HoppingWindowLifetime

Moves each event into overlapping windows of a fixed size that start every period.

When size is a multiple of period, as in the diagram, HoppingWindowLifetime(size, period) snaps each event’s start up to the next multiple of period (a start already on a boundary stays) and gives it a lifetime of size. The event then stays alive across several consecutive hops, so an aggregate over the result sees it in each overlapping window.

Two other cases behave differently (see HoppingWindowLifetime in LifetimeExtensions.cs):

• When period is larger than size, the windows have gaps between them. Events whose start falls in a gap are dropped. The others are snapped up as above and get a lifetime of size.
• When size is larger than period but not a multiple of it, Trill snaps the start and the original start plus size to the period grid separately, so lifetimes can differ from size.

In the diagram (size 4, period 2), a:1 at 1 and b:2 at 2 both live in [2,6), a:3 at 4 in [4,8), b:4 at 7 in [8,12) and a:5 at 9 in [10,14).

Follow it with an aggregate to compute per-window results: see Sum.

See also: TumblingWindowLifetime, Sum (hopping window)