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use std::sync::{Mutex, Arc};
use super::LoadBalancingStrategy;
#[derive(Debug)]
pub struct RoundRobin<N> {
cluster: Vec<Arc<N>>,
prev_idx: Mutex<usize>,
}
impl<N> RoundRobin<N> {
pub fn new() -> Self {
RoundRobin {
prev_idx: Mutex::new(0),
cluster: vec![],
}
}
}
impl<N> From<Vec<Arc<N>>> for RoundRobin<N> {
fn from(cluster: Vec<Arc<N>>) -> RoundRobin<N> {
RoundRobin {
prev_idx: Mutex::new(0),
cluster: cluster,
}
}
}
impl<N> LoadBalancingStrategy<N> for RoundRobin<N> where N: Sync + Send {
fn init(&mut self, cluster: Vec<Arc<N>>) {
self.cluster = cluster;
}
fn next(&self) -> Option<Arc<N>> {
let mut prev_idx = self.prev_idx.lock().unwrap();
let next_idx = (*prev_idx + 1) % self.cluster.len();
*prev_idx = next_idx;
self.cluster.get(next_idx).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 round_robin() {
let nodes = vec!["a", "b", "c"];
let nodes_c = nodes.clone();
let load_balancer = RoundRobin::from(nodes.iter().map(|value| Arc::new(*value)).collect::<Vec<Arc<&str>>>());
for i in 0..10 {
assert_eq!(&nodes_c[(i + 1) % 3], load_balancer.next().unwrap().as_ref());
}
}
#[test]
fn remove_from_round_robin() {
let nodes = vec!["a", "b"];
let mut load_balancer = RoundRobin::from(nodes.iter().map(|value| Arc::new(*value)).collect::<Vec<Arc<&str>>>());
assert_eq!(&"b", load_balancer.next().unwrap().as_ref());
load_balancer.remove_node(|n| n == &"a");
assert_eq!(&"b", load_balancer.next().unwrap().as_ref());
}
}