Struct WatermarkController 

pub struct WatermarkController<C: Clock = MonotonicClock> { /* private fields */ }

Per-pipeline-thread pause/resume state machine with hysteresis.

The controller never calls anything: WatermarkController::tick returns a Transition and the driver applies it, which keeps this module free of source and metrics dependencies. Transitions strictly alternate (Pause, Resume, Pause, …) and each full cycle takes at least BackpressureParams::min_pause.

Implementations

impl WatermarkController<MonotonicClock>

pub fn new(params: BackpressureParams) -> Self

Controller on the real monotonic clock.

impl<C: Clock> WatermarkController<C>

pub fn with_clock(params: BackpressureParams, clock: C) -> Self

Controller with an injected clock (tests).

pub fn on_send_rejected(&mut self)

Record that a try_send to a downstream queue was rejected. Cheap; call from the poll loop’s rejection path. While paused this restarts the minimum-pause timer — a rejection is proof downstream is still congested.

pub fn tick( &mut self, budget: &InflightBudget, queues_below_low: bool, ) -> Option<Transition>

Evaluate the state machine once per poll iteration.

queues_below_low is the driver’s view of its downstream queues (all below the low-watermark fill ratio). Returns a transition for the driver to apply, or None.

pub fn is_paused(&self) -> bool

Whether the controller currently holds its lanes paused.

pub fn params(&self) -> &BackpressureParams

The hysteresis parameters in force.

Trait Implementations

impl<C: Debug + Clock> Debug for WatermarkController<C>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.