Subscriptions keep clients alive until dropped

Author: A-Manning

client/http-client/src/client.rs

@@ -483,14 +483,16 @@ where
 		> + Send
 		+ Sync,
 {
+	type SubscriptionClient = Self;
+
 	/// Send a subscription request to the server. Not implemented for HTTP; will always return
 	/// [`Error::HttpNotImplemented`].
 	fn subscribe<'a, N, Params>(
 		&self,
 		_subscribe_method: &'a str,
 		_params: Params,
 		_unsubscribe_method: &'a str,
-	) -> impl Future<Output = Result<Subscription<N>, Error>>
+	) -> impl Future<Output = Result<Subscription<Self::SubscriptionClient, N>, Error>>
 	where
 		Params: ToRpcParams + Send,
 		N: DeserializeOwned,
@@ -499,7 +501,10 @@ where
 	}
 
 	/// Subscribe to a specific method. Not implemented for HTTP; will always return [`Error::HttpNotImplemented`].
-	fn subscribe_to_method<N>(&self, _method: &str) -> impl Future<Output = Result<Subscription<N>, Error>>
+	fn subscribe_to_method<N>(
+		&self,
+		_method: &str,
+	) -> impl Future<Output = Result<Subscription<Self::SubscriptionClient, N>, Error>>
 	where
 		N: DeserializeOwned,
 	{

client/ws-client/src/tests.rs

@@ -159,7 +159,7 @@ async fn subscription_works() {
 	let uri = to_ws_uri_string(server.local_addr());
 	let client = WsClientBuilder::default().build(&uri).with_default_timeout().await.unwrap().unwrap();
 	{
-		let mut sub: Subscription<String> = client
+		let mut sub: Subscription<_, String> = client
 			.subscribe("subscribe_hello", rpc_params![], "unsubscribe_hello")
 			.with_default_timeout()
 			.await
@@ -183,7 +183,7 @@ async fn notification_handler_works() {
 	let uri = to_ws_uri_string(server.local_addr());
 	let client = WsClientBuilder::default().build(&uri).with_default_timeout().await.unwrap().unwrap();
 	{
-		let mut nh: Subscription<String> =
+		let mut nh: Subscription<_, String> =
 			client.subscribe_to_method("test").with_default_timeout().await.unwrap().unwrap();
 		let response: String = nh.next().with_default_timeout().await.unwrap().unwrap().unwrap();
 		assert_eq!("server originated notification works".to_owned(), response);
@@ -203,7 +203,7 @@ async fn notification_no_params() {
 	let uri = to_ws_uri_string(server.local_addr());
 	let client = WsClientBuilder::default().build(&uri).with_default_timeout().await.unwrap().unwrap();
 	{
-		let mut nh: Subscription<serde_json::Value> =
+		let mut nh: Subscription<_, serde_json::Value> =
 			client.subscribe_to_method("no_params").with_default_timeout().await.unwrap().unwrap();
 		let response = nh.next().with_default_timeout().await.unwrap().unwrap().unwrap();
 		assert_eq!(response, serde_json::Value::Null);
@@ -244,15 +244,15 @@ async fn batched_notifs_works() {
 	// Ensure that subscription is returned back to the correct handle
 	// and is handled separately from ordinary notifications.
 	{
-		let mut nh: Subscription<String> =
+		let mut nh: Subscription<_, String> =
 			client.subscribe("sub", rpc_params![], "unsub").with_default_timeout().await.unwrap().unwrap();
 		let response: String = nh.next().with_default_timeout().await.unwrap().unwrap().unwrap();
 		assert_eq!("sub_notif", response);
 	}
 
 	// Ensure that method notif is returned back to the correct handle.
 	{
-		let mut nh: Subscription<String> =
+		let mut nh: Subscription<_, String> =
 			client.subscribe_to_method("sub").with_default_timeout().await.unwrap().unwrap();
 		let response: String = nh.next().with_default_timeout().await.unwrap().unwrap().unwrap();
 		assert_eq!("method_notif", response);
@@ -279,7 +279,7 @@ async fn notification_close_on_lagging() {
 		.await
 		.unwrap()
 		.unwrap();
-	let mut nh: Subscription<String> =
+	let mut nh: Subscription<_, String> =
 		client.subscribe_to_method("test").with_default_timeout().await.unwrap().unwrap();
 
 	// Don't poll the notification stream for 2 seconds, should be full now.
@@ -297,7 +297,7 @@ async fn notification_close_on_lagging() {
 	assert!(nh.next().with_default_timeout().await.unwrap().is_none());
 
 	// The same subscription should be possible to register again.
-	let mut other_nh: Subscription<String> =
+	let mut other_nh: Subscription<_, String> =
 		client.subscribe_to_method("test").with_default_timeout().await.unwrap().unwrap();
 
 	// check that the new subscription works.

core/src/client/async_client/mod.rs

@@ -360,14 +360,16 @@ impl<L> ClientBuilder<L> {
 
 		tokio::spawn(wait_for_shutdown(send_receive_task_sync_rx, client_dropped_rx, disconnect_reason.clone()));
 
-		Client {
+		let inner = ClientInner {
 			to_back: to_back.clone(),
 			service: self.service_builder.service(RpcService::new(to_back.clone())),
 			request_timeout: self.request_timeout,
 			error: ErrorFromBack::new(to_back, disconnect_reason),
 			id_manager: RequestIdManager::new(self.id_kind),
 			on_exit: Some(client_dropped_tx),
-		}
+		};
+
+		Client { inner: Arc::new(inner) }
 	}
 
 	/// Build the client with given transport.
@@ -430,9 +432,8 @@ impl<L> ClientBuilder<L> {
 	}
 }
 
-/// Generic asynchronous client.
 #[derive(Debug)]
-pub struct Client<L = RpcLogger<RpcService>> {
+struct ClientInner<L = RpcLogger<RpcService>> {
 	/// Channel to send requests to the background task.
 	to_back: mpsc::Sender<FrontToBack>,
 	error: ErrorFromBack,
@@ -445,6 +446,21 @@ pub struct Client<L = RpcLogger<RpcService>> {
 	service: L,
 }
 
+impl<L> Drop for ClientInner<L> {
+	fn drop(&mut self) {
+		if let Some(e) = self.on_exit.take() {
+			let _ = e.send(());
+		}
+	}
+}
+
+/// Generic asynchronous client.
+#[derive(Debug)]
+#[repr(transparent)]
+pub struct Client<L = RpcLogger<RpcService>> {
+	inner: Arc<ClientInner<L>>
+}
+
 impl Client<Identity> {
 	/// Create a builder for the client.
 	pub fn builder() -> ClientBuilder {
@@ -455,13 +471,13 @@ impl Client<Identity> {
 impl<L> Client<L> {
 	/// Checks if the client is connected to the target.
 	pub fn is_connected(&self) -> bool {
-		!self.to_back.is_closed()
+		!self.inner.to_back.is_closed()
 	}
 
 	async fn run_future_until_timeout<T>(&self, fut: impl Future<Output = Result<T, Error>>) -> Result<T, Error> {
 		tokio::pin!(fut);
 
-		match futures_util::future::select(fut, futures_timer::Delay::new(self.request_timeout)).await {
+		match futures_util::future::select(fut, futures_timer::Delay::new(self.inner.request_timeout)).await {
 			Either::Left((Ok(r), _)) => Ok(r),
 			Either::Left((Err(Error::ServiceDisconnect), _)) => Err(self.on_disconnect().await),
 			Either::Left((Err(e), _)) => Err(e),
@@ -476,20 +492,18 @@ impl<L> Client<L> {
 	///
 	/// This method is cancel safe.
 	pub async fn on_disconnect(&self) -> Error {
-		self.error.read_error().await
+		self.inner.error.read_error().await
 	}
 
 	/// Returns configured request timeout.
 	pub fn request_timeout(&self) -> Duration {
-		self.request_timeout
+		self.inner.request_timeout
 	}
 }
 
-impl<L> Drop for Client<L> {
-	fn drop(&mut self) {
-		if let Some(e) = self.on_exit.take() {
-			let _ = e.send(());
-		}
+impl<L> Clone for Client<L> {
+	fn clone(&self) -> Self {
+		Self { inner: self.inner.clone() }
 	}
 }
 
@@ -508,9 +522,9 @@ where
 	{
 		async {
 			// NOTE: we use this to guard against max number of concurrent requests.
-			let _req_id = self.id_manager.next_request_id();
+			let _req_id = self.inner.id_manager.next_request_id();
 			let params = params.to_rpc_params()?.map(StdCow::Owned);
-			let fut = self.service.notification(jsonrpsee_types::Notification::new(method.into(), params));
+			let fut = self.inner.service.notification(jsonrpsee_types::Notification::new(method.into(), params));
 			self.run_future_until_timeout(fut).await?;
 			Ok(())
 		}
@@ -522,9 +536,9 @@ where
 		Params: ToRpcParams + Send,
 	{
 		async {
-			let id = self.id_manager.next_request_id();
+			let id = self.inner.id_manager.next_request_id();
 			let params = params.to_rpc_params()?;
-			let fut = self.service.call(Request::borrowed(method, params.as_deref(), id.clone()));
+			let fut = self.inner.service.call(Request::borrowed(method, params.as_deref(), id.clone()));
 			let rp = self.run_future_until_timeout(fut).await?;
 			let success = ResponseSuccess::try_from(rp.into_response().into_inner())?;
 
@@ -541,15 +555,15 @@ where
 	{
 		async {
 			let batch = batch.build()?;
-			let id = self.id_manager.next_request_id();
+			let id = self.inner.id_manager.next_request_id();
 			let id_range = generate_batch_id_range(id, batch.len() as u64)?;
 
 			let mut b = Batch::with_capacity(batch.len());
 
 			for ((method, params), id) in batch.into_iter().zip(id_range.clone()) {
 				b.push(Request {
 					jsonrpc: TwoPointZero,
-					id: self.id_manager.as_id_kind().into_id(id),
+					id: self.inner.id_manager.as_id_kind().into_id(id),
 					method: method.into(),
 					params: params.map(StdCow::Owned),
 					extensions: Extensions::new(),
@@ -558,7 +572,7 @@ where
 
 			b.extensions_mut().insert(IsBatch { id_range });
 
-			let fut = self.service.batch(b);
+			let fut = self.inner.service.batch(b);
 			let json_values = self.run_future_until_timeout(fut).await?;
 
 			let mut responses = Vec::with_capacity(json_values.len());
@@ -592,6 +606,8 @@ where
 		> + Send
 		+ Sync,
 {
+	type SubscriptionClient = Self;
+
 	/// Send a subscription request to the server.
 	///
 	/// The `subscribe_method` and `params` are used to ask for the subscription towards the
@@ -601,7 +617,7 @@ where
 		subscribe_method: &'a str,
 		params: Params,
 		unsubscribe_method: &'a str,
-	) -> impl Future<Output = Result<Subscription<Notif>, Error>> + Send
+	) -> impl Future<Output = Result<Subscription<Self::SubscriptionClient, Notif>, Error>> + Send
 	where
 		Params: ToRpcParams + Send,
 		Notif: DeserializeOwned,
@@ -611,8 +627,8 @@ where
 				return Err(RegisterMethodError::SubscriptionNameConflict(unsubscribe_method.to_owned()).into());
 			}
 
-			let req_id_sub = self.id_manager.next_request_id();
-			let req_id_unsub = self.id_manager.next_request_id();
+			let req_id_sub = self.inner.id_manager.next_request_id();
+			let req_id_unsub = self.inner.id_manager.next_request_id();
 			let params = params.to_rpc_params()?;
 
 			let mut ext = Extensions::new();
@@ -626,24 +642,25 @@ where
 				extensions: ext,
 			};
 
-			let fut = self.service.call(req);
+			let fut = self.inner.service.call(req);
 			let sub = self
 				.run_future_until_timeout(fut)
 				.await?
 				.into_subscription()
 				.expect("Extensions set to subscription, must return subscription; qed");
-			Ok(Subscription::new(self.to_back.clone(), sub.stream, SubscriptionKind::Subscription(sub.sub_id)))
+			Ok(Subscription::new(self.clone(), self.inner.to_back.clone(), sub.stream, SubscriptionKind::Subscription(sub.sub_id)))
 		}
 	}
 
 	/// Subscribe to a specific method.
-	fn subscribe_to_method<N>(&self, method: &str) -> impl Future<Output = Result<Subscription<N>, Error>> + Send
+	fn subscribe_to_method<N>(&self, method: &str) -> impl Future<Output = Result<Subscription<Self::SubscriptionClient, N>, Error>> + Send
 	where
 		N: DeserializeOwned,
 	{
 		async {
 			let (send_back_tx, send_back_rx) = oneshot::channel();
 			if self
+				.inner
 				.to_back
 				.clone()
 				.send(FrontToBack::RegisterNotification(RegisterNotificationMessage {
@@ -656,15 +673,15 @@ where
 				return Err(self.on_disconnect().await);
 			}
 
-			let res = call_with_timeout(self.request_timeout, send_back_rx).await;
+			let res = call_with_timeout(self.inner.request_timeout, send_back_rx).await;
 
 			let (rx, method) = match res {
 				Ok(Ok(val)) => val,
 				Ok(Err(err)) => return Err(err),
 				Err(_) => return Err(self.on_disconnect().await),
 			};
 
-			Ok(Subscription::new(self.to_back.clone(), rx, SubscriptionKind::Method(method)))
+			Ok(Subscription::new(self.clone(), self.inner.to_back.clone(), rx, SubscriptionKind::Method(method)))
 		}
 	}
 }

core/src/client/mod.rs

@@ -119,6 +119,8 @@ pub trait ClientT {
 
 /// [JSON-RPC](https://www.jsonrpc.org/specification) client interface that can make requests, notifications and subscriptions.
 pub trait SubscriptionClientT: ClientT {
+	type SubscriptionClient;
+
 	/// Initiate a subscription by performing a JSON-RPC method call where the server responds with
 	/// a `Subscription ID` that is used to fetch messages on that subscription,
 	///
@@ -136,7 +138,7 @@ pub trait SubscriptionClientT: ClientT {
 		subscribe_method: &'a str,
 		params: Params,
 		unsubscribe_method: &'a str,
-	) -> impl Future<Output = Result<Subscription<Notif>, Error>> + Send
+	) -> impl Future<Output = Result<Subscription<Self::SubscriptionClient, Notif>, Error>> + Send
 	where
 		Params: ToRpcParams + Send,
 		Notif: DeserializeOwned;
@@ -148,7 +150,7 @@ pub trait SubscriptionClientT: ClientT {
 	fn subscribe_to_method<Notif>(
 		&self,
 		method: &str,
-	) -> impl Future<Output = Result<Subscription<Notif>, Error>> + Send
+	) -> impl Future<Output = Result<Subscription<Self::SubscriptionClient, Notif>, Error>> + Send
 	where
 		Notif: DeserializeOwned;
 }
@@ -272,7 +274,7 @@ pub enum SubscriptionCloseReason {
 /// You can call [`Subscription::close_reason`] to determine why
 /// the subscription was closed.
 #[derive(Debug)]
-pub struct Subscription<Notif> {
+pub struct Subscription<Client, Notif> {
 	is_closed: bool,
 	/// Channel to send requests to the background task.
 	to_back: mpsc::Sender<FrontToBack>,
@@ -282,16 +284,18 @@ pub struct Subscription<Notif> {
 	kind: Option<SubscriptionKind>,
 	/// Marker in order to pin the `Notif` parameter.
 	marker: PhantomData<Notif>,
+	/// Keep client alive at least until subscription is dropped
+	_client: Client,
 }
 
 // `Subscription` does not automatically implement this due to `PhantomData<Notif>`,
 // but type type has no need to be pinned.
-impl<Notif> std::marker::Unpin for Subscription<Notif> {}
+impl<Client, Notif> std::marker::Unpin for Subscription<Client, Notif> {}
 
-impl<Notif> Subscription<Notif> {
+impl<Client, Notif> Subscription<Client, Notif> {
 	/// Create a new subscription.
-	fn new(to_back: mpsc::Sender<FrontToBack>, rx: SubscriptionReceiver, kind: SubscriptionKind) -> Self {
-		Self { to_back, rx, kind: Some(kind), marker: PhantomData, is_closed: false }
+	fn new(client: Client, to_back: mpsc::Sender<FrontToBack>, rx: SubscriptionReceiver, kind: SubscriptionKind) -> Self {
+		Self { _client: client, to_back, rx, kind: Some(kind), marker: PhantomData, is_closed: false }
 	}
 
 	/// Return the subscription type and, if applicable, ID.
@@ -404,7 +408,7 @@ enum FrontToBack {
 	SubscriptionClosed(SubscriptionId<'static>),
 }
 
-impl<Notif> Subscription<Notif>
+impl<Client, Notif> Subscription<Client, Notif>
 where
 	Notif: DeserializeOwned,
 {
@@ -421,7 +425,7 @@ where
 	}
 }
 
-impl<Notif> Stream for Subscription<Notif>
+impl<Client, Notif> Stream for Subscription<Client, Notif>
 where
 	Notif: DeserializeOwned,
 {
@@ -439,7 +443,7 @@ where
 	}
 }
 
-impl<Notif> Drop for Subscription<Notif> {
+impl<Client, Notif> Drop for Subscription<Client, Notif> {
 	fn drop(&mut self) {
 		// We can't actually guarantee that this goes through. If the background task is busy, then
 		// the channel's buffer will be full.