[AURON #2407] [BUILD] Fix the invalid Spark 4.1 Docker build example.

CONTRIBUTING.md

@@ -114,7 +114,7 @@ Auron provides a unified build script `auron-build.sh` that supports both local
 
 ```bash
 # Build inside Docker container
-./auron-build.sh --docker true --image centos7 --release \
+./auron-build.sh --docker true --image rockylinux8 --release \
   --sparkver 3.5 --scalaver 2.12
 ```
 
@@ -130,6 +130,28 @@ Run `./auron-build.sh --help` to see all available options, including:
 - `--sparktests`: Run Spark integration tests
 - `--threads`: Maven build threads (e.g. 1, 4, 1C). Defaults to single-threaded local builds; Docker defaults to 8 unless overridden.
 
+### Build Compatibility Matrix
+
+The examples printed by `./auron-build.sh --help` use the following documented build
+configurations based on the current compatibility checks. A dash (`—`) means that the
+integration is not supported for that Spark version and must not be passed to
+`auron-build.sh`.
+
+| Spark | Scala | JDK | Docker image | Flink | Celeborn | Uniffle | Paimon | Iceberg | Hudi |
+| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
+| 3.5 | 2.12 | 8+ | `rockylinux8` | 1.18 | 0.6 | 0.10 | 1.2 | 1.10.1 | 0.15 |
+| 4.0 | 2.13 | 17+ | `rockylinux8` | 1.18 | 0.6 | 0.10 | 1.2 | 1.10.1 | — |
+| 4.1 | 2.13 | 17+ | `rockylinux8` | 1.18 | 0.6 | 0.10 | 1.2 | — | — |
+
+Spark 4.x requires Scala 2.13 and JDK 17 or later. In Docker mode,
+`auron-build.sh` selects JDK 17 for Spark 4.x, and the `rockylinux8` image applies that
+selection. The `centos7` image only provides JDK 8 and must not be used for Spark 4.x.
+
+Iceberg 1.10.1 supports Spark 3.4, 3.5, and 4.0 in Auron. Spark 4.1 support requires a
+future upgrade to Iceberg 1.11.0 or later. Hudi 0.15 supports Spark 3.0 through 3.5.
+When a supported version or compatibility rule changes, update this matrix and the
+examples in `auron-build.sh` together.
+
 ### Running Tests
 
 By default, the build script skips unit tests (`--skiptests true`). To run them, you must explicitly set `--skiptests false`, as shown in the examples below:

auron-build.sh

@@ -72,16 +72,33 @@ print_help() {
     echo "Examples:"
     echo "  $0 --pre --sparkver ${SUPPORTED_SPARK_VERSIONS[*]: -1}" \
          "--scalaver ${SUPPORTED_SCALA_VERSIONS[*]: -1} -DskipBuildNative"
-    echo "  $0 --docker true --image ${SUPPORTED_OS_IMAGES[*]:0:1}" \
+    echo "  # Spark 3.5 with all supported third-party integrations"
+    echo "  $0 --docker true --image rockylinux8" \
          "--clean true --skiptests true --release" \
-         "--sparkver ${SUPPORTED_SPARK_VERSIONS[*]: -1}" \
+         "--sparkver 3.5 --scalaver 2.12" \
          "--flinkver ${SUPPORTED_FLINK_VERSIONS[*]: -1}" \
-         "--scalaver ${SUPPORTED_SCALA_VERSIONS[*]: -1}" \
          "--celeborn ${SUPPORTED_CELEBORN_VERSIONS[*]: -1}" \
          "--uniffle ${SUPPORTED_UNIFFLE_VERSIONS[*]: -1}" \
          "--paimon ${SUPPORTED_PAIMON_VERSIONS[*]: -1}" \
          "--iceberg ${SUPPORTED_ICEBERG_VERSIONS[*]: -1}" \
          "--hudi ${SUPPORTED_HUDI_VERSIONS[*]: -1}"
+    echo "  # Spark 4.0 (Hudi is not supported)"
+    echo "  $0 --docker true --image rockylinux8" \
+         "--clean true --skiptests true --release" \
+         "--sparkver 4.0 --scalaver 2.13" \
+         "--flinkver ${SUPPORTED_FLINK_VERSIONS[*]: -1}" \
+         "--celeborn ${SUPPORTED_CELEBORN_VERSIONS[*]: -1}" \
+         "--uniffle ${SUPPORTED_UNIFFLE_VERSIONS[*]: -1}" \
+         "--paimon ${SUPPORTED_PAIMON_VERSIONS[*]: -1}" \
+         "--iceberg ${SUPPORTED_ICEBERG_VERSIONS[*]: -1}"
+    echo "  # Spark 4.1 (Iceberg and Hudi are not supported)"
+    echo "  $0 --docker true --image rockylinux8" \
+         "--clean true --skiptests true --release" \
+         "--sparkver 4.1 --scalaver 2.13" \
+         "--flinkver ${SUPPORTED_FLINK_VERSIONS[*]: -1}" \
+         "--celeborn ${SUPPORTED_CELEBORN_VERSIONS[*]: -1}" \
+         "--uniffle ${SUPPORTED_UNIFFLE_VERSIONS[*]: -1}" \
+         "--paimon ${SUPPORTED_PAIMON_VERSIONS[*]: -1}"
     exit 0
 }