[GE users] qstat -j -xml output information

John Marshall John.Marshall at ec.gc.ca
Wed May 7 15:42:31 BST 2008


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Olesen, Mark wrote:
> The first thing that would ease the task would be an
> xml output that is structured with a view to the user instead of being
> more or less a dump of the internal cull list.
>   
If possible, I agree with you and think this would be the best. Severing
the obvious dependence (especially for field names) between the xml
output and the internal representation would:
- allow for the xml markup to become stable, allow for internal
    representation to be flexible
- limit the impact of internal representation which makes the current
    xml markup more difficult to work with than necessary. E.g.,
-----

<JB_env_list>
    <job_sublist>
        <VA_variable>__SGE_PREFIX__O_PATH</VA_variable>
        <VA_value>/opt/ssm/gridengine_6.1_multi/bin/lx26-x86:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/games</VA_value>
    </job_sublist>
</JB_env_list>

-----
could be (if it makes sense in the context; and depending on one's
take of XML elements vs attributes):
-----

<env_list>
    <var name="__SGE_PREFIX__O_PATH" value="/opt/ssm/gridengine_6.1_multi/bin/lx26-x86:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/games"/>
</env_list>

-----

> Assuming that many people have faced with a similar problem - parsing
> massive xml output and extracting particular bits of information - why
> not invert the problem? If the user could simply query the bits of
> information required, a large amount of repetitive parsing could be
> eliminated. It should also help reduce bandwidth between client and
> qmaster. The "ps -o ..." interface could be a suitable model as could
> some XPath type of query.
>   
qstat options specifically for XML output might be worthwhile. The 
difficulty
I see with a 'ps -o ...' type interface is that the XML is hierarchical 
whereas ps
is record oriented, unless nodes (and all their children) in the XML 
document
tree were selectable (i.e., ask for them to be included or not).

My concerns about supporting XPath type querying is that SGE would then
be tied to an XPath implementation and be a dependency and also put a
load on the qmaster in order to process the query. I'd be content with 
getting
more information, faster, and then leave the processing burden to the user.

John

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