The late tap
A tap from a phone in a tunnel arrives twenty seconds late. How long should the server wait before showing a count, and what does each extra second buy?
Phones send taps, and each tap carries the second it happened. Phone B goes into a tunnel, so its taps arrive long after the rest. The server counts taps in windows and must decide when a window is finished. Wait longer and fewer taps are thrown away, but every number reaches the screen later.
Board: Stream Processing →On a narrow screen the three panels stack below the dials. Both tables scroll sideways.
try this Drag How long to wait for stragglers and watch Thrown away fall while Seconds waited climbs.
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see also The Dataflow Model: A Practical Approach to Balancing Correctness, Latency, and Cost in Massive-Scale, Unbounded, Out-of-Order Data Processing in Papers.