Event Time is the timestamp representing when an event actually occurred at its source system or device, before it even entered the stream processing pipeline. It's embedded within the event's data payload itself (e.g., a sensor reading timestamp, a transaction timestamp, a log entry timestamp).
Event Time processing allows for analyzing events based on when they actually happened, regardless of delays in ingestion or processing. This is crucial for achieving deterministic and accurate results, especially when dealing with Windowing over time or joining streams based on when events occurred relative to each other.
It's important to distinguish Event Time from:
Example:
For accurate windowed analysis (e.g., calculating the average temperature between 10:00 and 10:05), using Event Time (10:00:00 AM) is essential. Processing Time (10:00:10 AM) would place the event in the wrong window.
RisingWave fully supports Event Time processing:
By leveraging Event Time and Watermarks, RisingWave enables accurate stateful stream processing based on the actual occurrence time of events.