Hi Fabian,

Sorry, for the late reply, this message somehow ended up in my spam filter!? 

I think having the Flink 2.1 upgrade included in the move to Flink Connector 
Kafka 5.0 makes sense. 
I am hoping to find the time to work on the upgrade to Flink 2.1 at end of this 
week or next. 
Unless, of course, you are plan to work on that?

Regards,

Tom Cooper
@tomcooper.dev | https://tomcooper.dev


On Tuesday, 29 July 2025 at 09:08, Fabian Paul <fp...@confluent.io.INVALID> 
wrote:

> Hi Tom,
> 
> Sounds good to me, I can start with the 4.0.1 release.
> Regarding the 5.0 release, I am not super sure yet what to include.
> Since releasing always takes some effort, I would also be okay with
> doing the 5.0 release with incorporating Flink 2.1. The connector
> already offers a release that is compatible with Flink 2.0, and in
> theory, 2.1 should not introduce breaking changes that affect the
> connector.
> 
> Best,
> Fabian
> 
> On Mon, Jul 28, 2025 at 11:03 AM Tom Cooper c...@tomcooper.dev wrote:
> 
> > Hi Fabian,
> > 
> > You make a good point, as there are only dependency updates, a 4.0.1 
> > release makes more sense.
> > 
> > At this point the 5.0 connector release could include the soon to be 
> > released Kafka 4.0.1 client libraries (the RC for that is out already).
> > I assume we would want to leave the flink 2.1 upgrade to a future 5.1 
> > release?
> > 
> > Thanks for looking at this.
> > 
> > Regards,
> > 
> > Tom Cooper
> > @tomcooper.dev | https://tomcooper.dev
> > 
> > On Monday, 28 July 2025 at 09:51, Fabian Paul fp...@apache.org wrote:
> > 
> > > Hi Tom,
> > > 
> > > Thanks for starting this discussion. I think it's a good idea to do
> > > another 4.1.0 release before proceeding with 5.0 to offer a release
> > > with the vulnerability fixed without requiring users to upgrade to
> > > Kafka 4.0. Is there a reason you prefer to do the 4.1.0 release
> > > instead of the 4.0.1 release? I reviewed the changes between the
> > > current main and the release 4.0.0 [1], and they are mostly dependency
> > > upgrades and some fixes, but without any new features. What do you
> > > think about doing a 4.0.1 release and then kicking off 5.0.0 with the
> > > Kafka client upgrade?
> > > 
> > > Best,
> > > Fabian
> > > 
> > > [1] https://github.com/apache/flink-connector-kafka/compare/v4.0...main
> > > 
> > > On Fri, Jul 25, 2025 at 11:58 AM Tom Cooper c...@tomcooper.dev wrote:
> > > 
> > > > Bumping this thread as we are now ready to merge the Kafka 4.0.0 client 
> > > > update PR [1]. This will bump the major version of the connector to 
> > > > 5.0, as we are dropping support for Kafka brokers running version 2.0.0 
> > > > or earlier.
> > > > 
> > > > However, I still think it would be worth doing a 4.1.0 release of the 
> > > > connector (with the Kafka 3.9.1 client), before the Kafka 4.0.0 client 
> > > > update is merged.
> > > > 
> > > > The current Flink Kafka Connector (4.0) has a critical CVE [2], which 
> > > > is patched in the 3.9.1 Kafka client library (which the current main 
> > > > branch of the Flink connector is using). Doing a 4.1 release of the 
> > > > connector would cover any users of older Kafka versions that want this 
> > > > CVE patched and also give a stable release of the connector using a 
> > > > point release of the Kafka client (with all the bug fixes that 
> > > > entails). This would be a good option for users who don't want to jump 
> > > > straight onto the new major Kafka client version.
> > > > 
> > > > What do people think?
> > > > 
> > > > Tom Cooper
> > > > @tomcooper.dev | https://tomcooper.dev
> > > > 
> > > > [1] https://github.com/apache/flink-connector-kafka/pull/161
> > > > [2] https://nvd.nist.gov/vuln/detail/CVE-2025-27817
> > > > 
> > > > On Wednesday, 9 July 2025 at 09:35, Tom Cooper c...@tomcooper.dev wrote:
> > > > 
> > > > > Hi,
> > > > > 
> > > > > I would like to start a conversation about releases for the Flink 
> > > > > Connector Kafka project.
> > > > > 
> > > > > We have recently updated [0] to version 3.9.1 of the Kafka client 
> > > > > library, which fixes a critical CVE [1]. With that in mind, I think 
> > > > > it would be prudent to have a 4.1.0 release as soon as possible that 
> > > > > includes this. It would also be good to include the dependency bumps 
> > > > > from this PR [2] in that release.
> > > > > 
> > > > > With the 4.1.0 release out, we could then move to looking at the 
> > > > > Kafka 4.0 upgrade (there is already a PR [3] for that). The main 
> > > > > point with the Kafka 4.0 upgrade is that it drops support for Kafka 
> > > > > brokers running version 2.0.0 and lower. Given this, I think it would 
> > > > > make sense to move the Connector version to 5.0.0 and maybe even move 
> > > > > to Flink 2.1.0 (which should be available in a month or so). This 
> > > > > 5.0.0 release could also remove all the Zookeeper specific test infra 
> > > > > and move to KRaft based clusters for testing. We could also move to a 
> > > > > new, updated Flink Connector Parent pom version [4] which would 
> > > > > harmonise the java versions and plugins with the main Flink project.
> > > > > 
> > > > > I think, if the above is acceptable, that these changes warrant a 
> > > > > major version bump. Users of older Kafka clusters would still be able 
> > > > > to use 4.1.0 (which is an argument for making sure that release has 
> > > > > the most up-to-date dependencies).
> > > > > 
> > > > > Anyway, I would love to hear what the community think of the above.
> > > > > 
> > > > > Thanks,
> > > > > 
> > > > > Tom Cooper
> > > > > @tomcooper.dev | https://tomcooper.dev
> > > > > 
> > > > > [0] https://github.com/apache/flink-connector-kafka/pull/180
> > > > > [1] https://nvd.nist.gov/vuln/detail/CVE-2025-27817
> > > > > [2] https://github.com/apache/flink-connector-kafka/pull/181
> > > > > [3] https://github.com/apache/flink-connector-kafka/pull/161
> > > > > [4] https://github.com/apache/flink-connector-shared-utils/pull/48

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