dtrace discuss - Aug 2007 - Looking for ideas for a problem to solve during a presentation

Hi all,

I just recently took Sun''s S10 Internals and DTrace classes and
I''m
giving a presentation to my group Friday morning. I''m trying to come up
with a good example of a problem which I could walk through using
DTrace, mdb and internals knowledge (as well as other tools to narrow
down the scope, e.g. vmstat, lockstat, etc.) to solve, perhaps over
about 15-30 minutes of the presentation. I do have a C programming
background but my co-workers do not (we''re all Unix admins), so
I''d like
a problem that would require some knowledge of internals but without
getting too hairy.

I would appreciate any suggestions you all might have for such a
problem. It could be something as simple as a misconfigured file that
results in strange but predictable behavior, or possibly an intermittent
problem that could involve the use of speculative tracing (we tend to
get a lot of intermittent problems in our production environment).

Thanks,
Justin

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It''s been suggested that I provide some examples of problems
we''ve had that might help generate ideas. I did respond to that
suggestion by saying that my dtrace and internals knowledge is pretty new and I
haven''t had the depth of experience with either to be effective at
solving the problems that have arisen, often due to a lack of cycles to really
immerse myself in a given problem.

So that being said, one problem I recall was intermittently unresponsive web
service calls from Oracle HTTP Server to OC4J (maybe 15-20/day out of 340K
txn/day), and these failures were causing larger transaction-oriented processes
to fail. This was ultimately fixed by upgrading OAS, but it took a lot of
man-hours to follow multiple troubleshooting routes.

I had found an article at SDN called "DTrace by Example: Solving a
Real-World Problem"
(http://developers.sun.com/solaris/articles/dtrace_example.html) that is the
kind of process I''m looking to perform. In fact, I think this could be
a better technique for my presentation, using a problem to teach about dtrace
and mdb, rather than trying a more lecture/lab approach. Also, I''ve
postponed the presentation I''m giving until I can spend some more time
absorbing knowledge and developing a good presentation.

I''m not necessarily looking for a problem similar to any that
we''ve had here. I''m just looking for a good idea that would
require a variety of tools and knowledge but without being TOO complicated.

Thanks,
Justin


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