apache/iceberg · error · GradleException

Found unsupported Flink versions:

Error message

Found unsupported Flink versions: 

What it means

settings.gradle validates the requested Flink versions against the knownFlinkVersions system property. Any requested version (from -DflinkVersions or the default) not present in the known list causes a GradleException listing the unsupported versions, so the build never configures modules for Flink versions Iceberg cannot build.

Solutions

1. Use only versions listed in knownFlinkVersions (check gradle.properties for the supported set).
2. Omit -DflinkVersions to use defaultFlinkVersions.
3. If adding a new Flink version intentionally, add it to knownFlinkVersions and update the Flink module build logic and CI matrix.
4. Fix typos in the version string (e.g. '1,18' vs '1.18').

Example fix

// before
./gradlew build -DflinkVersions=1.16
// after
./gradlew build -DflinkVersions=1.19,1.20

KNOWN=$(grep knownFlinkVersions gradle.properties | cut -d= -f2); for v in $(echo $FLINK_VERSIONS | tr ',' ' '); do [[ ",$KNOWN," == *",$v,"* ]] || echo "Unsupported Flink: $v"; done

When it happens

Trigger: Running Gradle with -DflinkVersions=1.17 (or another retired/unreleased version) that is not in knownFlinkVersions; also triggered if knownFlinkVersions is misconfigured in gradle.properties.

Common situations: Building an older Iceberg branch with flags copied from a newer one (or vice versa); trying to add support for a brand-new Flink release before the build was updated; typos like 'flink-1.19' vs '1.19'.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• Found unsupported Kafka versions:
• Found unsupported Scala version:
• Found unsupported Spark versions:
• Class does not implement DynamicRecordGeneratorSQL
• Class does not implement DynamicRecordGeneratorSQL

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/d86b476e8ea814f7. Report an issue: GitHub.

Appendix: source

Thrown at settings.gradle:84

project(':bigquery').name = 'iceberg-bigquery'
project(':dell').name = 'iceberg-dell'
project(':snowflake').name = 'iceberg-snowflake'
project(':delta-lake').name = 'iceberg-delta-lake'
project(':open-api').name = 'iceberg-open-api'
project(':mr').name = 'iceberg-mr'

if (null != System.getProperty("allModules")) {
  System.setProperty("flinkVersions", System.getProperty("knownFlinkVersions"))
  System.setProperty("sparkVersions", System.getProperty("knownSparkVersions"))
  System.setProperty("kafkaVersions", System.getProperty("knownKafkaVersions"))
}

List<String> knownFlinkVersions = System.getProperty("knownFlinkVersions").split(",")
String flinkVersionsString = System.getProperty("flinkVersions") != null ? System.getProperty("flinkVersions") : System.getProperty("defaultFlinkVersions")
List<String> flinkVersions = flinkVersionsString != null && !flinkVersionsString.isEmpty() ? flinkVersionsString.split(",") : []

if (!knownFlinkVersions.containsAll(flinkVersions)) {
  throw new GradleException("Found unsupported Flink versions: " + (flinkVersions - knownFlinkVersions))
}

List<String> knownSparkVersions = System.getProperty("knownSparkVersions").split(",")
String sparkVersionsString = System.getProperty("sparkVersions") != null ? System.getProperty("sparkVersions") : System.getProperty("defaultSparkVersions")
List<String> sparkVersions = sparkVersionsString != null && !sparkVersionsString.isEmpty() ? sparkVersionsString.split(",") : []

if (!knownSparkVersions.containsAll(sparkVersions)) {
  throw new GradleException("Found unsupported Spark versions: " + (sparkVersions - knownSparkVersions))
}

List<String> knownKafkaVersions = System.getProperty("knownKafkaVersions").split(",")
String kafkaVersionsString = System.getProperty("kafkaVersions") != null ? System.getProperty("kafkaVersions") : System.getProperty("defaultKafkaVersions")
List<String> kafkaVersions = kafkaVersionsString != null && !kafkaVersionsString.isEmpty() ? kafkaVersionsString.split(",") : []

if (!knownKafkaVersions.containsAll(kafkaVersions)) {
  throw new GradleException("Found unsupported Kafka versions: " + (kafkaVersions - knownKafkaVersions))
}

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