G'Day Folks,
On Tue, Feb 10, 2009 at 08:03:17PM +0000, Peter Tribble wrote:
[...]
> Create a net-snmp module that exposes well known Solaris performance
> metrics via SNMP. If possible, this will include presenting kstat
> metrics in a generic fashion via SNMP.
Writing an SNMP agent to export kstats isn't too hard. What will be the hard
part is designing the MIB - picking which statistics should be exported, and
documenting them. Some challanges:
1) kstats aren't generally documented in the first place.
although the source code gives you a good idea what they are for.
2) kstats aren't generally a stable interface.
some end up generally stable as they are used by tools such as iostat
and vmstat, which have an expectation of stability.
3) customers don't need more numbers.
useful numbers, sure, but lets not export kstats just because they
are there.
We could pick a small set of kstats that are most useful and document them, and
the code to export them via SNMP will suggest that these are now supposed to
be stable. It's picking which kstats (or other statistic source) to use that
will be (or should be) tough.
There may be too much 'making do' with which kstats kernel engineers leave
behind. I'd much rather we picked ideal statistics first, then saw if kstats
satisfied them - and added kstats if needed.
To help pick useful statistics, we can list use cases. When designing the
DTrace IP provider (and others), I had written the end-user scripts before
completing the provider - which helped guide the design towards what was and
wasn't useful, and highlight what was missing (I stalled writing a few scripts
when I realized crucial data was missing - which I wasn't able to spot from
the design alone.) From there, if have use cases for statistics that don't
exist as kstats - we can then add the kstats!
... and if we start with what's needed instead of what Solaris provides, then
we may have a generic enough performance MIB to port to other systems. :)
Brendan
--
Brendan Gregg, Sun Microsystems Fishworks. http://blogs.sun.com/brendan
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