Implementation:Apache Flink FatalExceptionClassifier IsFatal

Knowledge Sources	Apache Flink
Domains	Stream_Processing, Error_Handling
Last Updated	2026-02-09 00:00 GMT

Overview

Concrete tool for classifying exceptions as fatal or retryable in async sink operations provided by the Apache Flink connector-base module.

Description

The FatalExceptionClassifier uses a Predicate<Throwable> to match exceptions and a Function<Throwable, Exception> to map them. The isFatal method walks the exception chain to find the root cause and tests it against the predicate. Multiple classifiers can be chained via createChain. The static factory withRootCauseOfType creates a classifier matching a specific exception class.

Usage

Create classifiers for your custom async sink to define which destination-specific exceptions should fail the job vs. be retried.

Code Reference

Source Location

• Repository: Apache Flink
• File: flink-connectors/flink-connector-base/src/main/java/org/apache/flink/connector/base/sink/throwable/FatalExceptionClassifier.java
• Lines: L32-86

Signature

@Internal
public class FatalExceptionClassifier {

    public FatalExceptionClassifier(
            Predicate<Throwable> validator,
            Function<Throwable, Exception> throwableMapper);

    public boolean isFatal(Throwable err, Consumer<Exception> throwableConsumer);

    public static FatalExceptionClassifier withRootCauseOfType(
            Class<? extends Throwable> type,
            Function<Throwable, Exception> mapper);

    public static FatalExceptionClassifier createChain(
            FatalExceptionClassifier... classifiers);
}

Import

import org.apache.flink.connector.base.sink.throwable.FatalExceptionClassifier;

I/O Contract

Inputs

Name	Type	Required	Description
err	Throwable	Yes	Exception to classify
throwableConsumer	Consumer<Exception>	Yes	Callback for fatal exceptions

Outputs

Name	Type	Description
isFatal	boolean	true if the exception is fatal, false if retryable

Usage Examples

Creating a Classifier Chain

FatalExceptionClassifier classifier = FatalExceptionClassifier.createChain(
    FatalExceptionClassifier.withRootCauseOfType(
        AccessDeniedException.class,
        err -> new FlinkRuntimeException("Access denied", err)),
    FatalExceptionClassifier.withRootCauseOfType(
        ResourceNotFoundException.class,
        err -> new FlinkRuntimeException("Resource not found", err))
);

// Usage in ResultHandler:
// if (classifier.isFatal(exception, fatalConsumer)) {
//     // Job will fail
// } else {
//     // Re-buffer failed entries for retry
// }

Related Pages

Implements Principle

• Principle:Apache_Flink_Fatal_Exception_Classification