diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000000000000000000000000000000000000..00b0cdf9260f7d88b75c0baa8acadaf2887f833a
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,123 @@
+
+// use tokio::io;
+// use tokio::net::TcpListener;
+// use tokio::net::TcpStream;
+// use std::sync::{Arc, Mutex};
+// use signal_hook::{consts::SIGUSR1, iterator::Signals};
+// use std::time::Duration;
+// use tokio::time::{sleep, timeout};
+
+struct UpstreamState {
+ is_up: bool,
+ address: String,
+}
+
+struct JunctionState {
+ upstreams: Vec<UpstreamState>,
+ preference: usize,
+}
+
+impl JunctionState {
+ fn current(&self) -> String {
+ for offset in 0..self.upstreams.len() {
+ let idx = (self.preference + offset) % self.upstreams.len();
+ if self.upstreams[idx].is_up {
+ return self.upstreams[idx].address.clone();
+ }
+ }
+ self.upstreams[self.preference].address.clone() // all upstreams are down
+ }
+
+ fn mark(&mut self, idx: usize, is_up: bool) -> bool {
+ if self.upstreams[idx].is_up != is_up {
+ self.upstreams[idx].is_up = is_up;
+ return true;
+ }
+ false
+ }
+
+ fn advance(&mut self) {
+ self.preference = (self.preference + 1) % self.upstreams.len();
+ }
+}
+
+#[cfg(test)]
+mod test;
+
+// type SharedState = Arc<Mutex<State>>;
+//
+// #[tokio::main]
+// async fn main() {
+// let server = TcpListener::bind("0.0.0.0:8080").await.unwrap();
+//
+// let state: SharedState = Arc::new(Mutex::new(State {
+// a_up: false,
+// b_up: false,
+// prefer_a: true,
+// a: "localhost:8001".to_string(),
+// b: "localhost:8002".to_string(),
+// }));
+//
+//
+// {
+// let state = state.clone();
+// tokio::spawn(async move {
+// let mut signals = Signals::new([SIGUSR1]).unwrap();
+// for _ in signals.forever() {
+// let mut state = state.lock().unwrap();
+// state.prefer_a = !state.prefer_a;
+// println!("Update to server preference: prefer_a={:?}", state.prefer_a)
+// }
+// });
+// }
+//
+// {
+// let state = state.clone();
+// tokio::spawn(async move {
+// probe_upstream(true, state).await
+// });
+// }
+// {
+// let state = state.clone();
+// tokio::spawn(async move {
+// probe_upstream(false, state).await
+// });
+// }
+//
+// loop {
+// let (socket, _) = server.accept().await.unwrap();
+// let state = state.clone();
+// tokio::spawn(async move {
+// handle_client(socket, state).await;
+// });
+// }
+// }
+//
+// async fn handle_client(client: TcpStream, state: SharedState) {
+// let address = state.lock().unwrap().addr();
+// let server = TcpStream::connect(address.as_str()).await.unwrap();
+//
+// let (mut eread, mut ewrite) = client.into_split();
+// let (mut oread, mut owrite) = server.into_split();
+//
+// tokio::spawn(async move { io::copy(&mut eread, &mut owrite).await });
+// tokio::spawn(async move { io::copy(&mut oread, &mut ewrite).await });
+// }
+//
+// async fn probe_upstream(probe_a: bool, state: SharedState) {
+// loop {
+// let address = match probe_a {
+// true => state.lock().unwrap().a.clone(),
+// false => state.lock().unwrap().b.clone(),
+// };
+// let upstream = timeout(
+// Duration::from_millis(1000),
+// TcpStream::connect(address.as_str())
+// ).await;
+// match upstream {
+// Ok(Ok(_)) => state.lock().unwrap().mark_up(probe_a),
+// _ => state.lock().unwrap().mark_down(probe_a),
+// }
+// sleep(Duration::from_millis(1000)).await;
+// }
+// }
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index 5b3d8a76b30b3ace89427828df698b657bd9f898..e71fdf55421d043f171eba8c32329338498cad17 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,133 +1 @@
-use tokio::io;
-use tokio::net::TcpListener;
-use tokio::net::TcpStream;
-use std::sync::{Arc, Mutex};
-use signal_hook::{consts::SIGUSR1, iterator::Signals};
-use std::time::Duration;
-use tokio::time::{sleep, timeout};
-
-struct State {
- a_up: bool,
- b_up: bool,
- a: String,
- b: String,
- prefer_a: bool
-}
-
-
-impl State {
- fn use_a(&self) -> bool {
- match (self.a_up, self.b_up) {
- (true, true) => self.prefer_a,
- (false, true) => false,
- (true, false) => true,
- (false, false) => self.prefer_a,
- }
- }
-
- fn addr(&self) -> String {
- if self.use_a() {
- self.a.clone()
- } else {
- self.b.clone()
- }
- }
-
- fn mark_up(&mut self, probe_a: bool) {
- if probe_a && !self.a_up {
- self.a_up = true;
- println!("Marked a as up")
- } else if !probe_a && !self.b_up {
- self.b_up = true;
- println!("Marked b as up")
- }
- }
-
- fn mark_down(&mut self, probe_a: bool) {
- if probe_a && self.a_up {
- self.a_up = false;
- println!("Marked a as down")
- } else if !probe_a && self.b_up {
- self.b_up = false;
- println!("Marked b as down")
- }
- }
-}
-
-type SharedState = Arc<Mutex<State>>;
-
-#[tokio::main]
-async fn main() {
- let server = TcpListener::bind("0.0.0.0:8080").await.unwrap();
-
- let state: SharedState = Arc::new(Mutex::new(State {
- a_up: false,
- b_up: false,
- prefer_a: true,
- a: "localhost:8001".to_string(),
- b: "localhost:8002".to_string(),
- }));
-
-
- {
- let state = state.clone();
- tokio::spawn(async move {
- let mut signals = Signals::new([SIGUSR1]).unwrap();
- for _ in signals.forever() {
- let mut state = state.lock().unwrap();
- state.prefer_a = !state.prefer_a;
- println!("Update to server preference: prefer_a={:?}", state.prefer_a)
- }
- });
- }
-
- {
- let state = state.clone();
- tokio::spawn(async move {
- probe_upstream(true, state).await
- });
- }
- {
- let state = state.clone();
- tokio::spawn(async move {
- probe_upstream(false, state).await
- });
- }
-
- loop {
- let (socket, _) = server.accept().await.unwrap();
- let state = state.clone();
- tokio::spawn(async move {
- handle_client(socket, state).await;
- });
- }
-}
-
-async fn handle_client(client: TcpStream, state: SharedState) {
- let address = state.lock().unwrap().addr();
- let server = TcpStream::connect(address.as_str()).await.unwrap();
-
- let (mut eread, mut ewrite) = client.into_split();
- let (mut oread, mut owrite) = server.into_split();
-
- tokio::spawn(async move { io::copy(&mut eread, &mut owrite).await });
- tokio::spawn(async move { io::copy(&mut oread, &mut ewrite).await });
-}
-
-async fn probe_upstream(probe_a: bool, state: SharedState) {
- loop {
- let address = match probe_a {
- true => state.lock().unwrap().a.clone(),
- false => state.lock().unwrap().b.clone(),
- };
- let upstream = timeout(
- Duration::from_millis(1000),
- TcpStream::connect(address.as_str())
- ).await;
- match upstream {
- Ok(Ok(_)) => state.lock().unwrap().mark_up(probe_a),
- _ => state.lock().unwrap().mark_down(probe_a),
- }
- sleep(Duration::from_millis(1000)).await;
- }
-}
\ No newline at end of file
+fn main() {}
\ No newline at end of file
diff --git a/src/test.rs b/src/test.rs
new file mode 100644
index 0000000000000000000000000000000000000000..4c8dec5ced13c27db32aee017512cd1f5f769934
--- /dev/null
+++ b/src/test.rs
@@ -0,0 +1,138 @@
+
+use super::{JunctionState, UpstreamState};
+
+#[test]
+fn test_current_single() {
+ let state = JunctionState {
+ preference: 0,
+ upstreams: vec![
+ UpstreamState {
+ address: "server".to_string(),
+ is_up: true
+ }
+ ]
+ };
+
+ assert_eq!(state.current(), "server");
+}
+
+#[test]
+fn test_current_replica() {
+ let mut state = JunctionState {
+ preference: 0,
+ upstreams: vec![
+ UpstreamState {
+ address: "server-0".to_string(),
+ is_up: true
+ },
+ UpstreamState {
+ address: "server-1".to_string(),
+ is_up: true
+ }
+ ]
+ };
+
+ /////////////////////////////////////////////////////
+ state.preference = 0;
+
+ // UP -- up
+ state.upstreams[0].is_up = true;
+ state.upstreams[1].is_up = true;
+ assert_eq!(state.current(), "server-0");
+
+ // DOWN -- up
+ state.upstreams[0].is_up = false;
+ state.upstreams[1].is_up = true;
+ assert_eq!(state.current(), "server-1");
+
+ // UP -- down
+ state.upstreams[0].is_up = true;
+ state.upstreams[1].is_up = false;
+ assert_eq!(state.current(), "server-0");
+
+ // DOWN -- down
+ state.upstreams[0].is_up = false;
+ state.upstreams[1].is_up = false;
+ assert_eq!(state.current(), "server-0");
+
+ /////////////////////////////////////////////////////
+ state.preference = 1;
+
+ // up -- UP
+ state.upstreams[0].is_up = true;
+ state.upstreams[1].is_up = true;
+ assert_eq!(state.current(), "server-1");
+
+ // down -- UP
+ state.upstreams[0].is_up = false;
+ state.upstreams[1].is_up = true;
+ assert_eq!(state.current(), "server-1");
+
+ // up -- DOWN
+ state.upstreams[0].is_up = true;
+ state.upstreams[1].is_up = false;
+ assert_eq!(state.current(), "server-0");
+
+ // down -- DOWN
+ state.upstreams[0].is_up = false;
+ state.upstreams[1].is_up = false;
+ assert_eq!(state.current(), "server-1");
+}
+
+#[test]
+fn test_advance() {
+ let mut state = JunctionState {
+ preference: 0,
+ upstreams: vec![
+ UpstreamState {
+ address: "server-0".to_string(),
+ is_up: true
+ },
+ UpstreamState {
+ address: "server-1".to_string(),
+ is_up: true
+ }
+ ]
+ };
+
+ assert_eq!(state.preference, 0);
+
+ state.advance();
+ assert_eq!(state.preference, 1);
+
+ state.advance();
+ assert_eq!(state.preference, 0);
+}
+
+#[test]
+fn test_mark() {
+ let mut state = JunctionState {
+ preference: 0,
+ upstreams: vec![
+ UpstreamState {
+ address: "server-0".to_string(),
+ is_up: true
+ },
+ UpstreamState {
+ address: "server-1".to_string(),
+ is_up: true
+ }
+ ]
+ };
+
+ let changed = state.mark(0, false);
+ assert_eq!(state.upstreams[0].is_up, false);
+ assert_eq!(state.upstreams[1].is_up, true);
+ assert_eq!(changed, true);
+
+ let changed = state.mark(0, false);
+ assert_eq!(changed, false);
+
+ state.mark(1, false);
+ assert_eq!(state.upstreams[0].is_up, false);
+ assert_eq!(state.upstreams[1].is_up, false);
+
+ state.mark(0, true);
+ assert_eq!(state.upstreams[0].is_up, true);
+ assert_eq!(state.upstreams[1].is_up, false);
+}