cdrs/load_balancing/
round_robin_sync.rs

1use std::sync::Mutex;
2
3use super::LoadBalancingStrategy;
4
5pub struct RoundRobinSync<N> {
6    cluster: Vec<N>,
7    prev_idx: Mutex<usize>,
8}
9
10impl<N> RoundRobinSync<N> {
11    pub fn new() -> Self {
12        RoundRobinSync {
13            prev_idx: Mutex::new(0),
14            cluster: vec![],
15        }
16    }
17}
18
19impl<N> From<Vec<N>> for RoundRobinSync<N> {
20    fn from(cluster: Vec<N>) -> RoundRobinSync<N> {
21        RoundRobinSync {
22            prev_idx: Mutex::new(0),
23            cluster: cluster,
24        }
25    }
26}
27
28impl<N> LoadBalancingStrategy<N> for RoundRobinSync<N> {
29    fn init(&mut self, cluster: Vec<N>) {
30        self.cluster = cluster;
31    }
32
33    /// Returns next node from a cluster
34    fn next(&self) -> Option<&N> {
35        let mut prev_idx = self.prev_idx.lock();
36        if let Ok(ref mut mtx) = prev_idx {
37            let next_idx = (**mtx + 1) % self.cluster.len();
38            **mtx = next_idx;
39            self.cluster.get(next_idx)
40        } else {
41            return None;
42        }
43    }
44
45    fn remove_node<F>(&mut self, filter: F)
46    where
47        F: FnMut(&N) -> bool,
48    {
49        if let Some(i) = self.cluster.iter().position(filter) {
50            self.cluster.remove(i);
51        }
52    }
53}
54
55#[cfg(test)]
56mod tests {
57    use super::*;
58
59    #[test]
60    fn next_round_robin() {
61        let nodes = vec!["a", "b", "c"];
62        let nodes_c = nodes.clone();
63        let load_balancer = RoundRobinSync::from(nodes);
64        for i in 0..10 {
65            assert_eq!(&nodes_c[(i + 1) % 3], load_balancer.next().unwrap());
66        }
67    }
68
69    #[test]
70    fn remove_from_round_robin() {
71        let nodes = vec!["a", "b"];
72        let mut load_balancer = RoundRobinSync::from(nodes);
73        assert_eq!(&"b", load_balancer.next().unwrap());
74
75        load_balancer.remove_node(|n| n == &"a");
76        assert_eq!(&"b", load_balancer.next().unwrap());
77    }
78}
cdrs/load_balancing/round_robin_sync.rs

cdrs/load_balancing/
round_robin_sync.rs
