Struct Admission 

pub struct Admission { /* private fields */ }

Per-source incremental admission controller.

Feed it the aggregate goodput observed at each concurrency level. It compares the marginal gain against min_gain_frac of the goodput achieved by the first connection — a scale-free threshold, so it behaves identically on a 1 MB/s and a 1 GB/s path.

Implementations

impl Admission

pub fn new(min_gain_frac: f64, max_conns: usize) -> Self

pub fn observe_at(&mut self, level: usize, goodput: f64) -> Admit

Record the aggregate goodput (bytes/s) observed with self.level() + 1 connections, and decide whether to admit another. Record the goodput measured while level connections were active.

Why the level is a parameter and not the sample count

This originally inferred the level from samples.len(), which is correct only if callers admit one connection per observation. The in-band ramp doubles (1, 2, 4, 8) because incrementing takes max - 1 windows and costs more clock than the concurrency saves. Under doubling the third sample describes FOUR connections, so returning samples.len() - 1 returned a sample index dressed as a connection count.

HISTORICAL MEASUREMENT (pre-fix implementation; retained to document why this design exists, not as a current result). 11 MB object, five repetitions: settled counts came back [2, 8, 8, 8, 8] on a path a single stream already saturates. The 2 is the index bug reporting sample 3 as “2”; the four 8s are the ceiling arm firing because the sample-count test n >= max_conns needs eight samples and doubling only ever takes four. The search could not settle anywhere sensible, and the mode was no faster than hard-coding the ceiling (0.99x, p = 0.63) while a single connection was 1.97x faster than both.

pub fn clamp_max(&mut self, max: usize)

Lower the ceiling the search may reach.

Raising it is deliberately not possible: the caller lowers this when the ORIGIN has refused a request, and a ceiling learned from a refusal must not be undone by the search that provoked it. Recovery from a momentary limit is the transfer loop’s business, not the controller’s.

pub fn observe(&mut self, goodput: f64) -> Admit

Back-compatible entry point for callers that admit one connection at a time.

pub fn level(&self) -> usize

Connections currently probed.

pub fn settled(&self) -> Option<usize>

The settled allocation, once probing has stopped.

pub fn best_goodput(&self) -> f64

Best goodput seen, for reporting.

Trait Implementations

impl Clone for Admission

fn clone(&self) -> Admission

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Admission

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

Formats the value using the given formatter.