المدربA timer wheel is a circular array of slots, each covering an interval of time (its granularity): a timer is filed in the slot of its expiry time modulo the wheel’s span, and advancing the wheel visits the slots of the time that has passed and fires the timers due in them; scheduling costs a constant time whatever the number of timers. An injected clock is a clock passed to the code that needs the time instead of being read by it: the same code runs on the simulated clock of a recorded day (One Quant Book 7, chapter 17) or on the machine’s real clock.
