Google SRE's client-side throttling breaker (← go-zero's googleBreaker).
The algorithm is moonward's Breaker; this binds it to a Clock and asource of draws, the shape go-zero's breaker has, so a call site asks withno arguments. go-zero's constants are moonward's preset sre.
A breaker over a buckets × bucket_ms window (go-zero's ten seconds inforty slices by default) reading time from clock. rand supplies the shedroll as a draw from [0, 1); without it the breaker draws from asystem-seeded generator.