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Apache Kafka 4.4.0 Adds Dead-Letter Queues for Share Groups and Transactional State Stores, and Deprecates broker.id; 4.3.2 Fixes Two Tiered-Storage Data-Loss Bugs

Kafka's 4.4.0 announcement lists 25 KIPs, including share-group dead-letter queues and opt-in transactional state stores; the 4.3.2 bugfix release fixes two potential data-loss issues in tiered storage.

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apache-kafka kafka-streams kafka-connect release data-infrastructure tiered-storage
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Overview

The Apache Kafka project released version 4.4.0 on October 22, 2026, and the bugfix release 4.3.2 on October 23, 2026, according to its downloads page. The 4.4.0 announcement, written by Omnia Ibrahim, says the release has “25 KIPs and 963 commits since 4.3.0”. The Herald has separately reported on the project’s CVE page in Apache Kafka’s CVE List Shows 12 Entries Announced October 28, Including a JWT Signature-Verification Skip and Broker Memory-Allocation Flaws; this article covers the features and fixes the project itself highlights in the two release announcements.

What 4.4.0 Adds

The announcement groups changes by component. For brokers, controllers and clients, it lists:

  • Dead-letter queues for share groups (KIP-1191). Per the announcement, records “released beyond the max delivery count, or rejected by the share consumer, become eligible for the DLQ once the share.version feature is upgraded to 2.” Behavior is configured dynamically through a set of errors.deadletterqueue.* settings.
  • Delayed tiered-storage upload (KIP-1241). The announcement says it introduces the remote.copy.lag.bytes and remote.copy.lag.ms configs, “allowing tiered storage redundancy to be reduced with delayed upload.”
  • Controller unregistration (KIP-1312). Controllers can be unregistered from the cluster metadata through a new kafka-cluster.sh unregister-controller command; the announcement says this requires metadata version 4.4-IV2.
  • Asynchronous bootstrap resolution (KIP-909). A new client setting, bootstrap.resolve.timeout.ms, has a default of 0 that, per the announcement, “preserves the historical synchronous behavior”. The announcement says Kafka Streams and Kafka Connect do not yet support asynchronous bootstrap resolution.

For Kafka Streams, the announcement describes KIP-892 as adding transactional state stores, enabled with a new config, enable.transactional.statestores, whose default is false. When enabled, it says, state stores are no longer wiped and rebuilt on error under exactly-once processing; “only writes since the last successful commit are lost and replayed.” It also lists broker-side custom task assignors for Streams groups (KIP-1357) and a Streams group topology description plugin (KIP-1331). For Kafka Connect, KIP-1209 adds internal.topics.automatic.creation.enable, which defaults to true; when set to false, the announcement says, Connect “fails at startup if any are missing” of its internal topics.

Deprecations and Compatibility Notes

The announcement lists three deprecations. KIP-1232 deprecates the broker.id broker configuration; KIP-1200 deprecates ClientQuotaCallback#updateClusterMetadata, which the announcement says will be removed in Kafka 5.0; and KIP-1301 deprecates the remaining Yammer-based classic-group metrics in GroupCoordinatorMetrics. It also states that kafka-broker-api-versions.sh is deprecated and will be removed in the next major release, with kafka-cluster.sh api-versions as its replacement.

One change affects rollbacks and tooling. Under KIP-1170, per the announcement, storage directories formatted by the kafka-storage tool “are no longer forward-compatible: a broker must now be the same version as, or newer than, the kafka-storage tool that formatted its directory.” The announcement points readers to the Upgrading to 4.4 section of the documentation for the full list of notable changes.

What 4.3.2 Fixes

The 4.3.2 announcement, written by Ken Huang, calls it “a bugfix release that fixes around 60 issues since the 4.3.1 release, most notably two potential data loss issues in tiered storage size-based retention and time index truncation.” It names two fixes:

  • KAFKA-20732: a tiered storage bug in which size-based retention “could delete data that was still within retention from both local and remote tiers after a leader election.”
  • KAFKA-20979: a potential data loss issue in which the time index “could be truncated across a broker restart, causing segments that were still within retention to be deleted by time-based retention.”

The announcement also lists fixes for several Kafka Streams bugs that could cause a StreamThread to die, one for a state directory that could be cleaned prematurely, and dependency updates “to address published CVEs in jackson-databind, lz4-java, log4j and Jetty.” The downloads page lists 4.4.0, 4.3.2 and 4.2.2 as the supported releases.

What the Sources Do Not Say

Both announcements are the project’s own, and no independent testing of the new features is cited here. The 4.4.0 announcement does not report performance figures for the new features. It credits “our 151 contributors (and 8 AIs)” without describing the AI entries. The 4.3.2 announcement does not say which deployments are exposed to the two data-loss issues beyond the conditions in each description, namely a leader election with size-based retention in the first and a broker restart with time-based retention in the second.