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new 3ecd6fe6ec MINOR: Add 4.2.1 (#874)
3ecd6fe6ec is described below
commit 3ecd6fe6ec1ee787fdfcd05c2fcec2ff21a90745
Author: PoAn Yang <[email protected]>
AuthorDate: Tue Jun 2 20:35:19 2026 +0900
MINOR: Add 4.2.1 (#874)
Signed-off-by: PoAn Yang <[email protected]>
---
content/en/42/design/design.md | 2 +-
content/en/42/getting-started/upgrade.md | 28 ++++++++++++++++++++++++++++
content/en/43/getting-started/upgrade.md | 7 +++++++
content/en/blog/releases/ak-4.2.1.md | 31 +++++++++++++++++++++++++++++++
content/en/community/downloads.md | 28 ++++++++++++++++++++--------
5 files changed, 87 insertions(+), 9 deletions(-)
diff --git a/content/en/42/design/design.md b/content/en/42/design/design.md
index fa99468ff2..01c83590a5 100644
--- a/content/en/42/design/design.md
+++ b/content/en/42/design/design.md
@@ -386,7 +386,7 @@ Log compaction gives us a more granular retention mechanism
so that we are guara
Let's start by looking at a few use cases where this is useful, then we'll see
how it can be used.
- 1. _Database change subscription_. It is often necessary to have a data set
in multiple data systems, and often one of these systems is a database of some
kind (either a RDBMS or perhaps a new-fangled key-value store). For example you
might have a database, a cache, a search cluster, and a Hadoop cluster. Each
change to the database will need to be reflected in the cache, the search
cluster, and eventually in Hadoop. In the case that one is only handling the
real-time updates you only [...]
+ 1. _Database change subscription_. It is often necessary to have a data set
in multiple data systems, and often one of these systems is a database of some
kind (either a RDBMS or perhaps a new-fangled key-value store). For example you
might have a database, a cache, a search cluster, and a Hadoop cluster. Each
change to the database will need to be reflected in the cache, the search
cluster, and eventually in Hadoop. In the case that one is only handling the
real-time updates you only [...]
2. _Event sourcing_. This is a style of application design which co-locates
query processing with application design and uses a log of changes as the
primary store for the application.
3. _Journaling for high-availability_. A process that does local computation
can be made fault-tolerant by logging out changes that it makes to its local
state so another process can reload these changes and carry on if it should
fail. A concrete example of this is handling counts, aggregations, and other
"group by"-like processing in a stream query system. Samza, a real-time
stream-processing framework, [uses this
feature](https://samza.apache.org/learn/documentation/0.7.0/container/s [...]
In each of these cases one needs primarily to handle the real-time feed of
changes, but occasionally, when a machine crashes or data needs to be re-loaded
or re-processed, one needs to do a full load. Log compaction allows feeding
both of these use cases off the same backing topic. This style of usage of a
log is described in more detail in [this blog
post](https://engineering.linkedin.com/distributed-systems/log-what-every-software-engineer-should-know-about-real-time-datas-unifying).
diff --git a/content/en/42/getting-started/upgrade.md
b/content/en/42/getting-started/upgrade.md
index bdbf058632..25eaaa1ef6 100644
--- a/content/en/42/getting-started/upgrade.md
+++ b/content/en/42/getting-started/upgrade.md
@@ -25,11 +25,19 @@ type: docs
limitations under the License.
-->
+## Upgrading to 4.2.1
+
+### Notable changes in 4.2.1
+
+ * Includes a fix for a critical deadlock in the
[KIP-932](https://cwiki.apache.org/confluence/x/4hA0Dw) Share Group path
([KAFKA-20505](https://issues.apache.org/jira/browse/KAFKA-20505)).
+ * Includes a fix for a rolling upgrade issue
([KAFKA-20322](https://issues.apache.org/jira/browse/KAFKA-20322)) that could
cause `UnsupportedVersionException` for clusters using transactional producers.
## Upgrading to 4.2.0
### Upgrading Servers to 4.2.0 from any version 3.3.x through 4.1.x
+ * If you wish to use share groups in a cluster with fewer than 3 brokers,
you must set the broker configurations
`share.coordinator.state.topic.replication.factor` and
`share.coordinator.state.topic.min.isr` to 1 before you start using share
groups. This is because share groups make use of a new internal topic called
`__share_group_state` which is automatically created when you first use share
groups. In common with the other internal topics, the default configuration
uses 3 replicas a [...]
+
### Notable changes in 4.2.0
* The `--max-partition-memory-bytes` option in `kafka-console-producer` is
deprecated and will be removed in Kafka 5.0. Please use `--batch-size` instead.
@@ -88,12 +96,32 @@ For further details, please refer to
[KIP-1120](https://cwiki.apache.org/conflue
* Added an optional `--node-id` flag to the `FeatureCommand` command. It
specifies the node to describe. If not provided, an arbitrary node is used.
+
+## Upgrading to 4.1.2
+
+### Notable changes in 4.1.2
+
+* Includes a fix for the rare Kafka producer bug
([KAFKA-19012](https://issues.apache.org/jira/browse/KAFKA-19012)), in which a
record could end up on the incorrect topic.
+
+
+
+## Upgrading to 4.1.1
+
+### Notable changes in 4.1.1
+
+* Includes a fix for the critical Kafka Streams bug
([KAFKA-19748](https://issues.apache.org/jira/browse/KAFKA-19748)), solving the
memory leak issues that affected users of range scans and certain DSL operators
(session windows, sliding windows, stream-stream joins, foreign-key joins).
+* Includes a fix for the critical Kafka Streams bug
([KAFKA-19479](https://issues.apache.org/jira/browse/KAFKA-19479)), related to
potential data loss.
+
+
+
## Upgrading to 4.1.0
**Note:** Kafka Streams 4.1.0 contains a critical memory leak bug
([KAFKA-19748](https://issues.apache.org/jira/browse/KAFKA-19748)) that affects
users of range scans and certain DSL operators (session windows, sliding
windows, stream-stream joins, foreign-key joins). Users running Kafka Streams
should consider upgrading directly to 4.1.1, which includes the fix for it.
### Upgrading Servers to 4.1.0 from any version 3.3.x through 4.0.x
+The rolling upgrade procedure for 4.1.x is identical to the 4.0 upgrade.
Please refer to the [Upgrading Servers to
4.0.x](#upgrading-servers-to-401-from-any-version-33x-through-39x) section for
detailed step-by-step instructions.
+
### Notable changes in 4.1.0
* Apache Kafka 4.1 ships with a preview of Queues for Kafka
([KIP-932](https://cwiki.apache.org/confluence/x/4hA0Dw)). This feature
introduces a new kind of group called share groups, as an alternative to
consumer groups. Consumers in a share group cooperatively consume records from
topics, without assigning each partition to just one consumer. Share groups
also introduce per-record acknowledgement and counting of delivery attempts.
Use share groups in cases where records are processed [...]
diff --git a/content/en/43/getting-started/upgrade.md
b/content/en/43/getting-started/upgrade.md
index 6682473c90..d161dee2f6 100644
--- a/content/en/43/getting-started/upgrade.md
+++ b/content/en/43/getting-started/upgrade.md
@@ -55,6 +55,13 @@ Note: Apache Kafka 4.3 only supports KRaft mode - ZooKeeper
mode has been remove
* A new dynamic broker configuration
`follower.fetch.last.tiered.offset.enable` (default: `false`) has been added.
When enabled on a cluster with tiered storage, a newly added follower replica
that has no local data will skip directly to the earliest pending upload offset
on the leader, avoiding re-fetching data that is already stored in remote
storage. This reduces bootstrap time significantly for large tiered-storage
topics. For further details, please refer to [KIP-1023](https://cwi [...]
* The `ListOffsets` API has been extended to version 11, adding support for
the `EARLIEST_PENDING_UPLOAD_TIMESTAMP` (-6) timestamp type. This allows
clients to query the earliest offset on the leader that has not yet been
uploaded to tiered storage. For further details, please refer to
[KIP-1023](https://cwiki.apache.org/confluence/x/8op3EQ).
+## Upgrading to 4.2.1
+
+### Notable changes in 4.2.1
+
+ * Includes a fix for a critical deadlock in the
[KIP-932](https://cwiki.apache.org/confluence/x/4hA0Dw) Share Group path
([KAFKA-20505](https://issues.apache.org/jira/browse/KAFKA-20505)).
+ * Includes a fix for a rolling upgrade issue
([KAFKA-20322](https://issues.apache.org/jira/browse/KAFKA-20322)) that could
cause `UnsupportedVersionException` for clusters using transactional producers.
+
## Upgrading to 4.2.0
### Upgrading Servers to 4.2.0 from any version 3.3.x through 4.1.x
diff --git a/content/en/blog/releases/ak-4.2.1.md
b/content/en/blog/releases/ak-4.2.1.md
new file mode 100644
index 0000000000..17578bb947
--- /dev/null
+++ b/content/en/blog/releases/ak-4.2.1.md
@@ -0,0 +1,31 @@
+---
+date: 2026-05-30
+title: Apache Kafka 4.2.1 Release Announcement
+linkTitle: AK 4.2.1
+author: PoAn Yang
+---
+
+<!--
+ Licensed to the Apache Software Foundation (ASF) under one or more
+ contributor license agreements. See the NOTICE file distributed with
+ this work for additional information regarding copyright ownership.
+ The ASF licenses this file to You under the Apache License, Version 2.0
+ (the "License"); you may not use this file except in compliance with
+ the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+-->
+
+We are proud to announce the release of Apache Kafka 4.2.1. This is a bugfix
release that includes several critical fixes. For a full list of changes, be
sure to check the [release
notes](https://downloads.apache.org/kafka/4.2.1/RELEASE_NOTES.html).
+
+See the [Upgrading to 4.2.1 from any version 0.8.x through
4.1.x](https://kafka.apache.org/42/getting-started/upgrade/#upgrading-to-421)
section in the documentation for the list of notable changes and detailed
upgrade steps.
+
+## Summary
+
+This was a community effort, so thank you to everyone who contributed to this
release, including all our users and our 45 contributors: Abhinav Dixit, Alieh
Saeedi, Andrew Schofield, Apoorv Mittal, Artem Livshits, averemee-si, Bolin
Lin, Chia-Ping Tsai, Chia-Yi Chiu, Chirag Wadhwa, Christo, Christo Lolov, Daeho
Kwon, David Jacot, Ding, Edoardo Comar, Federico Valeri, Giuseppe Lillo, Hector
Geraldino, José Armando García Sancio, Josep Prat, Ken Huang, Kevin Wu, Kirk
True, Lianet Magrans, [...]
diff --git a/content/en/community/downloads.md
b/content/en/community/downloads.md
index 03cc4e51cb..fb083756ea 100644
--- a/content/en/community/downloads.md
+++ b/content/en/community/downloads.md
@@ -39,16 +39,16 @@ The project goal is to have 3 releases a year, which means
a release every 4 mon
Kafka 4.3.0 includes a significant number of new features and fixes. For more
information, please read our [blog
post](https://kafka.apache.org/blog/2026/05/22/apache-kafka-4.3.0-release-announcement/),
the detailed [Upgrade
Notes](https://kafka.apache.org/43/getting-started/upgrade/) and the [Release
Notes](https://www.apache.org/dyn/closer.lua/kafka/4.3.0/RELEASE_NOTES.html?action=download).
-### 4.2.0
+### 4.2.1
-* Released February 17, 2026
-* [Release
Notes](https://www.apache.org/dyn/closer.lua/kafka/4.2.0/RELEASE_NOTES.html?action=download)
-* Docker image:
[apache/kafka:4.2.0](https://hub.docker.com/layers/apache/kafka/4.2.0).
-* Docker Native image:
[apache/kafka-native:4.2.0](https://hub.docker.com/layers/apache/kafka-native/4.2.0).
-* Source download:
[kafka-4.2.0-src.tgz](https://www.apache.org/dyn/closer.lua/kafka/4.2.0/kafka-4.2.0-src.tgz?action=download)
([asc](https://downloads.apache.org/kafka/4.2.0/kafka-4.2.0-src.tgz.asc),
[sha512](https://downloads.apache.org/kafka/4.2.0/kafka-4.2.0-src.tgz.sha512))
-* Binary download:
[kafka_2.13-4.2.0.tgz](https://www.apache.org/dyn/closer.lua/kafka/4.2.0/kafka_2.13-4.2.0.tgz?action=download)
([asc](https://downloads.apache.org/kafka/4.2.0/kafka_2.13-4.2.0.tgz.asc),
[sha512](https://downloads.apache.org/kafka/4.2.0/kafka_2.13-4.2.0.tgz.sha512))
+* Released May 30, 2026
+* [Release
Notes](https://www.apache.org/dyn/closer.lua/kafka/4.2.1/RELEASE_NOTES.html?action=download)
+* Docker image:
[apache/kafka:4.2.1](https://hub.docker.com/layers/apache/kafka/4.2.1).
+* Docker Native image:
[apache/kafka-native:4.2.1](https://hub.docker.com/layers/apache/kafka-native/4.2.1).
+* Source download:
[kafka-4.2.1-src.tgz](https://www.apache.org/dyn/closer.lua/kafka/4.2.1/kafka-4.2.1-src.tgz?action=download)
([asc](https://downloads.apache.org/kafka/4.2.1/kafka-4.2.1-src.tgz.asc),
[sha512](https://downloads.apache.org/kafka/4.2.1/kafka-4.2.1-src.tgz.sha512))
+* Binary download:
[kafka_2.13-4.2.1.tgz](https://www.apache.org/dyn/closer.lua/kafka/4.2.1/kafka_2.13-4.2.1.tgz?action=download)
([asc](https://downloads.apache.org/kafka/4.2.1/kafka_2.13-4.2.1.tgz.asc),
[sha512](https://downloads.apache.org/kafka/4.2.1/kafka_2.13-4.2.1.tgz.sha512))
-Kafka 4.2.0 includes a significant number of new features and fixes. For more
information, please read our [blog
post](https://kafka.apache.org/blog/2026/02/17/apache-kafka-4.2.0-release-announcement/),
the detailed [Upgrade
Notes](https://kafka.apache.org/42/getting-started/upgrade/) and the [Release
Notes](https://www.apache.org/dyn/closer.lua/kafka/4.2.0/RELEASE_NOTES.html?action=download).
+Kafka 4.2.1 fixes around 25 issues since the 4.2.0 release. For more
information, please read our [blog
post](https://kafka.apache.org/blog/2026/05/30/apache-kafka-4.2.1-release-announcement/),
the detailed [Upgrade
Notes](https://kafka.apache.org/42/getting-started/upgrade/#upgrading-to-421)
and the [Release
Notes](https://www.apache.org/dyn/closer.lua/kafka/4.2.1/RELEASE_NOTES.html?action=download).
### 4.1.2
@@ -93,6 +93,18 @@ Kafka 3.9.2 fixes 35 issues since the 3.9.1 release. For
more information, pleas
## Archived Releases
+### 4.2.0
+
+* Released February 17, 2026
+* [Release
Notes](https://www.apache.org/dyn/closer.lua/kafka/4.2.0/RELEASE_NOTES.html?action=download)
+* Docker image:
[apache/kafka:4.2.0](https://hub.docker.com/layers/apache/kafka/4.2.0).
+* Docker Native image:
[apache/kafka-native:4.2.0](https://hub.docker.com/layers/apache/kafka-native/4.2.0).
+* Source download:
[kafka-4.2.0-src.tgz](https://www.apache.org/dyn/closer.lua/kafka/4.2.0/kafka-4.2.0-src.tgz?action=download)
([asc](https://downloads.apache.org/kafka/4.2.0/kafka-4.2.0-src.tgz.asc),
[sha512](https://downloads.apache.org/kafka/4.2.0/kafka-4.2.0-src.tgz.sha512))
+* Binary download:
[kafka_2.13-4.2.0.tgz](https://www.apache.org/dyn/closer.lua/kafka/4.2.0/kafka_2.13-4.2.0.tgz?action=download)
([asc](https://downloads.apache.org/kafka/4.2.0/kafka_2.13-4.2.0.tgz.asc),
[sha512](https://downloads.apache.org/kafka/4.2.0/kafka_2.13-4.2.0.tgz.sha512))
+
+Kafka 4.2.0 includes a significant number of new features and fixes. For more
information, please read our [blog
post](https://kafka.apache.org/blog/2026/02/17/apache-kafka-4.2.0-release-announcement/),
the detailed [Upgrade
Notes](https://kafka.apache.org/42/getting-started/upgrade/) and the [Release
Notes](https://www.apache.org/dyn/closer.lua/kafka/4.2.0/RELEASE_NOTES.html?action=download).
+
+
### 4.1.1
* Released November 12, 2025
