2020-03-31 10:10:47 -07:00
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use super::super::error;
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2019-06-04 13:59:47 -07:00
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use super::Balance;
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2020-03-31 10:10:47 -07:00
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use crate::discover::Discover;
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2019-09-10 15:15:32 -07:00
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use futures_core::ready;
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use pin_project::pin_project;
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2019-12-19 10:44:07 -08:00
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use rand::{rngs::SmallRng, SeedableRng};
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2019-07-05 20:46:33 -07:00
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use std::marker::PhantomData;
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2019-09-10 15:15:32 -07:00
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use std::{
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future::Future,
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pin::Pin,
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task::{Context, Poll},
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};
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2019-06-04 13:59:47 -07:00
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use tower_service::Service;
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/// Makes `Balancer`s given an inner service that makes `Discover`s.
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#[derive(Clone, Debug)]
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pub struct BalanceMake<S, Req> {
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inner: S,
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rng: SmallRng,
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_marker: PhantomData<fn(Req)>,
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}
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/// Makes a balancer instance.
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2019-09-23 14:28:14 -07:00
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#[pin_project]
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#[derive(Debug)]
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pub struct MakeFuture<F, Req> {
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#[pin]
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inner: F,
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rng: SmallRng,
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_marker: PhantomData<fn(Req)>,
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}
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2019-07-05 20:46:33 -07:00
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impl<S, Req> BalanceMake<S, Req> {
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pub(crate) fn new(inner: S, rng: SmallRng) -> Self {
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Self {
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inner,
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rng,
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_marker: PhantomData,
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}
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2019-06-04 13:59:47 -07:00
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}
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/// Initializes a P2C load balancer from the OS's entropy source.
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pub fn from_entropy(make_discover: S) -> Self {
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Self::new(make_discover, SmallRng::from_entropy())
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}
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}
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2019-07-05 20:46:33 -07:00
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impl<S, Target, Req> Service<Target> for BalanceMake<S, Req>
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where
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S: Service<Target>,
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S::Response: Discover,
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<S::Response as Discover>::Service: Service<Req>,
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<<S::Response as Discover>::Service as Service<Req>>::Error: Into<error::Error>,
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{
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type Response = Balance<S::Response, Req>;
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type Error = S::Error;
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type Future = MakeFuture<S::Future, Req>;
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2019-09-10 15:15:32 -07:00
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fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
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self.inner.poll_ready(cx)
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}
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fn call(&mut self, target: Target) -> Self::Future {
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MakeFuture {
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inner: self.inner.call(target),
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rng: self.rng.clone(),
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_marker: PhantomData,
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}
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}
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}
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2019-09-10 15:15:32 -07:00
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impl<F, T, E, Req> Future for MakeFuture<F, Req>
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where
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F: Future<Output = Result<T, E>>,
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T: Discover,
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<T as Discover>::Service: Service<Req>,
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<<T as Discover>::Service as Service<Req>>::Error: Into<error::Error>,
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{
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type Output = Result<Balance<T, Req>, E>;
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2019-09-30 11:58:27 -07:00
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fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
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let this = self.project();
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let inner = ready!(this.inner.poll(cx))?;
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let svc = Balance::new(inner, this.rng.clone());
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Poll::Ready(Ok(svc))
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}
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}
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