feat(app): prevent multiple instances

Cargo.lock

@@ -1156,6 +1156,16 @@ dependencies = [
  "percent-encoding",
 ]
 
+[[package]]
+name = "fs2"
+version = "0.4.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9564fc758e15025b46aa6643b1b77d047d1a56a1aea6e01002ac0c7026876213"
+dependencies = [
+ "libc",
+ "winapi",
+]
+
 [[package]]
 name = "futures"
 version = "0.3.32"
@@ -1265,6 +1275,7 @@ dependencies = [
  "axum",
  "chrono",
  "dotenv",
+ "fs2",
  "serde",
  "serde_json",
  "serde_with",

Cargo.toml

@@ -43,6 +43,7 @@ validator = { version = "0.20", features = ["derive"] }
 
 # Error handling
 anyhow = "1.0"
+fs2 = "0.4"
 
 [target.'cfg(windows)'.dependencies]
 tray-icon = "0.15"

src/main.rs

@@ -1,3 +1,5 @@
+#![cfg_attr(all(windows, not(debug_assertions)), windows_subsystem = "windows")]
+
 mod control;
 mod config;
 mod connection;
@@ -47,6 +49,17 @@ pub struct AppState {
 async fn main() {
     dotenv::dotenv().ok();
     util::log::init_logger();
+    let _single_instance = match util::single_instance::try_acquire("PLCControl.Gateway") {
+        Ok(guard) => guard,
+        Err(err) if err.kind() == std::io::ErrorKind::AlreadyExists => {
+            tracing::warn!("Another PLC Control instance is already running");
+            return;
+        }
+        Err(err) => {
+            tracing::error!("Failed to initialize single instance guard: {}", err);
+            return;
+        }
+    };
 
     let config = AppConfig::from_env().expect("Failed to load configuration");
     let pool = init_database(&config.database_url)

src/util.rs

@@ -2,4 +2,5 @@ pub mod datetime;
 pub mod log;
 pub mod pagination;
 pub mod response;
+pub mod single_instance;
 pub mod validator;

src/util/single_instance.rs

@@ -0,0 +1,65 @@
+use fs2::FileExt;
+use std::{
+    fs::{File, OpenOptions},
+    io,
+    path::PathBuf,
+};
+
+pub fn try_acquire(name: &str) -> io::Result<SingleInstanceGuard> {
+    SingleInstanceGuard::acquire(name)
+}
+
+pub struct SingleInstanceGuard {
+    _file: File,
+}
+
+impl SingleInstanceGuard {
+    fn acquire(name: &str) -> io::Result<Self> {
+        let lock_path = lock_file_path(name);
+        let file = OpenOptions::new()
+            .create(true)
+            .read(true)
+            .write(true)
+            .truncate(false)
+            .open(lock_path)?;
+
+        if let Err(err) = file.try_lock_exclusive() {
+            if err.kind() == io::ErrorKind::WouldBlock {
+                return Err(io::Error::new(
+                    io::ErrorKind::AlreadyExists,
+                    "another PLC Control instance is already running",
+                ));
+            }
+            return Err(io::Error::new(
+                err.kind(),
+                format!("failed to lock single-instance file: {}", err),
+            ));
+        }
+
+        Ok(Self { _file: file })
+    }
+}
+
+fn lock_file_path(name: &str) -> PathBuf {
+    let sanitized: String = name
+        .chars()
+        .map(|ch| match ch {
+            'a'..='z' | 'A'..='Z' | '0'..='9' | '-' | '_' => ch,
+            _ => '_',
+        })
+        .collect();
+
+    std::env::temp_dir().join(format!("{}.lock", sanitized))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::lock_file_path;
+
+    #[test]
+    fn lock_path_is_sanitized() {
+        let path = lock_file_path("PLCControl/Gateway:test");
+        let path_str = path.to_string_lossy();
+        assert!(path_str.ends_with("PLCControl_Gateway_test.lock"));
+    }
+}