How to select the type of time semantics when working with tumbling windows?

Question

I am working on kafka streams windowing , particularly tumbling windows for my use case.

TimeWindowedKStream<String, Blob> windowedStreams = groupedStreams
                .windowedBy(TimeWindows.of(TimeUnit.MINUTES.toMillis(5)));

this is a tumbling window for 5 minutes per record key and advances by 5 minutes. For my use case, I want no old message to be dropped and hence I want it to consider processing time as time semantic.

what is the default behaviour of tumbling window for time semantics, how does I specify in tumbling windows which time semantic to pick ?event time/processing time/ingestion time.

Answer 1

The time semantics are not specified on the window definition, but depend on the configured TimestampeExtractor . If you want to switch to processing time semantics, you can set default.timestamp.extractor to WallclockTimestampExtractor.class in the KafkaStreams config.

Compare

• https://docs.confluent.io/current/streams/concepts.html#time
• https://docs.confluent.io/current/streams/developer-guide/config-streams.html#streams-developer-guide-timestamp-extractor