Disallow concurrent swaps

swap/src/api/request.rs

@@ -22,6 +22,11 @@ use structopt::lazy_static::lazy_static;
 use tokio::sync::broadcast::Receiver;
 use tracing::{debug_span, Instrument};
 use uuid::Uuid;
+use tokio::sync::Mutex;
+
+lazy_static! {
+    static ref SWAP_MUTEX: Mutex<Option<Uuid>> = Mutex::new(None);
+}
 
 #[derive(PartialEq, Debug)]
 pub struct Request {
@@ -558,10 +563,26 @@ impl Request {
     pub async fn call(self, context: Arc<Context>) -> Result<serde_json::Value> {
         // If the swap ID is set, we add it to the span
         let call_span = debug_span!(
-            "call",
+            "cmd",
             method = ?self.cmd,
         );
 
+        if let Some(swap_id) = self.has_lockable_swap_id() {
+            println!("taking lock for swap_id: {}", swap_id);
+            let mut guard = SWAP_MUTEX.try_lock().context("Another swap is already running")?;
+            if guard.is_some() {
+                bail!("Another swap is already running");
+            }
+
+            let _ = guard.insert(swap_id.clone());
+
+            let result = self.handle_cmd(context).instrument(call_span).await;
+            guard.take();
+
+            println!("releasing lock for swap_id: {}", swap_id);
+
+            return result;
+        }
         self.handle_cmd(context).instrument(call_span).await
     }
 }
@@ -584,7 +605,7 @@ pub async fn determine_btc_to_swap<FB, TB, FMG, TMG, FS, TS, FFE, TFE>(
     sync: FS,
     estimate_fee: FFE,
 ) -> Result<(bitcoin::Amount, bitcoin::Amount)>
-where
+    where
         TB: Future<Output = Result<bitcoin::Amount>>,
         FB: Fn() -> TB,
         TMG: Future<Output = Result<bitcoin::Amount>>,
@@ -667,3 +688,4 @@ where
 
     Ok((btc_swap_amount, fees))
 }
+