README.md

Overview

This repository contains an example of reproducing the ClassCastException error when using Slick and Kamon:

java.lang.ClassCastException: class kamon.instrumentation.executor.CaptureContextOnSubmitInstrumentation$ContextAwareRunnable cannot be cast to class slick.util.AsyncExecutor$PrioritizedRunnable (kamon.instrumentation.executor.CaptureContextOnSubmitInstrumentation$ContextAwareRunnable and slick.util.AsyncExecutor$PrioritizedRunnable are in unnamed module of loader 'app')
	at slick.util.ManagedArrayBlockingQueue.offer(ManagedArrayBlockingQueue.scala:17)
	at java.base/java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1347)
	at slick.util.AsyncExecutor$$anon$1$$anon$4.execute(AsyncExecutor.scala:163)
	at scala.concurrent.impl.Promise$Transformation.submitWithValue(Promise.scala:429)
	at scala.concurrent.impl.Promise$DefaultPromise.submitWithValue(Promise.scala:338)
	at scala.concurrent.impl.Promise$DefaultPromise.dispatchOrAddCallbacks(Promise.scala:312)
	at scala.concurrent.impl.Promise$DefaultPromise.map(Promise.scala:182)
	at scala.concurrent.Future$.apply(Future.scala:678)
	at slick.jdbc.JdbcBackend$DatabaseDef.io(JdbcBackend.scala:65)

The error appears when using kamon-jdbc with configuration settings:

kanela.modules.executor-service-capture-on-submit.enabled = true

Also, to reproduce the error, it is necessary that HicariCP did not immediately process the tasks, but queued them by calling the java.util.concurrent method.BlockingQueue.offer(E). To do this, you can specify in the configuration:

db {
  numThreads = 1
  maxConnections = 1
  minConnections = 1
}

Run

You can run the example through the gradle run task:

.\gradlew clean run