ClassNotFoundException with custom reporter

[cdavid]

Hi

I am trying to replicate the work discussed https://github.com/kamon-io/Kamon/discussions/878, but instead use Java and Play Framework (I am currently trying to reduce this to a very simple example, so if you need the code, I can provide). The idea is to emit the span data to logs (would appreciate help in this area if my approach is wrong).

I have added this to my application.conf:

kamon {
  modules {
    my-log-reporter {
      enabled = true,
      name = "Log-reporter",
      description = "Send to log"
      factory = "common.util.KamonLogReporterFactory"
    }
  }
  trace.tick-interval = 1 second
  trace.sampler = always
}

And have created the class. At runtime (sbt run), I can see that the module fails to be imported:

[warn] k.m.ModuleRegistry - Failed to create instance of module [Log-reporter]
java.lang.ClassNotFoundException: common.util..KamonLogReporterFactory
	at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:419)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:352)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:352)
	at kamon.instrumentation.sbt.KanelaOnSystemClassLoader.loadClass(KanelaOnSystemClassLoader.java:31)
	at kamon.instrumentation.sbt.play.SbtKanelaRunnerPlay$SbtKanelaClassLoader.loadClass(SbtKanelaRunnerPlay.scala:76)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:352)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:348)
	at kamon.util.DynamicAccess.getClassFor(DynamicAccess.scala:37)

I was a bit baffled by this, so I added this to my Module.java:

log.error("AAAAA");
      try {
          Class.forName("common.util.KamonLogReporterFactory");
          log.error("FOUND IT!");
      } catch (Exception e) {
          log.error("ex:", e);
      }

and the class is found:

[info] compiling 2 Java sources to /Users/cdavid/code/test/otel/play-samples/play-java-rest-api-example/target/scala-2.13/classes ...
[error] Module - AAAAA
[error] Module - FOUND IT!
[info] p.a.d.DefaultDBApi - Database [default] initialized
[info] p.a.d.HikariCPConnectionPool - Creating Pool for datasource 'default'
[info] p.a.d.HikariCPConnectionPool - datasource [default] bound to JNDI as DefaultDS
[info] a.e.s.Slf4jLogger - Slf4jLogger started
[warn] k.m.ModuleRegistry - Failed to create instance of module [Log-reporter]
java.lang.ClassNotFoundException: common.util.KamonLogReporterFactory
	at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:419)
	at kamon.instrumentation.sbt.KanelaOnSystemClassLoader.loadClass(KanelaOnSystemClassLoader.java:33)
	at kamon.instrumentation.sbt.play.SbtKanelaRunnerPlay$SbtKanelaClassLoader.loadClass(SbtKanelaRunnerPlay.scala:76)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:352)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:348)
	at kamon.util.DynamicAccess.getClassFor(DynamicAccess.scala:37)
	at kamon.util.DynamicAccess.createInstanceFor(DynamicAccess.scala:60)
	at kamon.ClassLoading.createInstance(ClassLoading.scala:58)

I am suspecting some weird interaction between Play Framework and Kamon/Kanela - somehow, the libraries in the Play Framework are not available, but I don't know enough to tell exactly what is going on. Would appreciate suggestions on solving the original problem if there are better ways to do it.

Thanks!