Description: A watermark is a mechanism used in stream processing systems for handling event time processing, allowing the system to track the progress of event time. This concept is crucial in stream data processing, where events may arrive out of order due to the distributed nature of applications. Watermarks enable systems to identify how far events have been processed based on their timestamps, facilitating the management of time windows and the execution of aggregation operations. Watermarks are generated at regular intervals and are used to indicate that all events with a timestamp earlier than the watermark have been processed. This helps manage latency and ensure that results are accurate, even in situations where events arrive late or out of order. Additionally, watermarks are essential for state management in stream processing, as they allow for recovery and continuous data processing in real-time, ensuring that the system can adapt to variations in data flow without losing critical information.
