fix: fix resource leak (#136)

When a running service is dropped, its connections should be closed and its resources should be
cleaned up.

This changes the default from leaving services running to closing them. Library users who want
their services to remain running should call `waiting` on their running service, in a new task
where necessary.

Co-authored-by: Paul Ellenbogen <pe5@cs.princeton.edu>

crates/rmcp/src/service.rs

@@ -21,7 +21,7 @@ mod server;
 pub use server::*;
 #[cfg(feature = "tower")]
 mod tower;
-use tokio_util::sync::CancellationToken;
+use tokio_util::sync::{CancellationToken, DropGuard};
 #[cfg(feature = "tower")]
 pub use tower::*;
 use tracing::instrument;
@@ -429,8 +429,8 @@ pub struct RunningService<R: ServiceRole, S: Service<R>> {
     service: Arc<S>,
     peer: Peer<R>,
     handle: tokio::task::JoinHandle<QuitReason>,
-    /// cancellation token
-    ct: CancellationToken,
+    /// cancellation token with drop guard
+    dg: DropGuard,
 }
 impl<R: ServiceRole, S: Service<R>> Deref for RunningService<R, S> {
     type Target = Peer<R>;
@@ -453,8 +453,9 @@ impl<R: ServiceRole, S: Service<R>> RunningService<R, S> {
         self.handle.await
     }
     pub async fn cancel(self) -> Result<QuitReason, tokio::task::JoinError> {
-        self.ct.cancel();
-        self.waiting().await
+        let RunningService { dg, handle, .. } = self;
+        dg.disarm().cancel();
+        handle.await
     }
 }
 
@@ -759,6 +760,6 @@ where
         service,
         peer: peer_return,
         handle,
-        ct,
+        dg: ct.drop_guard(),
     })
 }

examples/servers/src/generic_service.rs

@@ -13,6 +13,6 @@ async fn main() -> Result<(), Box<dyn Error>> {
 
     let io = (tokio::io::stdin(), tokio::io::stdout());
 
-    serve_server(generic_service, io).await?;
+    serve_server(generic_service, io).await?.waiting().await?;
     Ok(())
 }