mimaison commented on code in PR #668:
URL: https://github.com/apache/kafka-site/pull/668#discussion_r1989856752
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blog.html:
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@@ -22,6 +22,286 @@
<!--#include virtual="includes/_nav.htm" -->
<div class="right">
<h1 class="content-title">Blog</h1>
+ <article>
+ <h2 class="bullet">
+ <a id="apache_kafka_400_release_announcement"></a>
+ <a href="#apache_kafka_400_release_announcement">Apache
Kafka 4.0.0 Release Announcement</a>
+ </h2>
+ 17 March 2025 - David Jacot
+
+ <p>
+ We are proud to announce the release of Apache Kafka®
4.0 This release contains many new
+ features and improvements. This blog post will highlight
some of the more prominent features.
+ For a full list of changes, be sure to check the <a
href="https://archive.apache.org/dist/kafka/4.0.0/RELEASE_NOTES.html";>release
notes</a>.
+ </p>
+ <p>
+ See the <a
href="https://kafka.apache.org/documentation.html#upgrade_4_0_0";>Upgrading to
4.0 from any versions 0.8.x through 3.9.x</a> section in the
+ documentation for the list of notable changes and detailed
upgrade steps.
+ </p>
+ <p>
+ Apache Kafka 4.0 is a significant milestone, marking the
first major release to operate entirely
+ without Apache ZooKeeper®. By running in KRaft mode
by default, Kafka simplifies
+ deployment and management, eliminating the complexity of
maintaining a separate ZooKeeper
+ ensemble. This change significantly reduces operational
overhead, enhances scalability, and
+ streamlines administrative tasks. We want to take this as
an opportunity to express our gratitude
+ to the ZooKeeper community and say, thank you! ZooKeeper
was the backbone of Kafka for
+ more than 10 years, and it did serve Kafka very well.
Kafka would most likely not be what it is
+ today without it. We don’t take this for granted and
highly appreciate all the hard work the
+ community invested to build ZooKeeper. Thank you!
+ </p>
+ <p>
+ Kafka 4.0 also brings the general availability of <a
href="https://cwiki.apache.org/confluence/x/HhD1D";>KIP-848</a> introducing a
powerful new consumer
+ group protocol designed to dramatically improve rebalance
performance. This optimization
+ significantly reduces downtime and latency, enhancing the
reliability and responsiveness of
+ consumer groups, especially in large-scale deployments.
+ </p>
+ <p>
+ Additionally, we are excited to offer <a
href="https://cwiki.apache.org/confluence/x/i4ogF";>early access</a> to
+ Queues for Kafka (<a
href="https://cwiki.apache.org/confluence/x/4hA0Dw";>KIP-932</a>), enabling
Kafka to support traditional queue semantics directly. This
+ feature extends Kafka’s versatility, making it an ideal
messaging platform for a wider range of
+ use cases, particularly those requiring point-to-point
messaging patterns.
+ </p>
+ <p>
+ These highlights illustrate Kafka's continued evolution to
meet the demands of modern,
+ scalable, and efficient data streaming and messaging
architectures.
+ </p>
+
+ <h3>Kafka Broker, Controller, Producer, Consumer and Admin
Client</h3>
+
+ <ul>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/HhD1D";>KIP-848: The Next Generation
of the Consumer Rebalance Protocol</a>
+ <br>
+ Apache Kafka also says goodbye to “stop-the-world”
rebalances with the general availability of the
+ next generation of the consumer rebalance protocol. It
increases the stability and the performance
+ of consumer groups while simplifying clients. The new
protocol is enabled by default on the server
+ side. Consumers must opt-in by setting
<code>group.protocol=consumer</code>.
+ See <a
href="https://kafka.apache.org/40/documentation.html#consumer_rebalance_protocol";>here</a>
for details.
+ </li>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/B40ODg";>KIP-890: Transactions
Server-Side Defense</a>
+ <br>
+ The second phase of KIP-890 has been completed. It
reduces the chances of “zombie transactions”
+ during producer failures. See <a
href="https://kafka.apache.org/40/documentation.html#transaction_protocol";>here</a>
for details.
+ </li>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/4hA0Dw";>KIP-932: Queues for Kafka
(Early Access)</a>
+ <br>
+ This KIP introduces the concept of a share group as a
way of enabling cooperative consumption
+ using Kafka topics. It does not add the concept of a
“queue” to Kafka per se, but rather that
+ introduces cooperative consumption to accommodate
these queuing use-cases using regular Kafka
+ topics. Share groups make this possible. You can think
of a share group as roughly equivalent to a
+ “durable shared subscription” in existing systems.
+ Please see the <a
href="https://cwiki.apache.org/confluence/x/i4ogF";>Early Access Release
Notes</a>
+ for limitations and configurations.
+ </li>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/mpOzDw";>KIP-966: Eligible Leader
Replicas (Preview)</a>
+ <br>
+ KIP-966 introduces Eligible Leader Replicas (ELR) in
preview in 4.0. ELR is a subset of the ISR
+ replicas guaranteed to have complete data up to the
high-watermark. ELRs are safe for leader
+ election, preventing data loss. See <a
href="https://kafka.apache.org/40/documentation.html#eligible_leader_replicas";>here</a>
for details.
+ </li>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/MYtEE";>KIP-996: Pre-Vote</a>
+ <br>
+ KIP-996 introduces a "Pre-Vote" mechanism to reduce
unnecessary KRaft leader elections in Apache
+ Kafka clusters. By allowing nodes to check their
eligibility for leadership before initiating an election,
+ this approach minimizes disruptions caused by network
partitions or transient issues.
+ </li>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/joqzDw";>KIP-950: Tiered Storage
Disablement</a>
+ <br>
+ This feature will allow customers to selectively
disable Tiered Storage on a per-topic basis.
+ </li>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/XA-OEg";>KIP-1076: Metrics for
client applications KIP-714 extension</a>
+ <br>
+ With KIP-714, cluster operators can now collect client
metrics directly from brokers using a plugin.
+ This makes it much easier to monitor client behavior.
However, KIP-714 only gathers metrics from
+ Kafka clients (admin, consumer, and producer) and
doesn't cover application-level metrics for
+ embedded clients, such as Kafka Streams. To fully
understand performance, it's important to collect
+ both client metrics and application-specific metrics.
This KIP introduces a way for applications that
+ use Kafka clients to include their own metrics
alongside the existing client metrics.
+ </li>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/NIyMEw";>KIP-1106: Add duration
based offset reset option for consumer clients</a>
+ <br>
+ Kafka consumer supports auto.offset.reset config
option, which is used when there is no initial
+ offset in Kafka or if the current offset does not
exist any more on the server. This config currently
+ supports earliest/latest/none options. Currently
consumer resets might force applications to
+ reprocess large amounts of data from earlier offsets.
With infinite storage, its beneficial to have a
+ duration based offset reset strategy. This KIP allows
applications to consume/initialise from a fixed
+ duration when there is no initial offset in Kafka.
+ </li>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/XoowEg";>KIP-1043: Administration of
groups</a>
+ <br>
+ KIP-848 and KIP-932 introduce new group types,
consumer and share respectively. The Admin Client
+ API has limitations when dealing with newer group
types, sometimes returning errors or incorrectly
+ stating that groups don't exist. To address this
challenge a new command-line tool, kafka-groups.sh,
+ and updates to existing command line tools,
kafka-consumer-groups.sh and kafka-share-groups.sh,
+ were made in Kafka 4.0 to enable users to view all
groups in a cluster, along with their types and
+ protocols, providing accurate information even when
the Admin Client API fails.
+ </li>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/w4mMEw";>KIP-1099: Extend
kafka-consumer-groups command line tool to support new consumer group</a>
+ <br>
+ This KIP extends the kafka-consumer-groups and the
kafka-share-groups command line tools to
+ provide more information related to consumer and share
groups. This helps when it comes to
+ troubleshooting consumer and share groups,
respectively introduced by KIP-848 and KIP-932.
+ </li>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/KYuMEw";>KIP-1102: Enable clients to
rebootstrap based on timeout or error code</a>
+ <br>
+ KIP-1102 enhances Kafka client resilience by
proactively triggering metadata rebootstrap when no
+ updates occur within a timeout period and allowing
servers to explicitly signal clients to rebootstrap.
+ This addresses previous limitations in KIP-899, where
clients could become stuck with outdated
+ metadata unless all brokers were unreachable.
+ </li>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/K5sODg";>KIP-896: Remove old client
protocol API versions in Kafka 4.0</a>
+ <br>
+ For the first time, old protocol API versions have
been removed. Users should ensure brokers are
+ version 2.1 or higher before upgrading Java clients
(including Connect and Streams to 4.0. Similarly,
+ users should ensure their Java clients version is 2.1
or higher before upgrading brokers to 4.0.
+ </li>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/y4kgF";>KIP-1124: Providing a clear
Kafka Client upgrade path for 4.x</a>
+ <br>
+ This KIP outlines the upgrade patch for Kafka Clients,
Streams and Connect to 4.0. It is a must read
+ before upgrading your clusters and clients.
+ </li>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/GCx4CQ";>KIP-653: Upgrade log4j to
log4j2</a>
+ <br>
+ The logging framework has been migrated from Log4j to
Log4j2. Users can use the
+ log4j-transform-cli tool to automatically convert
their existing Log4j configuration files to Log4j2
+ format.
+ </li>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/RomNCg";>KIP-724: Drop support for
message formats v0 and v1</a>
+ <br>
+ The message formats v0 and v1 were deprecated in
Apache Kafka 3.0. They were removed in 4.0.
+ </li>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/P4vOCg";>KIP-750: Drop support for
Java 8 in Kafka 4.0 (deprecate in 3.0)</a> &
+ <a
href="https://cwiki.apache.org/confluence/x/Bov5E";>KIP-1013: Drop broker and
tools support for Java 11 in Kafka 4.0 (deprecate in 3.7)</a>
+ <br>
+ Kafka Clients and Kafka Streams require Java 11 while
Kafka Brokers, Connect and Tools now requires Java 17.
+ </li>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/FAqpEQ";>KIP-1030: Change
constraints and default values for various configurations</a>
+ <br>
+ KIP-1030 has changed the default values of some
configurations in order to provide better default to
+ users starting using Apache Kafka. Check out the KIP
for the details.
+ </li>
+ </ul>
+
+ <h3>Kafka Streams</h3>
+
+ <ul>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/gIuMEw";>KIP-1104: Allow Foreign Key
Extraction from Both Key and Value in KTable Joins</a>
+ <br>
+ KIP-1104 enhances Kafka Streams by allowing foreign
keys to be extracted directly from both
+ record keys and values, removing the need to duplicate
keys into values for foreign-key joins.
+ This improvement simplifies joins, reduces storage
overhead, and provides a more intuitive
+ developer experience.
+ </li>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/TZCMEw";>KIP-1112: allow custom
processor wrapping</a>
+ <br>
+ KIP-1112 simplifies applying cross-cutting logic in
Kafka Streams by introducing the
+ ProcessorWrapper interface, enabling seamless
injection of custom logic around Processor API
+ and DSL processors. This eliminates previous
redundancy and reduces the maintenance
+ overhead caused by manually integrating logic into
each processor individually.
+ </li>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/LQ6TEg";>KIP-1065: Add "retry"
return-option to ProductionExceptionHandler</a>
+ <br>
+ KIP-1065 addresses persistent errors in Kafka Streams
by allowing users to break retry loops
+ via a new "RETRY" option in the
ProductionExceptionHandler. This enhancement provides
+ customizable error handling, enabling retries,
graceful failures, or dropping problematic records
+ to continue processing efficiently.
+ </li>
+ <li>
+ <a
href="https://cwiki.apache.org/confluence/x/IgstEw";>KIP-1091: Improved Kafka
Streams operator metrics</a>
+ <br>
+ Kafka Streams exposes its metrics with KIP-1076. The
KIP especially adds a state metric for
+ each StreamThread and the client instance itself. It
also provides detailed visibility into the
+ application state.
+ </li>
+ </ul>
+
+ <h3>Kafka Connect</h3>
Review Comment:
Should we also mention
[KIP-1032](https://cwiki.apache.org/confluence/display/KAFKA/KIP-1032%3A+Upgrade+to+Jakarta+and+JavaEE+10+in+Kafka+4.0)
as now Connect requires Java 17 (like brokers and tools).
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