UWS 1.1 job list, sorting NULL values -- problems with LAST redirect

[Kristin Riebe]

Hi all,

I have one (last?) comment to make:

I was experimenting with thousands of jobs, where a limit to the size of
the job list would be useful. The new UWS1.1 standard takes this into
account by suggesting to use a LAST filter in a 303 redirection response
(section 2.2.2.1. Job List), and in principle I like the idea very much
to tell the client this way that there was a cut applied.

But (of course there must be a BUT now :-)) after the recent discussions
I am aware now that the LAST filter ignores all jobs with startTime=NULL.
I.e. PENDING and QUEUED jobs (and those aborted by the client during
these phases) will *never ever* be returned in the jobs list, if the
server always applies the LAST-redirect to indicate the cut made.

Even adding a PHASE=PENDING or PHASE=QUEUED filter would not help, if
the server redirects this to e.g. PHASE=PENDING&LAST=1000, since then
both filter-conditions are used and jobs with startTime=NULL still being
ignored.

One solution may be that the server first checks if the cut is really
needed and only makes a redirect if the jobs list is larger than the
limit. Then PENDING and QUEUED jobs are only returned if the jobs list
is smaller than a given limit, which may or may not be the expected
behaviour. Introducing a creation time for jobs and using it for time
filtering if there is no startTime available may be another solution in
the future.

Since the document only says "A server may use the LAST filter in a 303
redirection ..." this isn't such a big problem, since it gives me the
freedom to choose a different solution. But it makes the LAST-redirect
less useful than it may have been intended. I just wanted to make
everyone aware of this.

Cheers,

Kristin


-- 
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Dr. Kristin Riebe
E-Science & GAVO

Email: kriebe at aip.de
Phone: +49 331 7499-377
Room:  B6/25
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Leibniz-Institut für Astrophysik Potsdam (AIP)
An der Sternwarte 16, D-14482 Potsdam
Vorstand: Prof. Dr. Matthias Steinmetz, Matthias Winker
Stiftung bürgerlichen Rechts
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