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Subject: Re: [OMPI devel] XML request
From: Greg Watson (g.watson_at_[hidden])
Date: 2009-08-28 08:33:08


Ralph,

Would this be doable? If we could guarantee that the only output that
went to the file was XML then that would solve the problem.

Greg

On Aug 28, 2009, at 5:39 AM, Ashley Pittman wrote:

> On Thu, 2009-08-27 at 23:46 -0400, Greg Watson wrote:
>> I didn't realize it would be such a problem. Unfortunately there is
>> simply no way to reliably parse this kind of output, because it is
>> impossible to know what the error messages are going to be, and
>> presumably they could include XML-like formatting as well. The whole
>> point of the XML was to try and simplify the parsing of the mpirun
>> output, but it now looks like it's actually more difficult.
>
> I thought this might be difficult when I saw you were attempting it.
>
> Let me tell you about what Valgrind does because they have similar
> problems. Initially they just had added --xml=yes option which put
> most
> of the valgrind (as distinct from application) output in xml tags.
> This
> works for simple cases and if you mix it with --log-file=<filename> it
> keeps the valgrind output separate from the application output.
>
> Unfortunately there are lots of places throughout the code where
> developers have inserted print statements (in the valgrind case these
> all go to the logfile) which means the xml is interspersed with non-
> xml
> output and hence impossibly to parse reliably.
>
> What they have now done in the current release is to add a extra
> --xml-file=<file> option as well as the --log-file=<file> option. Now
> in the simple case all output from a normal run goes well formatted to
> the xml file and the log file remains empty, any tool that wraps
> around
> valgrind can parse the xml which is guaranteed to be well formatted
> and
> it can detect the presence of other messages by looking for output in
> the standard log file. The onus is then on tool writers to look at
> the
> remaining cases and decide if they are common or important enough to
> wrap in xml and propose a patch or removal of the non-formatted
> message
> entirely.
>
> The above seems to work well, having a separate log file for xml is a
> huge step forward as it means whilst the xml isn't necessarily
> complete
> you can both parse it and are able to tell when it's missing
> something.
>
> Of course when looking at this level of tool integration it's better
> to
> use sockets that files (e.g. --xml-socket=localhost:1234 rather than
> --xml-file=/tmp/app_XXXX.xml) but I'll leave that up to you.
>
> I hope this gives you something to think over.
>
> Ashley,
>
> --
>
> Ashley Pittman, Bath, UK.
>
> Padb - A parallel job inspection tool for cluster computing
> http://padb.pittman.org.uk
>
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