Event Time

This documentation is for an out-of-date version of Apache Flink. We recommend you use the latest stable version.

In this section you will learn about writing time-aware Flink programs. Please take a look at Timely Stream Processing to learn about the concepts behind timely stream processing.

For information about how to use time in Flink programs refer to windowing and ProcessFunction.

Note that in order to use event-time aware operations, the program needs to either use sources that directly define event time for the data and emit watermarks themselves, or the program must inject a Timestamp Assigner & Watermark Generator after the sources. Those functions describe how to access the event timestamps, and what degree of out-of-orderness the event stream exhibits.

Where to go next?

Generating Watermarks: Shows how to write timestamp assigners and watermark generators, which are needed for event-time aware Flink applications.
Builtin Watermark Generators: Gives an overview of the builtin watermark generators.
Debugging Windows & Event Time: Show how to debug problems around watermarks and timestamps in event-time Flink applications.