Struct flo_stream::ExpiringPublisher

pub struct ExpiringPublisher<Message> { /* fields omitted */ }

An ‘expiring’ publisher is one that responds to backpressure from its subscribers by expiring the most recent message.

Usually when a subscriber stalls in processing, a publisher will refuse to accept further messages and block. This will avoid blocking by instead expiring messages that cannot be processed.

This is useful in a few situations. One important example is distributing state: say you want to indicate to another thread what your current state is, but if it’s busy you don’t want to wait for it to consume the previous state before you can finish updating the latest state.

Another example is signalling. An ExpiringPublisher<()> can be used to signal that an event has occurred but will not block if all subscribers have not responded in the case where the event occurs multiple times.

Implementations

impl<Message: Clone> ExpiringPublisher<Message>

pub fn new(buffer_size: usize) -> ExpiringPublisher<Message>

Creates a new expiring publisher with a particular buffer size

Once a subscriber has buffer_size messages, this publisher will start to drop the oldest messages.

pub fn count_subscribers(&self) -> usize

Counts the number of subscribers in this publisher

pub fn republish(&self) -> Self

Creates a duplicate publisher that can be used to publish to the same streams as this object

Trait Implementations

impl<Message> Drop for ExpiringPublisher<Message>

fn drop(&mut self)

Executes the destructor for this type.

impl<Message: 'static + Send + Clone> MessagePublisher for ExpiringPublisher<Message>

fn subscribe(&mut self) -> Subscriber<Message>

Subscribes to this publisher

Subscribers only receive messages sent to the publisher after they are created.

fn when_ready(&mut self) -> BoxFuture<'static, MessageSender<Message>>

Reserves a space for a message with the subscribers, returning when it’s ready

fn when_empty(&mut self) -> BoxFuture<'static, ()>

Waits until all subscribers have consumed all pending messages

fn is_closed(&self) -> bool

Returns true if this publisher is closed (will not publish any further messages to its subscribers)

fn when_closed(&self) -> BoxFuture<'static, ()>

Future that returns when this publisher is closed

type Message = Message

fn publish(&mut self, message: Self::Message) -> BoxFuture<'static, ()>

Publishes a message to the subscribers of this object