[Hawkular-dev] Hawkular APM and instrumenting clojure

[Neil Okamoto]

As an experiment I'm instrumenting a service written in clojure using
opentracing-java.  Through the clojure/java interop I've mostly succeeded
in getting trace information reported through to the Hawkular APM server.

I say "mostly succeeded" because sooner or later in every one of my hacking
sessions I get to the point where the spans I am creating in the app are no
longer reported in the web ui.

For convenience I'm using the Hawkular dev docker image
<https://hub.docker.com/r/jboss/hawkular-apm-server-dev>. In my test app
I'm doing nothing more than initializing an APMTracer
<https://github.com/hawkular/hawkular-apm/blob/master/client/opentracing/src/main/java/org/hawkular/apm/client/opentracing/APMTracer.java>
with
the appropriate environment variables set, and then calling
buildSpan("foo"), withTag("sampling.priority", 1), start(), sleep for a
while, and then finish().  Where all of the previous was done in clojure,
but I'm talking in pseudocode here just to make the intent clear.

So like I said, sometimes these traces are reported, other times they seem
to be silently dropped. I can't detect any consistent pattern how or why
this happens...

(1) Is using a "sampling.priority" of 1 merely advisory?  It would explain
everything if those traces are meant to be dropped.

(2) Is there any convenient way I can see, with increased logging or
something, which traces are actually being sent from the client, and which
are actually received by the server?
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