Struct UpdateStream 

pub struct UpdateStream { /* private fields */ }

Multiplexed per-market update stream. There is exactly one UpdateStream per dispatcher; calling OrderBookWebSocket::updates() twice returns None the second time.

Why take-once semantics: the underlying channel is MPMC, so cloning the receiver and handing one out per call would split messages between receivers in a way callers cannot detect — every test harness or debug sidecar that “just adds a second consumer” would silently lose half the stream. Take-once turns that footgun into a compile-checked None at the call site.

Backed by flume, an MPMC channel with lighter-weight wakers than async-channel’s; the per-message recv on the consumer side is a significant fraction of the WS pipeline p99, and flume’s atomic-only fast path stays out of the parking_lot machinery on uncontended recv. The channel is bounded; when full the producer raises SessionEvent::Lagged + SessionEvent::BookInvalidated rather than dropping deltas silently.

Implementations

impl UpdateStream

pub async fn next(&self) -> Option<WsUpdate>

Await the next update. None once the producer has been dropped.

pub fn try_next(&self) -> Result<Option<WsUpdate>, TryRecvError>

Non-blocking peek. Returns Ok(Some) if an update is ready, Ok(None) if the channel is empty, Err if closed.

pub fn len(&self) -> usize

pub fn is_empty(&self) -> bool

pub fn is_closed(&self) -> bool