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Posted to users@kafka.apache.org by Christo Lolov <ch...@gmail.com> on 2026/02/02 16:40:43 UTC
[VOTE] 4.2.0 RC3
Hello Kafka users, developers and client-developers,
This is the RC3 candidate for release of Apache Kafka 4.2.0.
This release has many exciting changes:
* Kafka Queues (Share Groups) is now production-ready with new
features like the RENEW acknowledgement type for extended processing
times, adaptive batching for coordinators, and comprehensive lag
metrics.
* Kafka Streams brings the server-side rebalance protocol to GA with a
limited feature set, adds dead letter queue support in exception
handlers, introduces anchored wall-clock punctuation for deterministic
scheduling, and gives users full control over whether to send a leave
group request on closing.
* This release also delivers significant improvements to consistency
and observability: CLI tools now feature standardized arguments like
--bootstrap-server across all tools, metric naming has been corrected
to follow the kafka.COMPONENT convention, and new idle ratio metrics
provide better visibility into controller and MetadataLoader
performance.
* Security is enhanced with a new allowlist connector client
configuration override policy, while thread-safety improvements to
RecordHeader eliminate concurrency risks.
* Additional highlights include external schema support in
JsonConverter for reduced message sizes, dynamic configuration for
remote log manager thread pools, and rack ID exposure in the Admin API
for consumer and share group members.
Release notes for the 4.2.0 release:
https://dist.apache.org/repos/dist/dev/kafka/4.2.0-rc3/RELEASE_NOTES.html
*** Please download, test and vote by Thursday, February 5, 5pm 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-rc3/
* Docker release artifacts to be voted upon:
apache/kafka:4.2.0-rc3
apache/kafka-native:4.2.0-rc3
* 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-rc3/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-rc3
* Documentation:
* Protocol:
https://github.com/apache/kafka-site/pull/785
* Successful CI builds for the 4.2 branch:
Unit/integration tests:
https://github.com/apache/kafka/actions/runs/21591368372
System tests: I have started the tests in my environment and will share test
results in the next ~24 hours.
* Successful Docker Image Github Actions Pipeline for 4.2 branch:
Docker Build Test Pipeline (JVM):
https://github.com/apache/kafka/actions/runs/21591979775
Docker Build Test Pipeline (Native):
https://github.com/apache/kafka/actions/runs/21592431252
Thanks,
Christo
Re: [VOTE] 4.2.0 RC3
Posted by Christo Lolov <ch...@gmail.com>.
Thanks David,
I saw that the fix to KAFKA-20115 landed in 4.2 earlier today!
Thanks Matthias,
I have now merged 21423 into 4.2 alongside
https://github.com/apache/kafka/pull/21366 and
https://github.com/apache/kafka/pull/21397.
I am now closing the vote for RC3 and will be raising a new RC tomorrow
morning (this gives a chance for some last-minute changes if any are
uncovered :)) with the aim to get a vote by Friday this week!
Best,
Christo
On Mon, 9 Feb 2026 at 19:38, Matthias J. Sax <mj...@apache.org> wrote:
> Thanks Christo,
>
> For the bug-fix, it doesn't cherry-pick cleanly, so we prepared a PR for
> it: https://github.com/apache/kafka/pull/21423
>
> -Matthias
>
> On 2/9/26 12:01 AM, David Jacot via dev wrote:
> > Hey all,
> >
> > While I agree that KAFKA-20115 is not a regression in 4.2, I think that
> > releasing 4.2 without the fix would be really bad as it impacts all
> groups
> > using the classic protocol. They experience long rebalances when the
> > underlying __consumer_offsets hosting them is reassigned in the cluster,
> > which is common with tools such as Cruise Control. It is pretty
> disruptive.
> >
> > Best,
> > David
> >
> > On Sun, Feb 8, 2026 at 12:32 PM Christo Lolov <ch...@gmail.com>
> > wrote:
> >
> >> Hello Mickael,
> >>
> >> In my opinion KAFKA-20115 is a blocker and necessitates another RC once
> >> merged. My hope is that one will be the last RC for 4.2.0. Let me know
> if
> >> you disagree with the classification.
> >>
> >> Hello Matthias,
> >>
> >> Before I prepare a new RC, I will cherry-pick the changes.
> >>
> >> Best,
> >> Christo
> >>
> >>> On 7 Feb 2026, at 00:03, Matthias J. Sax <mj...@apache.org> wrote:
> >>>
> >>> Hello,
> >>>
> >>> If we do a new RC, can we merge and cherry-pick two minor docs PRs?
> >>>
> >>> - https://github.com/apache/kafka/pull/21366
> >>> - https://github.com/apache/kafka/pull/21397
> >>>
> >>> Both already approved -- did just hold off to merge to `trunk`, to not
> >> later forget to do the cherry-pick.
> >>>
> >>>
> >>> I also just approved a bug-fix for
> >> https://issues.apache.org/jira/browse/KAFKA-19960 (
> >> https://github.com/apache/kafka/pull/21365) which is a critical bug.
> Also
> >> ok to only get into 4.2.1, but of course better to get into 4.2.0
> directly
> >> if there is no objection?
> >>>
> >>>
> >>> -Matthias
> >>>
> >>>
> >>>> On 2/6/26 6:59 AM, Mickael Maison wrote:
> >>>> Hi Christo,
> >>>> Can you clarify how you've triaged
> >>>> https://issues.apache.org/jira/browse/KAFKA-20115?
> >>>> Is it a regression that requires a new RC or not?
> >>>> Thanks,
> >>>> Mickael
> >>>>> On Tue, Feb 3, 2026 at 7:00 PM Sean Quah via dev <
> dev@kafka.apache.org>
> >> wrote:
> >>>>>
> >>>>> Hi all,
> >>>>> Unfortunately we discovered a regression in 4.2 today:
> >>>>> https://issues.apache.org/jira/browse/KAFKA-20115
> >>>>> The impact is that when we have a group coordinator leadership change
> >> in
> >>>>> the middle of consumer group rebalancing, we can leave parked
> >> JoinGroup and
> >>>>> SyncGroup requests hanging until clients time out the request. I
> think
> >> the
> >>>>> timeout interval is the rebalance timeout/max.poll.interval.ms which
> >> is 5
> >>>>> minutes long by default, so it can be fairly disruptive to consumer
> >>>>> applications.
> >>>>>
> >>>>> A fix is in progress at https://github.com/apache/kafka/pull/21396.
> >>>>>
> >>>>> Thanks,
> >>>>> Sean
> >>>>>
> >>>>>> On Mon, Feb 2, 2026 at 4:42 PM Christo Lolov <
> christololov@gmail.com>
> >> wrote:
> >>>>>
> >>>>>> Hello Kafka users, developers and client-developers,
> >>>>>>
> >>>>>> This is the RC3 candidate for release of Apache Kafka 4.2.0.
> >>>>>>
> >>>>>> This release has many exciting changes:
> >>>>>> * Kafka Queues (Share Groups) is now production-ready with new
> >>>>>> features like the RENEW acknowledgement type for extended processing
> >>>>>> times, adaptive batching for coordinators, and comprehensive lag
> >>>>>> metrics.
> >>>>>> * Kafka Streams brings the server-side rebalance protocol to GA
> with a
> >>>>>> limited feature set, adds dead letter queue support in exception
> >>>>>> handlers, introduces anchored wall-clock punctuation for
> deterministic
> >>>>>> scheduling, and gives users full control over whether to send a
> leave
> >>>>>> group request on closing.
> >>>>>> * This release also delivers significant improvements to consistency
> >>>>>> and observability: CLI tools now feature standardized arguments like
> >>>>>> --bootstrap-server across all tools, metric naming has been
> corrected
> >>>>>> to follow the kafka.COMPONENT convention, and new idle ratio metrics
> >>>>>> provide better visibility into controller and MetadataLoader
> >>>>>> performance.
> >>>>>> * Security is enhanced with a new allowlist connector client
> >>>>>> configuration override policy, while thread-safety improvements to
> >>>>>> RecordHeader eliminate concurrency risks.
> >>>>>> * Additional highlights include external schema support in
> >>>>>> JsonConverter for reduced message sizes, dynamic configuration for
> >>>>>> remote log manager thread pools, and rack ID exposure in the Admin
> API
> >>>>>> for consumer and share group members.
> >>>>>>
> >>>>>> Release notes for the 4.2.0 release:
> >>>>>>
> >>
> https://dist.apache.org/repos/dist/dev/kafka/4.2.0-rc3/RELEASE_NOTES.html
> >>>>>>
> >>>>>> *** Please download, test and vote by Thursday, February 5, 5pm 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-rc3/
> >>>>>>
> >>>>>> * Docker release artifacts to be voted upon:
> >>>>>> apache/kafka:4.2.0-rc3
> >>>>>> apache/kafka-native:4.2.0-rc3
> >>>>>>
> >>>>>> * 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-rc3/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-rc3
> >>>>>>
> >>>>>> * Documentation:
> >>>>>> * Protocol:
> >>>>>> https://github.com/apache/kafka-site/pull/785
> >>>>>>
> >>>>>> * Successful CI builds for the 4.2 branch:
> >>>>>> Unit/integration tests:
> >>>>>> https://github.com/apache/kafka/actions/runs/21591368372
> >>>>>> System tests: I have started the tests in my environment and will
> >> share
> >>>>>> test
> >>>>>> results in the next ~24 hours.
> >>>>>>
> >>>>>> * Successful Docker Image Github Actions Pipeline for 4.2 branch:
> >>>>>> Docker Build Test Pipeline (JVM):
> >>>>>> https://github.com/apache/kafka/actions/runs/21591979775
> >>>>>> Docker Build Test Pipeline (Native):
> >>>>>> https://github.com/apache/kafka/actions/runs/21592431252
> >>>>>>
> >>>>>> Thanks,
> >>>>>> Christo
> >>>>>>
> >>>
> >>
> >
>
>
Re: [VOTE] 4.2.0 RC3
Posted by "Matthias J. Sax" <mj...@apache.org>.
Thanks Christo,
For the bug-fix, it doesn't cherry-pick cleanly, so we prepared a PR for
it: https://github.com/apache/kafka/pull/21423
-Matthias
On 2/9/26 12:01 AM, David Jacot via dev wrote:
> Hey all,
>
> While I agree that KAFKA-20115 is not a regression in 4.2, I think that
> releasing 4.2 without the fix would be really bad as it impacts all groups
> using the classic protocol. They experience long rebalances when the
> underlying __consumer_offsets hosting them is reassigned in the cluster,
> which is common with tools such as Cruise Control. It is pretty disruptive.
>
> Best,
> David
>
> On Sun, Feb 8, 2026 at 12:32 PM Christo Lolov <ch...@gmail.com>
> wrote:
>
>> Hello Mickael,
>>
>> In my opinion KAFKA-20115 is a blocker and necessitates another RC once
>> merged. My hope is that one will be the last RC for 4.2.0. Let me know if
>> you disagree with the classification.
>>
>> Hello Matthias,
>>
>> Before I prepare a new RC, I will cherry-pick the changes.
>>
>> Best,
>> Christo
>>
>>> On 7 Feb 2026, at 00:03, Matthias J. Sax <mj...@apache.org> wrote:
>>>
>>> Hello,
>>>
>>> If we do a new RC, can we merge and cherry-pick two minor docs PRs?
>>>
>>> - https://github.com/apache/kafka/pull/21366
>>> - https://github.com/apache/kafka/pull/21397
>>>
>>> Both already approved -- did just hold off to merge to `trunk`, to not
>> later forget to do the cherry-pick.
>>>
>>>
>>> I also just approved a bug-fix for
>> https://issues.apache.org/jira/browse/KAFKA-19960 (
>> https://github.com/apache/kafka/pull/21365) which is a critical bug. Also
>> ok to only get into 4.2.1, but of course better to get into 4.2.0 directly
>> if there is no objection?
>>>
>>>
>>> -Matthias
>>>
>>>
>>>> On 2/6/26 6:59 AM, Mickael Maison wrote:
>>>> Hi Christo,
>>>> Can you clarify how you've triaged
>>>> https://issues.apache.org/jira/browse/KAFKA-20115?
>>>> Is it a regression that requires a new RC or not?
>>>> Thanks,
>>>> Mickael
>>>>> On Tue, Feb 3, 2026 at 7:00 PM Sean Quah via dev <de...@kafka.apache.org>
>> wrote:
>>>>>
>>>>> Hi all,
>>>>> Unfortunately we discovered a regression in 4.2 today:
>>>>> https://issues.apache.org/jira/browse/KAFKA-20115
>>>>> The impact is that when we have a group coordinator leadership change
>> in
>>>>> the middle of consumer group rebalancing, we can leave parked
>> JoinGroup and
>>>>> SyncGroup requests hanging until clients time out the request. I think
>> the
>>>>> timeout interval is the rebalance timeout/max.poll.interval.ms which
>> is 5
>>>>> minutes long by default, so it can be fairly disruptive to consumer
>>>>> applications.
>>>>>
>>>>> A fix is in progress at https://github.com/apache/kafka/pull/21396.
>>>>>
>>>>> Thanks,
>>>>> Sean
>>>>>
>>>>>> On Mon, Feb 2, 2026 at 4:42 PM Christo Lolov <ch...@gmail.com>
>> wrote:
>>>>>
>>>>>> Hello Kafka users, developers and client-developers,
>>>>>>
>>>>>> This is the RC3 candidate for release of Apache Kafka 4.2.0.
>>>>>>
>>>>>> This release has many exciting changes:
>>>>>> * Kafka Queues (Share Groups) is now production-ready with new
>>>>>> features like the RENEW acknowledgement type for extended processing
>>>>>> times, adaptive batching for coordinators, and comprehensive lag
>>>>>> metrics.
>>>>>> * Kafka Streams brings the server-side rebalance protocol to GA with a
>>>>>> limited feature set, adds dead letter queue support in exception
>>>>>> handlers, introduces anchored wall-clock punctuation for deterministic
>>>>>> scheduling, and gives users full control over whether to send a leave
>>>>>> group request on closing.
>>>>>> * This release also delivers significant improvements to consistency
>>>>>> and observability: CLI tools now feature standardized arguments like
>>>>>> --bootstrap-server across all tools, metric naming has been corrected
>>>>>> to follow the kafka.COMPONENT convention, and new idle ratio metrics
>>>>>> provide better visibility into controller and MetadataLoader
>>>>>> performance.
>>>>>> * Security is enhanced with a new allowlist connector client
>>>>>> configuration override policy, while thread-safety improvements to
>>>>>> RecordHeader eliminate concurrency risks.
>>>>>> * Additional highlights include external schema support in
>>>>>> JsonConverter for reduced message sizes, dynamic configuration for
>>>>>> remote log manager thread pools, and rack ID exposure in the Admin API
>>>>>> for consumer and share group members.
>>>>>>
>>>>>> Release notes for the 4.2.0 release:
>>>>>>
>> https://dist.apache.org/repos/dist/dev/kafka/4.2.0-rc3/RELEASE_NOTES.html
>>>>>>
>>>>>> *** Please download, test and vote by Thursday, February 5, 5pm 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-rc3/
>>>>>>
>>>>>> * Docker release artifacts to be voted upon:
>>>>>> apache/kafka:4.2.0-rc3
>>>>>> apache/kafka-native:4.2.0-rc3
>>>>>>
>>>>>> * 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-rc3/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-rc3
>>>>>>
>>>>>> * Documentation:
>>>>>> * Protocol:
>>>>>> https://github.com/apache/kafka-site/pull/785
>>>>>>
>>>>>> * Successful CI builds for the 4.2 branch:
>>>>>> Unit/integration tests:
>>>>>> https://github.com/apache/kafka/actions/runs/21591368372
>>>>>> System tests: I have started the tests in my environment and will
>> share
>>>>>> test
>>>>>> results in the next ~24 hours.
>>>>>>
>>>>>> * Successful Docker Image Github Actions Pipeline for 4.2 branch:
>>>>>> Docker Build Test Pipeline (JVM):
>>>>>> https://github.com/apache/kafka/actions/runs/21591979775
>>>>>> Docker Build Test Pipeline (Native):
>>>>>> https://github.com/apache/kafka/actions/runs/21592431252
>>>>>>
>>>>>> Thanks,
>>>>>> Christo
>>>>>>
>>>
>>
>
Re: [VOTE] 4.2.0 RC3
Posted by David Jacot via dev <de...@kafka.apache.org>.
Hey all,
While I agree that KAFKA-20115 is not a regression in 4.2, I think that
releasing 4.2 without the fix would be really bad as it impacts all groups
using the classic protocol. They experience long rebalances when the
underlying __consumer_offsets hosting them is reassigned in the cluster,
which is common with tools such as Cruise Control. It is pretty disruptive.
Best,
David
On Sun, Feb 8, 2026 at 12:32 PM Christo Lolov <ch...@gmail.com>
wrote:
> Hello Mickael,
>
> In my opinion KAFKA-20115 is a blocker and necessitates another RC once
> merged. My hope is that one will be the last RC for 4.2.0. Let me know if
> you disagree with the classification.
>
> Hello Matthias,
>
> Before I prepare a new RC, I will cherry-pick the changes.
>
> Best,
> Christo
>
> > On 7 Feb 2026, at 00:03, Matthias J. Sax <mj...@apache.org> wrote:
> >
> > Hello,
> >
> > If we do a new RC, can we merge and cherry-pick two minor docs PRs?
> >
> > - https://github.com/apache/kafka/pull/21366
> > - https://github.com/apache/kafka/pull/21397
> >
> > Both already approved -- did just hold off to merge to `trunk`, to not
> later forget to do the cherry-pick.
> >
> >
> > I also just approved a bug-fix for
> https://issues.apache.org/jira/browse/KAFKA-19960 (
> https://github.com/apache/kafka/pull/21365) which is a critical bug. Also
> ok to only get into 4.2.1, but of course better to get into 4.2.0 directly
> if there is no objection?
> >
> >
> > -Matthias
> >
> >
> >> On 2/6/26 6:59 AM, Mickael Maison wrote:
> >> Hi Christo,
> >> Can you clarify how you've triaged
> >> https://issues.apache.org/jira/browse/KAFKA-20115?
> >> Is it a regression that requires a new RC or not?
> >> Thanks,
> >> Mickael
> >>> On Tue, Feb 3, 2026 at 7:00 PM Sean Quah via dev <de...@kafka.apache.org>
> wrote:
> >>>
> >>> Hi all,
> >>> Unfortunately we discovered a regression in 4.2 today:
> >>> https://issues.apache.org/jira/browse/KAFKA-20115
> >>> The impact is that when we have a group coordinator leadership change
> in
> >>> the middle of consumer group rebalancing, we can leave parked
> JoinGroup and
> >>> SyncGroup requests hanging until clients time out the request. I think
> the
> >>> timeout interval is the rebalance timeout/max.poll.interval.ms which
> is 5
> >>> minutes long by default, so it can be fairly disruptive to consumer
> >>> applications.
> >>>
> >>> A fix is in progress at https://github.com/apache/kafka/pull/21396.
> >>>
> >>> Thanks,
> >>> Sean
> >>>
> >>>> On Mon, Feb 2, 2026 at 4:42 PM Christo Lolov <ch...@gmail.com>
> wrote:
> >>>
> >>>> Hello Kafka users, developers and client-developers,
> >>>>
> >>>> This is the RC3 candidate for release of Apache Kafka 4.2.0.
> >>>>
> >>>> This release has many exciting changes:
> >>>> * Kafka Queues (Share Groups) is now production-ready with new
> >>>> features like the RENEW acknowledgement type for extended processing
> >>>> times, adaptive batching for coordinators, and comprehensive lag
> >>>> metrics.
> >>>> * Kafka Streams brings the server-side rebalance protocol to GA with a
> >>>> limited feature set, adds dead letter queue support in exception
> >>>> handlers, introduces anchored wall-clock punctuation for deterministic
> >>>> scheduling, and gives users full control over whether to send a leave
> >>>> group request on closing.
> >>>> * This release also delivers significant improvements to consistency
> >>>> and observability: CLI tools now feature standardized arguments like
> >>>> --bootstrap-server across all tools, metric naming has been corrected
> >>>> to follow the kafka.COMPONENT convention, and new idle ratio metrics
> >>>> provide better visibility into controller and MetadataLoader
> >>>> performance.
> >>>> * Security is enhanced with a new allowlist connector client
> >>>> configuration override policy, while thread-safety improvements to
> >>>> RecordHeader eliminate concurrency risks.
> >>>> * Additional highlights include external schema support in
> >>>> JsonConverter for reduced message sizes, dynamic configuration for
> >>>> remote log manager thread pools, and rack ID exposure in the Admin API
> >>>> for consumer and share group members.
> >>>>
> >>>> Release notes for the 4.2.0 release:
> >>>>
> https://dist.apache.org/repos/dist/dev/kafka/4.2.0-rc3/RELEASE_NOTES.html
> >>>>
> >>>> *** Please download, test and vote by Thursday, February 5, 5pm 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-rc3/
> >>>>
> >>>> * Docker release artifacts to be voted upon:
> >>>> apache/kafka:4.2.0-rc3
> >>>> apache/kafka-native:4.2.0-rc3
> >>>>
> >>>> * 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-rc3/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-rc3
> >>>>
> >>>> * Documentation:
> >>>> * Protocol:
> >>>> https://github.com/apache/kafka-site/pull/785
> >>>>
> >>>> * Successful CI builds for the 4.2 branch:
> >>>> Unit/integration tests:
> >>>> https://github.com/apache/kafka/actions/runs/21591368372
> >>>> System tests: I have started the tests in my environment and will
> share
> >>>> test
> >>>> results in the next ~24 hours.
> >>>>
> >>>> * Successful Docker Image Github Actions Pipeline for 4.2 branch:
> >>>> Docker Build Test Pipeline (JVM):
> >>>> https://github.com/apache/kafka/actions/runs/21591979775
> >>>> Docker Build Test Pipeline (Native):
> >>>> https://github.com/apache/kafka/actions/runs/21592431252
> >>>>
> >>>> Thanks,
> >>>> Christo
> >>>>
> >
>
Re: [VOTE] 4.2.0 RC3
Posted by Christo Lolov <ch...@gmail.com>.
Hello Mickael,
In my opinion KAFKA-20115 is a blocker and necessitates another RC once merged. My hope is that one will be the last RC for 4.2.0. Let me know if you disagree with the classification.
Hello Matthias,
Before I prepare a new RC, I will cherry-pick the changes.
Best,
Christo
> On 7 Feb 2026, at 00:03, Matthias J. Sax <mj...@apache.org> wrote:
>
> Hello,
>
> If we do a new RC, can we merge and cherry-pick two minor docs PRs?
>
> - https://github.com/apache/kafka/pull/21366
> - https://github.com/apache/kafka/pull/21397
>
> Both already approved -- did just hold off to merge to `trunk`, to not later forget to do the cherry-pick.
>
>
> I also just approved a bug-fix for https://issues.apache.org/jira/browse/KAFKA-19960 (https://github.com/apache/kafka/pull/21365) which is a critical bug. Also ok to only get into 4.2.1, but of course better to get into 4.2.0 directly if there is no objection?
>
>
> -Matthias
>
>
>> On 2/6/26 6:59 AM, Mickael Maison wrote:
>> Hi Christo,
>> Can you clarify how you've triaged
>> https://issues.apache.org/jira/browse/KAFKA-20115?
>> Is it a regression that requires a new RC or not?
>> Thanks,
>> Mickael
>>> On Tue, Feb 3, 2026 at 7:00 PM Sean Quah via dev <de...@kafka.apache.org> wrote:
>>>
>>> Hi all,
>>> Unfortunately we discovered a regression in 4.2 today:
>>> https://issues.apache.org/jira/browse/KAFKA-20115
>>> The impact is that when we have a group coordinator leadership change in
>>> the middle of consumer group rebalancing, we can leave parked JoinGroup and
>>> SyncGroup requests hanging until clients time out the request. I think the
>>> timeout interval is the rebalance timeout/max.poll.interval.ms which is 5
>>> minutes long by default, so it can be fairly disruptive to consumer
>>> applications.
>>>
>>> A fix is in progress at https://github.com/apache/kafka/pull/21396.
>>>
>>> Thanks,
>>> Sean
>>>
>>>> On Mon, Feb 2, 2026 at 4:42 PM Christo Lolov <ch...@gmail.com> wrote:
>>>
>>>> Hello Kafka users, developers and client-developers,
>>>>
>>>> This is the RC3 candidate for release of Apache Kafka 4.2.0.
>>>>
>>>> This release has many exciting changes:
>>>> * Kafka Queues (Share Groups) is now production-ready with new
>>>> features like the RENEW acknowledgement type for extended processing
>>>> times, adaptive batching for coordinators, and comprehensive lag
>>>> metrics.
>>>> * Kafka Streams brings the server-side rebalance protocol to GA with a
>>>> limited feature set, adds dead letter queue support in exception
>>>> handlers, introduces anchored wall-clock punctuation for deterministic
>>>> scheduling, and gives users full control over whether to send a leave
>>>> group request on closing.
>>>> * This release also delivers significant improvements to consistency
>>>> and observability: CLI tools now feature standardized arguments like
>>>> --bootstrap-server across all tools, metric naming has been corrected
>>>> to follow the kafka.COMPONENT convention, and new idle ratio metrics
>>>> provide better visibility into controller and MetadataLoader
>>>> performance.
>>>> * Security is enhanced with a new allowlist connector client
>>>> configuration override policy, while thread-safety improvements to
>>>> RecordHeader eliminate concurrency risks.
>>>> * Additional highlights include external schema support in
>>>> JsonConverter for reduced message sizes, dynamic configuration for
>>>> remote log manager thread pools, and rack ID exposure in the Admin API
>>>> for consumer and share group members.
>>>>
>>>> Release notes for the 4.2.0 release:
>>>> https://dist.apache.org/repos/dist/dev/kafka/4.2.0-rc3/RELEASE_NOTES.html
>>>>
>>>> *** Please download, test and vote by Thursday, February 5, 5pm 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-rc3/
>>>>
>>>> * Docker release artifacts to be voted upon:
>>>> apache/kafka:4.2.0-rc3
>>>> apache/kafka-native:4.2.0-rc3
>>>>
>>>> * 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-rc3/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-rc3
>>>>
>>>> * Documentation:
>>>> * Protocol:
>>>> https://github.com/apache/kafka-site/pull/785
>>>>
>>>> * Successful CI builds for the 4.2 branch:
>>>> Unit/integration tests:
>>>> https://github.com/apache/kafka/actions/runs/21591368372
>>>> System tests: I have started the tests in my environment and will share
>>>> test
>>>> results in the next ~24 hours.
>>>>
>>>> * Successful Docker Image Github Actions Pipeline for 4.2 branch:
>>>> Docker Build Test Pipeline (JVM):
>>>> https://github.com/apache/kafka/actions/runs/21591979775
>>>> Docker Build Test Pipeline (Native):
>>>> https://github.com/apache/kafka/actions/runs/21592431252
>>>>
>>>> Thanks,
>>>> Christo
>>>>
>
Re: [VOTE] 4.2.0 RC3
Posted by "Matthias J. Sax" <mj...@apache.org>.
Hello,
If we do a new RC, can we merge and cherry-pick two minor docs PRs?
- https://github.com/apache/kafka/pull/21366
- https://github.com/apache/kafka/pull/21397
Both already approved -- did just hold off to merge to `trunk`, to not
later forget to do the cherry-pick.
I also just approved a bug-fix for
https://issues.apache.org/jira/browse/KAFKA-19960
(https://github.com/apache/kafka/pull/21365) which is a critical bug.
Also ok to only get into 4.2.1, but of course better to get into 4.2.0
directly if there is no objection?
-Matthias
On 2/6/26 6:59 AM, Mickael Maison wrote:
> Hi Christo,
>
> Can you clarify how you've triaged
> https://issues.apache.org/jira/browse/KAFKA-20115?
> Is it a regression that requires a new RC or not?
>
> Thanks,
> Mickael
>
> On Tue, Feb 3, 2026 at 7:00 PM Sean Quah via dev <de...@kafka.apache.org> wrote:
>>
>> Hi all,
>> Unfortunately we discovered a regression in 4.2 today:
>> https://issues.apache.org/jira/browse/KAFKA-20115
>> The impact is that when we have a group coordinator leadership change in
>> the middle of consumer group rebalancing, we can leave parked JoinGroup and
>> SyncGroup requests hanging until clients time out the request. I think the
>> timeout interval is the rebalance timeout/max.poll.interval.ms which is 5
>> minutes long by default, so it can be fairly disruptive to consumer
>> applications.
>>
>> A fix is in progress at https://github.com/apache/kafka/pull/21396.
>>
>> Thanks,
>> Sean
>>
>> On Mon, Feb 2, 2026 at 4:42 PM Christo Lolov <ch...@gmail.com> wrote:
>>
>>> Hello Kafka users, developers and client-developers,
>>>
>>> This is the RC3 candidate for release of Apache Kafka 4.2.0.
>>>
>>> This release has many exciting changes:
>>> * Kafka Queues (Share Groups) is now production-ready with new
>>> features like the RENEW acknowledgement type for extended processing
>>> times, adaptive batching for coordinators, and comprehensive lag
>>> metrics.
>>> * Kafka Streams brings the server-side rebalance protocol to GA with a
>>> limited feature set, adds dead letter queue support in exception
>>> handlers, introduces anchored wall-clock punctuation for deterministic
>>> scheduling, and gives users full control over whether to send a leave
>>> group request on closing.
>>> * This release also delivers significant improvements to consistency
>>> and observability: CLI tools now feature standardized arguments like
>>> --bootstrap-server across all tools, metric naming has been corrected
>>> to follow the kafka.COMPONENT convention, and new idle ratio metrics
>>> provide better visibility into controller and MetadataLoader
>>> performance.
>>> * Security is enhanced with a new allowlist connector client
>>> configuration override policy, while thread-safety improvements to
>>> RecordHeader eliminate concurrency risks.
>>> * Additional highlights include external schema support in
>>> JsonConverter for reduced message sizes, dynamic configuration for
>>> remote log manager thread pools, and rack ID exposure in the Admin API
>>> for consumer and share group members.
>>>
>>> Release notes for the 4.2.0 release:
>>> https://dist.apache.org/repos/dist/dev/kafka/4.2.0-rc3/RELEASE_NOTES.html
>>>
>>> *** Please download, test and vote by Thursday, February 5, 5pm 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-rc3/
>>>
>>> * Docker release artifacts to be voted upon:
>>> apache/kafka:4.2.0-rc3
>>> apache/kafka-native:4.2.0-rc3
>>>
>>> * 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-rc3/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-rc3
>>>
>>> * Documentation:
>>> * Protocol:
>>> https://github.com/apache/kafka-site/pull/785
>>>
>>> * Successful CI builds for the 4.2 branch:
>>> Unit/integration tests:
>>> https://github.com/apache/kafka/actions/runs/21591368372
>>> System tests: I have started the tests in my environment and will share
>>> test
>>> results in the next ~24 hours.
>>>
>>> * Successful Docker Image Github Actions Pipeline for 4.2 branch:
>>> Docker Build Test Pipeline (JVM):
>>> https://github.com/apache/kafka/actions/runs/21591979775
>>> Docker Build Test Pipeline (Native):
>>> https://github.com/apache/kafka/actions/runs/21592431252
>>>
>>> Thanks,
>>> Christo
>>>
Re: [VOTE] 4.2.0 RC3
Posted by Mickael Maison <mi...@gmail.com>.
Hi Christo,
Can you clarify how you've triaged
https://issues.apache.org/jira/browse/KAFKA-20115?
Is it a regression that requires a new RC or not?
Thanks,
Mickael
On Tue, Feb 3, 2026 at 7:00 PM Sean Quah via dev <de...@kafka.apache.org> wrote:
>
> Hi all,
> Unfortunately we discovered a regression in 4.2 today:
> https://issues.apache.org/jira/browse/KAFKA-20115
> The impact is that when we have a group coordinator leadership change in
> the middle of consumer group rebalancing, we can leave parked JoinGroup and
> SyncGroup requests hanging until clients time out the request. I think the
> timeout interval is the rebalance timeout/max.poll.interval.ms which is 5
> minutes long by default, so it can be fairly disruptive to consumer
> applications.
>
> A fix is in progress at https://github.com/apache/kafka/pull/21396.
>
> Thanks,
> Sean
>
> On Mon, Feb 2, 2026 at 4:42 PM Christo Lolov <ch...@gmail.com> wrote:
>
> > Hello Kafka users, developers and client-developers,
> >
> > This is the RC3 candidate for release of Apache Kafka 4.2.0.
> >
> > This release has many exciting changes:
> > * Kafka Queues (Share Groups) is now production-ready with new
> > features like the RENEW acknowledgement type for extended processing
> > times, adaptive batching for coordinators, and comprehensive lag
> > metrics.
> > * Kafka Streams brings the server-side rebalance protocol to GA with a
> > limited feature set, adds dead letter queue support in exception
> > handlers, introduces anchored wall-clock punctuation for deterministic
> > scheduling, and gives users full control over whether to send a leave
> > group request on closing.
> > * This release also delivers significant improvements to consistency
> > and observability: CLI tools now feature standardized arguments like
> > --bootstrap-server across all tools, metric naming has been corrected
> > to follow the kafka.COMPONENT convention, and new idle ratio metrics
> > provide better visibility into controller and MetadataLoader
> > performance.
> > * Security is enhanced with a new allowlist connector client
> > configuration override policy, while thread-safety improvements to
> > RecordHeader eliminate concurrency risks.
> > * Additional highlights include external schema support in
> > JsonConverter for reduced message sizes, dynamic configuration for
> > remote log manager thread pools, and rack ID exposure in the Admin API
> > for consumer and share group members.
> >
> > Release notes for the 4.2.0 release:
> > https://dist.apache.org/repos/dist/dev/kafka/4.2.0-rc3/RELEASE_NOTES.html
> >
> > *** Please download, test and vote by Thursday, February 5, 5pm 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-rc3/
> >
> > * Docker release artifacts to be voted upon:
> > apache/kafka:4.2.0-rc3
> > apache/kafka-native:4.2.0-rc3
> >
> > * 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-rc3/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-rc3
> >
> > * Documentation:
> > * Protocol:
> > https://github.com/apache/kafka-site/pull/785
> >
> > * Successful CI builds for the 4.2 branch:
> > Unit/integration tests:
> > https://github.com/apache/kafka/actions/runs/21591368372
> > System tests: I have started the tests in my environment and will share
> > test
> > results in the next ~24 hours.
> >
> > * Successful Docker Image Github Actions Pipeline for 4.2 branch:
> > Docker Build Test Pipeline (JVM):
> > https://github.com/apache/kafka/actions/runs/21591979775
> > Docker Build Test Pipeline (Native):
> > https://github.com/apache/kafka/actions/runs/21592431252
> >
> > Thanks,
> > Christo
> >
Re: [VOTE] 4.2.0 RC3
Posted by Sean Quah via dev <de...@kafka.apache.org>.
Hi all,
Unfortunately we discovered a regression in 4.2 today:
https://issues.apache.org/jira/browse/KAFKA-20115
The impact is that when we have a group coordinator leadership change in
the middle of consumer group rebalancing, we can leave parked JoinGroup and
SyncGroup requests hanging until clients time out the request. I think the
timeout interval is the rebalance timeout/max.poll.interval.ms which is 5
minutes long by default, so it can be fairly disruptive to consumer
applications.
A fix is in progress at https://github.com/apache/kafka/pull/21396.
Thanks,
Sean
On Mon, Feb 2, 2026 at 4:42 PM Christo Lolov <ch...@gmail.com> wrote:
> Hello Kafka users, developers and client-developers,
>
> This is the RC3 candidate for release of Apache Kafka 4.2.0.
>
> This release has many exciting changes:
> * Kafka Queues (Share Groups) is now production-ready with new
> features like the RENEW acknowledgement type for extended processing
> times, adaptive batching for coordinators, and comprehensive lag
> metrics.
> * Kafka Streams brings the server-side rebalance protocol to GA with a
> limited feature set, adds dead letter queue support in exception
> handlers, introduces anchored wall-clock punctuation for deterministic
> scheduling, and gives users full control over whether to send a leave
> group request on closing.
> * This release also delivers significant improvements to consistency
> and observability: CLI tools now feature standardized arguments like
> --bootstrap-server across all tools, metric naming has been corrected
> to follow the kafka.COMPONENT convention, and new idle ratio metrics
> provide better visibility into controller and MetadataLoader
> performance.
> * Security is enhanced with a new allowlist connector client
> configuration override policy, while thread-safety improvements to
> RecordHeader eliminate concurrency risks.
> * Additional highlights include external schema support in
> JsonConverter for reduced message sizes, dynamic configuration for
> remote log manager thread pools, and rack ID exposure in the Admin API
> for consumer and share group members.
>
> Release notes for the 4.2.0 release:
> https://dist.apache.org/repos/dist/dev/kafka/4.2.0-rc3/RELEASE_NOTES.html
>
> *** Please download, test and vote by Thursday, February 5, 5pm 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-rc3/
>
> * Docker release artifacts to be voted upon:
> apache/kafka:4.2.0-rc3
> apache/kafka-native:4.2.0-rc3
>
> * 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-rc3/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-rc3
>
> * Documentation:
> * Protocol:
> https://github.com/apache/kafka-site/pull/785
>
> * Successful CI builds for the 4.2 branch:
> Unit/integration tests:
> https://github.com/apache/kafka/actions/runs/21591368372
> System tests: I have started the tests in my environment and will share
> test
> results in the next ~24 hours.
>
> * Successful Docker Image Github Actions Pipeline for 4.2 branch:
> Docker Build Test Pipeline (JVM):
> https://github.com/apache/kafka/actions/runs/21591979775
> Docker Build Test Pipeline (Native):
> https://github.com/apache/kafka/actions/runs/21592431252
>
> Thanks,
> Christo
>