Struct tower::util::CallAll

pub struct CallAll<Svc, S> where
    Svc: Service<S::Item>,
    S: Stream,  { /* fields omitted */ }

This is a Stream of responses resulting from calling the wrapped Service for each request received on the wrapped Stream.

use futures::future::{ready, Ready};
use futures::StreamExt;
use futures::channel::mpsc;
use tower_service::Service;
use tower::util::ServiceExt;

// First, we need to have a Service to process our requests.
#[derive(Debug, Eq, PartialEq)]
struct FirstLetter;
impl Service<&'static str> for FirstLetter {
     type Response = &'static str;
     type Error = Box<dyn Error + Send + Sync>;
     type Future = Ready<Result<Self::Response, Self::Error>>;

     fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
         Poll::Ready(Ok(()))
     }

     fn call(&mut self, req: &'static str) -> Self::Future {
         ready(Ok(&req[..1]))
     }
}

#[tokio::main]
async fn main() {
    // Next, we need a Stream of requests.
    let (mut reqs, rx) = mpsc::unbounded();
    // Note that we have to help Rust out here by telling it what error type to use.
    // Specifically, it has to be From<Service::Error> + From<Stream::Error>.
    let mut rsps = FirstLetter.call_all(rx);

    // Now, let's send a few requests and then check that we get the corresponding responses.
    reqs.unbounded_send("one").unwrap();
    reqs.unbounded_send("two").unwrap();
    reqs.unbounded_send("three").unwrap();
    drop(reqs);

    // We then loop over the response Strem that we get back from call_all.
    let mut i = 0usize;
    while let Some(rsp) = rsps.next().await {
        // Each response is a Result (we could also have used TryStream::try_next)
        match (i + 1, rsp.unwrap()) {
            (1, "o") |
            (2, "t") |
            (3, "t") => {}
            (n, i) => {
                unreachable!("{}. response was '{}'", n, i);
            }
        }
        i += 1;
    }

    // And at the end, we can get the Service back when there are no more requests.
    assert_eq!(rsps.into_inner(), FirstLetter);
}

Implementations

impl<Svc, S> CallAll<Svc, S> where
    Svc: Service<S::Item>,
    Svc::Error: Into<BoxError>,
    S: Stream, 

pub fn new(service: Svc, stream: S) -> CallAll<Svc, S>

Create new CallAll combinator.

Each request yielded by stream is passed to svc, and the resulting responses are yielded in the same order by the implementation of Stream for CallAll.

pub fn into_inner(self) -> Svc

Extract the wrapped Service.

Panics

Panics if take_service was already called.

pub fn take_service(self: Pin<&mut Self>) -> Svc

Extract the wrapped Service.

This CallAll can no longer be used after this function has been called.

Panics

Panics if take_service was already called.

pub fn unordered(self) -> CallAllUnordered<Svc, S>

Return responses as they are ready, regardless of the initial order.

This function must be called before the stream is polled.

Panics

Panics if poll was called.

Trait Implementations

impl<Svc: Debug, S: Debug> Debug for CallAll<Svc, S> where
    Svc: Service<S::Item>,
    S: Stream,
    Svc::Future: Debug, 

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

Formats the value using the given formatter.

impl<Svc, S> Stream for CallAll<Svc, S> where
    Svc: Service<S::Item>,
    Svc::Error: Into<BoxError>,
    S: Stream, 

type Item = Result<Svc::Response, BoxError>

Values yielded by the stream.

fn poll_next(
    self: Pin<&mut Self>,
    cx: &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.

impl<'pin, Svc, S> Unpin for CallAll<Svc, S> where
    Svc: Service<S::Item>,
    S: Stream,
    __CallAll<'pin, Svc, S>: Unpin,