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Tumbling window

A fixed slice of time a stream is counted in, such as every five minutes, one after the other.

Taught in Chapter 34: Streams.

More from the same chapter

• Consumer group: A service reading a stream, with its own position in each partition.
• Count-min sketch: A small fixed table of approximate counts. It can count a key a little high, never low, and can't list its keys: a top K pairs it with a heap.
• Effectively once: Work that may be repeated but changes nothing the second time, because it's idempotent or its offset commits with its output.
• Log (stream): An append-only sequence of messages, kept in order within each partition for a retention window. Each consumer group reads it at its own pace and can replay it.
• Rebalance: Handing a consumer group's partitions out again when a consumer joins or leaves. Each partition resumes from its committed offset.
• Replay: Reading a stream from the beginning of what it still holds, to fill a new service or redo work.
• Retention: How long a stream keeps a message, whether or not it has been read.
• Stream: An ordered, partitioned log that keeps its messages until retention ends, so any number of groups can read them at their own pace.
• Top K: The K largest items of a set, such as the ten most-liked posts of the hour.
• Watermark: A stream consumer's running estimate of how far event time has got: no event older than it is expected any more. A window closes once the watermark passes its end.