the current spec they can adjust limits, clients 
can ask for different limits, and failing that clients can adjust the 
job to find a satisfactory limit.

It would more of a pain to keep creating new async jobs rather than 
negotiate over one of them and IMO changing the job can/should be part 
of the negotiation. This all happens in PENDING phase, before any 
execution, so there is no cancel per se (client could delete the old 
job). So this is "pre-queueing".

To be fair, I don't see this as a major issue for jobs like TAP queries 
or vospace transfers, but I could definitely see it being important for 
things like processing jobs. In that kind of system, the job description 
now usually contains things like number of cores to use, amount of 
memory, etc... one could easily imagine that request for lots of cores 
and rams could result in a large value of quote (waiting in the queue) 
and reducing one or both might reduce the quote so the job runs sooner.


Pat


On 04/11/14 10:16 AM, Walter Landry wrote:
> Why do allow modification of parameters?  All of the queuing systems
> that I have worked with in the past did not allow it.  If you want to
> modify parameters, you can cancel the old request and submit a new
> one.  That is essentially what would happen in the back end anyway.

-- 

Patrick Dowler
Canadian Astronomy Data Centre
National Research Council Canada
5071 West Saanich Road
Victoria, BC V9E 2E7

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