Plumb RPC listener up to caller

prdoc/pr_5038.prdoc

@@ -0,0 +1,15 @@
+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: Plumb RPC listener up to caller
+
+doc:
+  - audience: Node Dev
+    description:
+      This PR allows the RPC server's socket address to be returned when initializing the server.
+      This allows the library consumer to easily programmatically determine which port the RPC server is listening on.
+crates:
+  - name: sc-rpc-server
+    bump: major
+  - name: sc-service
+    bump: major

substrate/client/rpc-servers/src/lib.rs

@@ -28,7 +28,8 @@ use std::{error::Error as StdError, net::SocketAddr, num::NonZeroU32, sync::Arc,
 use jsonrpsee::{
 	core::BoxError,
 	server::{
-		serve_with_graceful_shutdown, stop_channel, ws, PingConfig, StopHandle, TowerServiceBuilder,
+		serve_with_graceful_shutdown, stop_channel, ws, PingConfig, ServerHandle, StopHandle,
+		TowerServiceBuilder,
 	},
 	Methods, RpcModule,
 };
@@ -49,8 +50,30 @@ pub use middleware::{Metrics, MiddlewareLayer, RpcMetrics};
 
 const MEGABYTE: u32 = 1024 * 1024;
 
-/// Type alias for the JSON-RPC server.
-pub type Server = jsonrpsee::server::ServerHandle;
+/// Type to encapsulate the server handle and listening address.
+pub struct Server {
+	/// Handle to the rpc server
+	handle: ServerHandle,
+	/// Listening address of the server
+	listen_addr: Option<SocketAddr>,
+}
+
+impl Server {
+	/// Creates a new Server.
+	pub fn new(handle: ServerHandle, listen_addr: Option<SocketAddr>) -> Server {
+		Server { handle, listen_addr }
+	}
+
+	/// Returns the `jsonrpsee::server::ServerHandle` for this Server. Can be used to stop the server.
+	pub fn handle(&self) -> &ServerHandle {
+		&self.handle
+	}
+
+	/// The listen address for the running RPC service.
+	pub fn listen_addr(&self) -> Option<&SocketAddr> {
+		self.listen_addr.as_ref()
+	}
+}
 
 /// RPC server configuration.
 #[derive(Debug)]
@@ -264,5 +287,5 @@ where
 		format_cors(cors)
 	);
 
-	Ok(server_handle)
+	Ok(Server::new(server_handle, local_addr))
 }

substrate/client/service/src/builder.rs

@@ -19,7 +19,7 @@
 use crate::{
 	build_network_future, build_system_rpc_future,
 	client::{Client, ClientConfig},
-	config::{Configuration, KeystoreConfig, PrometheusConfig},
+	config::{Configuration, KeystoreConfig, Multiaddr, PrometheusConfig},
 	error::Error,
 	metrics::MetricsService,
 	start_rpc_servers, BuildGenesisBlock, GenesisBlockBuilder, RpcHandlers, SpawnTaskHandle,
@@ -43,6 +43,7 @@ use sc_executor::{
 use sc_keystore::LocalKeystore;
 use sc_network::{
 	config::{FullNetworkConfiguration, SyncMode},
+	multiaddr::Protocol,
 	service::{
 		traits::{PeerStore, RequestResponseConfig},
 		NotificationMetrics,
@@ -376,6 +377,19 @@ pub struct SpawnTasksParams<'a, TBl: BlockT, TCl, TExPool, TRpc, Backend> {
 	pub telemetry: Option<&'a mut Telemetry>,
 }
 
+// Wrapper for HTTP and WS servers that makes sure they are properly shut down.
+mod waiting {
+	pub struct Server(pub Option<jsonrpsee::server::ServerHandle>);
+
+	impl Drop for Server {
+		fn drop(&mut self) {
+			if let Some(server) = self.0.take() {
+				// This doesn't not wait for the server to be stopped but fires the signal.
+				let _ = server.stop();
+			}
+		}
+	}
+}
 /// Spawn the tasks that are required to run a node.
 pub fn spawn_tasks<TBl, TBackend, TExPool, TRpc, TCl>(
 	params: SpawnTasksParams<TBl, TCl, TExPool, TRpc, TBackend>,
@@ -506,7 +520,17 @@ where
 	};
 
 	let rpc = start_rpc_servers(&config, gen_rpc_module, rpc_id_provider)?;
-	let rpc_handlers = RpcHandlers::new(Arc::new(gen_rpc_module(sc_rpc::DenyUnsafe::No)?.into()));
+	let listen_addrs = match rpc.listen_addr() {
+		Some(socket_addr) => {
+			let mut multiaddr: Multiaddr = socket_addr.ip().into();
+			multiaddr.push(Protocol::Tcp(socket_addr.port()));
+			vec![multiaddr]
+		},
+		None => vec![],
+	};
+
+	let rpc_handlers =
+		RpcHandlers::new(Arc::new(gen_rpc_module(sc_rpc::DenyUnsafe::No)?.into()), listen_addrs);
 
 	// Spawn informant task
 	spawn_handle.spawn(
@@ -515,7 +539,7 @@ where
 		sc_informant::build(client.clone(), network, sync_service.clone()),
 	);
 
-	task_manager.keep_alive((config.base_path, rpc));
+	task_manager.keep_alive((config.base_path, waiting::Server(Some(rpc.handle().to_owned()))));
 
 	Ok(rpc_handlers)
 }

substrate/client/service/src/lib.rs

@@ -34,6 +34,7 @@ mod client;
 mod metrics;
 mod task_manager;
 
+use crate::config::Multiaddr;
 use std::{collections::HashMap, net::SocketAddr};
 
 use codec::{Decode, Encode};
@@ -47,6 +48,7 @@ use sc_network::{
 };
 use sc_network_sync::SyncingService;
 use sc_network_types::PeerId;
+use sc_rpc_server::Server;
 use sc_utils::mpsc::TracingUnboundedReceiver;
 use sp_blockchain::HeaderMetadata;
 use sp_consensus::SyncOracle;
@@ -97,14 +99,22 @@ pub use task_manager::{SpawnTaskHandle, Task, TaskManager, TaskRegistry, DEFAULT
 
 const DEFAULT_PROTOCOL_ID: &str = "sup";
 
-/// RPC handlers that can perform RPC queries.
+/// A running RPC service that can perform in-memory RPC queries.
 #[derive(Clone)]
-pub struct RpcHandlers(Arc<RpcModule<()>>);
+pub struct RpcHandlers {
+	// This is legacy and may be removed at some point, it was for WASM stuff before smoldot was a
+	// thing. https://github.com/paritytech/polkadot-sdk/pull/5038#discussion_r1694971805
+	rpc_module: Arc<RpcModule<()>>,
+
+	// This can be used to introspect the port the RPC server is listening on. SDK consumers are
+	// depending on this and it should be supported even if in-memory query support is removed.
+	listen_addresses: Vec<Multiaddr>,
+}
 
 impl RpcHandlers {
 	/// Create PRC handlers instance.
-	pub fn new(inner: Arc<RpcModule<()>>) -> Self {
-		Self(inner)
+	pub fn new(rpc_module: Arc<RpcModule<()>>, listen_addresses: Vec<Multiaddr>) -> Self {
+		Self { rpc_module, listen_addresses }
 	}
 
 	/// Starts an RPC query.
@@ -126,12 +136,17 @@ impl RpcHandlers {
 		// This limit is used to prevent panics and is large enough.
 		const TOKIO_MPSC_MAX_SIZE: usize = tokio::sync::Semaphore::MAX_PERMITS;
 
-		self.0.raw_json_request(json_query, TOKIO_MPSC_MAX_SIZE).await
+		self.rpc_module.raw_json_request(json_query, TOKIO_MPSC_MAX_SIZE).await
 	}
 
 	/// Provides access to the underlying `RpcModule`
 	pub fn handle(&self) -> Arc<RpcModule<()>> {
-		self.0.clone()
+		self.rpc_module.clone()
+	}
+
+	/// Provides access to listen addresses
+	pub fn listen_addresses(&self) -> &[Multiaddr] {
+		&self.listen_addresses[..]
 	}
 }
 
@@ -359,26 +374,12 @@ pub async fn build_system_rpc_future<
 	debug!("`NetworkWorker` has terminated, shutting down the system RPC future.");
 }
 
-// Wrapper for HTTP and WS servers that makes sure they are properly shut down.
-mod waiting {
-	pub struct Server(pub Option<sc_rpc_server::Server>);
-
-	impl Drop for Server {
-		fn drop(&mut self) {
-			if let Some(server) = self.0.take() {
-				// This doesn't not wait for the server to be stopped but fires the signal.
-				let _ = server.stop();
-			}
-		}
-	}
-}
-
 /// Starts RPC servers.
 pub fn start_rpc_servers<R>(
 	config: &Configuration,
 	gen_rpc_module: R,
 	rpc_id_provider: Option<Box<dyn RpcSubscriptionIdProvider>>,
-) -> Result<Box<dyn std::any::Any + Send + Sync>, error::Error>
+) -> Result<Server, error::Error>
 where
 	R: Fn(sc_rpc::DenyUnsafe) -> Result<RpcModule<()>, Error>,
 {
@@ -425,7 +426,7 @@ where
 	match tokio::task::block_in_place(|| {
 		config.tokio_handle.block_on(sc_rpc_server::start_server(server_config))
 	}) {
-		Ok(server) => Ok(Box::new(waiting::Server(Some(server)))),
+		Ok(server) => Ok(server),
 		Err(e) => Err(Error::Application(e)),
 	}
 }