Allow start from outer runtime

We add a `Node::start_with_runtime` method that allows to reuse a
pre-existing runtime, e.g., to avoid stacking runtime contexts when
running in a tokio async environment.

Author: tnull

src/event.rs

@@ -354,7 +354,7 @@ where
 	network_graph: Arc<Graph>,
 	payment_store: Arc<PaymentStore<L>>,
 	peer_store: Arc<PeerStore<L>>,
-	runtime: Arc<RwLock<Option<tokio::runtime::Runtime>>>,
+	runtime: Arc<RwLock<Option<Arc<tokio::runtime::Runtime>>>>,
 	logger: L,
 	config: Arc<Config>,
 }
@@ -369,7 +369,7 @@ where
 		channel_manager: Arc<ChannelManager>, connection_manager: Arc<ConnectionManager<L>>,
 		output_sweeper: Arc<Sweeper>, network_graph: Arc<Graph>,
 		payment_store: Arc<PaymentStore<L>>, peer_store: Arc<PeerStore<L>>,
-		runtime: Arc<RwLock<Option<tokio::runtime::Runtime>>>, logger: L, config: Arc<Config>,
+		runtime: Arc<RwLock<Option<Arc<tokio::runtime::Runtime>>>>, logger: L, config: Arc<Config>,
 	) -> Self {
 		Self {
 			event_queue,

src/lib.rs

@@ -171,7 +171,7 @@ uniffi::include_scaffolding!("ldk_node");
 ///
 /// Needs to be initialized and instantiated through [`Builder::build`].
 pub struct Node {
-	runtime: Arc<RwLock<Option<tokio::runtime::Runtime>>>,
+	runtime: Arc<RwLock<Option<Arc<tokio::runtime::Runtime>>>>,
 	stop_sender: tokio::sync::watch::Sender<()>,
 	event_handling_stopped_sender: tokio::sync::watch::Sender<()>,
 	config: Arc<Config>,
@@ -211,6 +211,20 @@ impl Node {
 	/// After this returns, the [`Node`] instance can be controlled via the provided API methods in
 	/// a thread-safe manner.
 	pub fn start(&self) -> Result<(), Error> {
+		let runtime =
+			Arc::new(tokio::runtime::Builder::new_multi_thread().enable_all().build().unwrap());
+		self.start_with_runtime(runtime)
+	}
+
+	/// Starts the necessary background tasks (such as handling events coming from user input,
+	/// LDK/BDK, and the peer-to-peer network) on the the given `runtime`.
+	///
+	/// This allows to have LDK Node reuse an outer pre-existing runtime, e.g., to avoid stacking Tokio
+	/// runtime contexts.
+	///
+	/// After this returns, the [`Node`] instance can be controlled via the provided API methods in
+	/// a thread-safe manner.
+	pub fn start_with_runtime(&self, runtime: Arc<tokio::runtime::Runtime>) -> Result<(), Error> {
 		// Acquire a run lock and hold it until we're setup.
 		let mut runtime_lock = self.runtime.write().unwrap();
 		if runtime_lock.is_some() {
@@ -225,8 +239,6 @@ impl Node {
 			self.config.network
 		);
 
-		let runtime = tokio::runtime::Builder::new_multi_thread().enable_all().build().unwrap();
-
 		// Block to ensure we update our fee rate cache once on startup
 		let fee_estimator = Arc::clone(&self.fee_estimator);
 		let sync_logger = Arc::clone(&self.logger);
@@ -862,9 +874,6 @@ impl Node {
 			);
 		}
 
-		// Shutdown our runtime. By now ~no or only very few tasks should be left.
-		runtime.shutdown_timeout(Duration::from_secs(10));
-
 		log_info!(self.logger, "Shutdown complete.");
 		Ok(())
 	}

src/payment/bolt11.rs

@@ -33,7 +33,7 @@ use std::time::SystemTime;
 /// [BOLT 11]: https://github.com/lightning/bolts/blob/master/11-payment-encoding.md
 /// [`Node::bolt11_payment`]: crate::Node::bolt11_payment
 pub struct Bolt11Payment {
-	runtime: Arc<RwLock<Option<tokio::runtime::Runtime>>>,
+	runtime: Arc<RwLock<Option<Arc<tokio::runtime::Runtime>>>>,
 	channel_manager: Arc<ChannelManager>,
 	connection_manager: Arc<ConnectionManager<Arc<FilesystemLogger>>>,
 	keys_manager: Arc<KeysManager>,
@@ -46,7 +46,7 @@ pub struct Bolt11Payment {
 
 impl Bolt11Payment {
 	pub(crate) fn new(
-		runtime: Arc<RwLock<Option<tokio::runtime::Runtime>>>,
+		runtime: Arc<RwLock<Option<Arc<tokio::runtime::Runtime>>>>,
 		channel_manager: Arc<ChannelManager>,
 		connection_manager: Arc<ConnectionManager<Arc<FilesystemLogger>>>,
 		keys_manager: Arc<KeysManager>,

src/payment/bolt12.rs

@@ -28,15 +28,15 @@ use std::time::{Duration, SystemTime, UNIX_EPOCH};
 /// [BOLT 12]: https://github.com/lightning/bolts/blob/master/12-offer-encoding.md
 /// [`Node::bolt12_payment`]: crate::Node::bolt12_payment
 pub struct Bolt12Payment {
-	runtime: Arc<RwLock<Option<tokio::runtime::Runtime>>>,
+	runtime: Arc<RwLock<Option<Arc<tokio::runtime::Runtime>>>>,
 	channel_manager: Arc<ChannelManager>,
 	payment_store: Arc<PaymentStore<Arc<FilesystemLogger>>>,
 	logger: Arc<FilesystemLogger>,
 }
 
 impl Bolt12Payment {
 	pub(crate) fn new(
-		runtime: Arc<RwLock<Option<tokio::runtime::Runtime>>>,
+		runtime: Arc<RwLock<Option<Arc<tokio::runtime::Runtime>>>>,
 		channel_manager: Arc<ChannelManager>,
 		payment_store: Arc<PaymentStore<Arc<FilesystemLogger>>>, logger: Arc<FilesystemLogger>,
 	) -> Self {

src/payment/onchain.rs

@@ -15,7 +15,7 @@ use std::sync::{Arc, RwLock};
 ///
 /// [`Node::onchain_payment`]: crate::Node::onchain_payment
 pub struct OnchainPayment {
-	runtime: Arc<RwLock<Option<tokio::runtime::Runtime>>>,
+	runtime: Arc<RwLock<Option<Arc<tokio::runtime::Runtime>>>>,
 	wallet: Arc<Wallet>,
 	channel_manager: Arc<ChannelManager>,
 	config: Arc<Config>,
@@ -24,7 +24,7 @@ pub struct OnchainPayment {
 
 impl OnchainPayment {
 	pub(crate) fn new(
-		runtime: Arc<RwLock<Option<tokio::runtime::Runtime>>>, wallet: Arc<Wallet>,
+		runtime: Arc<RwLock<Option<Arc<tokio::runtime::Runtime>>>>, wallet: Arc<Wallet>,
 		channel_manager: Arc<ChannelManager>, config: Arc<Config>, logger: Arc<FilesystemLogger>,
 	) -> Self {
 		Self { runtime, wallet, channel_manager, config, logger }

src/payment/spontaneous.rs

@@ -23,7 +23,7 @@ use std::sync::{Arc, RwLock};
 ///
 /// [`Node::spontaneous_payment`]: crate::Node::spontaneous_payment
 pub struct SpontaneousPayment {
-	runtime: Arc<RwLock<Option<tokio::runtime::Runtime>>>,
+	runtime: Arc<RwLock<Option<Arc<tokio::runtime::Runtime>>>>,
 	channel_manager: Arc<ChannelManager>,
 	keys_manager: Arc<KeysManager>,
 	payment_store: Arc<PaymentStore<Arc<FilesystemLogger>>>,
@@ -33,7 +33,7 @@ pub struct SpontaneousPayment {
 
 impl SpontaneousPayment {
 	pub(crate) fn new(
-		runtime: Arc<RwLock<Option<tokio::runtime::Runtime>>>,
+		runtime: Arc<RwLock<Option<Arc<tokio::runtime::Runtime>>>>,
 		channel_manager: Arc<ChannelManager>, keys_manager: Arc<KeysManager>,
 		payment_store: Arc<PaymentStore<Arc<FilesystemLogger>>>, config: Arc<Config>,
 		logger: Arc<FilesystemLogger>,