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.

pub fn samples(&self) -> impl Iterator<Item = (usize, f64)> + '_

Every measurement taken, as (connections, bytes per second) in the order it was taken. For reporting what the search saw, not for deciding.

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.