Zebra/tower-batch/src/future.rs

108 lines
3.1 KiB
Rust

//! Future types for the `Batch` middleware.
use super::{error::Closed, message};
use futures_core::ready;
use pin_project::pin_project;
use std::{
fmt::Debug,
future::Future,
pin::Pin,
task::{Context, Poll},
};
use tower::Service;
/// Future that completes when the batch processing is complete.
#[pin_project]
pub struct ResponseFuture<S, E2, Response>
where
S: Service<crate::BatchControl<Response>>,
{
#[pin]
state: ResponseState<S, E2, Response>,
}
impl<S, E2, Response> Debug for ResponseFuture<S, E2, Response>
where
S: Service<crate::BatchControl<Response>>,
S::Future: Debug,
S::Error: Debug,
E2: Debug,
{
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.debug_struct("ResponseFuture")
.field("state", &self.state)
.finish()
}
}
#[pin_project(project = ResponseStateProj)]
enum ResponseState<S, E2, Response>
where
S: Service<crate::BatchControl<Response>>,
{
Failed(Option<E2>),
Rx(#[pin] message::Rx<S::Future, S::Error>),
Poll(#[pin] S::Future),
}
impl<S, E2, Response> Debug for ResponseState<S, E2, Response>
where
S: Service<crate::BatchControl<Response>>,
S::Future: Debug,
S::Error: Debug,
E2: Debug,
{
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
ResponseState::Failed(e) => f.debug_tuple("ResponseState::Failed").field(e).finish(),
ResponseState::Rx(rx) => f.debug_tuple("ResponseState::Rx").field(rx).finish(),
ResponseState::Poll(fut) => f.debug_tuple("ResponseState::Pool").field(fut).finish(),
}
}
}
impl<S, E2, Response> ResponseFuture<S, E2, Response>
where
S: Service<crate::BatchControl<Response>>,
{
pub(crate) fn new(rx: message::Rx<S::Future, S::Error>) -> Self {
ResponseFuture {
state: ResponseState::Rx(rx),
}
}
pub(crate) fn failed(err: E2) -> Self {
ResponseFuture {
state: ResponseState::Failed(Some(err)),
}
}
}
impl<S, E2, Response> Future for ResponseFuture<S, E2, Response>
where
S: Service<crate::BatchControl<Response>>,
S::Future: Future<Output = Result<S::Response, S::Error>>,
S::Error: Into<E2>,
crate::error::Closed: Into<E2>,
{
type Output = Result<S::Response, E2>;
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let mut this = self.project();
loop {
match this.state.as_mut().project() {
ResponseStateProj::Failed(e) => {
return Poll::Ready(Err(e.take().expect("polled after error")));
}
ResponseStateProj::Rx(rx) => match ready!(rx.poll(cx)) {
Ok(Ok(f)) => this.state.set(ResponseState::Poll(f)),
Ok(Err(e)) => return Poll::Ready(Err(e.into())),
Err(_) => return Poll::Ready(Err(Closed::new().into())),
},
ResponseStateProj::Poll(fut) => return fut.poll(cx).map_err(Into::into),
}
}
}
}