Add April 2026 Flink community update blog post

docs/content/posts/2026-04-13-community-update.md

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+---
+authors:
+- jlpayne72: null
+  name: Julian Payne
+date: "2026-04-13T08:00:00Z"
+excerpt: Flink Community update for April 2026
+title: Flink Community update for April 2026
+aliases:
+- /news/2026/04/13/community-update.html
+---
+
+This is the monthly Flink Community update for April 2026. We scour the latest updates from the Flink community so you don't have to! 
+We'll dive into a few hot topics and FLIPs (Flink Improvement Proposals) before providing the usual almanac-style listing of technical updates, user-facing updates, and governance and community.
+<!--more-->
+
+<!-- TOC -->
+  * [Hot Topics](#hot-topics)
+    * [Apache Flink 2.3 Release Draws Nearer](#apache-flink-23-release-draws-nearer)
+    * [Flink CDC 3.6.0 Release](#flink-cdc-360-release)
+    * [Flink Documentation Re-structure](#flink-documentation-re-structure)
+    * [Flink Native S3 FileSystem Connector](#flink-native-s3-filesystem-connector)
+  * [Developer/Technical Updates](#developertechnical-updates)
+    * [Table API & SQL](#table-api--sql)
+    * [Runtime & Execution](#runtime--execution)
+    * [Checkpointing & State](#checkpointing--state)
+    * [Metrics & Observability](#metrics--observability)
+    * [Python & Multi-language Support](#python--multi-language-support)
+  * [User-Facing Updates](#user-facing-updates)
+    * [Apache Flink CDC 3.6.0 Release](#apache-flink-cdc-360-release-1)
+    * [Apache Flink Agents 0.2.1 Release](#apache-flink-agents-021-release)
+    * [Documentation](#documentation)
+  * [Governance and Community](#governance-and-community)
+    * [FLIP Activity](#flip-activity)
+      * [Accepted - being implemented](#accepted---being-implemented)
+      * [Being discussed](#being-discussed)
+    * [Apache Flink Dev List activity](#apache-flink-dev-list-activity)
+  * [For more information](#for-more-information)
+<!-- TOC -->
+
+Previous Blog: [Flink community update March 2026](https://flink.apache.org/2026/03/01/flink-community-update-for-march-2026/)
+
+## Hot Topics
+
+### Apache Flink 2.3 Release Draws Nearer
+
+Four months after the release of Flink 2.2 (December 4th 2025), we are hotly anticipating the release of Flink 2.3. 
+The code freeze for Apache Flink 2.3 was invoked on April 14th and at time of writing we anticipate the version to be launched toward the end of April 2026. 
+The release will be subject to its own launch notices and blog, which we will not repeat here. Needless to say we're excited as the release scope includes important updates to Materialized Tables for Flink SQL, OTel gRPC exporter and watermark alignment for backlogged jobs in Runtime, and in Connectors, an update to the S3 Filesink connector. 
+We are also proposing a re-structure to the Flink documentation to make it easier to navigate for new and existing users. 
+You can see the full release scope here: [https://cwiki.apache.org/confluence/display/FLINK/2.3+Release](https://cwiki.apache.org/confluence/display/FLINK/2.3+Release)
+
+### Flink CDC 3.6.0 Release
+
+Flink CDC is used to capture and stream real-time changes from databases (inserts, updates, and deletes) as they happen. 
+If you missed it, you can read the [launch announcement](https://flink.apache.org/2026/03/30/apache-flink-cdc-3.6.0-release-announcement/). 
+Version 3.6.0 extends Flink version support to 1.20.x and 2.2.x, upgrades JDK version to 11, introduces new Oracle Source and Apache Hudi Sink Pipeline connectors and adds Lenient mode schema evolution support for Fluss Pipeline connector. 
+It also introduces PostgreSQL Schema Evolution support, enhances Schema Evolution capabilities for better multi-table synchronization scenarios and table name mapping flexibility, and strengthens the Transform framework with VARIANT type and JSON parsing support.
+
+### Flink Documentation Re-structure
+
+We want to re-structure Flink documentation to aid discoverability and reduce duplication (see [FLIP-561](https://cwiki.apache.org/confluence/display/FLINK/FLIP-561%3A+Restructure+Flink+documentation)). 
+Reflecting the broadening use of SQL we plan to create a dedicated Flink SQL section separate from Table API. 
+We will move shared concepts (Relational Streaming concepts like Dynamic Tables, Time Attributes) to the top-level Concepts section and also move shared architecture documentation (Source/Sink APIs) to the Connectors section. 
+Additionally, Python documentation will now be integrated within the Table API and DataStream API sections where applicable, with the rest moved to the Python API docs (PyDocs).
+
+### Flink Native S3 FileSystem Connector
+
+Amazon S3 is a popular sink and source destination for Apache Flink users. 
+Currently, Apache Flink provides two primary mechanisms for interacting with S3 (`flink-s3-fs-hadoop` and `flink-s3-fs-presto`), both of which are adapters wrapping external projects. 
+To improve performance and maintainability we propose the creation of `flink-s3-fs-native` ([FLIP-555](https://cwiki.apache.org/confluence/display/FLINK/FLIP-555%3A+Flink+Native+S3+FileSystem)), a clean-slate implementation built directly on the AWS SDK for Java v2. 
+We will remove the Hadoop dependency, making the connector a self-contained module depending only on the modular AWS SDK v2. 
+The connector will support both state access (FileSystem) and transactional sinks (RecoverableWriter), simplifying the user experience. Additionally, the connector leverages the non-blocking I/O capabilities of Netty and the AWS Common Runtime (CRT) to maximise throughput.
+
+## Developer/Technical Updates
+
+### Table API & SQL
+
+Continued work on Materialized Tables including `START_MODE` clause parser support ([[FLINK-39304]](https://issues.apache.org/jira/browse/FLINK-39304), [[#27843]](https://github.com/apache/flink/pull/27843)), interval reuse for `FRESHNESS` and `START MODE` ([[#27845]](https://github.com/apache/flink/pull/27845)), and `CREATE OR ALTER` now correctly respects existing table schemas ([[FLINK-39284]](https://issues.apache.org/jira/browse/FLINK-39284), [[#27854]](https://github.com/apache/flink/pull/27854)). `TO_CHANGELOG` retract/upsert stream conversion was also added ([[#27847]](https://github.com/apache/flink/pull/27847)).
+
+BITMAP Type support was introduced end-to-end: the core data type ([[FLINK-38852]](https://issues.apache.org/jira/browse/FLINK-38852), [[FLINK-39185]](https://issues.apache.org/jira/browse/FLINK-39185)), scalar functions ([[FLINK-39186]](https://issues.apache.org/jira/browse/FLINK-39186)), aggregate functions ([[FLINK-39187]](https://issues.apache.org/jira/browse/FLINK-39187)), and documentation ([[FLINK-39188]](https://issues.apache.org/jira/browse/FLINK-39188), [[#27835]](https://github.com/apache/flink/pull/27835)).
+
+Join Operations saw cascaded delta join support merged ([[FLINK-39233]](https://issues.apache.org/jira/browse/FLINK-39233), [[#27828]](https://github.com/apache/flink/pull/27828)), lookup join after delta join ([[FLINK-39174]](https://issues.apache.org/jira/browse/FLINK-39174)), and immutable column sink mode traits ([[FLINK-39287]](https://issues.apache.org/jira/browse/FLINK-39287), [[#27838]](https://github.com/apache/flink/pull/27838)).
+
+Code generation and correctness work included: NDU analyzer improvements for non-deterministic function detection ([[FLINK-39313]](https://issues.apache.org/jira/browse/FLINK-39313), [[#27819]](https://github.com/apache/flink/pull/27819)), duplicate function instance elimination ([[FLINK-39094]](https://issues.apache.org/jira/browse/FLINK-39094)), filter optimisation for upsert key groups ([[FLINK-39314]](https://issues.apache.org/jira/browse/FLINK-39314)), a UDF lambda expression argument fix ([[#27787]](https://github.com/apache/flink/pull/27787)), and JSON field name code generation fixes backported across multiple releases ([[#27850]](https://github.com/apache/flink/pull/27850), [[#27851]](https://github.com/apache/flink/pull/27851), [[#27856]](https://github.com/apache/flink/pull/27856)).
+
+### Runtime & Execution
+
+Adaptive scheduler and `ExecutionGraph` improvements will be part of Flink 2.3. Rescale history now records statistics ([[#27540]](https://github.com/apache/flink/pull/27540)) and rescale information ([[#27539]](https://github.com/apache/flink/pull/27539)). A configurable `ExecutionGraph` cache TTL was introduced ([[#27509]](https://github.com/apache/flink/pull/27509)), and the Flink Web UI was updated to surface rescale and configuration data for adaptive scheduler jobs ([[#27826]](https://github.com/apache/flink/pull/27826)).
+
+### Checkpointing & State
+
+Unaligned checkpoint recovery gained a new configuration option ([[FLINK-38541]](https://issues.apache.org/jira/browse/FLINK-38541), [[#27782]](https://github.com/apache/flink/pull/27782)), giving operators finer control over recovery behaviour under failure conditions. Session-mode HA recovery re-execution was also resolved ([[FLINK-38975]](https://issues.apache.org/jira/browse/FLINK-38975)).
+
+### Metrics & Observability
+
+gRPC batch export support was added to the metrics pipeline ([[#27692]](https://github.com/apache/flink/pull/27692)), providing a more robust export using gRPC for jobs with large numbers of operators or tasks.
+
+### Python & Multi-language Support
+
+Python users gained support for multiple compression formats in `python.files` ([[#27780]](https://github.com/apache/flink/pull/27780)), expanding deployment flexibility for Python UDF bundles.
+
+## User-Facing Updates
+
+### Apache Flink CDC 3.6.0 Release
+
+- **Announcement:** [Apache Flink CDC 3.6.0 Release Announcement](https://flink.apache.org/2026/03/30/apache-flink-cdc-3.6.0-release-announcement/) — *Yanquan Lv, March 30*
+- **Release Manager:** Yanquan Lv
+- **Key highlights:**
+  - Extended Flink version support to 1.20.x and 2.2.x
+  - Upgraded minimum JDK to version 11
+  - New connectors added
+  - Expanded schema evolution capabilities
+  - PostgreSQL pipeline connector schema change support [[FLINK-38959]](https://issues.apache.org/jira/browse/FLINK-38959)
+  - Oracle pipeline support for column nullable changes [[FLINK-39196]](https://issues.apache.org/jira/browse/FLINK-39196)
+
+### Apache Flink Agents 0.2.1 Release
+
+- **Announcement:** [Apache Flink Agents 0.2.1 Release Announcement](https://flink.apache.org/2026/03/26/apache-flink-agents-0-2-1-release-announcement/) — *Wenjin Xie, March 26*
+- **Release Manager:** Wenjin Xie
+- **Key highlights:**
+  - 3 targeted bug fixes
+  - Vulnerability fixes
+  - Minor improvements
+
+### Documentation
+
+March saw a documentation push across several areas:
+* Materialized tables `CREATE`/`ALTER` operations [[#27846]](https://github.com/apache/flink/pull/27846)
+* SQL function consistency improvements [[#27842]](https://github.com/apache/flink/pull/27842)
+* BITMAP type coverage [[#27835]](https://github.com/apache/flink/pull/27835)
+* PostgreSQL CDC `schema.change.enabled` parameter [[FLINK-39294]](https://issues.apache.org/jira/browse/FLINK-39294)
+* MySQL 8.4+ support [[FLINK-39295]](https://issues.apache.org/jira/browse/FLINK-39295)
+* MySQL connector consistency fixes [[FLINK-39344]](https://issues.apache.org/jira/browse/FLINK-39344)
+
+## Governance and Community
+
+### FLIP Activity
+
+#### Accepted - being implemented
+
+**[FLIP-561](https://cwiki.apache.org/confluence/display/FLINK/FLIP-561%3A+Restructure+Flink+documentation): Restructure Flink Documentation.** (Piotr Nowojski)
+- A major reorganisation to improve discoverability and reduce duplication across the Flink docs. Updated March 24, 2026.
+
+**[FLIP-558](https://cwiki.apache.org/confluence/display/FLINK/FLIP-558%3A+Improvements+to+SinkUpsertMaterializer+and+changelog+disorder): Improvements to SinkUpsertMaterializer and Changelog Disorder.**
+- Addresses correctness issues in upsert materialisation under out-of-order changelog events.
+
+**[FLIP-557](https://cwiki.apache.org/confluence/display/FLINK/FLIP-557%3A+Granular+Control+over+Data+Reprocessing+in+Materialized+Table+Evolution): Granular Control over Data Reprocessing in Materialized Table Evolution.**
+- Gives users finer control over which partitions are reprocessed when a materialized table definition changes.
+
+**[FLIP-551](https://cwiki.apache.org/confluence/display/FLINK/FLIP-551%3A+Make+FRESHNESS+Optional+for+Materialized+Tables): Make FRESHNESS Optional for Materialized Tables.** (targeting Flink 2.2)
+- Reduces the boilerplate required when defining materialized tables where freshness guarantees are not needed.
+
+#### Being discussed
+
+**[FLIP-202](https://cwiki.apache.org/confluence/display/FLINK/FLIP-202): [DRAFT] Introduce ClickHouse Connector.**
+- Community discussion ongoing for an officially supported ClickHouse sink connector.
+
+**[FLIP-332](https://cwiki.apache.org/confluence/display/FLINK/%5BWIP%5DFLIP-332%3A+Introduce+the+concept+of+state+self-sustained): [WIP] Introduce State Self-Sustained Concept.**
+- Explores state backends capable of managing their own lifecycle independently of checkpoints.
+
+**[FLIP-267](https://cwiki.apache.org/confluence/display/FLINK/FLIP+267%3A+Iceberg+Connector): Iceberg Connector.**
+- Continuing effort to formalise the Iceberg integration as a first-class Flink connector.
+
+### Apache Flink Dev List activity
+
+You can view the dev list archives [online](https://lists.apache.org/list.html?dev@flink.apache.org) or [subscribe](https://flink.apache.org/community.html#mailing-lists) to receive emails.
+
+## For more information
+
+Follow this blog to keep up to date with what is happening in the Flink community.
+
+If you have ideas for what you would like to see in these blogs or there is anything you think has been misrepresented, is wrong or missing, please let us know via the dev list (detail below) or [Slack](https://flink.apache.org/how-to-contribute/getting-help/#slack).
+
+If you would like to keep a closer eye on what's happening in the community, subscribe to one of the [Flink community mailing lists](https://flink.apache.org/community.html#mailing-lists) to get fine-grained weekly updates, upcoming event announcements and more.
+Two popular mailing lists are:
+* the [dev list](https://lists.apache.org/list.html?dev@flink.apache.org) for development related discussions
+* the [user list](https://lists.apache.org/list.html?user@flink.apache.org) for user support and questions