Packaging a Kotlin Kafka Connect Plugin

December 11, 2018
kafka-connect kotlin gradle

When building an UberJar for a Kotlin kafka-connect plugin, you need to include the Kotlin Runtime, or else you’ll run into the following error:

java.lang.NoClassDefFoundError: kotlin/jvm/internal/Intrinsics
at net.mongey.kafka.connect.slack.SlackSinkConnector.start(SlackSinkConnector.kt)
at org.apache.kafka.connect.runtime.WorkerConnector.doStart(WorkerConnector.java:111)
at org.apache.kafka.connect.runtime.WorkerConnector.start(WorkerConnector.java:136)
at org.apache.kafka.connect.runtime.WorkerConnector.transitionTo(WorkerConnector.java:195)
at org.apache.kafka.connect.runtime.Worker.startConnector(Worker.java:241)
at org.apache.kafka.connect.runtime.distributed.DistributedHerder.startConnector(DistributedHerder.java:916)
at org.apache.kafka.connect.runtime.distributed.DistributedHerder.access$1300(DistributedHerder.java:111)
at org.apache.kafka.connect.runtime.distributed.DistributedHerder$15.call(DistributedHerder.java:932)
at org.apache.kafka.connect.runtime.distributed.DistributedHerder$15.call(DistributedHerder.java:928)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Caused by:
java.lang.ClassNotFoundException: kotlin.jvm.internal.Intrinsics
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at org.apache.kafka.connect.runtime.isolation.PluginClassLoader.loadClass(PluginClassLoader.java:104)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 13 more

To do this, add the following to your Gradle build

jar {
    from {
      configurations.compile.collect {
        it.isDirectory() ? it : zipTree(it)
      }
    }
}

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