Struct ratelimit_meter::algorithms::leaky_bucket::LeakyBucket

pub struct LeakyBucket { /* private fields */ }

Implements the industry-standard leaky bucket rate-limiting as-a-meter. The bucket keeps a “fill height”, pretending to drip steadily (which reduces the fill height), and increases the fill height with every cell that is found conforming. If cells would make the bucket overflow, they count as non-conforming.

Drip implementation

Instead of having a background task update the bucket’s fill level, this implementation re-computes the fill level of the bucket on every call to check and related methods.

Wait time calculation

If the cell does not fit, this implementation computes the minimum wait time until the cell can be accommodated. This minimum wait time does not account for thundering herd effects or other problems in concurrent resource acquisition, so users of this library must take care to apply positive jitter to these wait times.

Example

let mut lb = DirectRateLimiter::<LeakyBucket>::per_second(nonzero!(2u32));
assert_eq!(Ok(()), lb.check());

Trait Implementations

impl Algorithm for LeakyBucket

type BucketState = State

The state of a single rate limiting bucket.

type NegativeDecision = TooEarly

The type returned when a rate limiting decision for a single cell is negative. Each rate limiting algorithm can decide to return the type that suits it best, but most algorithms’ decisions also implement NonConformance, to ease handling of how long to wait.

fn construct(
    capacity: NonZeroU32,
    cell_weight: NonZeroU32,
    per_time_unit: Duration
) -> Result<Self, InconsistentCapacity>

Constructs a rate limiter with the given parameters: capacity is the number of cells to allow, weighing cell_weight, every per_time_unit.

fn test_n_and_update(
    &self,
    state: &Self::BucketState,
    n: u32,
    t0: Instant
) -> Result<(), NegativeMultiDecision<TooEarly>>

Tests if n cells can be accommodated in the rate limiter at the instant at and updates the rate-limiter state to account for the weight of the cells and updates the ratelimiter state.

fn test_and_update(
    &self,
    state: &Self::BucketState,
    at: Instant
) -> Result<(), Self::NegativeDecision>

Tests if a single cell can be accommodated in the rate limiter at the instant at and updates the rate-limiter state to account for the weight of the cell.

impl Clone for LeakyBucket

fn clone(&self) -> LeakyBucket

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for LeakyBucket

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

Formats the value using the given formatter.

impl PartialEq<LeakyBucket> for LeakyBucket

fn eq(&self, other: &LeakyBucket) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl RateLimitState<LeakyBucket> for State

fn last_touched(&self, _params: &LeakyBucket) -> Instant

Returns the last time instant that the state had any relevance (i.e. the rate limiter would behave exactly as if it was a new rate limiter after this time).

impl Eq for LeakyBucket

impl StructuralEq for LeakyBucket

impl StructuralPartialEq for LeakyBucket