FYI I opened https://issues.apache.org/jira/browse/KAFKA-20076 and also a corresponding PR to fix the issue here https://github.com/apache/kafka/pull/21318 It's against trunk but I think we should (if/when approved) cherry-pick to 4.2.0.
Thanks, Paolo On Thu, 15 Jan 2026 at 17:01, Paolo Patierno <[email protected]> wrote: > Hello, > I think I have found a regression. > When running Kafka Connect and submitting an HTTP GET request to the > /connector-plugins endpoint, the JSON serialized "type" filed in the body > response is now uppercase instead of being lowercase as in the past. > Following a comparison between Apache Kafka 4.1 ... > > > [{"class":"org.apache.kafka.connect.mirror.MirrorCheckpointConnector","type":"source","version":"4.1.1"},{"class":"org.apache.kafka.connect.mirror.MirrorHeartbeatConnector","type":"source","version":"4.1.1"},{"class":"org.apache.kafka.connect.mirror.MirrorSourceConnector","type":"source","version":"4.1.1"}] > > ... and the current Apache Kafka 4.2 RC0 > > > [{"class":"org.apache.kafka.connect.mirror.MirrorCheckpointConnector","type":"SOURCE","version":"4.2.0"},{"class":"org.apache.kafka.connect.mirror.MirrorHeartbeatConnector","type":"SOURCE","version":"4.2.0"},{"class":"org.apache.kafka.connect.mirror.MirrorSourceConnector","type":"SOURCE","version":"4.2.0"}] > > As you can see it's "source" vs "SOURCE". I had same result with "sink" vs > "SINK". > > I think this is due to the last change from converting the PluginInfo from > being a class to a record which had an impact together with the JSON > serialization. > When it was a class, a dedicated type.toString() was used which explicitly > does a lower case transformation. > As a record, the "type" field is directly serialized by JSON by using the > enum values from PluginType which are all uppercase of course. > It means that this issue affects all the other values as well the way they > are serialized (not just SINK, SOURCE but also CONVERTER, TRANSFORMATION, > and so on). > > If you like I could provide a contribution for that. > > Thanks, > Paolo. > > On Tue, 13 Jan 2026 at 17:04, Christo Lolov <[email protected]> > wrote: > >> Hello Kafka users, developers and client-developers, >> >> This is the RC0 candidate for release of Apache Kafka 4.2.0. >> >> This release has many exciting changes such as Kafka Queues being >> marked as production-ready, dead letter queues in Kafka Streams, a >> preview of the new Kafka Streams rebalance protocol, improved >> consistency across Kafka CLI arguments and metrics! >> >> I will raise a PR with a new blog post to the kafka-site repository in >> the next 24 hours and share the link as a reply to this thread. >> >> Release notes for the 4.2.0 release: >> https://dist.apache.org/repos/dist/dev/kafka/4.2.0-rc0/RELEASE_NOTES.html >> >> *** Please download, test and vote by Wednesday, January 21, 10am UTC >> >> Kafka's KEYS file containing PGP keys we use to sign the release: >> https://kafka.apache.org/KEYS >> >> * Release artifacts to be voted upon (source and binary): >> https://dist.apache.org/repos/dist/dev/kafka/4.2.0-rc0/ >> >> * Docker release artifacts to be voted upon: >> apache/kafka:4.2.0-rc0 >> apache/kafka-native:4.2.0-rc0 >> >> * Maven artifacts to be voted upon: >> https://repository.apache.org/content/groups/staging/org/apache/kafka/ >> >> * Javadoc: >> https://dist.apache.org/repos/dist/dev/kafka/4.2.0-rc0/javadoc/index.html >> >> * Tag to be voted upon (off 4.2 branch) is the 4.2.0 tag: >> https://github.com/apache/kafka/releases/tag/4.2.0-rc0 >> >> * Documentation: >> I will raise a PR with the changes to the kafka-site repository in the >> next 24 hours and share the link as a reply to this thread. >> >> * Protocol: >> I will raise a PR with the changes to the kafka-site repository in the >> next 24 hours and share the link as a reply to this thread. >> >> * Successful CI builds for the 4.2 branch: >> Unit/integration tests: >> https://github.com/apache/kafka/actions/runs/20953445348/job/60245258542 >> System tests: My environment needs to be recreated before I can share >> results from my end, so any results shared by voters would be greatly >> appreciated! >> >> * Successful Docker Image Github Actions Pipeline for 4.2 branch: >> Docker Build Test Pipeline (JVM): >> https://github.com/apache/kafka/actions/runs/20962291986 >> Docker Build Test Pipeline (Native): >> https://github.com/apache/kafka/actions/runs/20958037429 >> >> Note - when I run the quickstart against the JVM Docker image I need >> to specify the process.roles. I do not seem to need to specify the >> process.roles if I run the 4.1.1 image. I will run this once again >> tomorrow in another clean environment, but if somebody else can >> confirm/deny whether they can reproduce this beforehand this would >> also be greatly appreciated! >> >> Thanks, >> Christo >> > > > -- > Paolo Patierno > > *Senior Principal Software Engineer @ IBM**CNCF Ambassador* > > Twitter : @ppatierno <http://twitter.com/ppatierno> > Linkedin : paolopatierno <http://it.linkedin.com/in/paolopatierno> > GitHub : ppatierno <https://github.com/ppatierno> > -- Paolo Patierno *Senior Principal Software Engineer @ IBM**CNCF Ambassador* Twitter : @ppatierno <http://twitter.com/ppatierno> Linkedin : paolopatierno <http://it.linkedin.com/in/paolopatierno> GitHub : ppatierno <https://github.com/ppatierno>
