Macro nros_debug_throttle_at 

macro_rules! nros_debug_throttle_at {
    ($logger:expr, $now_ns:expr, $interval_ms:expr, $($arg:tt)+) => { ... };
}

Emit at crate::Severity::Debug, at most once per interval_ms at this call site, measured against the now_ns the CALLER supplies.

rclcpp’s shape — RCLCPP_DEBUG_THROTTLE(logger, clock, …) names its clock too — and the only throttled form available with no platform clock.