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//! Future types
use super::{Policy, Retry};
use futures_core::ready;
use pin_project_lite::pin_project;
use std::future::Future;
use std::pin::Pin;
use std::task::{Context, Poll};
use tower_service::Service;
pin_project! {
/// The [`Future`] returned by a [`Retry`] service.
#[derive(Debug)]
pub struct ResponseFuture<P, S, Request>
where
P: Policy<Request, S::Response, S::Error>,
S: Service<Request>,
{
request: Option<Request>,
#[pin]
retry: Retry<P, S>,
#[pin]
state: State<S::Future, P::Future>,
}
}
pin_project! {
#[project = StateProj]
#[derive(Debug)]
enum State<F, P> {
// Polling the future from [`Service::call`]
Called {
#[pin]
future: F
},
// Polling the future from [`Policy::retry`]
Checking {
#[pin]
checking: P
},
// Polling [`Service::poll_ready`] after [`Checking`] was OK.
Retrying,
}
}
impl<P, S, Request> ResponseFuture<P, S, Request>
where
P: Policy<Request, S::Response, S::Error>,
S: Service<Request>,
{
pub(crate) fn new(
request: Option<Request>,
retry: Retry<P, S>,
future: S::Future,
) -> ResponseFuture<P, S, Request> {
ResponseFuture {
request,
retry,
state: State::Called { future },
}
}
}
impl<P, S, Request> Future for ResponseFuture<P, S, Request>
where
P: Policy<Request, S::Response, S::Error> + Clone,
S: Service<Request> + Clone,
{
type Output = Result<S::Response, S::Error>;
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let mut this = self.project();
loop {
match this.state.as_mut().project() {
StateProj::Called { future } => {
let result = ready!(future.poll(cx));
if let Some(ref req) = this.request {
match this.retry.policy.retry(req, result.as_ref()) {
Some(checking) => {
this.state.set(State::Checking { checking });
}
None => return Poll::Ready(result),
}
} else {
// request wasn't cloned, so no way to retry it
return Poll::Ready(result);
}
}
StateProj::Checking { checking } => {
this.retry
.as_mut()
.project()
.policy
.set(ready!(checking.poll(cx)));
this.state.set(State::Retrying);
}
StateProj::Retrying => {
// NOTE: we assume here that
//
// this.retry.poll_ready()
//
// is equivalent to
//
// this.retry.service.poll_ready()
//
// we need to make that assumption to avoid adding an Unpin bound to the Policy
// in Ready to make it Unpin so that we can get &mut Ready as needed to call
// poll_ready on it.
ready!(this.retry.as_mut().project().service.poll_ready(cx))?;
let req = this
.request
.take()
.expect("retrying requires cloned request");
*this.request = this.retry.policy.clone_request(&req);
this.state.set(State::Called {
future: this.retry.as_mut().project().service.call(req),
});
}
}
}
}
}