Struct mysteriouspants_throttle::Throttle

pub struct Throttle<TArg> { /* fields omitted */ }

Methods

impl<TArg> Throttle<TArg>

pub fn new_variable_throttle<TDelayCalculator: Fn(TArg, Duration) -> Duration + 'static>(     delay_calculator: TDelayCalculator ) -> Throttle<TArg>

Creates a new Throttle with a variable delay controlled by a closure. delay_calculator itself is an interesting type, any closure which satisfies Fn(TArg, Duration) -> Duration.

This lambda is called to determine the duration between iterations of your code - the Duration it returns does not signify the additional time to be waited, but the total time that ought to have elapsed, and the difference of the times will be waited. TArg is an argument passsed in from a call to acquire, so you may pass any state you may require into the lambda to make decisions about the wait time. The Duration argument the time that has already elapsed from the previous call to acquire and now. If the Duration you return is less than the Duration passed to you, or is zero, that means that no additional time ought to be waited.

An example use of a variable-rate throttle might be to wait different periods of time depending on whether your program is in backpressure, so "ease up" on your downstream call rate, so to speak.

let throttle = Throttle::new_variable_throttle(
    |in_backpressure: bool, time_since_previous_acquire: Duration|
        match in_backpressure {
            true => Duration::from_millis(2100),
            false => Duration::from_millis(1100)
        });

// the first one is free!
throttle.acquire(false);

let start_nopressure = Instant::now();
throttle.acquire(false);
assert_eq!(start_nopressure.elapsed().as_secs() == 1, true);

let start_yespressure = Instant::now();
throttle.acquire(true);
assert_eq!(start_yespressure.elapsed().as_secs() == 2, true);

pub fn new_tps_throttle(tps: f32) -> Throttle<TArg>

Creates a new Throttle with a constant delay of tps^-1 · 1000ms, or tps-transactions per second.

let throttle = Throttle::new_tps_throttle(0.9);

// the first one is free!
throttle.acquire(());

let start = Instant::now();
throttle.acquire(());
assert_eq!(start.elapsed().as_secs() == 1, true);

pub fn acquire(&self, arg: TArg)

Acquires the throttle, waiting (sleeping the current thread) until enough time has passed for the running code to be at or slower than the throttle allows. The first call to acquire will never wait because there has been an undefined or arguably infinite amount of time from the previous time acquire was called. The argument arg is passed to the closure governing the wait time.