Counts pool acquires recorded after the last completed acquire; fires when the oldest of
them has waited past the grace period, else returns null. The rule scans the whole buffer,
not a sliding window: a stalled pool emits nothing else, so a window would age the stall's
own evidence out. Clears itself — once an acquire completes, the pending set restarts.
Counts pool acquires recorded after the last completed acquire; fires when the oldest of them has waited past the grace period, else returns null. The rule scans the whole buffer, not a sliding window: a stalled pool emits nothing else, so a window would age the stall's own evidence out. Clears itself — once an acquire completes, the pending set restarts.