[VOTE] 4.0.0 RC4

[David Jacot]

Hello Kafka users, developers and client-developers,

This is the fourth candidate for release of Apache Kafka 4.0.0.

- This is the first release without Apache Zookeeper
- The Next Generation of the Consumer Rebalance Protocol is Generally Available
- The Transactions Server-Side Defense (Phase 2) is Generally Available
- Queues for Kafka is in Early Access
- Kafka uses log4j2
- Drop broker and tools support for Java 11
- Remove old client protocol API versions

Release notes for the 4.0.0 release:
https://dist.apache.org/repos/dist/dev/kafka/4.0.0-rc4/RELEASE_NOTES.html

*** Please download, test and vote by Monday, March 17, 9am PT.

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/4.0.0-rc4/

* Docker release artifacts to be voted upon:
apache/kafka:4.0.0-rc4
apache/kafka-native:4.0.0-rc4

* 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/4.0.0-rc4/javadoc/

* Tag to be voted upon (off 4.0 branch) is the 4.0.0 tag:
https://github.com/apache/kafka/releases/tag/4.0.0-rc4

* Documentation:
https://kafka.apache.org/40/documentation.html

* Protocol:
https://kafka.apache.org/40/protocol.html

* Successful CI builds for the 4.0 branch:
Unit/integration tests: https://github.com/apache/kafka/actions/runs/13846870683
System tests: https://confluent-open-source-kafka-branch-builder-system-test-results.s3-us-west-2.amazonaws.com/trunk/2025-03-13--001.6a14e68a-4791-44eb-a6be-24ce25bc1678--1741882266--apache--4.0--8f765a1886/report.html

* Successful Docker Image Github Actions Pipeline for 4.0 branch:
Docker Build Test Pipeline (JVM):
https://github.com/apache/kafka/actions/runs/13852844456
Docker Build Test Pipeline (Native):
https://github.com/apache/kafka/actions/runs/13853116713

/**************************************

Thanks,
David Jacot

[David Arthur]

David, thanks for running this behemoth of a release.

With the help of my coworker Mahsa Seifikar, we have verified the following upgrade scenario:

* Provision a ZK based Kafka cluster on 3.5 and create some topics

* Upgrade to 3.9

* Migrate to KRaft

* Upgrade to 4.0

We found a few docs issues which have since been fixed. One minor 3.9 docs issue is still pending, but that's not a blocker.

I also ran through the quickstart.

+1 binding

-David A

On Fri, Mar 14, 2025 at 7:57 AM Federico Valeri <fedev...@gmail.com> wrote:

Hi David, I've tested the RC4 and this is what I've done:

- Used the binaries to create a cluster and run clients from exampled module
- Tested the upgrade issue we found in KAFKA-18979
- Tested the dynamic quorum feature (both scale up and down)
- Tested group.protocol=consumer with a simple Java app
- Browsed the documentation and javadoc
- Tested the Docker images

+1 non binding

Thanks for running the release.

Cheers
Fede

--

David Arthur