2019-06-04 13:59:47 -07:00
|
|
|
use super::BalanceMake;
|
2019-12-19 10:44:07 -08:00
|
|
|
use rand::{rngs::SmallRng, Rng, SeedableRng};
|
2019-06-04 13:59:47 -07:00
|
|
|
use std::{fmt, marker::PhantomData};
|
|
|
|
use tower_layer::Layer;
|
|
|
|
|
|
|
|
/// Efficiently distributes requests across an arbitrary number of services
|
|
|
|
#[derive(Clone)]
|
2019-07-05 20:46:33 -07:00
|
|
|
pub struct BalanceLayer<D, Req> {
|
2019-06-04 13:59:47 -07:00
|
|
|
rng: SmallRng,
|
2019-07-05 20:46:33 -07:00
|
|
|
_marker: PhantomData<fn(D, Req)>,
|
2019-06-04 13:59:47 -07:00
|
|
|
}
|
|
|
|
|
2019-07-05 20:46:33 -07:00
|
|
|
impl<D, Req> BalanceLayer<D, Req> {
|
2019-06-04 13:59:47 -07:00
|
|
|
/// Builds a balancer using the system entropy.
|
|
|
|
pub fn new() -> Self {
|
|
|
|
Self {
|
|
|
|
rng: SmallRng::from_entropy(),
|
|
|
|
_marker: PhantomData,
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/// Builds a balancer from the provided RNG.
|
|
|
|
///
|
|
|
|
/// This may be preferrable when many balancers are initialized.
|
|
|
|
pub fn from_rng<R: Rng>(rng: &mut R) -> Result<Self, rand::Error> {
|
|
|
|
let rng = SmallRng::from_rng(rng)?;
|
|
|
|
Ok(Self {
|
|
|
|
rng,
|
|
|
|
_marker: PhantomData,
|
|
|
|
})
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2019-07-05 20:46:33 -07:00
|
|
|
impl<S, Req> Layer<S> for BalanceLayer<S, Req> {
|
|
|
|
type Service = BalanceMake<S, Req>;
|
2019-06-04 13:59:47 -07:00
|
|
|
|
|
|
|
fn layer(&self, make_discover: S) -> Self::Service {
|
|
|
|
BalanceMake::new(make_discover, self.rng.clone())
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2019-07-05 20:46:33 -07:00
|
|
|
impl<D, Req> fmt::Debug for BalanceLayer<D, Req> {
|
2019-06-04 13:59:47 -07:00
|
|
|
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
|
|
|
f.debug_struct("BalanceLayer")
|
|
|
|
.field("rng", &self.rng)
|
|
|
|
.finish()
|
|
|
|
}
|
|
|
|
}
|