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use super::{error::Error, future::ResponseFuture, Rate};
use futures::{Async, Future, Poll};
use tokio_timer::{clock, Delay};
use tower_service::Service;
use std::time::Instant;
#[derive(Debug)]
pub struct RateLimit<T> {
inner: T,
rate: Rate,
state: State,
}
#[derive(Debug)]
enum State {
Limited(Delay),
Ready { until: Instant, rem: u64 },
}
impl<T> RateLimit<T> {
pub fn new(inner: T, rate: Rate) -> Self {
let state = State::Ready {
until: clock::now(),
rem: rate.num(),
};
RateLimit {
inner,
rate,
state: state,
}
}
pub fn get_ref(&self) -> &T {
&self.inner
}
pub fn get_mut(&mut self) -> &mut T {
&mut self.inner
}
pub fn into_inner(self) -> T {
self.inner
}
}
impl<S, Request> Service<Request> for RateLimit<S>
where
S: Service<Request>,
Error: From<S::Error>,
{
type Response = S::Response;
type Error = Error;
type Future = ResponseFuture<S::Future>;
fn poll_ready(&mut self) -> Poll<(), Self::Error> {
match self.state {
State::Ready { .. } => return self.inner.poll_ready().map_err(Into::into),
State::Limited(ref mut sleep) => {
if let Async::NotReady = sleep.poll()? {
tracing::trace!("rate limited exceeded; sleeping.");
}
}
}
self.state = State::Ready {
until: clock::now() + self.rate.per(),
rem: self.rate.num(),
};
self.inner.poll_ready().map_err(Into::into)
}
fn call(&mut self, request: Request) -> Self::Future {
match self.state {
State::Ready { mut until, mut rem } => {
let now = clock::now();
if now >= until {
until = now + self.rate.per();
rem = self.rate.num();
}
if rem > 1 {
rem -= 1;
self.state = State::Ready { until, rem };
} else {
let sleep = Delay::new(until);
self.state = State::Limited(sleep);
}
let inner = self.inner.call(request);
ResponseFuture::new(inner)
}
State::Limited(..) => panic!("service not ready; poll_ready must be called first"),
}
}
}