Struct EventRing 

pub struct EventRing<T> { /* private fields */ }

A bounded, replayable buffer of stream events.

Generic over the payload because the ring is transport machinery: it must not name an MCP type, and a serde_json::Value in a domain signature is exactly the kind of raw JSON the layer rules keep out of here. The adapter supplies whatever its wire type is.

Implementations

impl<T> EventRing<T>

pub fn new(capacity: NonZeroUsize) -> Self

A ring retaining at most capacity events.

A capacity of zero is refused at the type level rather than tolerated: such a ring would accept a push, drop it, and report success, which is the eviction-as-success bug with no eviction to notice.

pub fn with_recommended_capacity() -> Self

Retains RECOMMENDED_CAPACITY events.

pub const fn capacity(&self) -> usize

The most events this ring will hold.

pub const fn last(&self) -> EventId

The newest id ever issued, or the watermark if nothing has been.

pub const fn len(&self) -> usize

How many events are currently retained.

pub const fn is_empty(&self) -> bool

Whether nothing is retained.

pub const fn evicted_through(&self) -> Option<EventId>

The newest event ever dropped, if the ring has dropped anything.

A client at or after this id can still be served contiguously; a client before it cannot.

pub fn push(&mut self, payload: T) -> EventId

Appends an event, dropping the oldest if the ring is full.

Returns the id assigned, which is the value a client will quote to resume after this event.

pub fn replay_from(&self, after: Option<EventId>) -> Replay<'_, T>

Answers a client that says where it stopped.

after is the client’s Last-Event-ID, or None for a client that has never seen this stream and wants everything. The four outcomes are described on Replay; the short version is that a request is only Replay::is_complete when the ring is still holding everything after the watermark.

Takes &self and hands back a borrow, so an adapter can answer from a shared reference without taking the stream’s lock exclusively.

pub fn clear(&mut self)

Empties the ring, keeping the id sequence going.

A new stream, not a continuing one: ids stay monotonic so a client that reconnects across the reset is refused with Replay::Unknown rather than being served events from a stream that no longer exists.

Trait Implementations

impl<T: Debug> Debug for EventRing<T>

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

Formats the value using the given formatter.

impl<T> Default for EventRing<T>

fn default() -> Self

Retains RECOMMENDED_CAPACITY, so EventRing::default() is the unmeasured-payload case and never a zero-capacity ring.