the algorithm is working, but will need more test

src/balancer/adaptive_weight.rs

@@ -2,7 +2,6 @@ use crate::netutils::Backend;
 use rand::prelude::*;
 use rand::rngs::SmallRng;
 use std::sync::Arc;
-use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
 
 
 #[derive(Debug, Clone)]
@@ -19,7 +18,7 @@ impl ServerMetrics {
         ServerMetrics { cpu: 0.0, mem: 0.0, net: 0.0, io: 0.0 }
     }
 
-    pub fn update(&mut self, cpu: f64, mem: f64, net: f64, io: f64, alpha: f64) {
+    pub fn update(&mut self, cpu: f64, mem: f64, net: f64, io: f64) {
         self.cpu = cpu;
         self.mem = mem;
         self.net = net;
@@ -64,18 +63,14 @@ impl AdaptiveBalancer {
     pub fn update_metrics(&mut self, backend_addr: &str, cpu: f64, mem: f64, net: f64, io: f64) {
         for s in &mut self.servers {
             if s.backend.to_string() == backend_addr {
-                s.metrics.update(cpu, mem, net, io, self.alpha);
+                s.metrics.update(cpu, mem, net, io);
                 return;
             }
         }
     }
 
     fn metrics_to_weight(metrics: &ServerMetrics, coeffs: &[f64; 4]) -> f64 {
-        let l = coeffs[0] * metrics.cpu + coeffs[1] * metrics.mem + coeffs[2] * metrics.net + coeffs[3] * metrics.io;
+        coeffs[0] * metrics.cpu + coeffs[1] * metrics.mem + coeffs[2] * metrics.net + coeffs[3] * metrics.io
-        // convert load to a score where higher is better: raw = 100 - L
-        let raw = (100.0 - l).max(0.0);
-        // amplify differences (square) and add small epsilon to avoid zero
-        raw * raw + 1e-6
     }
 
     /// Choose a backend using weighted random selection based on current weights.
@@ -89,17 +84,18 @@ impl AdaptiveBalancer {
         let rs: Vec<f64> = self.servers.iter().map(|s| {
             Self::metrics_to_weight(&s.metrics, &self.coeffs)
         }).collect();
-
         let ws: Vec<f64> = self.servers.iter().map(|s| s.weight).collect();
+        let ls: Vec<u32> = self.servers.iter().map(|s| s.backend.current_load).collect();
 
         let r_sum: f64 = rs.iter().copied().sum::<f64>();
         let w_sum: f64 = ws.iter().copied().sum::<f64>().max(1e-12);
+        let l_sum: u32 = ls.iter().copied().sum::<u32>();
         let threshold = self.alpha * (r_sum / w_sum);
 
         for (i, s) in self.servers.iter_mut().enumerate() {
             let ratio = if s.weight <= 0.0 { f64::INFINITY } else { rs[i] / s.weight };
             if ratio <= threshold {
-                Some(Arc::new(s.backend.clone()));
+                return Some(Arc::new(s.backend.clone()));
             }
         }
 
@@ -107,16 +103,20 @@ impl AdaptiveBalancer {
         // is relatively overloaded and we must adjust its weight using
         // formula (6).
     
-        // TODO: adjust weight
+        let lwi: Vec<f64> = self.servers.iter().enumerate().map(|(i, s)| {
+            s.backend.current_load as f64 * w_sum / ws[i] * l_sum as f64
+        }).collect();
+        let a_lwi: f64 = lwi.iter().copied().sum::<f64>() / lwi.len() as f64;
+        for (i, s) in self.servers.iter_mut().enumerate() {
+            s.weight += 1 as f64 - lwi[i] / a_lwi;
+        }
 
-        // Compute Li = Wi / Ri and choose server minimizing Li. This gives
+        // Compute Li = Wi / Ri and choose server minimizing Li.
-        // preference to servers with high remaining capacity relative to
-        // their weight (lower Li better).
         let mut best_idx: Option<usize> = None;
-        let mut best_li = AtomicUsize::new(usize::MAX);
+        let mut best_li = u32::MAX;
         for (i, s) in self.servers.iter().enumerate() {
             let li = s.backend.current_load;
-            if compare_atomic(&li, &best_li) == -1 {
+            if li < best_li {
                 best_li = li;
                 best_idx = Some(i);
             }
@@ -137,14 +137,6 @@ impl AdaptiveBalancer {
     }
 }
 
-fn compare_atomic(a: &AtomicUsize, b: &AtomicUsize) -> i32 {
-    let x = a.load(Ordering::SeqCst); 
-    let y = b.load(Ordering::SeqCst); 
-    if x < y { return -1; }
-    if x > y { return 1; }
-    return 0;
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -159,14 +151,11 @@ mod tests {
         // update one backend to be heavily loaded
         b.update_metrics("127.0.0.1:1", 90.0, 80.0, 10.0, 5.0);
         b.update_metrics("127.0.0.1:2", 10.0, 5.0, 1.0, 1.0);
-        let snaps2 = b.snapshot_weights();
-        println!("{:?}, {:?}", snaps, snaps2);
-        // after update the first server (127.0.0.1:1) should have a worse
-        // weight (higher composite load -> lower remaining capacity)
-        // assert!(snaps2[0].1 < snaps2[1].1);
 
         // Choose backend: should pick the less loaded host (127.0.0.1:2)
         let chosen = b.choose_backend().expect("should choose a backend");
+        let snaps2 = b.snapshot_weights();
+        println!("{:?}, {:?}", snaps, snaps2);
         assert_eq!(chosen.to_string(), "127.0.0.1:2");
     }
 }

src/main.rs

@@ -13,6 +13,7 @@ macro_rules! error {
 }
 
 mod netutils;
+mod balancer;
 
 use anywho::Error;
 use netutils::{Backend, tunnel};

src/netutils.rs

@@ -7,11 +7,15 @@ use std::error::Error;
 #[derive(Clone, Debug)]
 pub struct Backend {
     address: String,
+    pub current_load : u32
 }
 
 impl Backend {
     pub fn new(address: String) -> Self {
-        Backend { address }
+        Backend { 
+            address,  
+            current_load : 0 
+        }
     }
 }