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Apache Flink® uses watermarks to synchronize and process events in data streams accurately. These watermarks are timestamps embedded in the data stream that track the progression of event time.

Role of watermarks

Watermarks signal when all events up to a certain time have arrived, allowing Apache Flink operators to synchronize their event time clocks with these timestamps. This mechanism is crucial for timely and accurate event processing.

Apache Flink® defines the watermark logic using watermark strategies and watermark generators. For example, you can configure Apache Flink to generate watermarks either periodically at specific intervals or when an event or element with a specific marker triggers it.

For detailed information on watermarks and how to generate them in Apache Flink®, visit the official documentation.