added config hot reload

2025-12-10 15:37:02 -05:00
6 changed files with 431 additions and 188 deletions
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -15,12 +15,68 @@ dependencies = [
 "zerocopy",
 ]

+[[package]]
+name = "anstream"
+version = "0.6.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "43d5b281e737544384e969a5ccad3f1cdd24b48086a0fc1b2a5262a26b8f4f4a"
+dependencies = [
+ "anstyle",
+ "anstyle-parse",
+ "anstyle-query",
+ "anstyle-wincon",
+ "colorchoice",
+ "is_terminal_polyfill",
+ "utf8parse",
+]
+
+[[package]]
+name = "anstyle"
+version = "1.0.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5192cca8006f1fd4f7237516f40fa183bb07f8fbdfedaa0036de5ea9b0b45e78"
+
+[[package]]
+name = "anstyle-parse"
+version = "0.2.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4e7644824f0aa2c7b9384579234ef10eb7efb6a0deb83f9630a49594dd9c15c2"
+dependencies = [
+ "utf8parse",
+]
+
+[[package]]
+name = "anstyle-query"
+version = "1.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "40c48f72fd53cd289104fc64099abca73db4166ad86ea0b4341abe65af83dadc"
+dependencies = [
+ "windows-sys 0.61.2",
+]
+
+[[package]]
+name = "anstyle-wincon"
+version = "3.0.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "291e6a250ff86cd4a820112fb8898808a366d8f9f58ce16d1f538353ad55747d"
+dependencies = [
+ "anstyle",
+ "once_cell_polyfill",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "anywho"
 version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6136f131067f7e821582add37f0823fdba4dbdd8506833c1fd4b0e60a4ddaaf2"

+[[package]]
+name = "arc-swap"
+version = "1.7.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "69f7f8c3906b62b754cd5326047894316021dcfe5a194c8ea52bdd94934a3457"
+
 [[package]]
 name = "arraydeque"
 version = "0.5.1"
@@ -39,6 +95,12 @@ version = "0.22.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "72b3254f16251a8381aa12e40e3c4d2f0199f8c6508fbecb9d91f575e0fbb8c6"

+[[package]]
+name = "bitflags"
+version = "1.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
+
 [[package]]
 name = "bitflags"
 version = "2.10.0"
@@ -74,6 +136,52 @@ version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bd1b64030216239a2e7c364b13cd96a2097ebf0dfe5025f2dedee14a23f2ab60"

+[[package]]
+name = "clap"
+version = "4.5.53"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c9e340e012a1bf4935f5282ed1436d1489548e8f72308207ea5df0e23d2d03f8"
+dependencies = [
+ "clap_builder",
+ "clap_derive",
+]
+
+[[package]]
+name = "clap_builder"
+version = "4.5.53"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d76b5d13eaa18c901fd2f7fca939fefe3a0727a953561fefdf3b2922b8569d00"
+dependencies = [
+ "anstream",
+ "anstyle",
+ "clap_lex",
+ "strsim",
+]
+
+[[package]]
+name = "clap_derive"
+version = "4.5.49"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2a0b5487afeab2deb2ff4e03a807ad1a03ac532ff5a2cee5d86884440c7f7671"
+dependencies = [
+ "heck",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "clap_lex"
+version = "0.7.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1d728cc89cf3aee9ff92b05e62b19ee65a02b5702cff7d5a377e32c6ae29d8d"
+
+[[package]]
+name = "colorchoice"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b05b61dc5112cbb17e4b6cd61790d9845d13888356391624cbe7e41efeac1e75"
+
 [[package]]
 name = "cpufeatures"
 version = "0.2.17"
@@ -107,6 +215,15 @@ version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d9c4f5dac5e15c24eb999c26181a6ca40b39fe946cbe4c263c7209467bc83af2"

+[[package]]
+name = "fsevent-sys"
+version = "4.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "76ee7a02da4d231650c7cea31349b889be2f45ddb3ef3032d2ec8185f6313fd2"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "getrandom"
 version = "0.3.4"
@@ -137,18 +254,73 @@ dependencies = [
 "hashbrown",
 ]

+[[package]]
+name = "heck"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2304e00983f87ffb38b55b444b5e3b60a884b5d30c0fca7d82fe33449bbe55ea"
+
+[[package]]
+name = "inotify"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f37dccff2791ab604f9babef0ba14fbe0be30bd368dc541e2b08d07c8aa908f3"
+dependencies = [
+ "bitflags 2.10.0",
+ "inotify-sys",
+ "libc",
+]
+
+[[package]]
+name = "inotify-sys"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e05c02b5e89bff3b946cedeca278abc628fe811e604f027c45a8aa3cf793d0eb"
+dependencies = [
+ "libc",
+]
+
+[[package]]
+name = "is_terminal_polyfill"
+version = "1.70.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a6cb138bb79a146c1bd460005623e142ef0181e3d0219cb493e02f7d08a35695"
+
 [[package]]
 name = "itoa"
 version = "1.0.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4a5f13b858c8d314ee3e8f639011f7ccefe71f97f96e50151fb991f267928e2c"

+[[package]]
+name = "kqueue"
+version = "1.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eac30106d7dce88daf4a3fcb4879ea939476d5074a9b7ddd0fb97fa4bed5596a"
+dependencies = [
+ "kqueue-sys",
+ "libc",
+]
+
+[[package]]
+name = "kqueue-sys"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ed9625ffda8729b85e45cf04090035ac368927b8cebc34898e7c120f52e4838b"
+dependencies = [
+ "bitflags 1.3.2",
+ "libc",
+]
+
 [[package]]
 name = "l4lb"
 version = "0.1.0"
 dependencies = [
 "anywho",
+ "arc-swap",
 "cidr",
+ "clap",
+ "notify",
 "rand",
 "serde",
 "serde-saphyr",
@@ -170,6 +342,12 @@ dependencies = [
 "scopeguard",
 ]

+[[package]]
+name = "log"
+version = "0.4.29"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5e5032e24019045c762d3c0f28f5b6b8bbf38563a65908389bf7978758920897"
+
 [[package]]
 name = "memchr"
 version = "2.7.6"
@@ -183,6 +361,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "69d83b0086dc8ecf3ce9ae2874b2d1290252e2a30720bea58a5c6639b0092873"
 dependencies = [
 "libc",
+ "log",
 "wasi",
 "windows-sys 0.61.2",
 ]
@@ -193,6 +372,30 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2bf50223579dc7cdcfb3bfcacf7069ff68243f8c363f62ffa99cf000a6b9c451"

+[[package]]
+name = "notify"
+version = "8.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4d3d07927151ff8575b7087f245456e549fea62edf0ec4e565a5ee50c8402bc3"
+dependencies = [
+ "bitflags 2.10.0",
+ "fsevent-sys",
+ "inotify",
+ "kqueue",
+ "libc",
+ "log",
+ "mio",
+ "notify-types",
+ "walkdir",
+ "windows-sys 0.60.2",
+]
+
+[[package]]
+name = "notify-types"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5e0826a989adedc2a244799e823aece04662b66609d96af8dff7ac6df9a8925d"
+
 [[package]]
 name = "num-traits"
 version = "0.2.19"
@@ -208,6 +411,12 @@ version = "1.21.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "42f5e15c9953c5e4ccceeb2e7382a716482c34515315f7b03532b8b4e8393d2d"

+[[package]]
+name = "once_cell_polyfill"
+version = "1.70.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "384b8ab6d37215f3c5301a95a4accb5d64aa607f1fcb26a11b5303878451b4fe"
+
 [[package]]
 name = "parking_lot"
 version = "0.12.5"
@@ -284,7 +493,7 @@ version = "0.5.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ed2bf2547551a7053d6fdfafda3f938979645c44812fbfcda098faae3f1a362d"
 dependencies = [
- "bitflags",
+ "bitflags 2.10.0",
 ]

 [[package]]
@@ -293,6 +502,15 @@ version = "1.0.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "28d3b2b1366ec20994f1fd18c3c594f05c5dd4bc44d8bb0c1c632c8d6829481f"

+[[package]]
+name = "same-file"
+version = "1.0.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "93fc1dc3aaa9bfed95e02e6eadabb4baf7e3078b0bd1b4d7b6b0b68378900502"
+dependencies = [
+ "winapi-util",
+]
+
 [[package]]
 name = "saphyr-parser"
 version = "0.0.6"
@@ -401,6 +619,12 @@ dependencies = [
 "windows-sys 0.60.2",
 ]

+[[package]]
+name = "strsim"
+version = "0.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7da8b5736845d9f2fcb837ea5d9e2628564b3b043a70948a3f0b778838c5fb4f"
+
 [[package]]
 name = "syn"
 version = "2.0.110"
@@ -446,12 +670,28 @@ version = "1.0.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9312f7c4f6ff9069b165498234ce8be658059c6728633667c526e27dc2cf1df5"

+[[package]]
+name = "utf8parse"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "06abde3611657adf66d383f00b093d7faecc7fa57071cce2578660c9f1010821"
+
 [[package]]
 name = "version_check"
 version = "0.9.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0b928f33d975fc6ad9f86c8f283853ad26bdd5b10b7f1542aa2fa15e2289105a"

+[[package]]
+name = "walkdir"
+version = "2.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "29790946404f91d9c5d06f9874efddea1dc06c5efe94541a7d6863108e3a5e4b"
+dependencies = [
+ "same-file",
+ "winapi-util",
+]
+
 [[package]]
 name = "wasi"
 version = "0.11.1+wasi-snapshot-preview1"
@@ -467,6 +707,15 @@ dependencies = [
 "wit-bindgen",
 ]

+[[package]]
+name = "winapi-util"
+version = "0.1.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c2a7b1c03c876122aa43f3020e6c3c3ee5c05081c9a00739faf7503aeba10d22"
+dependencies = [
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "windows-link"
 version = "0.2.1"
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,3 +10,6 @@ rand = "0.10.0-rc.5"
 serde = { version = "1.0.228", features = ["derive"] }
 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"
--- a/config.yaml
+++ b/config.yaml
@@ -24,7 +24,6 @@ rules:

  - 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"
--- a/src/balancer/adaptive_weight.rs
+++ b/src/balancer/adaptive_weight.rs
@@ -27,7 +27,7 @@ impl AdaptiveWeightBalancer {
            .iter()
            .map(|b| AdaptiveNode {
                backend: b.clone(),
-                weight: 1f64,
+                weight: 0f64,
            })
            .collect();

@@ -85,6 +85,7 @@ impl Balancer for AdaptiveWeightBalancer {
            };

            let ratio = risk / node.weight;
+
            if ratio <= threshold {
                return Some(node.backend.clone());
            }
@@ -141,126 +142,3 @@ impl Balancer for AdaptiveWeightBalancer {
        }
    }
 }
-
-#[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");
-    }
-}
--- a/src/config/loader.rs
+++ b/src/config/loader.rs
@@ -14,24 +14,29 @@ pub struct RoutingTable {
    pub entries: Vec<(IpCidr, usize)>,
 }

-fn parse_client(s: &str) -> (IpCidr, u16) {
-    // just splits "0.0.0.0/0:80" into ("0.0.0.0/0", 80)
-    let (ip_part, port_part) = s.rsplit_once(':').expect("badly formatted client");
-
-    let port: u16 = port_part.parse().expect("bad port");
-    let cidr: IpCidr = ip_part.parse().expect("bad ip/mask");
-
-    (cidr, port)
-}
-
 pub type PortListeners = HashMap<u16, RoutingTable>;

-pub fn build_lb(config: AppConfig) -> PortListeners {
+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().unwrap();
+        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
@@ -80,7 +85,7 @@ pub fn build_lb(config: AppConfig) -> PortListeners {
        let mut port_groups: HashMap<u16, Vec<IpCidr>> = HashMap::new();

        for client_def in rule.clients {
-            let (cidr, port) = parse_client(&client_def);
+            let (cidr, port) = parse_client(&client_def)?;
            port_groups.entry(port).or_default().push(cidr);
        }

@@ -116,5 +121,5 @@ pub fn build_lb(config: AppConfig) -> PortListeners {
            .sort_by(|(a, _), (b, _)| a.network_length().cmp(&b.network_length()));
    }

-    listeners
+    Ok((listeners, healths))
 }
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,81 +3,190 @@ mod balancer;
 mod config;
 mod proxy;

-use crate::balancer::{Balancer, ConnectionInfo};
+use std::collections::HashMap;
+use crate::balancer::{ConnectionInfo};
 use crate::proxy::tcp::proxy_tcp_connection;
 use std::fs::File;
+use std::path::PathBuf;
+use std::net::IpAddr;
 use std::sync::atomic::{AtomicU64, Ordering};
+use std::sync::{Arc, Mutex, RwLock};
+use std::time::Duration;
+use anywho::Error;
 use tokio::net::TcpListener;
+use tokio::sync::mpsc;
+use crate::backend::ServerMetrics;
+use crate::config::loader::{build_lb, RoutingTable};
+
+use notify::{Watcher, RecursiveMode, Event};
+use clap::Parser;

 static NEXT_CONN_ID: AtomicU64 = AtomicU64::new(1);

+struct ProgramState {
+    tx_rt_map: HashMap<u16, mpsc::UnboundedSender<RoutingTable>>,
+    healths: HashMap<IpAddr, Arc<RwLock<ServerMetrics>>>,
+}
+
+#[derive(Parser, Debug)]
+#[command(author, version, about, long_about = None)]
+struct Args {
+    #[arg(short, long, default_value = "config.yaml")]
+    config: PathBuf,
+}
+
 #[tokio::main]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
-    let f = File::open("config.yaml").expect("couldn't open config.yaml");
-    let app_config: config::AppConfig = serde_saphyr::from_reader(f)?;
+    let args = Args::parse();
+
+    if !args.config.is_file() {
+        eprintln!("config file not found or not accessible");
+        std::process::exit(1);
+    }
+
+    println!("reading config from {:?}", args.config);
+
+    let state = Arc::new(Mutex::new(ProgramState {
+        tx_rt_map: HashMap::new(),
+        healths: HashMap::new(),
+    }));
+
+    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() {
+            if let Err(e) = load_config(&config_path, state_clone.clone()).await {
+                eprintln!("loading config failed: {}", e);
+            }
+        }
+    });
+
+    loop { tokio::time::sleep(Duration::from_hours(1)).await; }
+}
+
+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(()); }
+    };

    println!(
-        "Loaded {} backends, {} rules.",
+        "Loaded config, with {} backends, {} rules.",
        app_config.backends.len(),
        app_config.rules.len()
    );

-    let listeners = config::loader::build_lb(app_config);
+    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();

-    if listeners.is_empty() {
-        eprintln!("its a lawless land");
-        return Ok(());
+    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);
    }

-    let mut handles = Vec::new();
+    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);

-    for (port, mut routing_table) in listeners {
-        handles.push(tokio::spawn(async move {
-            let addr = format!("0.0.0.0:{}", port);
-            println!("Starting tcp listener on {}", addr);
+            tokio::spawn(run_listener(port, rx_rt, routing_table));
+        }
+    }

-            let listener = TcpListener::bind(&addr).await.expect("Failed to bind port");
+    println!("reload complete");
+    Ok(())
+}

-            loop {
-                let (socket, remote_addr) = match listener.accept().await {
-                    Ok(v) => v,
-                    Err(e) => {
-                        eprintln!("error: listener port {}: {}", port, e);
-                        continue;
+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;
                    }
-                };
-
-                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 routing_table.entries {
-                    if cidr.contains(&remote_ip) {
-                        let balancer = &mut routing_table.balancers[*balancer_idx];
-                        chosen_backend = balancer.choose_backend(ConnectionInfo {
-                            client_ip: remote_ip,
-                        });
+                    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);

-                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);
+                        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;
+                            }
                        }
-                    });
-                } else {
-                    println!("error: no matching rule for {} on port {}", remote_ip, port);
+
+                        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;
+                    }
                }
            }
-        }));
+        }
    }
-
-    for h in handles {
-        let _ = h.await;
-    }
-
-    Ok(())
 }