Classloading Error with Kotlin and Streams

[Avi Flax]

Hi all, I’m trying to experiment with Kotlin and Streams, and I’m encountering 
an error:

$ kotlinc -cp 
kafka-streams-0.11.0.0-cp1.jar:kafka-clients-0.11.0.0-cp1.jar:slf4j-api-1.7.25.jar
 -jvm-target 1.8 
Welcome to Kotlin version 1.1.4-3 (JRE 1.8.0_141-b15)
Type :help for help, :quit for quit
>>> import org.apache.kafka.streams.StreamsConfig
>>> val config = hashMapOf("application.id" to "t2p.normalizer", 
>>> "bootstrap.servers" to "localhost:9092")
>>> StreamsConfig(config)
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further 
details.
java.lang.ExceptionInInitializerError
Caused by: org.apache.kafka.common.config.ConfigException: Invalid value 
org.apache.kafka.common.serialization.Serdes$ByteArraySerde for configuration 
default.key.serde: Class 
org.apache.kafka.common.serialization.Serdes$ByteArraySerde could not be found.
        at 
org.apache.kafka.common.config.ConfigDef.parseType(ConfigDef.java:715)
        at 
org.apache.kafka.common.config.ConfigDef$ConfigKey.<init>(ConfigDef.java:944)
        at org.apache.kafka.common.config.ConfigDef.define(ConfigDef.java:137)
        at org.apache.kafka.common.config.ConfigDef.define(ConfigDef.java:157)
        at org.apache.kafka.common.config.ConfigDef.define(ConfigDef.java:196)
        at org.apache.kafka.common.config.ConfigDef.define(ConfigDef.java:358)
        at org.apache.kafka.common.config.ConfigDef.define(ConfigDef.java:371)
        at 
org.apache.kafka.streams.StreamsConfig.<clinit>(StreamsConfig.java:270)
        at Line_2.<init>(Unknown Source)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at 
sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
        at 
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
        at 
org.jetbrains.kotlin.cli.common.repl.GenericReplEvaluator$eval$1$scriptInstance$1.invoke(GenericReplEvaluator.kt:93)
   <cut>

I’ve put the entire thing into this gist:

https://gist.github.com/aviflax/d33ac2fbd77882fcb80fe8d3fd26feda

I took a look at ConfigDef.java, and I _think_ the error is being thrown from 
line 706:

https://github.com/apache/kafka/blob/0.11.0.0/clients/src/main/java/org/apache/kafka/common/config/ConfigDef.java#L706

which is:

return Class.forName(trimmed, true, Utils.getContextOrKafkaClassLoader());

so I tried running that in the Kotlin REPL:

>>> import org.apache.kafka.common.utils.Utils
>>> Class.forName("org.apache.kafka.common.serialization.Serdes\$ByteArraySerde",
>>>  true, Utils.getContextOrKafkaClassLoader())
java.lang.ClassNotFoundException: 
org.apache.kafka.common.serialization.Serdes$ByteArraySerde
        at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:348)

(that’s the whole trace)

I thought maybe I was missing a JAR file, but this works fine:

>>> Class.forName("org.apache.kafka.common.serialization.Serdes\$ByteArraySerde")
class org.apache.kafka.common.serialization.Serdes$ByteArraySerde

So I guess this has something to do with the ClassLoader being returned by 
Utils.getContextOrKafkaClassLoader()

But when I call that, the result looks sane to me:

>>> import org.apache.kafka.common.utils.Utils
>>> Utils.getContextOrKafkaClassLoader()
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further 
details.
sun.misc.Launcher$AppClassLoader@55f96302

Not that I know much about class loaders, but “AppClassLoader” sounds at least 
somewhat reasonable.

So if anyone has any ideas on what’s going on here, I’d very much appreciate 
any help!

Thanks,
Avi

————
Software Architect @ Park Assist » http://tech.parkassist.com/