Charles Loomis a écrit :
>> 2) Build a classad parser which does the best it can with the expression
>> it gets; that parser might be either in the WMS or in the CE.
>>
>> 2a) As 2, but insist that users restrict their requirement expressions
>> to things the parser can deal with.
>>
>> 3) Add new things in the JDL which match more directly with the kind of
>> thing you get in batch systems, e.g.:
>>
>> CPULimit = 3600;
>> MEMlimit = 511;
>> DiskLimit = 500;
>> Priority = 3;
>>
>> 3) is simpler on the batch system side, but you still have to adapt it
>> to specific systems, you still have to make it match the glue schema (or
>> vice versa), and you lose a lot of the potential richness of the classad
>> expressions.
>
>
> I would instead opt for a hybrid approach of 2) and 3). Allow people
> to define parameters like in 3) and have whatever processes the final
> JDL combine those with any explicit requirements to arrive at the full
> expression. Only those limits given separately would be passed to the
> local batch system. This makes it easy to parse, loses none of the
> functionality of the classad, and could be implemented in a finite
> amount of time. It is also closer to the spirit of the GGF job
> description.
I would even opt for a XML implementation approach... It seems to me
that the problem is basically to rewrite an expression (the JDL source)
in another one (the LRMS command to be performed). The XML technology
provides us with a very convenient and a very open way to do this.
Moreover, there would be no need to implement (yet another) parser and
we could possibly use an existing XML transformer (i.e. XSL Transformer)
to finally transform the XML data into the expected LRMS-specific command.
How could it work ?
the RB could provide the CE with the jdl/classad data expressed as an
XML document, and the CE could provide something like a XSL stylesheet
to rewrite the XML data into a local LRMS command expression to be applied.
What would be the implementation effort ?
1- At the RB level, to express the classad/jdl (or whatever you want) in
a XML format.
2- At the CE level, to provide an XSL stylesheet depending on the kinf
of LRMS, which would transform the XML data into a LRMS command.
I don't know the expressivness of the famous classad (is there somewhere
a classad specification document ?). Then I don't know whether a classad
expression could or not be expressed as an XML tree... ???
Pierre
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Pierre GIRARD
Grid Computing Team Member
IN2P3/CNRS Computing Centre - Lyon (FRANCE)
http://cc.in2p3.fr
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