tower_load_shed/
future.rs

1//! Future types
2
3use std::fmt;
4use std::future::Future;
5use std::pin::Pin;
6use std::task::{Context, Poll};
7
8use futures_core::ready;
9use pin_project::{pin_project, project};
10
11use crate::error::{Error, Overloaded};
12
13/// Future for the `LoadShed` service.
14#[pin_project]
15pub struct ResponseFuture<F> {
16    #[pin]
17    state: ResponseState<F>,
18}
19
20#[pin_project]
21enum ResponseState<F> {
22    Called(#[pin] F),
23    Overloaded,
24}
25
26impl<F> ResponseFuture<F> {
27    pub(crate) fn called(fut: F) -> Self {
28        ResponseFuture {
29            state: ResponseState::Called(fut),
30        }
31    }
32
33    pub(crate) fn overloaded() -> Self {
34        ResponseFuture {
35            state: ResponseState::Overloaded,
36        }
37    }
38}
39
40impl<F, T, E> Future for ResponseFuture<F>
41where
42    F: Future<Output = Result<T, E>>,
43    E: Into<Error>,
44{
45    type Output = Result<T, Error>;
46
47    #[project]
48    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
49        #[project]
50        match self.project().state.project() {
51            ResponseState::Called(fut) => Poll::Ready(ready!(fut.poll(cx)).map_err(Into::into)),
52            ResponseState::Overloaded => Poll::Ready(Err(Overloaded::new().into())),
53        }
54    }
55}
56
57impl<F> fmt::Debug for ResponseFuture<F>
58where
59    // bounds for future-proofing...
60    F: fmt::Debug,
61{
62    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
63        f.write_str("ResponseFuture")
64    }
65}
tower_load_shed/future.rs

tower_load_shed/
future.rs
