confluent build with 2.10 package contain scala 2.11 jar - apache-kafka

Question

I downloaded confluent-2.0.0-2.10.5.tar.gz, because I want to have scala 2.10 package
but still the kafka jar in /share/java/schema-registry is still kafka_2.11-0.9.0.0-cp1.jar
Is there anyway I can get a clean 2.10 scala confluent package

Answer 1

The 2.10 refers to the version of the Kafka subpackage, but a different version may be used by other subpackages.
The tar.gz packages use the 2.11 versions where a different subpackage requires access to the core Kafka jar that has a Scala dependency. (Actually, the version they depend on is really whichever Scala version is supported by Kafka and considered most stable and well supported upstream). This is necessary because Scala libraries aren't necessarily binary compatible between different Scala versions, which would mean that not doing this would require multiple versions of all the services that use the Kafka libraries, especially on platforms like Debian and RPM-based distros, i.e. we'd need a schema-registry-2.10 and schema-registry-2.11. Instead, we sort of vendorize the entire Kafka library for services that depend on it.
Note that the files under /share/java/kafka only use Scala 2.10 and if you need to pull in the clients, you can safely add that to your classpath. The use of 2.10 or 2.11 for any of the other services shouldn't matter as they are simply that: services that you execute. Any libraries that you might need to put on your classpath (e.g. serializers) only depend on the pure Java libraries in Kafka and are therefore safe to use with Kafka libraries compiled with any Scala version.