Struct Limiter 

pub struct Limiter { /* private fields */ }

Per-channel adaptive limiter.

Cheap to clone — both fields are Arc. Pass clones into hot loops; do not hold the lock across .await points (call sites observe with short critical sections only).

Implementations

impl Limiter

pub fn new(start: usize, config: LimiterConfig) -> Self

Create a new limiter starting at start, clamped into [min_concurrency, max_concurrency]. Sanitizes the config to guard against directly-constructed LimiterConfig literals with hostile float values (NaN, etc).

pub fn current(&self) -> usize

Snapshot current concurrency cap. Hot-path call: the value may change between this call and the next, but consumers (buffer_unordered(n)) capture it once per pipeline build.

pub fn observe(&self, outcome: Outcome, latency: Duration)

Record one observed operation. Updates the sliding window and re-evaluates the cap if the window is full enough.

pub fn observe_with_bytes( &self, outcome: Outcome, latency: Duration, bytes: u64, )

Record one observed operation with a payload byte count. Bytes are used by the fetch hill climber; AIMD channels ignore them.

pub fn warm_start(&self, start: usize)

Replace the current cap with start, clamped. Used for warm loads from persisted state. Does not clear the sliding window — fresh observations remain authoritative for adaptation decisions.

Slow-start state after a warm load depends on the channel’s slow_start_ramp_threshold:

• Default (threshold 0, i.e. quote/store): mark slow-start as already-left so a single healthy window doesn’t double a learned warm value — an over-aggressive jump. Subsequent increases are +1 per healthy window.
• Protected (threshold > clamped, i.e. fetch below the ceiling): keep slow-start armed. This is critical for the CLI usage pattern where every ant file download is a fresh process that warm-starts from the snapshot: if warm_start always exited slow-start, the fetch cap could only ever grow additively from the persisted value, which cannot climb back to the ceiling against an intermittent Decrease trickle (the exact pin-at-~20 behaviour observed on a fast-but-lossy VPS). Keeping slow-start armed lets the cap double back toward the capacity the connection can actually sustain.

pub fn snapshot(&self) -> usize

Snapshot of the current cap for persistence. Cheap, lock-only.

Trait Implementations

impl Clone for Limiter

fn clone(&self) -> Limiter

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Limiter

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

Formats the value using the given formatter.