Struct Broadcaster 

pub struct Broadcaster<K, T>
where
    K: Hash + Eq + Clone + Send + Sync + 'static,
    T: Clone + Send + Sync + 'static,
{ /* private fields */ }

Keyed broadcast channel registry for fan-out SSE delivery.

Each key maps to an independent broadcast channel. All subscribers of a key receive every message sent to that key. Register one broadcaster per domain concept (e.g., chat messages, notifications, metrics).

Construction

use modo::sse::{Broadcaster, SseConfig};

let chat: Broadcaster<String, ChatMessage> =
    Broadcaster::new(128, SseConfig::default());
registry.add(chat);

Channel lifecycle

• Channels are created lazily on first subscribe()
• Channels are auto-cleaned when the last subscriber’s stream is dropped
• remove() forces immediate cleanup

Implementations

impl<K, T> Broadcaster<K, T>

where K: Hash + Eq + Clone + Send + Sync + 'static, T: Clone + Send + Sync + 'static,

pub fn new(buffer: usize, config: SseConfig) -> Self

Create a new broadcaster.

• buffer — per-channel buffer size. When a subscriber falls behind by this many messages, it lags. Typical values: 64–256 for chat, 16–64 for dashboards.
• config — SSE configuration (keep-alive interval).

pub fn subscribe(&self, key: &K) -> BroadcastStream<T>

Subscribe to a keyed channel.

Creates the channel lazily on first subscription. Returns a stream of raw T values. The stream carries a cleanup closure that removes the channel entry when the last subscriber drops.

pub fn send(&self, key: &K, event: T) -> usize

Send an event to all subscribers of a key.

Returns the number of receivers that got the message. Returns 0 if no subscribers exist for the key — does NOT create a channel.

pub fn subscriber_count(&self, key: &K) -> usize

Number of active subscribers for a key. Returns 0 if no channel exists.

pub fn remove(&self, key: &K)

Manually remove a channel and disconnect all its subscribers.

Typically not needed — channels auto-clean on last subscriber drop. Use for explicit teardown (e.g., deleting a chat room).

pub fn config(&self) -> &SseConfig

Access the SSE config.

pub fn channel<F, Fut>(&self, f: F) -> Response

where F: FnOnce(Sender) -> Fut + Send + 'static, Fut: Future<Output = Result<(), Error>> + Send,

Create an SSE response with an imperative sender.

Spawns the closure as a tokio task. The closure receives a super::Sender for pushing events. The task runs until:

• The closure returns Ok(()) — stream ends cleanly
• The closure returns Err(e) — error is logged, stream ends
• A tx.send() call fails — client disconnected

Panics in the closure are caught and logged.

pub fn response<S>(&self, stream: S) -> Response

where S: Stream<Item = Result<Event, Error>> + Send + 'static,

Wrap an event stream into an SSE HTTP response.

Applies keep-alive comments at the configured interval and sets the X-Accel-Buffering: no header for nginx compatibility.

Trait Implementations

impl<K, T> Clone for Broadcaster<K, T>

where K: Hash + Eq + Clone + Send + Sync + 'static, T: Clone + Send + Sync + 'static,

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.