KafkaSpout throws NoClassDefFoundError for log4j

Question

For some reason I get the following error when I try to run my topology on a Storm cluster:

java.lang.NoClassDefFoundError: Could not initialize class org.ap         


        

Answer 1

Do you use the "right" logging framework?

From https://storm.apache.org/2013/12/08/storm090-released.html

Logging Changes

Another important change in 0.9.0 has to do with logging. Storm has largely switched over to the slf4j API (backed by a logback logger implementation). Some Storm dependencies rely on the log4j API, so Storm currently depends on log4j-over-slf4j.

These changes have implications for existing topologies and topology components that use the log4j API.

In general, and when possible, Storm topologies and topology components should use the slf4j API for logging.

If you do not use the same logging framework as Storm, you need to include the used libraries into your jar file together with your topology code.