feat: improved logging

gh action

.github/workflows/rust.yml

@@ -0,0 +1,22 @@
+name: Rust
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v4
+    - name: Build
+      run: cargo build --verbose
+    - name: Run tests
+      run: cargo test --verbose

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.

src/backend/mod.rs

@@ -1,58 +0,0 @@
-use core::fmt;
-use std::net::SocketAddr;
-use std::sync::RwLock;
-use std::sync::Arc;
-use std::sync::atomic::{AtomicUsize, Ordering};
-
-#[derive(Debug)]
-pub struct Backend {
-    pub id: String,
-    pub address: SocketAddr,
-    pub active_connections: AtomicUsize,
-}
-
-impl Backend {
-    pub fn new(id: String, address: SocketAddr) -> Self {
-        Self {
-            id: id.to_string(),
-            address,
-            active_connections: AtomicUsize::new(0),
-        }
-    }
-
-    // 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)
-    }
-}
-
-#[derive(Clone, Debug)]
-pub struct BackendPool {
-    pub backends: Arc<RwLock<Vec<Arc<Backend>>>>,
-}
-
-impl BackendPool {
-    pub fn new() -> Self {
-        BackendPool {
-            backends: Arc::new(RwLock::new(Vec::new())),
-        }
-    }
-
-    pub fn add(&self, backend: Backend) {
-        self.backends.write().unwrap().push(Arc::new(backend));
-    }
-}

src/balancer/mod.rs

@@ -1,9 +0,0 @@
-pub mod round_robin;
-
-use std::fmt::Debug;
-use std::sync::Arc;
-use crate::backend::Backend;
-
-pub trait Balancer: Debug + Send + Sync + 'static {
-    fn choose_backend(&mut self) -> Option<Arc<Backend>>;
-}

src/balancer/round_robin.rs

@@ -1,33 +0,0 @@
-use std::sync::{Arc, RwLock};
-use std::fmt::Debug;
-use crate::backend::{Backend, BackendPool};
-use crate::balancer::Balancer;
-
-// 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) -> Option<Arc<Backend>> {
-        let backends = self.pool.backends.read().unwrap();
-        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.rs

@@ -1,6 +0,0 @@
-// TODO: "routing" rules
-// backends defined as ip + port
-// define sets of backends
-// allowed set operations for now is just union
-// rules are ip + mask and ports, maps to some of the sets
-//  defined earlier, along with a routing strategy

src/main.rs

@@ -1,52 +1,55 @@
-extern crate core;
+macro_rules! info {
+    ($($arg:tt)*) => {{
+        print!("info: ");
+        println!($($arg)*);
+    }};
+}
 
-mod balancer;
+macro_rules! error {
-mod config;
+    ($($arg:tt)*) => {
-mod backend;
+        eprint!("error: ");
-mod proxy;
+        eprintln!($($arg)*);
+    };
+}
+
+mod netutils;
+
+use anywho::Error;
+use netutils::{Backend, tunnel};
+use std::sync::Arc;
 
 use tokio::net::TcpListener;
-use tokio::io::{AsyncReadExt, AsyncWriteExt};
+use tokio::sync::Mutex;
-use std::sync::Arc;
-use std::sync::atomic::AtomicU64;
-use crate::backend::{Backend, BackendPool};
-use crate::balancer::Balancer;
-use crate::balancer::round_robin::RoundRobinBalancer;
-use crate::proxy::tcp::proxy_tcp_connection;
-
-static NEXT_CONN_ID: AtomicU64 = AtomicU64::new(1);
 
 #[tokio::main]
-async fn main() -> Result<(), Box<dyn std::error::Error>> {
+async fn main() -> Result<(), Error> {
-    let pool = BackendPool::new();
+    let backends = Arc::new(vec![
+        Backend::new("127.0.0.1:8081".to_string()),
+        Backend::new("127.0.0.1:8082".to_string()),
+    ]);
 
-    pool.add(Backend::new(
+    let current_index = Arc::new(Mutex::new(0));
-        "backend 1".into(),
-        "127.0.0.1:8081".parse().unwrap(),
-    ));
 
-    pool.add(Backend::new(
+    info!("enginewhy starting on 0.0.0.0:8080");
-        "backend 2".into(),
+    info!("backends: {:?}", backends);
-        "127.0.0.1:8082".parse().unwrap(),
-    ));
 
-    let mut balancer = RoundRobinBalancer::new(pool.clone());
+    let listener = TcpListener::bind("0.0.0.0:8080").await?;
-
-    let listener = TcpListener::bind("127.0.0.1:8080").await?;
 
     loop {
-        let (socket, _) = listener.accept().await?;
+        let (client, addr) = listener.accept().await?;
+        info!("new connection from {}", addr);
 
-        let conn_id = NEXT_CONN_ID.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
+        let backend = {
+            let mut index = current_index.lock().await;
+            let selected_backend = backends[*index].clone();
+            *index = (*index + 1) % backends.len();
+            selected_backend
+        };
 
-        if let Some(backend) = balancer.choose_backend() {
+        info!("routing client {} to backend {}", addr, backend);
-            tokio::spawn(async move {
+
-                if let Err(e) = proxy_tcp_connection(conn_id, socket, backend).await {
+        if let Err(e) = tunnel(client, backend).await {
-                    eprintln!("error: conn_id={} proxy failed: {}", conn_id, e);
+            error!("proxy failed for {}: {}", addr, e);
-                }
-            });
-        } else {
-            eprintln!("error: no backendsd for conn_id={}", conn_id);
         }
     }
 }

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

@@ -1,43 +0,0 @@
-use std::net::SocketAddr;
-use std::sync::Arc;
-use std::time::Instant;
-use crate::backend::Backend;
-
-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

@@ -1,26 +0,0 @@
-use std::sync::Arc;
-use tokio::io;
-use tokio::net::TcpStream;
-use anywho::Error;
-use crate::backend::Backend;
-use crate::proxy::ConnectionContext;
-
-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(())
-}