Merge pull request #1 from psun256/merge

Merge & Refactor

Cargo.toml

@@ -6,12 +6,3 @@ edition = "2024"
 [dependencies]
 anywho = "0.1.2"
 tokio = { version = "1.48.0", features = ["full"] }
-rand = "0.10.0-rc.5"
-serde = { version = "1.0.228", features = ["derive"] }
-serde_json = "1.0.145"
-rperf3-rs = "0.3.9"
-cidr = "0.3.1"
-serde-saphyr = "0.0.10"
-arc-swap = "1.7.1"
-clap = { version = "4.5.53", features = ["derive"] }
-notify = "8.2.0"

Dockerfile

@@ -36,5 +36,4 @@ FROM alpine:latest AS runtime
 # RUN apk add --no-cache ca-certificates curl netcat-openbsd bind-tools strace
 WORKDIR /enginewhy
 COPY --from=builder /enginewhy/target/x86_64-unknown-linux-musl/release/l4lb /usr/bin/l4lb
-COPY config.yaml .
-ENTRYPOINT ["l4lb"]
+ENTRYPOINT ["l4lb"]

README.md

@@ -5,25 +5,10 @@ Production't graden't load balancer.
 
 ## Todo
 - [ ] architecture astronauting
-  - balancer module
-    - just the algorithms i guess
-- 
-  - backend module
-    - manages the backend pool
-    - deals with health / load check
-    - BackendPool for all the backends stored together
-    - Backend for individual backends
-    - has some methods used by balancer module to pick a suitable backend
-  - proxy module 
-    - all the different supported protocols to handle
-    - will create a session / stream context structure (ConnectionContext)
-      - not globally tracked (this might change for UDP!)
-      - mainly some metadata
-  - config module
-    - set up all the stuff or something
 - [ ] stream / session handling (i think wrapper around tokio TcpStream)
 - [ ] basic backend pooling
-- [ ] layer 4 load balancing
+- [ ] layer 4 load balancing 
+- [ ] load balancing algorithm from the paper (https://www.wcse.org/WCSE_2018/W110.pdf) 
 
 ## notes
 tcp, for nginx (and haproxy, its similar):
@@ -36,7 +21,7 @@ struct ngx_connection_s {
 
     ngx_socket_t        fd;
 
-    ngx_recv_pt         recv; // fn pointer to whatever recv fn used (different for idfferent platforms / protocol
+    ngx_recv_pt         recv; // fn pointer to whatever recv fn used (different for dfferent platforms / protocol
     ngx_send_pt         send; // ditto
     ngx_recv_chain_pt   recv_chain;
     ngx_send_chain_pt   send_chain;
@@ -119,10 +104,3 @@ process to load balance:
 - connect to the server
 - proxy the data (copy_bidirectional? maybe we want some metrics or logging, so might do manually)
 - cleanup when smoeone leavesr or something goes wrong (with TCP, OS / tokio will tell us, with UDP probably just timeout based, and a periodic sweep of all sessions)
-
-
-### UDP
-UDP is connectionless, and i don't think UdpSocket or UdpFramed implement the traits required for tokio copy_bidirectional
-but async write and read don't work on just regular datagrams, so probably not possible.
-
-Would require us to implement our own bidirectional copying / proxying, as well as tracking "active" connections.

config.yaml

@@ -1,39 +0,0 @@
-healthcheck_addr: "127.0.0.1:9000"
-
-iperf_addr: "0.0.0.0:5200"
-
-backends:
-  - id: "srv-1"
-    ip: "127.0.0.1"
-    port: 8081
-
-  - id: "srv-2"
-    ip: "127.0.0.1"
-    port: 8082
-
-clusters:
-  main-api:
-    - "srv-1"
-    - "srv-2"
-  priority-api:
-    - "srv-1"
-
-rules:
-  - clients:
-      - "0.0.0.0/0:8888"
-    targets:
-      - "main-api"
-    strategy:
-      type: "RoundRobin"
-
-  - clients:
-      - "0.0.0.0/0:6767"
-      - "0.0.0.0/0:6969"
-    targets: # no issues with duplicate servers or clusters
-      - "priority-api"
-      - "priority-api"
-      - "priority-api"
-    strategy:
-      type: "Adaptive"
-      coefficients: [ 1.5, 1.0, 0.5, 0.1 ]
-      alpha: 0.75

docker-compose.yml

@@ -1,89 +0,0 @@
-services:
-  # two-arm load balancer  
-  load-balancer:
-    image: neoslhp/enginewhy-lb
-    container_name: load-balancer
-    tty: true
-    deploy:
-      resources:
-        limits:
-          cpus: "4.0"
-          memory: 8G 
-    cap_add:
-      - NET_ADMIN
-      - SYS_ADMIN
-    networks:
-      internal:
-        ipv4_address: 172.67.67.67
-      external:
-        ipv4_address: 192.67.67.67
-
-
-  server1-high-cpu:
-    image: neoslhp/enginewhy-server
-    container_name: server1
-    tty: true
-    deploy:
-      resources:
-        limits:
-          cpus: "4.0"
-          memory: 8G
-    depends_on:
-      - load-balancer
-    cap_add:
-    - NET_ADMIN
-    networks: 
-      external:
-        ipv4_address: 192.67.67.2
-
-  server2-low-cpu:
-    image: neoslhp/enginewhy-server
-    container_name: server2
-    tty: true
-    deploy:
-      resources:
-        limits:
-          cpus: "2.0"
-          memory: 4G
-    depends_on:
-      - load-balancer
-    cap_add:
-    - NET_ADMIN
-    networks:
-      external:
-        ipv4_address: 192.67.67.3
-  
-  client:
-    image: neoslhp/enginewhy-ubuntu22.04
-    container_name: client
-    tty: true
-    deploy:
-      resources:
-        limits:
-          cpus: "4.0"
-          memory: 4G
-    depends_on:
-      - load-balancer
-    cap_add:
-    - NET_ADMIN
-    networks:
-      internal:
-        ipv4_address: 172.67.67.2
-  
-networks:
-  internal:
-    driver: bridge
-    ipam:
-      config:
-      - subnet: 172.67.67.0/24
-  external:
-    driver: bridge
-    ipam:
-      config:
-      - subnet: 192.67.67.0/24
-  
-# Resources:
-# https://networkgeekstuff.com/networking/basic-load-balancer-scenarios-explained/
-# https://hub.docker.com/r/linuxserver/wireshark 
-# https://www.wcse.org/WCSE_2018/W110.pdf 
-# Deepseek

infra/enginewhy-lb.rs

@@ -1,68 +0,0 @@
-use rperf3::{Server, Config};
-use std::net::{TcpListener, TcpStream};
-use std::thread;
-use std::io::{Read, Write};
-use std::env;
-use tokio::task;
-
-async fn start_iperf_server() -> Result<(), Box<dyn std::error::Error>> {
-    let config = Config::server(5001);
-    let server = Server::new(config);
-    server.run().await?;
-    Ok(())
-}
-
-fn handle_connection(mut stream: TcpStream) -> std::io::Result<()> {
-    loop {
-        let mut buffer = [0u8; 512];
-        let bytes_read = stream.read(&mut buffer)?; 
-        let received = String::from_utf8_lossy(&buffer[..bytes_read]);
-        println!("Received: {}", received);
-    }
-    Ok(())
-}
-
-fn start_tcp_server(addr: &str) -> std::io::Result<()> {
-    let listener = TcpListener::bind(addr)?;
-    println!("TCP server listening on {}", addr);
-    let mut handles = Vec::new();
-    for stream in listener.incoming() {
-        match stream {
-            Ok(stream) => {
-                let handle = thread::spawn(move || {
-                    if let Err(e) = handle_connection(stream) {
-                        eprintln!("connection handler error: {}", e);
-                    }
-                });
-                handles.push(handle);
-            }
-            Err(e) => eprintln!("incoming connection failed: {}", e),
-        }
-    }
-
-    // When the incoming stream iterator ends (listener closed), join all handlers.
-    for h in handles {
-        let _ = h.join();
-    }
-    Ok(())
-}
-
-#[tokio::main]
-async fn main() {
-    // Choose IP based on `--localhost` flag for debugging
-    let use_localhost = env::args().any(|a| a == "--localhost");
-    let ip = if use_localhost { "127.0.0.1" } else { "192.67.67.67" };
-    let tcp_addr = format!("{}:8080", ip);
-
-    let iperf_server = task::spawn(async {
-        start_iperf_server().await;
-    });
-
-    let tcp_ip = tcp_addr.clone();
-    let tcp_server = thread::spawn(move || {
-        start_tcp_server(&tcp_ip).unwrap();
-    });
-
-    iperf_server.await.unwrap();
-    tcp_server.join().unwrap();
-}

infra/enginewhy-server.rs

@@ -1,162 +0,0 @@
-use sysinfo::{CpuRefreshKind, RefreshKind, System};
-use sysinfo::{Networks};
-use sysinfo::{Disks};
-use std::thread;
-use std::time::Duration;
-use std::net::{TcpStream};
-use std::env;
-use std::collections::HashMap;
-use std::io::Write;
-use serde_json::Value;
-use rperf3::{Client, Config, Protocol};
-
-
-// Default server addresses
-const DEFAULT_REMOTE_IP: &str = "192.67.67.67";
-const DEFAULT_LOCAL_IP: &str = "127.0.0.1";
-const PORT: u16 = 8080;
-const IPERF_PORT: u16 = 5001;
-
-fn get_io_usage_percentage() -> Result<f64, String> {
-    let mut sys = Disks::new_with_refreshed_list();
-    
-    // Refresh disk information
-    sys.refresh(true);
-    
-    // Get first disk (usually main disk)
-    if let Some(disk) = sys.list().first() {
-        let initial_read = disk.usage().total_read_bytes;
-        let initial_write = disk.usage().total_written_bytes;
-        
-        thread::sleep(Duration::from_secs(1));   // 1s
-        
-        sys.refresh(true);
-        let disk = sys.list().first().ok_or("Disk disappeared")?;
-        
-        let new_read = disk.usage().total_read_bytes;
-        let new_write = disk.usage().total_written_bytes;
-        
-        // Calculate Bps
-        let read_per_sec = (new_read - initial_read) as f64; 
-        let write_per_sec = (new_write - initial_write) as f64;
-        
-        // Get disk type to estimate max speed (these are rough estimates)
-        let max_speed = match disk.kind() {
-            sysinfo::DiskKind::SSD => 500_000_000.0, // 500 MBps
-            sysinfo::DiskKind::HDD => 200_000_000.0, // 200 MBps
-            _ => 300_000_000.0, // Default
-        };
-        
-        let io_percentage = f64::min(100.0, ((read_per_sec + write_per_sec) / max_speed) * 100.0);
-        Ok(io_percentage) 
-    } else {
-        Err("No disks found".to_string())
-    }
-}
-
-async fn measure_iperf_bandwidth(server_ip: &str, port: u16) -> Result<f64, Box<dyn std::error::Error>> {
-    // Configure the test (use the provided port)
-    let config = Config::client(server_ip.to_string(), port)
-        .with_duration(Duration::from_secs(10));
-
-    // Run the test
-    let client = Client::new(config)?;
-    client.run().await?;
-
-    // Get results
-    let measurements = client.get_measurements();
-    let bandwidth_bps = measurements.total_bits_per_second();
-    println!("iperf3 reported max bandwidth: {:.2} Mbps", bandwidth_bps / 1_000_000.0);
-    
-    Ok(bandwidth_bps)
-}
-
-#[tokio::main]
-async fn main() -> std::io::Result<()> {
-    // Determine server IP from CLI: `--localhost` -> local, otherwise remote
-    let args: Vec<String> = env::args().collect();
-    let server_ip = if args.iter().any(|a| a == "--localhost") {
-        DEFAULT_LOCAL_IP.to_string()
-    } else {
-        DEFAULT_REMOTE_IP.to_string()
-    };
-
-    let mut stream = TcpStream::connect(format!("{}:{}", server_ip, PORT))?;
-    println!("server connected to {}:{}", server_ip, PORT);
-
-    // Initialize the system struct
-    let mut sys = System::new_with_specifics(
-        RefreshKind::nothing().with_cpu(CpuRefreshKind::everything()),
-    );
-    let mut networks = Networks::new();
-    networks.refresh(true);
-
-    // Probe max bandwidth using iperf3
-    let mut max_bps: f64 = 0.0;
-    match measure_iperf_bandwidth(&server_ip, IPERF_PORT).await {
-        Ok(bps) => {
-            max_bps = bps;
-            println!("iperf3 reported max bandwidth: {:.2} bits/sec ({:.2} Mbps)", max_bps, max_bps / 1e6);
-        }   
-        Err(e) => println!("iperf3 failed: {}", e),
-    }
-
-    // Wait a bit because CPU usage is based on diff.
-    std::thread::sleep(sysinfo::MINIMUM_CPU_UPDATE_INTERVAL);
-    loop {
-        sys.refresh_all();
-
-        sys.refresh_cpu_usage(); // Refreshing CPU usage.
-        let mut cpu_usage: f64 = 0.0;
-        for cpu in sys.cpus() {
-            cpu_usage += cpu.cpu_usage() as f64;
-        }
-        cpu_usage /= sys.cpus().len() as f64;
-        println!("CPU usage is {}%", cpu_usage);
-
-        // Memory usage
-        let total_mem = sys.total_memory();
-        let used_mem = sys.used_memory();
-        let mem_usage = total_mem as f64 / used_mem as f64;
-        println!("Memory usage is {}%", mem_usage);
-
-        // Network bandwidth usage
-        let mut bandwidth: f64 = 0.0;  // Bps
-        for (interface_name, network) in &networks {
-            if interface_name == "wlp2s0" {
-                bandwidth = network.transmitted() as f64;
-                println!("[{interface_name}] transferred {:?} %", bandwidth / max_bps * 100.0);
-            }
-        }
-        networks.refresh(true);
-
-        // Calculate percent usage of measured max bandwidth (if available)
-        let net_usage_pct: f64 = if max_bps > 0.0 {
-            f64::min(100.0, (bandwidth / max_bps) * 100.0)
-        } else { 0.0 };
-
-        // IO usage
-        let mut io_usage = 0.0;
-        match get_io_usage_percentage() {
-            Ok(percentage) => {
-                io_usage = percentage;
-                println!("I/O usage is {}%", percentage)
-            },
-            Err(e) => println!("Error: {}", e)
-        }
-        println!();
-
-        let mut packet: HashMap<String, Value> = HashMap::new();
-        packet.insert("cpu".to_string(), Value::from(cpu_usage));    // %
-        packet.insert("mem".to_string(), Value::from(mem_usage));    // %
-        packet.insert("net".to_string(), Value::from(net_usage_pct));
-        packet.insert("io".to_string(), Value::from(io_usage));
-
-        let serialized_packet = serde_json::to_string(&packet)?;
-        serialized_packet.push('\n');
-        let _ = stream.write(serialized_packet.as_bytes());
-
-        thread::sleep(Duration::from_secs(10));
-    }
-}
-

src/backend/health.rs

@@ -1,134 +0,0 @@
-use std::collections::HashMap;
-use std::net::{IpAddr, SocketAddr};
-use std::sync::{Arc, RwLock};
-use serde_json::Value;
-use rperf3::{Config, Server};
-use tokio::net::{TcpListener, TcpSocket, TcpStream};
-use tokio::io::AsyncBufReadExt;
-
-// Physical server health statistics, used for certain load balancing algorithms
-#[derive(Debug, Default)]
-pub struct ServerMetrics {
-    pub cpu: f64,
-    pub mem: f64,
-    pub net: f64,
-    pub io: f64,
-}
-
-impl ServerMetrics {
-    pub fn update(&mut self, cpu: f64, mem: f64, net: f64, io: f64) {
-        self.cpu = cpu;
-        self.mem = mem;
-        self.net = net;
-        self.io = io;
-    }
-}
-
-pub async fn start_healthcheck_listener(
-    addr: &str,
-    healths: HashMap<IpAddr, Arc<RwLock<ServerMetrics>>>,
-) -> std::io::Result<()> {
-    let addrs = tokio::net::lookup_host(addr).await?;
-    let mut listener = None;
-
-    for a in addrs {
-        let socket = match a {
-            SocketAddr::V4(_) => TcpSocket::new_v4()?,
-            SocketAddr::V6(_) => TcpSocket::new_v6()?,
-        };
-
-        socket.set_reuseaddr(true)?;
-
-        if socket.bind(a).is_ok() {
-            listener = Some(socket.listen(1024)?);
-            break;
-        }
-    }
-
-    let listener = listener.ok_or_else(|| {
-        eprintln!("health listener could not bind to port");
-        std::io::Error::new(std::io::ErrorKind::Other, "health listener failed")
-    })?;
-
-    println!("healthcheck server listening on {}", addr);
-    loop {
-        let (stream, remote_addr) = match listener.accept().await {
-            Ok(v) => v,
-            Err(e) => {
-                continue;
-            }
-        };
-
-        if let Err(e) = handle_metrics_stream(stream, &healths).await {
-            eprintln!("connection handler error: {}", e);
-        }
-    }
-}
-
-pub async fn start_iperf_server(addr: &str) -> Result<(), Box<dyn std::error::Error>> {
-    let sock = addr.parse::<SocketAddr>()?;
-    let mut config = Config::server(sock.port());
-    config.bind_addr = Some(sock.ip());
-    let server = Server::new(config);
-    println!("iperf server listening on {}", addr);
-    server.run().await?;
-    Ok(())
-}
-
-async fn handle_metrics_stream(
-    stream: TcpStream,
-    healths: &HashMap<IpAddr, Arc<RwLock<ServerMetrics>>>,
-) -> std::io::Result<()> {
-    let server_ip = stream.peer_addr()?.ip();
-    let mut reader = tokio::io::BufReader::new(stream);
-    let mut line = String::new();
-
-    loop {
-        line.clear();
-
-        match reader.read_line(&mut line).await {
-            Ok(0) => break,
-            Ok(_) => {
-                if let Err(e) = process_metrics(server_ip, &line, healths) {
-                    eprintln!("skipping invalid packet: {}", e);
-                }
-            }
-            Err(e) => {
-                eprintln!("connection error: {}", e);
-                break;
-            }
-        }
-    }
-    Ok(())
-}
-
-fn process_metrics(
-    server_ip: IpAddr,
-    json_str: &str,
-    healths: &HashMap<IpAddr, Arc<RwLock<ServerMetrics>>>,
-) -> Result<(), String> {
-    let parsed: Value =
-        serde_json::from_str(json_str).map_err(|e| format!("parse error: {}", e))?;
-
-    let metrics_lock = healths
-        .get(&server_ip)
-        .ok_or_else(|| format!("unknown server: {}", server_ip))?;
-
-    let get_f64 = |key: &str| -> Result<f64, String> {
-        parsed
-            .get(key)
-            .and_then(|v| v.as_f64())
-            .ok_or_else(|| format!("invalid '{}'", key))
-    };
-
-    if let Ok(mut guard) = metrics_lock.write() {
-        guard.update(
-            get_f64("cpu")?,
-            get_f64("mem")?,
-            get_f64("net")?,
-            get_f64("io")?,
-        );
-    }
-
-    Ok(())
-}

src/backend/mod.rs

@@ -1,76 +0,0 @@
-pub mod health;
-
-use crate::backend::health::ServerMetrics;
-use core::fmt;
-use std::net::SocketAddr;
-use std::sync::Arc;
-use std::sync::RwLock;
-use std::sync::atomic::{AtomicUsize, Ordering};
-
-// A possible endpoint for a proxied connection.
-// Note that multiple may live on the same server, hence the Arc<RwLock<ServerMetric>>
-#[derive(Debug)]
-pub struct Backend {
-    pub id: String,
-    pub address: SocketAddr,
-    pub active_connections: AtomicUsize,
-    pub metrics: Arc<RwLock<ServerMetrics>>,
-}
-
-impl Backend {
-    pub fn new(
-        id: String,
-        address: SocketAddr,
-        server_metrics: Arc<RwLock<ServerMetrics>>,
-    ) -> Self {
-        Self {
-            id: id.to_string(),
-            address,
-            active_connections: AtomicUsize::new(0),
-            metrics: server_metrics,
-        }
-    }
-
-    // Ordering::Relaxed means the ops could be in any order, but since this
-    // is just a metric, and we assume the underlying system is sane
-    // enough not to behave poorly, so SeqCst is probably overkill.
-    pub fn inc_connections(&self) {
-        self.active_connections.fetch_add(1, Ordering::Relaxed);
-        println!(
-            "{} has {} connections open",
-            self.id,
-            self.active_connections.load(Ordering::Relaxed)
-        );
-    }
-
-    pub fn dec_connections(&self) {
-        self.active_connections.fetch_sub(1, Ordering::Relaxed);
-        println!(
-            "{} has {} connections open",
-            self.id,
-            self.active_connections.load(Ordering::Relaxed)
-        );
-    }
-}
-
-impl fmt::Display for Backend {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{} ({})", self.address, self.id)
-    }
-}
-
-// A set of endpoints that can be load balanced around.
-// Each Balancer owns one of these. Backend instances may be shared
-// with other Balancer instances, hence Arc<Backend>.
-#[derive(Clone, Debug)]
-pub struct BackendPool {
-    pub backends: Arc<Vec<Arc<Backend>>>,
-}
-
-impl BackendPool {
-    pub fn new(backends: Vec<Arc<Backend>>) -> Self {
-        BackendPool {
-            backends: Arc::new(backends),
-        }
-    }
-}

src/balancer/adaptive_weight.rs

@@ -1,267 +0,0 @@
-use crate::backend::{Backend, BackendPool};
-use crate::backend::health::ServerMetrics;
-use crate::balancer::{Balancer, ConnectionInfo};
-use rand::prelude::*;
-use rand::rngs::SmallRng;
-use std::fmt::Debug;
-use std::fs::Metadata;
-use std::sync::{Arc, RwLock};
-
-#[derive(Debug)]
-struct AdaptiveNode {
-    backend: Arc<Backend>,
-    weight: f64,
-}
-
-#[derive(Debug)]
-pub struct AdaptiveWeightBalancer {
-    pool: Vec<AdaptiveNode>,
-    coefficients: [f64; 4],
-    alpha: f64,
-    rng: SmallRng,
-}
-
-impl AdaptiveWeightBalancer {
-    pub fn new(pool: BackendPool, coefficients: [f64; 4], alpha: f64) -> Self {
-        let nodes = pool
-            .backends
-            .iter()
-            .map(|b| AdaptiveNode {
-                backend: b.clone(),
-                weight: 1f64,
-            })
-            .collect();
-
-        AdaptiveWeightBalancer {
-            pool: nodes,
-            coefficients,
-            alpha,
-            rng: SmallRng::from_rng(&mut rand::rng()),
-        }
-    }
-
-    pub fn metrics_to_weight(&self, metrics: &ServerMetrics) -> f64 {
-        self.coefficients[0] * metrics.cpu
-            + self.coefficients[1] * metrics.mem
-            + self.coefficients[2] * metrics.net
-            + self.coefficients[3] * metrics.io
-    }
-}
-
-impl Balancer for AdaptiveWeightBalancer {
-    fn choose_backend(&mut self, ctx: ConnectionInfo) -> Option<Arc<Backend>> {
-        if self.pool.is_empty() {
-            return None;
-        }
-
-        // Compute remaining capacity R_i = 100 - composite_load
-        let mut r_sum = 0.0;
-        let mut w_sum = 0.0;
-        let mut l_sum = 0;
-
-        for node in &self.pool {
-            if let Ok(health) = node.backend.metrics.read() {
-                r_sum += self.metrics_to_weight(&health);
-            }
-            w_sum += node.weight;
-            l_sum += node
-                .backend
-                .active_connections
-                .load(std::sync::atomic::Ordering::Relaxed);
-        }
-
-        let safe_w_sum = w_sum.max(1e-12);
-        let threshold = self.alpha * (r_sum / safe_w_sum);
-        
-        for idx in 0..self.pool.len() {
-            let node = &self.pool[idx];
-
-            if node.weight <= 0.001 {
-                continue;
-            }
-
-            let risk = match node.backend.metrics.read() {
-                Ok(h) => self.metrics_to_weight(&h),
-                Err(_) => f64::MAX,
-            };
-
-            let ratio = risk / node.weight;
-            if ratio <= threshold {
-                return Some(node.backend.clone());
-            }
-        }
-
-        // If any server satisfies Ri/Wi <= threshold, it means the server
-        // is relatively overloaded, and we must adjust its weight using
-        // formula (6).
-        let mut total_lwi = 0.0;
-        let l_sum_f64 = l_sum as f64;
-
-        for node in &self.pool {
-            let load = node
-                .backend
-                .active_connections
-                .load(std::sync::atomic::Ordering::Relaxed) as f64;
-            let weight = node.weight.max(1e-12);
-            let lwi = load * (safe_w_sum / weight) * l_sum_f64;
-            total_lwi += lwi;
-        }
-
-        let avg_lwi = (total_lwi / self.pool.len() as f64).max(1e-12);
-
-        // Compute Li = Wi / Ri and choose server minimizing Li.
-        let mut best_backend: Option<Arc<Backend>> = None;
-        let mut min_load = usize::MAX;
-
-        for node in &mut self.pool {
-            let load = node
-                .backend
-                .active_connections
-                .load(std::sync::atomic::Ordering::Relaxed);
-            let load_f64 = load as f64;
-            let weight = node.weight.max(1e-12);
-
-            let lwi = load_f64 * (safe_w_sum / weight) * l_sum_f64;
-
-            let adj = 1.0 - (lwi / avg_lwi);
-            node.weight += adj;
-
-            node.weight = node.weight.clamp(0.1, 100.0);
-            if load < min_load {
-                min_load = load;
-                best_backend = Some(node.backend.clone());
-            }
-        }
-
-        match best_backend {
-            Some(backend) => Some(backend),
-            None => {
-                let i = (self.rng.next_u32() as usize) % self.pool.len();
-                Some(self.pool[i].backend.clone())
-            }
-        }
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use crate::backend::Backend;
-    use std::net::SocketAddr;
-
-    fn backend_factory(id: &str, ip: &str, port: u16) -> Arc<Backend> {
-        Arc::new(Backend::new(
-            id.to_string(),
-            SocketAddr::new(ip.parse().unwrap(), port),
-            Arc::new(RwLock::new(ServerMetrics::default())),
-        ))
-    }
-
-    fn unused_ctx() -> ConnectionInfo {
-        ConnectionInfo {
-            client_ip: ("0.0.0.0".parse().unwrap()),
-        }
-    }
-
-    #[test]
-    fn basic_weight_update_and_choose() {
-        let backends = BackendPool::new(vec![
-            backend_factory("server-0", "127.0.0.1", 3000),
-            backend_factory("server-1", "127.0.0.1", 3001),
-        ]);
-        let mut b = AdaptiveWeightBalancer::new(backends.clone(), [0.5, 0.2, 0.2, 0.1], 0.5);
-        // initially equal weights
-        // update one backend to be heavily loaded
-        {
-            let mut sm0_guard = backends.backends.get(0).unwrap().metrics.write().unwrap();
-            sm0_guard.update(90.0, 80.0, 10.0, 5.0);
-        }
-        {
-            let mut sm1_guard = backends.backends.get(1).unwrap().metrics.write().unwrap();
-            sm1_guard.update(10.0, 5.0, 1.0, 1.0);
-        }
-
-        // Choose backend: should pick the less loaded host server1
-        let chosen = b
-            .choose_backend(unused_ctx())
-            .expect("should choose a backend");
-
-        let sm0: &ServerMetrics = &backends.backends.get(0).unwrap().metrics.read().unwrap();
-        let sm1: &ServerMetrics = &backends.backends.get(1).unwrap().metrics.read().unwrap();
-        println!("{:?}, {:?}", sm0, sm1);
-        assert_eq!(chosen.id, "server-1");
-    }
-
-    #[test]
-    fn choose_none_when_empty() {
-        let mut b =
-            AdaptiveWeightBalancer::new(BackendPool::new(vec![]), [0.5, 0.2, 0.2, 0.1], 0.5);
-        assert!(b.choose_backend(unused_ctx()).is_none());
-    }
-
-    #[test]
-    fn ratio_triggers_immediate_selection() {
-        // Arrange two servers where server 1 has composite load 0 and server 2 has composite load 100.
-        // With alpha = 1.0 and two servers, threshold = 1.0 * (r_sum / w_sum) = 1.0 * (100 / 2) = 50.
-        // Server 0 ratio = 0 / 1 = 0 <= 50 so it should be chosen immediately.
-        let backends = BackendPool::new(vec![
-            backend_factory("server-0", "127.0.0.1", 3000),
-            backend_factory("server-1", "127.0.0.1", 3001),
-        ]);
-        let mut b = AdaptiveWeightBalancer::new(backends.clone(), [0.25, 0.25, 0.25, 0.25], 1.0);
-
-        {
-            let mut sm0_guard = backends.backends.get(0).unwrap().metrics.write().unwrap();
-            sm0_guard.update(0.0, 0.0, 0.0, 0.0);
-        }
-        {
-            let mut sm1_guard = backends.backends.get(1).unwrap().metrics.write().unwrap();
-            sm1_guard.update(100.0, 100.0, 100.0, 100.0);
-        }
-
-        let chosen = b
-            .choose_backend(unused_ctx())
-            .expect("should choose a backend");
-        assert_eq!(chosen.id, "server-0");
-    }
-
-    #[test]
-    fn choose_min_current_load_when_no_ratio() {
-        // Arrange three servers with identical composite loads so no server satisfies Ri/Wi <= threshold
-        // (set alpha < 1 so threshold < ratio). The implementation then falls back to picking the
-        // server with minimum current_load
-        let backends = BackendPool::new(vec![
-            backend_factory("server-0", "127.0.0.1", 3000),
-            backend_factory("server-1", "127.0.0.1", 3001),
-            backend_factory("server-2", "127.0.0.1", 3002),
-        ]);
-
-        // set current_loads (field expected to be public)
-
-        {
-            let mut sm0_guard = backends.backends.get(0).unwrap().metrics.write().unwrap();
-            sm0_guard.update(10.0, 10.0, 10.0, 10.0);
-        }
-        {
-            let mut sm1_guard = backends.backends.get(1).unwrap().metrics.write().unwrap();
-            sm1_guard.update(5.0, 5.0, 5.0, 5.0);
-        }
-        {
-            let mut sm2_guard = backends.backends.get(2).unwrap().metrics.write().unwrap();
-            sm2_guard.update(20.0, 20.0, 20.0, 20.0);
-        }
-
-        // Use coeffs that only consider CPU so composite load is easy to reason about.
-        let mut bal = AdaptiveWeightBalancer::new(backends.clone(), [1.0, 0.0, 0.0, 0.0], 0.5);
-
-        // set identical composite loads > 0 for all so ratio = x and threshold = alpha * x < x
-        // you will have threshold = 25 for all 3 backend servers and ratio = 50
-        // so that forces to choose the smallest current load backend
-
-        let chosen = bal
-            .choose_backend(unused_ctx())
-            .expect("should choose a backend");
-        // expect server with smallest current_load server-1
-        assert_eq!(chosen.id, "server-1");
-    }
-}

src/balancer/ip_hashing.rs

@@ -1,109 +0,0 @@
-use crate::backend::{Backend, BackendPool};
-use crate::balancer::{Balancer, ConnectionInfo};
-use std::hash::{DefaultHasher, Hash, Hasher};
-use std::sync::Arc;
-
-#[derive(Debug)]
-pub struct SourceIPHash {
-    pool: BackendPool,
-}
-
-impl SourceIPHash {
-    pub fn new(pool: BackendPool) -> SourceIPHash {
-        Self { pool }
-    }
-}
-
-impl Balancer for SourceIPHash {
-    fn choose_backend(&mut self, ctx: ConnectionInfo) -> Option<Arc<Backend>> {
-        let client_ip = ctx.client_ip;
-
-        let mut hasher = DefaultHasher::new();
-        client_ip.hash(&mut hasher);
-        let hash = hasher.finish();
-        let idx = (hash as usize) % self.pool.backends.len();
-
-        Some(self.pool.backends[idx].clone())
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use crate::backend::health::ServerMetrics;
-    use std::net::IpAddr;
-    use std::sync::RwLock;
-
-    fn create_dummy_backends(count: usize) -> BackendPool {
-        let mut backends = Vec::new();
-        for i in 1..=count {
-            backends.push(Arc::new(Backend::new(
-                format!("backend {}", i),
-                format!("127.0.0.1:808{}", i).parse().unwrap(),
-                Arc::new(RwLock::new(ServerMetrics::default())),
-            )));
-        }
-        BackendPool::new(backends)
-    }
-
-    #[test]
-    fn test_same_ip_always_selects_same_backend() {
-        let backends = create_dummy_backends(3);
-        let mut balancer = SourceIPHash::new(backends);
-
-        let client_ip: IpAddr = "192.168.1.100".parse().unwrap();
-
-        let first_choice = balancer.choose_backend(ConnectionInfo { client_ip });
-        let second_choice = balancer.choose_backend(ConnectionInfo { client_ip });
-
-        assert!(first_choice.is_some());
-        assert!(second_choice.is_some());
-
-        let first = first_choice.unwrap();
-        let second = second_choice.unwrap();
-
-        assert_eq!(first.id, second.id);
-    }
-
-    #[test]
-    fn test_different_ips_may_select_different_backends() {
-        let backends = create_dummy_backends(2);
-        let mut balancer = SourceIPHash::new(backends);
-
-        let ip1: IpAddr = "192.168.1.100".parse().unwrap();
-        let choice1 = balancer.choose_backend(ConnectionInfo { client_ip: ip1 });
-
-        let ip2: IpAddr = "192.168.1.101".parse().unwrap();
-        let choice2 = balancer.choose_backend(ConnectionInfo { client_ip: ip2 });
-
-        assert!(choice1.is_some());
-        assert!(choice2.is_some());
-    }
-
-    #[test]
-    fn test_hash_distribution_across_backends() {
-        let pool = create_dummy_backends(3);
-        let backends_ref = pool.backends.clone();
-
-        let mut balancer = SourceIPHash::new(pool);
-        let mut distribution = [0, 0, 0];
-
-        // Test 30 different IPs
-        for i in 0..30 {
-            let client_ip: IpAddr = format!("192.168.1.{}", 100 + i).parse().unwrap();
-
-            if let Some(backend) = balancer.choose_backend(ConnectionInfo { client_ip }) {
-                for (idx, b) in backends_ref.iter().enumerate() {
-                    if backend.id == b.id && backend.address == b.address {
-                        distribution[idx] += 1;
-                        break;
-                    }
-                }
-            }
-        }
-
-        assert!(distribution[0] > 0, "Backend 0 received no traffic");
-        assert!(distribution[1] > 0, "Backend 1 received no traffic");
-        assert!(distribution[2] > 0, "Backend 2 received no traffic");
-    }
-}

src/balancer/least_connections.rs

@@ -1 +0,0 @@
-// use super::*;

src/balancer/mod.rs

@@ -1,18 +0,0 @@
-pub mod adaptive_weight;
-pub mod ip_hashing;
-pub mod least_connections;
-pub mod round_robin;
-
-use crate::backend::Backend;
-use std::fmt::Debug;
-use std::net::IpAddr;
-use std::sync::Arc;
-
-#[derive(Clone, Debug)]
-pub struct ConnectionInfo {
-    pub client_ip: IpAddr,
-}
-
-pub trait Balancer: Debug + Send + Sync + 'static {
-    fn choose_backend(&mut self, ctx: ConnectionInfo) -> Option<Arc<Backend>>;
-}

src/balancer/round_robin.rs

@@ -1,32 +0,0 @@
-use crate::backend::{Backend, BackendPool};
-use crate::balancer::{Balancer, ConnectionInfo};
-use std::fmt::Debug;
-use std::sync::Arc;
-
-// only the main thread for receiving connections should be
-// doing the load balancing. alternatively, each thread
-// that handles load balancing should get their own instance.
-#[derive(Debug)]
-pub struct RoundRobinBalancer {
-    pool: BackendPool,
-    index: usize,
-}
-
-impl RoundRobinBalancer {
-    pub fn new(pool: BackendPool) -> RoundRobinBalancer {
-        Self { pool, index: 0 }
-    }
-}
-
-impl Balancer for RoundRobinBalancer {
-    fn choose_backend(&mut self, ctx: ConnectionInfo) -> Option<Arc<Backend>> {
-        let backends = self.pool.backends.clone();
-        if backends.is_empty() {
-            return None;
-        }
-
-        let backend = backends[self.index % backends.len()].clone();
-        self.index = self.index.wrapping_add(1);
-        Some(backend)
-    }
-}

src/config/loader.rs

@@ -1,128 +0,0 @@
-use cidr::IpCidr;
-use std::collections::HashMap;
-use std::net::{IpAddr, SocketAddr};
-use std::sync::{Arc, RwLock};
-
-use crate::backend::health::*;
-use crate::backend::*;
-use crate::balancer::Balancer;
-use crate::balancer::adaptive_weight::AdaptiveWeightBalancer;
-use crate::balancer::round_robin::RoundRobinBalancer;
-use crate::config::*;
-
-pub struct RoutingTable {
-    pub balancers: Vec<Box<dyn Balancer + Send>>,
-    pub entries: Vec<(IpCidr, usize)>,
-}
-
-pub type PortListeners = HashMap<u16, RoutingTable>;
-
-fn parse_client(s: &str) -> Result<(IpCidr, u16), String> {
-    // just splits "0.0.0.0/0:80" into ("0.0.0.0/0", 80)
-    let (ip_part, port_part) = s
-        .rsplit_once(':')
-        .ok_or_else(|| format!("badly formatted client: {}", s))?;
-
-    let port = port_part.parse().map_err(|_| format!("bad port: {}", s))?;
-    let cidr = ip_part.parse().map_err(|_| format!("bad ip/mask: {}", s))?;
-
-    Ok((cidr, port))
-}
-
-pub fn build_lb(
-    config: &AppConfig,
-) -> Result<(PortListeners, HashMap<IpAddr, Arc<RwLock<ServerMetrics>>>), String> {
-    let mut healths: HashMap<IpAddr, Arc<RwLock<ServerMetrics>>> = HashMap::new();
-    let mut backends: HashMap<String, Arc<Backend>> = HashMap::new();
-
-    for backend_cfg in &config.backends {
-        let ip: IpAddr = backend_cfg
-            .ip
-            .parse()
-            .map_err(|_| format!("bad ip: {}", backend_cfg.ip))?;
-        let addr = SocketAddr::new(ip, backend_cfg.port);
-
-        let health = healths
-            .entry(ip)
-            .or_insert_with(|| Arc::new(RwLock::new(ServerMetrics::default())))
-            .clone();
-
-        let backend = Arc::new(Backend::new(backend_cfg.id.clone(), addr, health));
-
-        backends.insert(backend_cfg.id.clone(), backend);
-    }
-
-    let mut listeners: PortListeners = HashMap::new();
-
-    for rule in &config.rules {
-        let mut target_backends = Vec::new();
-
-        for target_name in &rule.targets {
-            if let Some(members) = config.clusters.get(target_name) {
-                for member_id in members {
-                    if let Some(backend) = backends.get(member_id) {
-                        target_backends.push(backend.clone());
-                    }
-                }
-            } else if let Some(backend) = backends.get(target_name) {
-                target_backends.push(backend.clone());
-            } else {
-                eprintln!("warning: target {} not found", target_name);
-            }
-        }
-
-        // possible for multiple targets of the same rule to have common backends.
-        target_backends.sort_by(|a, b| a.id.cmp(&b.id));
-        target_backends.dedup_by(|a, b| a.id == b.id);
-
-        if target_backends.is_empty() {
-            eprintln!("warning: rule has no valid targets, skipping.");
-            continue;
-        }
-
-        // for each different client port on this rule, we unfortunately need to make a new
-        // Balancer, since Balancer is not thread safe, requires &mut self for the backend
-        // selection.
-        // a good enough compromise to make a new one for each port, avoids using Mutex, at the
-        // cost of minor penalty to load balancing "quality" when you have several client ports.
-        let mut port_groups: HashMap<u16, Vec<IpCidr>> = HashMap::new();
-
-        for client_def in &rule.clients {
-            let (cidr, port) = parse_client(&client_def)?;
-            port_groups.entry(port).or_default().push(cidr);
-        }
-
-        for (port, cidrs) in port_groups {
-            let table = listeners.entry(port).or_insert_with(|| RoutingTable {
-                balancers: Vec::new(),
-                entries: Vec::new(),
-            });
-
-            let pool = BackendPool::new(target_backends.clone());
-
-            let balancer: Box<dyn Balancer + Send> = match &rule.strategy {
-                LoadBalancerStrategy::RoundRobin => Box::new(RoundRobinBalancer::new(pool)),
-                LoadBalancerStrategy::Adaptive {
-                    coefficients,
-                    alpha,
-                } => Box::new(AdaptiveWeightBalancer::new(pool, *coefficients, *alpha)),
-            };
-
-            let balancer_idx = table.balancers.len();
-            table.balancers.push(balancer);
-
-            for cidr in cidrs {
-                table.entries.push((cidr, balancer_idx));
-            }
-        }
-    }
-
-    // sort to make most specific first, so that first match == longest prefix match
-    for table in listeners.values_mut() {
-        table
-            .entries
-            .sort_by(|(a, _), (b, _)| a.network_length().cmp(&b.network_length()));
-    }
-
-    Ok((listeners, healths))
-}

src/config/mod.rs

@@ -1,62 +0,0 @@
-// config is written as a YAML file, the path will be passed to the program.
-//
-// the high level structure of the config is that we
-// first define the individual backends (ip + port) we are going
-// to load balance around.
-//
-// next we define some clusters, which are really more like a short
-// alias for a group of backends.
-//
-// next we define the rules. these are written as a list of
-// "ip/subnet:port" for the clients, and then a list of clusters
-// for which backends these are balanced around. and of course
-// specify which algorithm to use.
-pub mod loader;
-
-use serde::Deserialize;
-use std::collections::HashMap;
-
-fn default_healthcheck_addr() -> String {
-    "0.0.0.0:8080".to_string()
-}
-
-fn default_iperf_addr() -> String {
-    "0.0.0.0:5201".to_string()
-}
-
-#[derive(Debug, Deserialize)]
-pub struct AppConfig {
-    #[serde(default = "default_healthcheck_addr")]
-    pub healthcheck_addr: String,
-
-    #[serde(default = "default_iperf_addr")]
-    pub iperf_addr: String,
-
-    pub backends: Vec<BackendConfig>,
-
-    #[serde(default)]
-    pub clusters: HashMap<String, Vec<String>>,
-
-    pub rules: Vec<RuleConfig>,
-}
-
-#[derive(Debug, Deserialize)]
-pub struct BackendConfig {
-    pub id: String,
-    pub ip: String,
-    pub port: u16,
-}
-
-#[derive(Debug, Deserialize)]
-pub struct RuleConfig {
-    pub clients: Vec<String>,
-    pub targets: Vec<String>,
-    pub strategy: LoadBalancerStrategy,
-}
-
-#[derive(Debug, Deserialize)]
-#[serde(tag = "type")]
-pub enum LoadBalancerStrategy {
-    RoundRobin,
-    Adaptive { coefficients: [f64; 4], alpha: f64 },
-}

src/main.rs

@@ -1,252 +1,55 @@
-mod backend;
-mod balancer;
-mod config;
-mod proxy;
+macro_rules! info {
+    ($($arg:tt)*) => {{
+        print!("info: ");
+        println!($($arg)*);
+    }};
+}
+
+macro_rules! error {
+    ($($arg:tt)*) => {
+        eprint!("error: ");
+        eprintln!($($arg)*);
+    };
+}
+
+mod netutils;
 
-use crate::backend::health::{start_healthcheck_listener, start_iperf_server, ServerMetrics};
-use crate::balancer::ConnectionInfo;
-use crate::config::loader::{build_lb, RoutingTable};
-use crate::proxy::tcp::proxy_tcp_connection;
 use anywho::Error;
-use std::collections::HashMap;
-use std::fs::File;
-use std::hash::Hash;
-use std::net::{IpAddr, SocketAddr};
-use std::path::PathBuf;
-use std::sync::atomic::{AtomicU64, Ordering};
-use std::sync::{Arc, Mutex, RwLock};
-use std::time::Duration;
-use tokio::io::AsyncBufReadExt;
+use netutils::{Backend, tunnel};
+use std::sync::Arc;
+
 use tokio::net::TcpListener;
-use tokio::sync::mpsc;
-use clap::Parser;
-use notify::{Event, RecursiveMode, Watcher};
-use std::cmp;
-
-static NEXT_CONN_ID: AtomicU64 = AtomicU64::new(1);
-
-struct ProgramState {
-    tx_rt_map: HashMap<u16, mpsc::UnboundedSender<RoutingTable>>,
-    healths: HashMap<IpAddr, Arc<RwLock<ServerMetrics>>>,
-    health_listener: Option<tokio::task::JoinHandle<()>>,
-    iperf_server: Option<tokio::task::JoinHandle<()>>,
-    health_listener_addr: Option<String>,
-    iperf_server_addr: Option<String>,
-}
-
-#[derive(Parser, Debug)]
-#[command(author, version, about, long_about = None)]
-struct Args {
-    #[arg(short, long, default_value = "config.yaml")]
-    config: PathBuf,
-}
+use tokio::sync::Mutex;
 
 #[tokio::main]
-async fn main() -> Result<(), Box<dyn std::error::Error>> {
-    let args = Args::parse();
+async fn main() -> Result<(), Error> {
+    let backends = Arc::new(vec![
+        Backend::new("127.0.0.1:8081".to_string()),
+        Backend::new("127.0.0.1:8082".to_string()),
+    ]);
 
-    if !args.config.is_file() {
-        eprintln!("config file not found or not accessible");
-        std::process::exit(1);
-    }
+    let current_index = Arc::new(Mutex::new(0));
 
-    println!("reading config from {:?}", args.config);
+    info!("enginewhy starting on 0.0.0.0:8080");
+    info!("backends: {:?}", backends);
 
-    let state = Arc::new(Mutex::new(ProgramState {
-        tx_rt_map: HashMap::new(),
-        healths: HashMap::new(),
-        health_listener: None,
-        iperf_server: None,
-        health_listener_addr: None,
-        iperf_server_addr: None,
-    }));
-
-    if let Err(e) = load_config(&args.config, state.clone()).await {
-        eprintln!("config file loading failed: {}", e);
-    }
-
-    let config_path = args.config.clone();
-    let state_clone = state.clone();
-
-    tokio::spawn(async move {
-        let (tx, mut rx) = mpsc::channel(1);
-
-        let mut watcher = notify::recommended_watcher(move |res: Result<Event, notify::Error>| {
-            if let Ok(event) = res {
-                if event.kind.is_modify() {
-                    let _ = tx.blocking_send(());
-                }
-            }
-        })
-        .unwrap();
-
-        watcher
-            .watch(&config_path, RecursiveMode::NonRecursive)
-            .unwrap();
-        println!("watching for changes to {:?}", config_path);
-
-        while rx.recv().await.is_some() {
-            // for some reason, saving on certain text editors fires several events,
-            // and this causes us to reload a lot. try to flush some events, add a tiny delay
-            // to mitigate this
-
-            while rx.try_recv().is_ok() {}
-            tokio::time::sleep(Duration::from_millis(50)).await;
-            while rx.try_recv().is_ok() {}
-
-            if let Err(e) = load_config(&config_path, state_clone.clone()).await {
-                eprintln!("loading config failed: {}", e);
-            }
-        }
-    });
+    let listener = TcpListener::bind("0.0.0.0:8080").await?;
 
     loop {
-        tokio::time::sleep(Duration::from_hours(1)).await;
-    }
-}
+        let (client, addr) = listener.accept().await?;
+        info!("new connection from {}", addr);
 
-async fn load_config(path: &PathBuf, state: Arc<Mutex<ProgramState>>) -> Result<(), Error> {
-    let f = File::open(path)?;
-    let app_config: config::AppConfig = match serde_saphyr::from_reader(f) {
-        Ok(app_config) => app_config,
-        Err(e) => {
-            eprintln!("error parsing config {}", e);
-            return Ok(());
-        }
-    };
+        let backend = {
+            let mut index = current_index.lock().await;
+            let selected_backend = backends[*index].clone();
+            *index = (*index + 1) % backends.len();
+            selected_backend
+        };
 
-    println!(
-        "Loaded config, with {} backends, {} rules.",
-        app_config.backends.len(),
-        app_config.rules.len()
-    );
+        info!("routing client {} to backend {}", addr, backend);
 
-    let (mut listeners, health_monitors) = match build_lb(&app_config) {
-        Ok(v) => v,
-        Err(e) => {
-            eprintln!("config has logical errors: {}", e);
-            return Ok(());
-        }
-    };
-    let mut prog_state = state.lock().unwrap();
-
-    let ports_to_remove: Vec<u16> = prog_state
-        .tx_rt_map
-        .keys()
-        .cloned()
-        .filter(|port| !listeners.contains_key(port))
-        .collect();
-
-    for port in ports_to_remove {
-        prog_state.tx_rt_map.remove(&port);
-    }
-
-    if let Some(handle) = prog_state.health_listener.take() {
-        handle.abort();
-    }
-    let health_map: HashMap<IpAddr, Arc<RwLock<ServerMetrics>>> = health_monitors.clone();
-    let health_addr = app_config.healthcheck_addr.clone();
-    let health_addr_c = health_addr.clone();
-    let health_handle = tokio::spawn(async move {
-        if let Err(e) = start_healthcheck_listener(&health_addr, health_map).await {
-            eprintln!("health check listener failed: {}", e);
-        }
-    });
-    prog_state.health_listener = Some(health_handle);
-    prog_state.health_listener_addr = Some(health_addr_c);
-
-    // maybe restart iperf server
-    let iperf_addr = app_config.iperf_addr.clone();
-    if prog_state.iperf_server_addr.as_ref() != Some(&iperf_addr) {
-        if let Some(handle) = prog_state.iperf_server.take() {
-            handle.abort();
-        }
-
-        let iperf_addr_c = iperf_addr.clone();
-        let iperf_handle = tokio::spawn(async move {
-            if let Err(e) = start_iperf_server(iperf_addr.as_str()).await {
-                eprintln!("iperf server failed: {}", e);
-            }
-        });
-
-        prog_state.iperf_server = Some(iperf_handle);
-        prog_state.iperf_server_addr = Some(iperf_addr_c);
-    }
-
-    prog_state.healths = health_monitors;
-    for (port, routing_table) in listeners.drain() {
-        if let Some(x) = prog_state.tx_rt_map.get_mut(&port) {
-            x.send(routing_table)?;
-            println!("updated rules on port {}", port);
-        } else {
-            let (tx_rt, rx_rt) = mpsc::unbounded_channel();
-            prog_state.tx_rt_map.insert(port, tx_rt);
-
-            tokio::spawn(run_listener(port, rx_rt, routing_table));
-        }
-    }
-
-    println!("reload complete");
-    Ok(())
-}
-
-async fn run_listener(
-    port: u16,
-    mut rx_rt: mpsc::UnboundedReceiver<RoutingTable>,
-    mut current_table: RoutingTable,
-) {
-    let addr = format!("0.0.0.0:{}", port);
-    println!("Starting tcp listener on {}", addr);
-
-    let listener = TcpListener::bind(&addr).await.expect("Failed to bind port");
-
-    loop {
-        tokio::select! {
-            msg = rx_rt.recv() => {
-                match msg {
-                    Some(new_table) => {
-                        current_table = new_table;
-                    }
-                    None => {
-                        println!("Unbinding listener on port {}", port);
-                        break;
-                    }
-                }
-            }
-            accept_result = listener.accept() => {
-                match accept_result {
-                    Ok((socket, remote_addr)) => {
-                        let remote_ip = remote_addr.ip();
-                        let conn_id = NEXT_CONN_ID.fetch_add(1, Ordering::Relaxed);
-
-                        let mut chosen_backend = None;
-
-                        for (cidr, balancer_idx) in &mut current_table.entries {
-                            if cidr.contains(&remote_ip) {
-                                let balancer = &mut current_table.balancers[*balancer_idx];
-                                chosen_backend = balancer.choose_backend(ConnectionInfo {
-                                    client_ip: remote_ip,
-                                });
-                                break;
-                            }
-                        }
-
-                        if let Some(backend) = chosen_backend {
-                            tokio::spawn(async move {
-                                if let Err(e) = proxy_tcp_connection(conn_id, socket, backend).await {
-                                    eprintln!("error: conn_id={} proxy failed: {}", conn_id, e);
-                                }
-                            });
-                        } else {
-                            println!("error: no matching rule for {} on port {}", remote_ip, port);
-                        }
-                    }
-                    Err(e) => {
-                        eprintln!("error: listener port {}: {}", port, e);
-                    continue;
-                    }
-                }
-            }
+        if let Err(e) = tunnel(client, backend).await {
+            error!("proxy failed for {}: {}", addr, e);
         }
     }
 }

src/netutils.rs

@@ -0,0 +1,52 @@
+use std::fmt;
+use tokio::io;
+use tokio::net::TcpStream;
+
+use std::error::Error;
+
+#[derive(Clone, Debug)]
+pub struct Backend {
+    address: String,
+}
+
+impl Backend {
+    pub fn new(address: String) -> Self {
+        Backend { address }
+    }
+}
+
+impl fmt::Display for Backend {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.address)
+    }
+}
+
+pub async fn tunnel(client_stream: TcpStream, backend: Backend) -> Result<(), Box<dyn Error>> {
+    let backend_address: String = backend.address.clone();
+
+    tokio::spawn(async move {
+        let backend_stream: TcpStream = match TcpStream::connect(&backend_address).await {
+            Ok(s) => {
+                info!("connected to backend {backend_address}");
+                s
+            }
+            Err(e) => {
+                error!("failed connecting to backend {backend_address}: {e}");
+                return;
+            }
+        };
+
+        let (mut read_client, mut write_client) = client_stream.into_split();
+        let (mut read_backend, mut write_backend) = backend_stream.into_split();
+
+        let client_to_backend =
+            tokio::spawn(async move { io::copy(&mut read_client, &mut write_backend).await });
+
+        let backend_to_client =
+            tokio::spawn(async move { io::copy(&mut read_backend, &mut write_client).await });
+
+        let _ = tokio::join!(client_to_backend, backend_to_client);
+    });
+
+    Ok(())
+}

src/proxy/mod.rs

@@ -1,44 +0,0 @@
-use crate::backend::Backend;
-use std::net::SocketAddr;
-use std::sync::Arc;
-use std::time::Instant;
-
-pub mod tcp;
-
-pub struct ConnectionContext {
-    pub id: u64,
-    pub client_addr: SocketAddr,
-    pub start_time: Instant,
-    pub backend: Arc<Backend>,
-    pub bytes_transferred: u64,
-}
-
-impl ConnectionContext {
-    pub fn new(id: u64, client_addr: SocketAddr, backend: Arc<Backend>) -> Self {
-        backend.inc_connections();
-
-        Self {
-            id,
-            client_addr,
-            start_time: Instant::now(),
-            backend,
-            bytes_transferred: 0,
-        }
-    }
-}
-
-impl Drop for ConnectionContext {
-    fn drop(&mut self) {
-        self.backend.dec_connections();
-        let duration = self.start_time.elapsed();
-
-        println!(
-            "info: conn_id={} closed. client={} backend={} bytes={} duration={:.2?}",
-            self.id,
-            self.client_addr,
-            self.backend.address,
-            self.bytes_transferred,
-            duration.as_secs_f64()
-        );
-    }
-}

src/proxy/tcp.rs

@@ -1,30 +0,0 @@
-use crate::backend::Backend;
-use crate::proxy::ConnectionContext;
-use anywho::Error;
-use std::sync::Arc;
-use tokio::io;
-use tokio::net::TcpStream;
-
-pub async fn proxy_tcp_connection(
-    connection_id: u64,
-    mut client_stream: TcpStream,
-    backend: Arc<Backend>,
-) -> Result<(), Error> {
-    let client_addr = client_stream.peer_addr()?;
-
-    let mut ctx = ConnectionContext::new(connection_id, client_addr, backend.clone());
-
-    #[cfg(debug_assertions)]
-    println!(
-        "info: conn_id={} connecting to {}",
-        connection_id, ctx.backend.id
-    );
-
-    let mut backend_stream = TcpStream::connect(&backend.address).await?;
-
-    let (tx, rx) = io::copy_bidirectional(&mut client_stream, &mut backend_stream).await?;
-
-    ctx.bytes_transferred = tx + rx;
-
-    Ok(())
-}