[runners-spark] Add Spark 4 runner (#38255)

* build: add Spark 4.0.2 version property and Scala 2.13 support

Add spark4_version (4.0.2) to BeamModulePlugin alongside the existing
spark3_version. Update spark_runner.gradle to conditionally select the
correct Scala library (2.13 vs 2.12), Jackson module, Kafka test
dependency, and require Java 17 when building against Spark 4.

Register the new :runners:spark:4 module in settings.gradle.kts.

These changes are purely additive — all conditionals gate on
spark_version.startsWith("4") or spark_scala_version == '2.13', leaving
the Spark 3 build path untouched.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* refactor: make shared Spark source compatible with Scala 2.12 and 2.13

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* build: add runners/spark/4/ build configuration

Add the Gradle build file for the Spark 4 structured streaming runner.
The module mirrors runners/spark/3/ — it inherits the shared RDD-base
source from runners/spark/src/ via copySourceBase and adds its own
Structured Streaming implementation in src/main/java.

Key differences from the Spark 3 build:
- Uses spark4_version (4.0.2) with Scala 2.13.
- Excludes DStream-based streaming tests (Spark 4 supports only
  structured streaming batch).
- Unconditionally adds --add-opens JVM flags required by Kryo on
  Java 17 (Spark 4's minimum).
- Binds Spark driver to 127.0.0.1 for macOS compatibility.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* feat: add Spark 4 structured streaming runner source

Add the Spark 4 structured streaming runner implementation and tests.
Most files are adapted from the Spark 3 structured streaming runner
with targeted changes for Spark 4 / Scala 2.13 API compatibility.

Key Spark 4-specific changes (diff against runners/spark/3/src/):

EncoderFactory — Replaced the direct ExpressionEncoder constructor
  (removed in Spark 4) with BeamAgnosticEncoder, a named class
  implementing both AgnosticExpressionPathEncoder (for expression
  delegation via toCatalyst/fromCatalyst) and AgnosticEncoders
  .StructEncoder (so Dataset.select(TypedColumn) creates an N-attribute
  plan, preventing FIELD_NUMBER_MISMATCH). The toCatalyst/fromCatalyst
  methods substitute the provided input expression via transformUp,
  enabling correct nesting inside composite encoders like
  Encoders.tuple().

EncoderHelpers — Added toExpressionEncoder() helper to handle Spark 4
  built-in encoders that are AgnosticEncoder subclasses rather than
  ExpressionEncoder.

GroupByKeyTranslatorBatch — Migrated from internal catalyst Expression
  API (CreateNamedStruct, Literal$) to public Column API (struct(),
  lit(), array()), as required by Spark 4.

BoundedDatasetFactory — Use classic.Dataset$.MODULE$.ofRows() as
  Dataset moved to org.apache.spark.sql.classic in Spark 4.

ScalaInterop — Replace WrappedArray.ofRef (removed in Scala 2.13)
  with JavaConverters.asScalaBuffer().toList() in seqOf().

GroupByKeyHelpers, CombinePerKeyTranslatorBatch — Replace
  TraversableOnce with IterableOnce (Scala 2.13 rename).

SparkStructuredStreamingPipelineResult — Replace sparkproject.guava
  with Beam's vendored Guava.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* ci: add Spark 4 PreCommit and PostCommit workflows

Add GitHub Actions workflows for the Spark 4 runner module:

- beam_PreCommit_Java_Spark4_Versions: runs sparkVersionsTest on
  changes to runners/spark/**.  Currently a no-op (the sparkVersions
  map is empty) but scaffolds future patch version coverage.
- beam_PostCommit_Java_ValidatesRunner_Spark4StructuredStreaming: runs
  the structured streaming test suite on Java 17.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Add PreCommit Java Spark4 Versions workflow

* Add cancellation support to Spark pipeline execution

* Remove unused endOfData() call in close method

Remove endOfData() call in close method.

* build: add Spark 4 job-server and container modules

Add job-server and container build configurations for Spark 4,
mirroring the existing Spark 3 job-server setup. The container
uses eclipse-temurin:17 (Spark 4 requires Java 17). The shared
spark_job_server.gradle gains a requireJavaVersion conditional
for Spark 4 parent projects.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* build: remove spark.driver.host workaround from Spark 4 build

The hostname binding hack is no longer needed now that the local
machine resolves its hostname to 127.0.0.1 via /etc/hosts.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* docs: add Spark 4 runner entry to CHANGES.md

Called out in /ultrareview as a missing contributor checklist item.
Adds a Highlight line and a New Features / Improvements entry under
the 2.74.0 Unreleased section, referencing issue #36841.

* docs: explain classic.SparkSession downcast in BoundedDatasetFactory

Per /ultrareview feedback: the one-line comment didn't make clear why
the cast is safe. Expand it to note that SparkSession.builder() always
returns a classic.SparkSession at runtime, which is why the downcast
avoids reflection.

* fix: log warning when neither WrappedArray nor ArraySeq class is found

Per /ultrareview feedback: the fallback branch silently swallowed the
second ClassNotFoundException. In practice one of the two classes is
always present (Scala 2.12 vs 2.13 stdlib), but a silent skip could
mask a broken classpath. Emit a LOG.warn instead.

* build: compare spark_version numerically via isSparkAtLeast helper

Per /ultrareview feedback: the five `"$spark_version" >= "3.5.0"` checks
were lexicographic string comparisons. They happened to work for 3.5.0
and 4.0.2 only because '4' > '3' as chars — a future "3.10.0" release
would compare less than "3.5.0" and silently drop the Spark 3.5+
dependencies and exclusions.

Introduce an `isSparkAtLeast` closure that tokenizes on `.` and `-`,
keeps numeric parts, and compares component-by-component. Replace all
five call sites.

* [Spark Runner] Slim Spark 4 to override-only files

With spark_runner.gradle now layering per-major source overrides on top
of the shared base, runners/spark/4/src/ no longer needs to duplicate
62 byte-identical structured-streaming files. Keep only the 11 files
that actually differ for Spark 4 / Scala 2.13. Switch the build.gradle
to spark_major = '4' (the new mechanism) and bump spark_versions to 3,4.

Compiled output unchanged — the deleted files are reproduced identically
inside build/source-overrides by the Copy task.

* [Spark Runner] Use java.io.Serializable in DoFnRunnerFactory base

scala.Serializable was removed in Scala 2.13. java.io.Serializable
works identically on both Scala 2.12 and 2.13, so this can live in
the shared base instead of needing a Spark-4-only override file.

* [Spark Runner] Null-guard error message logging in EvaluationContext base

Wrap Throwables.getRootCause(e).getMessage() in String.valueOf(...)
to make the error logging robust to a null root-cause message. The
behaviour change applies equally to Spark 3 and Spark 4, so the
fix lives in the shared base and the Spark-4 override is dropped.

* [Spark Runner] Cancel execution future and use Beam-vendored Guava in PipelineResult

Two changes that previously lived only in the Spark-4 override and
are equally valid for Spark 3:

1. cancel() now actually cancels the executing future
   (pipelineExecution.cancel(true)) in addition to setting the state
   to CANCELLED. Without this, calling cancel() left the pipeline
   running silently — a real bug, not a Spark-4 specific concern.

2. Switch from Spark's shaded guava (org.sparkproject.guava) to the
   Beam-vendored guava that is already on the classpath. Spark 4
   no longer exposes the sparkproject guava package; using the
   vendored one removes the version coupling for both runners.

* ci: re-trigger to clear flaky UnboundedScheduledExecutorServiceTest

Empty commit to re-run CI. The only failure on the prior head was
UnboundedScheduledExecutorServiceTest.testThreadsAreAddedOnlyAsNeededWithContention,
a known flake (#31590) — the test itself acknowledges
contention-induced extra threads in its inline comment. Squash or
drop on rebase before merge.

* [Spark Runner] Fix maxTimestamp to handle multi-window values

Iterables.getOnlyElement(windows) crashes with IllegalArgumentException
when a WindowedValue is associated with more than one window (e.g. after
a sliding window assignment). Compute the max maxTimestamp() across all
associated windows instead, falling back to a clear error if the iterable
is unexpectedly empty.

Applied identically to the shared base and the Spark 4 override. Flagged
by Gemini Code Assist on PR #38255.

* [Spark Runner] Drop unchecked cast in BoundedDatasetFactory.split

source.split returns List<? extends BoundedSource<T>>, which already
satisfies the subsequent stream usage. The cast was unchecked and would
trip heap-pollution warnings. Applied identically to the shared base
and the Spark 4 override. Flagged by Gemini Code Assist on PR #38255.

* [Spark Runner] Drop redundant Iterator cast in Spark 4 GroupByKeyTranslatorBatch

The (Iterator<V>) cast inside fun2 is redundant: fun2's signature
infers the iterator type. The shared base translator at the analogous
call site already calls iterableOnce(it) without a cast. Flagged by
Gemini Code Assist on PR #38255.

* [Spark Runner] Spark 4 EncoderFactory: stable constructor lookup + document trait setter

Replace getConstructors()[0] (JVM-defined ordering, not stable) with a
helper that picks the widest public constructor. The downstream switch
already dispatches on parameter count to pick the right argument shape
per Spark version, so this just makes the choice deterministic.

Also document the org$apache$spark...$_setter_$isStruct_$eq method —
it is the synthetic setter the Scala compiler emits for trait val fields,
required when implementing AgnosticEncoders.StructEncoder from Java.

Both flagged by Gemini Code Assist on PR #38255.

* [Spark Runner] Fix Javadoc/comment typos flagged by Gemini

Three trivial typos flagged on PR #38255 round 2 review, applied
identically to the shared base and the Spark 4 override:

- CombinePerKeyTranslatorBatch: "other there other missing features?"
  -> "are there other missing features?"
- GroupByKeyTranslatorBatch: "build-in" -> "built-in"
- EncoderHelpers: PRIMITIV_TYPES -> PRIMITIVE_TYPES (constant + caller)

* [Spark Runner] Switch EncoderFactory.invoke on the right constructor

In EncoderFactory.invoke(Expression obj, ...), the switch was keyed on
STATIC_INVOKE_CONSTRUCTOR.getParameterCount() but the body actually
calls INVOKE_CONSTRUCTOR. This worked by coincidence: across the
supported Spark 3.x versions both constructors happen to share the
same parameter counts at the same dispatch points. A future Spark
release where the two diverge would silently pick the wrong branch.

Switch on INVOKE_CONSTRUCTOR.getParameterCount() to match the
constructor that is actually invoked, and align with the convention
used by newInstance() further down. In the Spark 4 override this also
lets us collapse the `case 8: case 9:` fallthrough back to a single
`case 8:`, since INVOKE_CONSTRUCTOR remains 8 params in Spark 4 even
though STATIC_INVOKE_CONSTRUCTOR grew to 9.

Applied identically to the shared base and the Spark 4 override.
Flagged by Gemini Code Assist on PR #38255.

* Update CHANGES.md

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

* [Spark 4] Drop redundant Collection cast in GroupByKeyHelpers

WindowedValue#getWindows() returns Collection<? extends BoundedWindow>,
which is already an Iterable and can be passed straight to
ScalaInterop.scalaIterator(...). The intermediate local variable and the
unchecked cast to Collection<BoundedWindow> were redundant.

Applied in both the shared base and the Spark 4 override.

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

* [Spark 4] Add module README with slf4j-jdk14 known-issue note

Documents the Spark 4 runner's requirements (Java 17, Scala 2.13,
Spark 4.0.x, batch-only) and the slf4j-jdk14 ↔ jul-to-slf4j conflict
that is the Spark 4 manifestation of #26985 (fixed for Spark 3 in
#27001). The shared spark_runner.gradle already excludes slf4j-jdk14
for in-tree builds; this note tells downstream consumers to mirror the
exclude when assembling their own runtime classpath against
beam-runners-spark-4.

* [runners-spark] Address Gemini nits: use encoder terminology in exception messages

* Trigger Build

* ci: re-trigger to clear flaky FlinkRequiresStableInputTest

The PreCommit Java failure on the previous run was a single timeout in
FlinkRequiresStableInputTest.testParDoRequiresStableInputPortable
(:runners:flink:1.17:test) — known flake tracked in #21333. This PR
does not touch any Flink code. Squash or drop on rebase before merge.

* ci: re-trigger to clear flaky SqsIOWriteBatchesTest.testWriteBatchesToDynamicWithStrictTimeout

Wall-clock-timing test (100ms inter-message + 150ms strict batch
timeout) in sdks/java/io/amazon-web-services2 SQS — unrelated to
this PR (no AWS2/SQS/Direct-runner files touched), and master is
green for the same PreCommit on 6106b30.

* ci: re-trigger to clear Maven Central 403 on Windows wordcount

`Java Wordcount Direct Runner (windows-latest)` failed at the
:buildSrc configure step with HTTP 403 fetching legacy Spotless
5.6.1 transitive deps from repo.maven.apache.org
(spotless-lib:2.7.0, durian-*:1.2.0, jgit:5.8.0). Network/infra
flake — PR doesn't touch examples or buildSrc, master 'Java Tests'
workflow consistently green.

* ci: re-trigger to clear flaky Spotless + GCP IO Direct PreCommits

Both checks failed on the prior empty retry commit (e19b80c).
Reproduced locally at e19b80c: spotlessCheck and Spark
checkStyleMain/Test all pass. PR doesn't touch any GCP IO code,
and both checks were green on the immediately preceding branch
commits (5abbb21, 604037f) and on master (6106b30, e01f711).
Treating as infra flakes; squash before merge.

* [runners-spark] Cover Scala-array fallback and EvaluationContext error paths

Address codecov/patch on PR #38255 by exercising the new branches added for
Scala 2.13 / null-safe error logging:

- Refactor SparkRunnerKryoRegistrator's nested Scala-array Class.forName
  fallback into a small @VisibleForTesting findFirstAvailableClass helper
  and add unit tests for first-hit, fallback, no-match, and empty-input
  paths.
- Add EvaluationContextTest covering the catch (RuntimeException) /
  catch (Exception) blocks in evaluate() and collect(), including the
  null-message path that motivated the String.valueOf wrap.

* [runners-spark] spotless: inline two findFirstAvailableClass calls in test

* flaky SqsIOWriteBatchesTest retry

* flaky ExampleEchoPipelineTest retry

* rebase cleanup: drop duplicate isSparkAtLeast helper now in master via #38324

* Address @Abacn 2026-05-07 review

- SparkRunnerKryoRegistrator: throw IllegalStateException instead of
  LOG.warn when neither ArraySeq$ofRef (Scala 2.13) nor WrappedArray$ofRef
  (Scala 2.12) is on the classpath, so the missing class isn't silently
  ignored. Drops the now-unused Logger field and slf4j imports.
- spark_runner.gradle: declare org.apache.spark:spark-connect-shims_2.13
  as a provided dep gated on isSparkAtLeast("4.0.0"). Spark 4 splits the
  Connect shim classes out of spark-sql; with enableStrictDependencies
  this surfaced as analyzeClassesDependencies usedUndeclaredArtifacts.
  The artifact does not exist for Spark 3, so the gate prevents Spark 3
  resolution failures.
- runners/spark/4/build.gradle: drop the empty sparkVersions test
  scaffolding (no additional Spark 4.x patch versions to test against
  yet) and delete the now-unused
  .github/workflows/beam_PreCommit_Java_Spark4_Versions.yml workflow
  + its README.md row.
- EncoderFactory (shared base): revert the line 94 switch to
  STATIC_INVOKE_CONSTRUCTOR.getParameterCount(), keeping Spark 3 behavior
  byte-for-byte unchanged. Spark 4's complete EncoderFactory override
  under runners/spark/4/src/.../EncoderFactory.java is unaffected.
- CHANGES.md: drop the Highlights line for Spark 4. Will re-add when
  ValidatesRunner tests are set up and confirmed working, matching the
  Phase 1 #38324 pattern.
- runners/spark/4/job-server/container: delete the entire module
  (build.gradle + Dockerfile) and remove its include() from
  settings.gradle.kts. Per @Abacn's offer to defer the container module
  to portable runner support later. The fat-jar :runners:spark:4:job-server
  module is kept.

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: 3 people

.github/trigger_files/beam_PostCommit_Java_ValidatesRunner_Spark4StructuredStreaming.json

@@ -0,0 +1,3 @@
+{
+  "comment": "Modify this file in a trivial way to cause this test suite to run"
+}

.github/trigger_files/beam_PreCommit_Java_Spark4_Versions.json

@@ -0,0 +1,3 @@
+{
+  "comment": "Modify this file in a trivial way to cause this test suite to run"
+}

.github/workflows/README.md

@@ -370,6 +370,7 @@ PostCommit Jobs run in a schedule against master branch and generally do not get
 | [ PostCommit Java ValidatesRunner Flink ](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java_ValidatesRunner_Flink.yml) | N/A |`beam_PostCommit_Java_ValidatesRunner_Flink.json`| [![.github/workflows/beam_PostCommit_Java_ValidatesRunner_Flink.yml](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java_ValidatesRunner_Flink.yml/badge.svg?event=schedule)](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java_ValidatesRunner_Flink.yml?query=event%3Aschedule) |
 | [ PostCommit Java ValidatesRunner Spark ](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java_ValidatesRunner_Spark.yml) | N/A |`beam_PostCommit_Java_ValidatesRunner_Spark.json`| [![.github/workflows/beam_PostCommit_Java_ValidatesRunner_Spark.yml](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java_ValidatesRunner_Spark.yml/badge.svg?event=schedule)](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java_ValidatesRunner_Spark.yml?query=event%3Aschedule) |
 | [ PostCommit Java ValidatesRunner SparkStructuredStreaming ](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java_ValidatesRunner_SparkStructuredStreaming.yml) | N/A |`beam_PostCommit_Java_ValidatesRunner_SparkStructuredStreaming.json`| [![.github/workflows/beam_PostCommit_Java_ValidatesRunner_SparkStructuredStreaming.yml](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java_ValidatesRunner_SparkStructuredStreaming.yml/badge.svg?event=schedule)](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java_ValidatesRunner_SparkStructuredStreaming.yml?query=event%3Aschedule) |
+| [ PostCommit Java ValidatesRunner Spark4StructuredStreaming ](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java_ValidatesRunner_Spark4StructuredStreaming.yml) | N/A |`beam_PostCommit_Java_ValidatesRunner_Spark4StructuredStreaming.json`| [![.github/workflows/beam_PostCommit_Java_ValidatesRunner_Spark4StructuredStreaming.yml](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java_ValidatesRunner_Spark4StructuredStreaming.yml/badge.svg?event=schedule)](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java_ValidatesRunner_Spark4StructuredStreaming.yml?query=event%3Aschedule) |
 | [ PostCommit Java ValidatesRunner Twister2 ](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java_ValidatesRunner_Twister2.yml) | N/A |`beam_PostCommit_Java_ValidatesRunner_Twister2.json`| [![.github/workflows/beam_PostCommit_Java_ValidatesRunner_Twister2.yml](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java_ValidatesRunner_Twister2.yml/badge.svg?event=schedule)](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java_ValidatesRunner_Twister2.yml?query=event%3Aschedule) |
 | [ PostCommit Java ValidatesRunner ULR ](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java_ValidatesRunner_ULR.yml) | N/A |`beam_PostCommit_Java_ValidatesRunner_ULR.json`| [![.github/workflows/beam_PostCommit_Java_ValidatesRunner_ULR.yml](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java_ValidatesRunner_ULR.yml/badge.svg?event=schedule)](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java_ValidatesRunner_ULR.yml?query=event%3Aschedule) |
 | [ PostCommit Java ](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java.yml) | N/A |`beam_PostCommit_Java.json`| [![.github/workflows/beam_PostCommit_Java.yml](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java.yml/badge.svg?event=schedule)](https://github.com/apache/beam/actions/workflows/beam_PostCommit_Java.yml?query=event%3Aschedule) |

.github/workflows/beam_PostCommit_Java_ValidatesRunner_Spark4StructuredStreaming.yml

@@ -0,0 +1,97 @@
+# 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.
+
+name: PostCommit Java ValidatesRunner Spark4 StructuredStreaming
+
+on:
+  schedule:
+    - cron: '45 4/6 * * *'
+  pull_request_target:
+    paths: ['release/trigger_all_tests.json', '.github/trigger_files/beam_PostCommit_Java_ValidatesRunner_Spark4StructuredStreaming.json']
+  workflow_dispatch:
+
+#Setting explicit permissions for the action to avoid the default permissions which are `write-all` in case of pull_request_target event
+permissions:
+  actions: write
+  pull-requests: write
+  checks: write
+  contents: read
+  deployments: read
+  id-token: none
+  issues: write
+  discussions: read
+  packages: read
+  pages: read
+  repository-projects: read
+  security-events: read
+  statuses: read
+
+# This allows a subsequently queued workflow run to interrupt previous runs
+concurrency:
+  group: '${{ github.workflow }} @ ${{ github.event.pull_request.number || github.sha || github.head_ref || github.ref }}-${{ github.event.schedule || github.event.comment.id || github.event.sender.login }}'
+  cancel-in-progress: true
+
+env:
+  DEVELOCITY_ACCESS_KEY: ${{ secrets.DEVELOCITY_ACCESS_KEY }}
+  GRADLE_ENTERPRISE_CACHE_USERNAME: ${{ secrets.GE_CACHE_USERNAME }}
+  GRADLE_ENTERPRISE_CACHE_PASSWORD: ${{ secrets.GE_CACHE_PASSWORD }}
+
+jobs:
+  beam_PostCommit_Java_ValidatesRunner_Spark4StructuredStreaming:
+    name: ${{ matrix.job_name }} (${{ matrix.job_phrase }})
+    runs-on: [self-hosted, ubuntu-24.04, main]
+    timeout-minutes: 120
+    strategy:
+      matrix:
+        job_name: [beam_PostCommit_Java_ValidatesRunner_Spark4StructuredStreaming]
+        job_phrase: [Run Spark4 StructuredStreaming ValidatesRunner]
+    if: |
+      github.event_name == 'workflow_dispatch' ||
+      github.event_name == 'pull_request_target' ||
+      (github.event_name == 'schedule' && github.repository == 'apache/beam') ||
+      github.event.comment.body == 'Run Spark4 StructuredStreaming ValidatesRunner'
+    steps:
+      - uses: actions/checkout@v4
+      - name: Setup repository
+        uses: ./.github/actions/setup-action
+        with:
+          comment_phrase: ${{ matrix.job_phrase }}
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          github_job: ${{ matrix.job_name }} (${{ matrix.job_phrase }})
+      - name: Setup environment
+        uses: ./.github/actions/setup-environment-action
+        with:
+          java-version: '17'
+      - name: run validatesStructuredStreamingRunnerBatch script
+        uses: ./.github/actions/gradle-command-self-hosted-action
+        with:
+          gradle-command: :runners:spark:4:validatesStructuredStreamingRunnerBatch
+          arguments: |
+            -PtestJavaVersion=17 \
+            -PdisableSpotlessCheck=true \
+      - name: Archive JUnit Test Results
+        uses: actions/upload-artifact@v4
+        if: ${{ !success() }}
+        with:
+          name: JUnit Test Results
+          path: "**/build/reports/tests/"
+      - name: Publish JUnit Test Results
+        uses: EnricoMi/publish-unit-test-result-action@v2
+        if: always()
+        with:
+          commit: '${{ env.prsha || env.GITHUB_SHA }}'
+          comment_mode: ${{ github.event_name == 'issue_comment'  && 'always' || 'off' }}
+          files: '**/build/test-results/**/*.xml'
+          large_files: true

CHANGES.md

@@ -60,7 +60,6 @@
 ## Highlights
 
 * New highly anticipated feature X added to Python SDK ([#X](https://github.com/apache/beam/issues/X)).
-* New highly anticipated feature Y added to Java SDK ([#Y](https://github.com/apache/beam/issues/Y)).
 
 ## I/Os
 

gradle.properties

@@ -41,6 +41,6 @@ docker_image_default_repo_prefix=beam_
 # supported flink versions
 flink_versions=1.17,1.18,1.19,1.20,2.0
 # supported spark versions
-spark_versions=3
+spark_versions=3,4
 # supported python versions
 python_versions=3.10,3.11,3.12,3.13,3.14

runners/spark/4/README.md

@@ -0,0 +1,73 @@
+<!--
+    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.
+-->
+# Apache Beam Spark 4 Runner
+
+Experimental Beam runner for Apache Spark 4 (batch-only). Built on the shared
+`runners/spark` source base via `spark_runner.gradle`'s per-version
+source-overrides mechanism: this module contributes the small set of files
+under `src/main/java/.../structuredstreaming/` that diverge from the Spark 3
+implementation. See the parent `runners/spark/` module for the bulk of the
+runner code.
+
+## Requirements
+
+* **Spark 4.0.2** (and other Spark 4.0.x patch releases)
+* **Scala 2.13**
+* **Java 17** — Spark 4 does not run on earlier JDKs
+
+## Status
+
+Batch only. Streaming is tracked in
+[#36841](https://github.com/apache/beam/issues/36841).
+
+## Known issues
+
+### `StackOverflowError` from `slf4j-jdk14` on the runtime classpath
+
+Spark 4 ships `org.slf4j:jul-to-slf4j` to route `java.util.logging` records
+into SLF4J. If `org.slf4j:slf4j-jdk14` is also resolved at runtime — it routes
+the other direction (SLF4J → JUL) — the first log line creates an infinite
+loop:
+
+```
+java.lang.StackOverflowError
+    at org.slf4j.bridge.SLF4JBridgeHandler.publish(...)
+    at java.util.logging.Logger.log(...)
+    at org.slf4j.impl.JDK14LoggerAdapter.log(...)
+    at org.slf4j.bridge.SLF4JBridgeHandler.publish(...)
+    ...
+```
+
+This is the same condition that broke the Spark 3 runner in
+[#26985](https://github.com/apache/beam/issues/26985), fixed in
+[#27001](https://github.com/apache/beam/pull/27001).
+
+The shared `spark_runner.gradle` already excludes `slf4j-jdk14` from the
+runner module's own `configurations.all`, so in-tree builds are unaffected.
+Downstream Gradle consumers that assemble a runtime classpath against
+`beam-runners-spark-4` should mirror that exclude:
+
+```groovy
+configurations.all {
+    exclude group: "org.slf4j", module: "slf4j-jdk14"
+}
+```
+
+For Maven, exclude `org.slf4j:slf4j-jdk14` from any dependency that pulls it
+transitively (commonly the Beam SDK harness and several IO connectors).

runners/spark/4/build.gradle

@@ -0,0 +1,53 @@
+/*
+ * 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.
+ */
+
+def basePath = '..'
+/* All properties required for loading the Spark build script */
+project.ext {
+  spark_major = '4'
+  // Spark 4 version as defined in BeamModulePlugin; requires Scala 2.13 and Java 17
+  spark_version = spark4_version
+  spark_scala_version = '2.13'
+  archives_base_name = 'beam-runners-spark-4'
+}
+
+// Load the main build script which contains all build logic.
+// spark_runner.gradle handles the per-version source-overrides Copy:
+// shared base (runners/spark/src/) + previous majors + this module's ./src/ are
+// merged into build/source-overrides/src using DuplicatesStrategy.INCLUDE so the
+// 11 files under runners/spark/4/src/.../structuredstreaming/ override the
+// shared-base versions.
+apply from: "$basePath/spark_runner.gradle"
+
+// Spark 4 always requires Java 17, so unconditionally add the --add-opens flags
+// required by Kryo and other libraries that use reflection on JDK internals.
+test {
+  jvmArgs "--add-opens=java.base/sun.nio.ch=ALL-UNNAMED",
+          "--add-opens=java.base/java.nio=ALL-UNNAMED",
+          "--add-opens=java.base/java.util=ALL-UNNAMED",
+          "--add-opens=java.base/java.lang.invoke=ALL-UNNAMED"
+}
+
+// Exclude DStream-based streaming tests from the shared-base copy: the Spark 4 module
+// supports only structured streaming (batch) and does not include legacy DStream support.
+// Streaming test utilities also depend on kafka.server.KafkaServerStartable which was
+// removed in Kafka 2.8.0 (the first Kafka version with a _2.13 artifact).
+tasks.named("copyTestSourceOverrides") {
+  exclude "**/translation/streaming/**"
+}
+

runners/spark/4/job-server/build.gradle

@@ -0,0 +1,31 @@
+/*
+ * 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.
+ */
+
+def basePath = '../../job-server'
+
+project.ext {
+  // Look for the source code in the parent module
+  main_source_dirs = ["$basePath/src/main/java"]
+  test_source_dirs = ["$basePath/src/test/java"]
+  main_resources_dirs = ["$basePath/src/main/resources"]
+  test_resources_dirs = ["$basePath/src/test/resources"]
+  archives_base_name = 'beam-runners-spark-4-job-server'
+}
+
+// Load the main build script which contains all build logic.
+apply from: "$basePath/spark_job_server.gradle"