Struct flo_stream::ExpiringPublisher

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

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: Clone> PublisherSink<Message> 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.

impl<Message: Clone> Sink for ExpiringPublisher<Message>

type SinkItem = Message

The type of value that the sink accepts.

type SinkError = ()

The type of value produced by the sink when an error occurs.

fn start_send(&mut self, item: Message) -> StartSend<Message, ()>

Begin the process of sending a value to the sink.

fn poll_complete(&mut self) -> Poll<(), ()>

Flush all output from this sink, if necessary.

fn close(&mut self) -> Result<Async<()>, Self::SinkError>

A method to indicate that no more values will ever be pushed into this sink.

fn wait(self) -> Wait<Self>where
    Self: Sized,

Creates a new object which will produce a synchronous sink.

fn with<U, F, Fut>(self, f: F) -> With<Self, U, F, Fut>where
    F: FnMut(U) -> Fut,
    Fut: IntoFuture<Item = Self::SinkItem>,
    <Fut as IntoFuture>::Error: From<Self::SinkError>,
    Self: Sized,

Composes a function in front of the sink.

fn with_flat_map<U, F, St>(self, f: F) -> WithFlatMap<Self, U, F, St>where
    F: FnMut(U) -> St,
    St: Stream<Item = Self::SinkItem, Error = Self::SinkError>,
    Self: Sized,

Composes a function in front of the sink.

fn sink_map_err<F, E>(self, f: F) -> SinkMapErr<Self, F>where
    F: FnOnce(Self::SinkError) -> E,
    Self: Sized,

Transforms the error returned by the sink.

fn sink_from_err<E>(self) -> SinkFromErr<Self, E>where
    E: From<Self::SinkError>,
    Self: Sized,

Map this sink’s error to any error implementing From for this sink’s Error, returning a new sink.

fn buffer(self, amt: usize) -> Buffer<Self>where
    Self: Sized,

Adds a fixed-size buffer to the current sink.

fn flush(self) -> Flush<Self>where
    Self: Sized,

A future that completes when the sink has finished processing all pending requests.

fn send(self, item: Self::SinkItem) -> Send<Self>where
    Self: Sized,

A future that completes after the given item has been fully processed into the sink, including flushing.

fn send_all<S>(self, stream: S) -> SendAll<Self, S>where
    S: Stream<Item = Self::SinkItem>,
    Self::SinkError: From<<S as Stream>::Error>,
    Self: Sized,

A future that completes after the given stream has been fully processed into the sink, including flushing.