apache/flink · error · RuntimeException

Could not instantiate org.apache.flink.formats.avro.utils.Av

Error message

Could not instantiate org.apache.flink.formats.avro.utils.AvroKryoSerializerUtils.

What it means

Thrown by AvroUtils.getAvroUtils() when the class org.apache.flink.formats.avro.utils.AvroKryoSerializerUtils was found on the classpath (so it is not ClassNotFoundException) but could not be instantiated — its no-arg constructor threw, the class was not a subclass of AvroUtils, or reflection failed. This means flink-avro is present but broken or version-mismatched.

Source

Thrown at flink-core/src/main/java/org/apache/flink/api/java/typeutils/AvroUtils.java:60

    protected static final String AVRO_SPECIFIC_RECORD_BASE_CLASS =
            "org.apache.avro.specific.SpecificRecordBase";

    /**
     * Returns either the default {@link AvroUtils} which throw an exception in cases where Avro
     * would be needed or loads the specific utils for Avro from flink-avro.
     */
    public static AvroUtils getAvroUtils() {
        // try and load the special AvroUtils from the flink-avro package
        try {
            Class<?> clazz =
                    Class.forName(
                            AVRO_KRYO_UTILS, false, Thread.currentThread().getContextClassLoader());
            return clazz.asSubclass(AvroUtils.class).getConstructor().newInstance();
        } catch (ClassNotFoundException e) {
            // cannot find the utils, return the default implementation
            return new DefaultAvroUtils();
        } catch (Exception e) {
            throw new RuntimeException("Could not instantiate " + AVRO_KRYO_UTILS + ".", e);
        }
    }

    /**
     * Returns either {@code Optional#EMPTY} which throw an exception in cases where Avro would be
     * needed or loads the specific utils for Avro from flink-avro.
     */
    public static Optional<AvroUtils> tryGetAvroUtils() {
        // try and load the special AvroUtils from the flink-avro package
        try {
            Class<?> clazz =
                    Class.forName(
                            AVRO_KRYO_UTILS, false, Thread.currentThread().getContextClassLoader());
            return Optional.of(clazz.asSubclass(AvroUtils.class).getConstructor().newInstance());
        } catch (ClassNotFoundException e) {
            // cannot find the utils, return none.
            return Optional.empty();
        } catch (Exception e) {

View on GitHub (pinned to 2f3c205e92)

Solutions

1. Inspect the chained exception to see the exact instantiation failure (NoSuchMethodError, ExceptionInInitializerError, etc.).
2. Align the Avro runtime version in your user jar with the version Flink's flink-avro expects.
3. Avoid relocating/shading org.apache.flink.formats.avro classes; use the provided Flink Avro jars unshaded.
4. Run dependency-tree / mvn dependency:tree to find and exclude conflicting avro-* artifacts.

Example fix

// before (pom): user jar forces an old avro
<dependency>
  <groupId>org.apache.avro</groupId><artifactId>avro</artifactId><version>1.7.7</version>
</dependency>

// after: align with Flink's BOM-managed avro version, do not shade flink-avro
<dependency>
  <groupId>org.apache.flink</groupId><artifactId>flink-avro</artifactId><version>${flink.version}</version><scope>provided</scope>
</dependency>

// Probe Avro utils availability before relying on it
try {
    Class.forName("org.apache.flink.formats.avro.utils.AvroKryoSerializerUtils", false, Thread.currentThread().getContextClassLoader());
} catch (ClassNotFoundException e) {
    // flink-avro absent -> use non-Avro types only
}

try {
    AvroUtils.getAvroUtils();
} catch (RuntimeException e) {
    // inspect chained cause; align avro versions or add flink-avro
    throw e;
}

When it happens

Trigger: Calling AvroUtils.getAvroUtils() during type registration/serializer setup. The class is loaded via the context ClassLoader; if the loaded version has an incompatible signature, an ExceptionInInitializerError, or a constructor that depends on a missing transitive dependency (e.g. wrong Avro runtime version), the generic catch(Exception) fires.

Common situations: Conflicting avro versions on the classpath (e.g. user jar ships avro 1.7 while flink-avro needs 1.11); a shaded/fat jar that relocated the AvroKryoSerializerUtils class; partial flink-avro dependency (JAR present but its transitive deps stripped by shading).

Related errors

• The program's entry point class '{className}' could not be l
• Could not load class for serialization config
• This object is a dummy TypeSerializer.
• Failed to serialize row.
• Failed to serialize schema registry.

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/54047d4786724055. Report an issue: GitHub.