Classes fail to load in Confluent Kafka 8.0 that uses JDK 21

[egg-r]

We are starting to build out a new Confluent Kafka 8.0 cluster that uses JDK 21. In confluent-kafka-connect, I'm seeing that classes within the kafka-connect-smt jar are failing to load. They're ignored by Confluent Kafka-Connect now and not mentioned in logs. I'm using the latest release's jar, version v1.4.0.

Particularly these classes relating to Headers fail to load:

io.lenses.connect.smt.header.InsertFieldTimestampHeaders
io.lenses.connect.smt.header.InsertRecordTimestampHeaders
io.lenses.connect.smt.header.InsertRollingFieldTimestampHeaders
io.lenses.connect.smt.header.InsertRollingWallclockHeaders
io.lenses.connect.smt.header.InsertWallclockHeaders

These load fine within our older clusters that runs confluent-kafka 7.9 with JDK 17.

I'm not sure if this is a known issue or not.

[J-Harmson]

I am also hitting this issue when upgrading Debezium to a version that uses Kafka 4. Not sure what version of Kafka confluent-kafka runs but if it's Kafka 4.x then it could be a compatibility issue causing the plugin scanner not be able to find all of the classes in the jar. I've raised this with Lenses directly recently so hopefully it's looked at soon :)

[J-Harmson]

Hi Stefan Bocutiu (@stheppi) Any idea when this might be worked on?