Struct Seen 

pub struct Seen { /* private fields */ }

The ids this application has already sequenced, and where each landed.

A bounded memory rather than a set: idempotency is a property of a recent retry, and a client that reconnects after the window has moved on gets a second copy of its command — which is the trade every at-least-once channel makes and is worth saying out loud.

Implementations

impl Seen

pub fn new(capacity: usize) -> Seen

pub fn position(&self, id: &str) -> Option<Seq>

Where this id’s command landed, if it is still remembered.