Re: Parfait and UoM (java) RPM packages

Heya Marko,

----- Original Message -----
> Hi,
> 
> On 2016-10-19 01:45, Nathan Scott wrote:
> >> Thank you.
> > 
> > No problem.  Have you had a chance to try them out?
> 
> I tried them out.

Thanks!

> Here are the steps I used on a fresh F24 installation,
> perhaps these coud serve as a basis for Quick Guide Java section when
> all the pieces are in place:

Definitely - there's lots we can simplify here too based on your
findings so far ...

> 1. Install PCP, enable pmcd, make sure MMV is on, and metrics ok
> # dnf install pcp pcp-doc pcp-system-tools
> # systemctl enable --now pmcd
> # pcp | grep mmv
> # pminfo -f mem.util.free
> # pminfo mmv | wc -l
> 3
> 
> 2. Install Java if needed, check it works
> # dnf install java-1.8.0-openjdk-headless
> # java -cp . HelloWorld

(I think we should install some sample/demo programs, too, so people
don't have to write their own like you have here just to try it out -
will look into that shortly.  Suyash, one of our GSoC students, has
actually prepared a few already - just need to merge those into the
maven world Parfait live in so we can ship 'em).

> 3. Install Parfait from the Copr repo
> # dnf copr enable nathans/pcp.io
> # dnf install parfait
> 
> (This adds 29 packages using 22 MB, seems ok.)

We may be able to do better too - it looks like at least half of
that is coming from dependencies that we don't need to install for
the part of Parfait being used here...

$ rpm -qi parfait | grep Size
Size        : 10473178

Collectively, the unitsofmeasurement modules are a few tens of K, which
is fine but its the other (Parfait API) things like spring, guava and so
on (and their dependencies) that get us to that 20+MB point.

But parfait-agent is standalone - we can make a parfait-agent sub-package
without those dependencies which will get us to a single package install,
with only deps on the jvm itself I think - should get us to approx 10MB.

> X. Fix parfait-agent.jar, can be skipped when the fix is in the next RPM
> build: unzip the jar, remove the top-most MANIFEST.MF, add the following
> line to META-INF/MANIFEST.MF, and re-create the jar:
> 
> Premain-Class: io.pcp.parfait.ParfaitAgent

As mentioned on IRC, I think this is a packaging botch re the specific
parfait-agent.jar file that ends up in the rpm - multiple jars are built
but we don't use the correct one.  Will fix up on the next build.

> 4. Start a Java application with the agent
> 
> # java -cp .:/usr/share/java/parfait
> -javaagent:/usr/share/java/parfait/parfait-agent.jar
> 
> Here we get an error message that can be ignored but probably should be
> addressed in the jar (or not, see below):
> 
> ERROR StatusLogger No log4j2 configuration file found. Using default
> configuration: logging only errors to the console.

Yep, there's definitely improvements to be made to logging, independent
of the WildFly issue below.  I'll chat with TallPaul, he's a log4j guru
and will likely have lots of good advice to offer here.

> So overall looks very promising, after fixing the few minor hickups and
> getting the packages included in the real repos we're getting quite
> close. The only notable concerns are that there are very few metrics,

For now, I've just gone with the original set I was given, from Paul - I
know they had per-thread stats tho, so I'll follow up on that.  But yes,
definitely alot of scope for starting to classify the missing metrics now
with correct PCP metric metadata.  Still need tools to help - maybe there
is a future GSoC project in that.

> [...] I wasn't
> able to run the application (WildFly 10) after enabling the agent:

This looks like 
https://issues.jboss.org/browse/WFLY-3152
https://bugzilla.redhat.com/show_bug.cgi?id=1037970

There's a workaround mentioned there, to add:
-Djava.util.logging.manager=org.jboss.logmanager.LogManager

to the command line before presenting the parfait-agent jar options.
If that resolves it, there may be some things we can do (in the code)
to avoid this automatically.


Thanks Marko, appreciate the open mind you're bringing.  Also mentioned
on IRC earlier, we could also now think about a parfait-jmxscanner module
(or some better name) that implements that jmx-pcp concept of being able
to find new JVMs on-the-fly and proxy them.  With the way Parfait code
is organised, this utility could be packaged such that it depends on the
JDK (not JRE) while parfait-agent and co don't.  But still sharing all
the metric definitions, MMV writing, proxying and so on via parfait jars.
Another possible GSoC project there perhaps.

cheers.

--
Nathan

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