Re: Parfait agent, docs, rpm updates

Hi Marko,

----- Original Message -----
> > [...]
> Let's try to be a bit more specific and look at concrete examples.

*nod* in the Aconex environment, hundreds of metrics (& tens of thousands of
values) have been used with good success for many years, so there's existence
proof this is readily achievable.  And that's actual, 24x7, 365-days-a-year
use, solving actual production performance problems - not just a few queries
of JMX values by us developers poking at JVMs and guesstimating ...

> (We saw last
> year that if querying for all the metrics from a WildFly instance its
> CPU usage goes momentarily trough the roof

OK - what was that due to though?

> and that's certainly not due to RMI/socket traffic.)
            ^^^^^^^^^^^

How are we certain?  What *is* it from then, OOC?  (needs someone to go
profile it methinks, to be certain about what it is or is not)

> In general, I'd guesstimate that most metrics
> cost-wise are somewhere between VmVersion and OpenFileDescriptorCount.

We can't guesstimate when doing performance analysis...

From the Aconex environment, using Parfait & MMV, querying metric values
introduces no measurable overhead and this includes all the JMX values
we access now in parfait-agent, and a bunch of application-specific ones
that we of course don't.  This has been measured, alot - there is a bunch
of code in Parfait for benchmarking itself, too - not to mention the load
testing they do regularly.

> How is Parfait/JMX different in this regard?
> [...] Also, what happens if there is a crisis and I determine I need to
> see the updated values every one second instead?

Again from that last mail, this would not be difficult to add to Parfait.
All the ground work is there, the intervals are already parameterised &
already use Java system properties, so easily externalised.  I've not seen
evidence this dynamic-live-sampling is needed though so I'll certainly not
be working on it.

And again, some other agent talking to Parfait could be used to drive those
intervals, (or MMV could be extended, or...) but someone who believes in it
would need to step forward to do that work.  For me, at this stage, it's a
hypothetical problem and there are many other real problems to be worked on.

> It's also a bit unclear what kind of "real world environments" we're
> talking about here; after all, it seemed to come as a surprise to all of
> us that the agent didn't work with WildFly which is very, very much used
> in real world environments in my experience.

Those are, unsurprisingly, Red Hat centric real world environments though.

Parfait came from the Aconex production environment, long before Red Hat
interest in PCP - and its (was at the time) a Tomcat-based Java environment
with a variety of JVM versions over the years.  It is the best historical
test bed we have - we don't need to make up performance problems, they've
seen them all already.  These folk have been doing this for many years and
have alot of experience with PCP + Java we can leverage and learn from.

Or not.  As I said - if the current parfait-agent is not floating peoples
boats - those people could go right ahead and extend it to suit, to use
different backends, make it more dynamic/adaptable - anything is possible
with a little creativity and duct tape.

cheers.

--
Nathan

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