Struct EventStream 

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

A live text/event-stream body.

Implements Stream directly rather than going through axum’s Sse helper because this stream has to emit a frame the helper has no spelling for: a frame carrying no id: is exactly the gap notice, and building it through a type whose every event implies a cursor is how a gap notice comes to carry one.

The item type is a Result because Body::from_stream requires it, not because a frame can fail — by the time a frame is queued it is already encoded.

Implementations

impl<T> EventStream<T>

pub const fn cursor(&self) -> EventId

The cursor this stream has written up to.

pub const fn is_subscribed(&self) -> bool

Whether a waker is currently registered with the tail.

The subscription is held only while the stream is parked, which is what keeps a client that disconnects between frames from leaving anything behind.

pub fn has_pending(&self) -> bool

Whether a frame is waiting to be written.

Distinct from “the tail is empty”: a frame can be buffered while the tail is already spent, which is the state a stream sits in between writing one frame and being polled for the next.

Trait Implementations

impl<T: Debug> Debug for EventStream<T>

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

Formats the value using the given formatter.

impl<T> Drop for EventStream<T>

fn drop(&mut self)

Releases the subscription.

In Drop and not in a method because a client disconnecting mid-stream is the normal way a stream ends, and after the response body is dropped there is no code path left for anyone to call a cleanup on. A registration removed anywhere other than here would be removed on a path a dropped client does not take.

fn pin_drop(self: Pin<&mut Self>)

🔬This is a nightly-only experimental API. (pin_ergonomics)

Execute the destructor for this type, but different to Drop::drop, it requires self to be pinned.

impl<T> Stream for EventStream<T>

where T: FramePayload,

type Item = Result<Bytes, StreamError>

Values yielded by the stream.

fn poll_next( self: Pin<&mut Self>, context: &mut Context<'_>, ) -> Poll<Option<Self::Item>>

Attempt to pull out the next value of this stream, registering the current task for wakeup if the value is not yet available, and returning None if the stream is exhausted.

fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the stream.