apache/flink · error · RuntimeException

Please ensure that flink-datastream in your class path

Error message

Please ensure that flink-datastream in your class path

What it means

Error "Please ensure that flink-datastream in your class path" thrown in apache/flink.

Source

Thrown at flink-datastream-api/src/main/java/org/apache/flink/datastream/api/extension/eventtime/strategy/EventTimeWatermarkGeneratorBuilder.java:122

                        this.idleTimeout,
                        this.maxOutOfOrderTime);

        try {
            return (OneInputStreamProcessFunction<T, T>)
                    getEventTimeExtensionImplClass()
                            .getMethod("buildAsProcessFunction", EventTimeWatermarkStrategy.class)
                            .invoke(null, watermarkStrategy);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    private static Class<?> getEventTimeExtensionImplClass() {
        try {
            return Class.forName(
                    "org.apache.flink.datastream.impl.extension.eventtime.EventTimeExtensionImpl");
        } catch (ClassNotFoundException e) {
            throw new RuntimeException("Please ensure that flink-datastream in your class path");
        }
    }
}

View on GitHub (pinned to 2f3c205e92)

Solutions

1. Address the cause reported by the error message: Please ensure that flink-datastream in your class path
2. Verify the inputs, configuration values, and classpath/dependency setup related to this operation, then retry.

Example fix

Correct the condition described ("Please ensure that flink-datastream in your class path") and rerun the job or command.

When it happens

Trigger: Triggered at runtime when the operation fails because: Please ensure that flink-datastream in your class path.

Common situations: Commonly caused by misconfiguration, missing dependencies or files, unsupported types or operations, or invalid user input leading to: Please ensure that flink-datastream in your class path.

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/82ab5ce3e1f37e08. Report an issue: GitHub.