java.lang.NoClassDefFoundError: io/opentracing/util/GlobalTracer in v.1.2.0

[orinciog]

Hi!

I'm using your sink, v1.2.0 in a custom Kafka Connect Docker Image, but when I try to start a connector, I receive the following message:

[2021-07-08 15:32:28,797] ERROR WorkerSinkTask{id=EchoSinkConnector-0} Task threw an uncaught and unrecoverable exception. Task is being killed and will not recover until manually restarted (org.apache.kafka.connect.runtime.WorkerTask:184)
java.lang.NoClassDefFoundError: io/opentracing/util/GlobalTracer
	at cz.scholz.kafka.connect.echosink.EchoSinkTask.start(EchoSinkTask.java:44)
	at org.apache.kafka.connect.runtime.WorkerSinkTask.initializeAndStart(WorkerSinkTask.java:308)
	at org.apache.kafka.connect.runtime.WorkerSinkTask.execute(WorkerSinkTask.java:196)
	at org.apache.kafka.connect.runtime.WorkerTask.doRun(WorkerTask.java:182)
	at org.apache.kafka.connect.runtime.WorkerTask.run(WorkerTask.java:231)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at java.base/java.lang.Thread.run(Thread.java:829)
Caused by: java.lang.ClassNotFoundException: io.opentracing.util.GlobalTracer
	at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:471)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:589)
	at org.apache.kafka.connect.runtime.isolation.PluginClassLoader.loadClass(PluginClassLoader.java:104)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522) 

The dockerfile that I'm using is:

FROM bitnami/kafka:2.8.0
USER root:root

RUN mkdir -p /opt/bitnami/kafka/plugins

RUN wget -q https://github.com/scholzj/echo-sink/releases/download/1.2.0/echo-sink-1.2.0.jar -O /opt/bitnami/kafka/plugins/echo-sink-1.2.0.jar

USER 1001
CMD ["/opt/bitnami/kafka/bin/connect-distributed.sh", "/opt/bitnami/kafka/config/connect-distributed.properties"]

and in connect-distributed.properties I have a line with:
plugin.path=/opt/bitnami/kafka/plugins

The configuration of connector is:

connector.class=cz.scholz.kafka.connect.echosink.EchoSinkConnector
key.converter.schemas.enable=false
topics=topic-test
tasks.max=2
value.converter.schemas.enable=false
value.converter=org.apache.kafka.connect.storage.StringConverter
key.converter=org.apache.kafka.connect.storage.StringConverter

Other connectors (i.e FileStreamSinkConnector) are working fine.

The error is correct, in echo-sink 1.2.0 jar there is no opentracing jar. Actually there are no extra jars inside provided jar.

How can I skip this error?

Thank you

[scholzj]

It looks like you are missing the tracing libraries. You will need to add the Jaeger Client and OpenTracing dependencies: https://github.com/scholzj/echo-sink/blob/main/pom.xml#L31-L40

I can try to have a look later if I can produce some fat-jar as an alternative. But adding these dependencies (and their dependencies) manually should get you started.

[orinciog]

Hi,

Thank you for your advice.

It worked by adding the following jars to /opt/bitnami/kafka/libs.

jaeger-tracerresolver-1.0.0.jar                           okhttp-3.9.0.jar                      opentracing-util-0.33.0.jar
gson-2.8.2.jar                                            okio-1.13.0.jar                       libthrift-0.12.0.jar   
jaeger-client-1.0.0.jar                                   opentracing-api-0.33.0.jar            
jaeger-core-1.0.0.jar                                     opentracing-noop-0.33.0.jar           
jaeger-thrift-1.0.0.jar                                   opentracing-tracerresolver-0.1.8.jar

For those who are interested, I downloaded required jars with:
echo-sink-1.2.0/META-INF/maven/cz.scholz.kafka.connect/echo-sink$ mvn dependency:resolve

and after I put in libs folder only those libs which were not present.

I think you should provide a single uber jar with all required jars in it. Actually, this is the way that confluent recommends to ship a connector

A Kafka Connect plugin can be:

a directory on the file system that contains all required JAR files and third-party dependencies for the plugin. This is most common and is preferred.
a single uber JAR containing all of the class files for the plugin and its third-party dependencies.

Important

A plugin should never contain any libraries provided by the Kafka Connect runtime.

Source: https://docs.confluent.io/home/connect/userguide.html

Thank you.

[scholzj]

Well, it is used mainly with Strimzi, which already packages the dependencies. And it is always better to avoid mixing dependencies since that might cause different versions to conflict etc. I might add fat-jar when I have time for it. But not sure when exactly will i get to it.