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use std::sync::Arc;
use rand;
use super::LoadBalancingStrategy;
pub struct Random<N> {
pub cluster: Vec<Arc<N>>,
}
impl<N> Random<N> {
pub fn new(cluster: Vec<Arc<N>>) -> Self {
Random { cluster }
}
fn rnd_idx(bounds: (usize, usize)) -> usize {
let min = bounds.0;
let max = bounds.1;
let rnd = rand::random::<usize>();
rnd % (max - min) + min
}
}
impl<N> From<Vec<Arc<N>>> for Random<N> {
fn from(cluster: Vec<Arc<N>>) -> Random<N> {
Random { cluster }
}
}
impl<N> LoadBalancingStrategy<N> for Random<N> where N: Sync {
fn init(&mut self, cluster: Vec<Arc<N>>) {
self.cluster = cluster;
}
fn next(&self) -> Option<Arc<N>> {
let len = self.cluster.len();
if len == 0 {
return None;
}
self.cluster.get(Self::rnd_idx((0, len))).map(|node| node.clone())
}
fn remove_node<F>(&mut self, mut filter: F)
where
F: FnMut(&N) -> bool,
{
if let Some(i) = self.cluster.iter().position(|node| filter(node)) {
self.cluster.remove(i);
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn next_random() {
let nodes = vec!["a", "b", "c", "d", "e", "f", "g"];
let load_balancer = Random::from(nodes.iter().map(|value| Arc::new(*value)).collect::<Vec<Arc<&str>>>());
for _ in 0..100 {
let s = load_balancer.next();
assert!(s.is_some());
}
}
#[test]
fn remove_from_random() {
let nodes = vec!["a"];
let mut load_balancer = Random::from(nodes.iter().map(|value| Arc::new(*value)).collect::<Vec<Arc<&str>>>());
let s = load_balancer.next();
assert!(s.is_some());
load_balancer.remove_node(|n| n == &"a");
let s = load_balancer.next();
assert!(s.is_none());
}
}