optimize further kafka docker image

Author: amuraru

docker/kafka/Dockerfile

@@ -86,8 +86,8 @@ RUN set -eux; \
 	; \
 	rm openjdk.tgz*; \
 	\
-# Remove JMODs (not needed for runtime, only for jlink custom images)
-	rm -rf "$JAVA_HOME/jmods"; \
+# Remove JMODs and src.zip (not needed for runtime, only for development)
+	rm -rf "$JAVA_HOME/jmods" "$JAVA_HOME/lib/src.zip"; \
 	\
 	apt-mark auto '.*' > /dev/null; \
 	[ -z "$savedAptMark" ] || apt-mark manual $savedAptMark > /dev/null; \

docker/kafka/README.md

@@ -9,5 +9,5 @@ Tags should be `kafka-<scala_version>-<kafka_version>` e.g `kafak-2.13-2.6.2`
 # Upstream base
 
 This is based on [wurstmeister/kafka-docker](https://github.com/wurstmeister/kafka-docker) with the following additions:
-1. Use `openjdk 17` in order to support container based resource monitoring
+1. Use `openjdk 21` in order to support container based resource monitoring
 2. Use custom `log4j.properties` to get all kafka logs to stdout only