[−][src]Struct ratelimit_meter::algorithms::gcra::GCRA
Implements the virtual scheduling description of the Generic Cell Rate Algorithm, attributed to ITU-T in recommendation I.371 Traffic control and congestion control in B-ISDN; from Wikipedia.
While algorithms like leaky-bucket rate limiters allow cells to be distributed across time in any way, GCRA is a rate-limiting and traffic-shaping algorithm. It mandates that a minimum amount of time passes between cells being measured. For example, if your API mandates that only 20 requests can be made per second, GCRA will ensure that each request is at least 50ms apart from the previous request. This makes GCRA suitable for shaping traffic in networking and telecom equipment (it was initially made for asynchronous transfer mode networks), or for outgoing workloads on consumers of attention, e.g. distributing outgoing emails across a day.
A note about batch decisions
In a blatant side-stepping of the above traffic-shaping criteria,
this implementation of GCRA comes with an extension that allows
measuring multiple cells at once, assuming that if a pause of
n*(the minimum time between cells)
has passed, we can allow a
single big batch of n
cells through. This assumption may not be
correct for your application, but if you depend on GCRA's
traffic-shaping properties, it's better to not use the _n
suffixed check functions.
Example
In this example, we construct a rate-limiter with the GCR algorithm that can accommodate 20 cells per second. This translates to the GCRA parameters τ=1s, T=50ms (that's 1s / 20 cells).
let mut limiter = DirectRateLimiter::<GCRA>::per_second(nonzero!(20u32)); let now = Instant::now(); let ms = Duration::from_millis(1); assert_eq!(Ok(()), limiter.check_at(now)); // the first cell is free for i in 0..20 { // Spam a lot: assert!(limiter.check_at(now).is_ok(), "at {}", i); } // We have exceeded the bucket capacity: assert!(limiter.check_at(now).is_err()); // After a sufficient time period, cells are allowed again: assert_eq!(Ok(()), limiter.check_at(now + ms*50));
Trait Implementations
impl<P: Relative> Algorithm<P> for GCRA<P>
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type BucketState = State<P>
The state of a single rate limiting bucket. Read more
type NegativeDecision = NotUntil<P>
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. Read more
fn construct(
capacity: NonZeroU32,
cell_weight: NonZeroU32,
per_time_unit: Duration
) -> Result<Self, InconsistentCapacity>
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capacity: NonZeroU32,
cell_weight: NonZeroU32,
per_time_unit: Duration
) -> Result<Self, InconsistentCapacity>
fn test_and_update(
&self,
state: &Self::BucketState,
t0: P
) -> Result<(), Self::NegativeDecision>
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&self,
state: &Self::BucketState,
t0: P
) -> Result<(), Self::NegativeDecision>
Tests if a single cell can be accommodated by the rate-limiter. This is a threadsafe implementation of the method described directly in the GCRA algorithm.
fn test_n_and_update(
&self,
state: &Self::BucketState,
n: u32,
t0: P
) -> Result<(), NegativeMultiDecision<Self::NegativeDecision>>
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&self,
state: &Self::BucketState,
n: u32,
t0: P
) -> Result<(), NegativeMultiDecision<Self::NegativeDecision>>
Tests if n
cells can be accommodated by the rate-limiter
and updates rate limiter state iff they can be.
As this method is an extension of GCRA (using multiplication), it is likely not as fast (and not as obviously "right") as the single-cell variant.
impl<P: Relative> RateLimitState<GCRA<P>, P> for State<P>
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impl<P: Absolute> RateLimitStateWithClock<GCRA<P>, P> for State<P>
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fn last_touched(&self, params: &GCRA<P>) -> P
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impl<P: Clone + Relative> Clone for GCRA<P>
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fn clone(&self) -> GCRA<P>
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fn clone_from(&mut self, source: &Self)
1.0.0[src]
Performs copy-assignment from source
. Read more
impl<P: Debug + Relative> Debug for GCRA<P>
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Auto Trait Implementations
Blanket Implementations
impl<T, U> Into for T where
U: From<T>,
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U: From<T>,
impl<T> ToOwned for T where
T: Clone,
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T: Clone,
impl<T> From for T
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impl<T, U> TryFrom for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T> Borrow for T where
T: ?Sized,
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T: ?Sized,
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<T> BorrowMut for T where
T: ?Sized,
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T: ?Sized,
ⓘImportant traits for &'_ mut Wfn borrow_mut(&mut self) -> &mut T
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impl<T, U> TryInto for T where
U: TryFrom<T>,
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U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.