WIP

crates/zed2/src/only_instance.rs

@@ -0,0 +1,104 @@
+use std::{
+    io::{Read, Write},
+    net::{Ipv4Addr, SocketAddr, SocketAddrV4, TcpListener, TcpStream},
+    thread,
+    time::Duration,
+};
+
+use util::channel::ReleaseChannel;
+
+const LOCALHOST: Ipv4Addr = Ipv4Addr::new(127, 0, 0, 1);
+const CONNECT_TIMEOUT: Duration = Duration::from_millis(10);
+const RECEIVE_TIMEOUT: Duration = Duration::from_millis(35);
+const SEND_TIMEOUT: Duration = Duration::from_millis(20);
+
+fn address() -> SocketAddr {
+    let port = match *util::channel::RELEASE_CHANNEL {
+        ReleaseChannel::Dev => 43737,
+        ReleaseChannel::Preview => 43738,
+        ReleaseChannel::Stable => 43739,
+    };
+
+    SocketAddr::V4(SocketAddrV4::new(LOCALHOST, port))
+}
+
+fn instance_handshake() -> &'static str {
+    match *util::channel::RELEASE_CHANNEL {
+        ReleaseChannel::Dev => "Zed Editor Dev Instance Running",
+        ReleaseChannel::Preview => "Zed Editor Preview Instance Running",
+        ReleaseChannel::Stable => "Zed Editor Stable Instance Running",
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum IsOnlyInstance {
+    Yes,
+    No,
+}
+
+pub fn ensure_only_instance() -> IsOnlyInstance {
+    // todo!("zed_stateless")
+    // if *db::ZED_STATELESS {
+    //     return IsOnlyInstance::Yes;
+    // }
+
+    if check_got_handshake() {
+        return IsOnlyInstance::No;
+    }
+
+    let listener = match TcpListener::bind(address()) {
+        Ok(listener) => listener,
+
+        Err(err) => {
+            log::warn!("Error binding to single instance port: {err}");
+            if check_got_handshake() {
+                return IsOnlyInstance::No;
+            }
+
+            // Avoid failing to start when some other application by chance already has
+            // a claim on the port. This is sub-par as any other instance that gets launched
+            // will be unable to communicate with this instance and will duplicate
+            log::warn!("Backup handshake request failed, continuing without handshake");
+            return IsOnlyInstance::Yes;
+        }
+    };
+
+    thread::spawn(move || {
+        for stream in listener.incoming() {
+            let mut stream = match stream {
+                Ok(stream) => stream,
+                Err(_) => return,
+            };
+
+            _ = stream.set_nodelay(true);
+            _ = stream.set_read_timeout(Some(SEND_TIMEOUT));
+            _ = stream.write_all(instance_handshake().as_bytes());
+        }
+    });
+
+    IsOnlyInstance::Yes
+}
+
+fn check_got_handshake() -> bool {
+    match TcpStream::connect_timeout(&address(), CONNECT_TIMEOUT) {
+        Ok(mut stream) => {
+            let mut buf = vec![0u8; instance_handshake().len()];
+
+            stream.set_read_timeout(Some(RECEIVE_TIMEOUT)).unwrap();
+            if let Err(err) = stream.read_exact(&mut buf) {
+                log::warn!("Connected to single instance port but failed to read: {err}");
+                return false;
+            }
+
+            if buf == instance_handshake().as_bytes() {
+                log::info!("Got instance handshake");
+                return true;
+            }
+
+            log::warn!("Got wrong instance handshake value");
+            false
+        }
+
+        Err(_) => false,
+    }
+}