[VOTE] 4.1.0 RC2

[Mickael Maison]

Hello Kafka users, developers and client-developers,

This is the third candidate for release of Apache Kafka 4.1.0.

The release brings many new features and improvements:
- Mechanism for plugin to register metrics
- Allow running multiple versions of connector plugins
- Queue are now in preview access
- New Streams rebalance protocol in early access
- Support for OAuth jwt-bearer grant type
- Improved metadata replication

Release notes for the 4.1.0 release:
https://dist.apache.org/repos/dist/dev/kafka/4.1.0-rc2/RELEASE_NOTES.html

*** Please download, test and vote by Friday August 8.

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/4.1.0-rc2/

* Docker release artifacts to be voted upon:
apache/kafka:4.1.0-rc2
apache/kafka-native:4.1.0-rc2

* 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/4.1.0-rc2/javadoc/

* Tag to be voted upon (off 4.1 branch) is the 4.1.0 tag:
https://github.com/apache/kafka/releases/tag/4.1.0-rc2

* Documentation:
https://kafka.apache.org/41/documentation.html
PR (https://github.com/apache/kafka-site/pull/702) updated for RC2 is
not merged yet

* Protocol:
https://kafka.apache.org/41/protocol.html
PR (https://github.com/apache/kafka-site/pull/702) updated for RC2 is
not merged yet

* Successful CI builds for the 4.1 branch:
Unit/integration tests: https://github.com/apache/kafka/actions/runs/16753255070
System tests: Tests are currently running, I'll post the results once
they complete

* Successful Docker Image Github Actions Pipeline for 4.1 branch:
Docker Build Test Pipeline (JVM):
https://github.com/apache/kafka/actions/runs/16753270537
Docker Build Test Pipeline (Native):
https://github.com/apache/kafka/actions/runs/16753280218

Thanks,
Mickael

[Mickael Maison]

Hi,

Here are the system test results. To speed it up I ran
kafkatest/tests/core and all the other ones in parallel:
- core: https://drive.google.com/file/d/1nvFq2L35FgFRF9PL6Zv7iRK56V2-ZBft/view?usp=drive_link
- non-core: https://drive.google.com/file/d/1vzdVxEBmaJYa32PWuobu_UvgKIrovrjZ/view?usp=drive_link

The only failure is still
kafkatest.tests.core.network_degrade_test.test_rate_device_name=eth0_latency_ms=50_metadata_quorum=COMBINED_KRAFT_rate_limit_kbit=1000000_task_name=rate-1000-latency-50
This is tracked in https://issues.apache.org/jira/browse/KAFKA-19549

Thanks,
Mickael

[Luke Chen]

Hi Mickael,

Thanks for running this release.

I’ve completed the following tasks:

1. Verify the signature and checksum

2. Run the quickstart

3. Upgrade from v4.0.0, make sure ELR features works, then downgrade the ELR to disable the feature, and make sure it still works well.

4. Browse the doc PR, it looks like the content is still in v4.0.0. It's not a blocker for sure. We can discuss that in PR.

+1 (binding) from me.

Thank you.

Luke

On Thu, Aug 7, 2025 at 2:36 PM Paolo Patierno <paolo.p...@gmail.com> wrote:

We ran all regression tests with Strimzi and everything looks good.

+1 (non binding)

Thanks,
Paolo

--
Paolo Patierno

*Senior Principal Software Engineer @ IBM**CNCF Ambassador*

Twitter : @ppatierno <http://twitter.com/ppatierno>
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GitHub : ppatierno <https://github.com/ppatierno>