Merge pull request #3194 from tnull/2024-07-om-event-notifier

Add `Notifier` to `OnionMessenger`

Author: TheBlueMatt

lightning-background-processor/src/lib.rs

@@ -492,23 +492,28 @@ pub(crate) mod futures_util {
 	pub(crate) struct Selector<
 		A: Future<Output = ()> + Unpin,
 		B: Future<Output = ()> + Unpin,
-		C: Future<Output = bool> + Unpin,
+		C: Future<Output = ()> + Unpin,
+		D: Future<Output = bool> + Unpin,
 	> {
 		pub a: A,
 		pub b: B,
 		pub c: C,
+		pub d: D,
 	}
+
 	pub(crate) enum SelectorOutput {
 		A,
 		B,
-		C(bool),
+		C,
+		D(bool),
 	}
 
 	impl<
 			A: Future<Output = ()> + Unpin,
 			B: Future<Output = ()> + Unpin,
-			C: Future<Output = bool> + Unpin,
-		> Future for Selector<A, B, C>
+			C: Future<Output = ()> + Unpin,
+			D: Future<Output = bool> + Unpin,
+		> Future for Selector<A, B, C, D>
 	{
 		type Output = SelectorOutput;
 		fn poll(
@@ -527,15 +532,43 @@ pub(crate) mod futures_util {
 				Poll::Pending => {},
 			}
 			match Pin::new(&mut self.c).poll(ctx) {
+				Poll::Ready(()) => {
+					return Poll::Ready(SelectorOutput::C);
+				},
+				Poll::Pending => {},
+			}
+			match Pin::new(&mut self.d).poll(ctx) {
 				Poll::Ready(res) => {
-					return Poll::Ready(SelectorOutput::C(res));
+					return Poll::Ready(SelectorOutput::D(res));
 				},
 				Poll::Pending => {},
 			}
 			Poll::Pending
 		}
 	}
 
+	/// A selector that takes a future wrapped in an option that will be polled if it is `Some` and
+	/// will always be pending otherwise.
+	pub(crate) struct OptionalSelector<F: Future<Output = ()> + Unpin> {
+		pub optional_future: Option<F>,
+	}
+
+	impl<F: Future<Output = ()> + Unpin> Future for OptionalSelector<F> {
+		type Output = ();
+		fn poll(mut self: Pin<&mut Self>, ctx: &mut core::task::Context<'_>) -> Poll<Self::Output> {
+			match self.optional_future.as_mut() {
+				Some(f) => match Pin::new(f).poll(ctx) {
+					Poll::Ready(()) => {
+						self.optional_future.take();
+						Poll::Ready(())
+					},
+					Poll::Pending => Poll::Pending,
+				},
+				None => Poll::Pending,
+			}
+		}
+	}
+
 	// If we want to poll a future without an async context to figure out if it has completed or
 	// not without awaiting, we need a Waker, which needs a vtable...we fill it with dummy values
 	// but sadly there's a good bit of boilerplate here.
@@ -557,7 +590,7 @@ pub(crate) mod futures_util {
 #[cfg(feature = "futures")]
 use core::task;
 #[cfg(feature = "futures")]
-use futures_util::{dummy_waker, Selector, SelectorOutput};
+use futures_util::{dummy_waker, OptionalSelector, Selector, SelectorOutput};
 
 /// Processes background events in a future.
 ///
@@ -782,18 +815,25 @@ where
 		scorer,
 		should_break,
 		{
+			let om_fut = if let Some(om) = onion_messenger.as_ref() {
+				let fut = om.get_om().get_update_future();
+				OptionalSelector { optional_future: Some(fut) }
+			} else {
+				OptionalSelector { optional_future: None }
+			};
 			let fut = Selector {
 				a: channel_manager.get_cm().get_event_or_persistence_needed_future(),
 				b: chain_monitor.get_update_future(),
-				c: sleeper(if mobile_interruptable_platform {
+				c: om_fut,
+				d: sleeper(if mobile_interruptable_platform {
 					Duration::from_millis(100)
 				} else {
 					Duration::from_secs(FASTEST_TIMER)
 				}),
 			};
 			match fut.await {
-				SelectorOutput::A | SelectorOutput::B => {},
-				SelectorOutput::C(exit) => {
+				SelectorOutput::A | SelectorOutput::B | SelectorOutput::C => {},
+				SelectorOutput::D(exit) => {
 					should_break = exit;
 				},
 			}
@@ -938,11 +978,19 @@ impl BackgroundProcessor {
 				scorer,
 				stop_thread.load(Ordering::Acquire),
 				{
-					Sleeper::from_two_futures(
-						&channel_manager.get_cm().get_event_or_persistence_needed_future(),
-						&chain_monitor.get_update_future(),
-					)
-					.wait_timeout(Duration::from_millis(100));
+					let sleeper = if let Some(om) = onion_messenger.as_ref() {
+						Sleeper::from_three_futures(
+							&channel_manager.get_cm().get_event_or_persistence_needed_future(),
+							&chain_monitor.get_update_future(),
+							&om.get_om().get_update_future(),
+						)
+					} else {
+						Sleeper::from_two_futures(
+							&channel_manager.get_cm().get_event_or_persistence_needed_future(),
+							&chain_monitor.get_update_future(),
+						)
+					};
+					sleeper.wait_timeout(Duration::from_millis(100));
 				},
 				|_| Instant::now(),
 				|time: &Instant, dur| time.elapsed().as_secs() > dur,

lightning/src/onion_message/messenger.rs

@@ -34,6 +34,7 @@ use super::packet::{BIG_PACKET_HOP_DATA_LEN, ForwardControlTlvs, Packet, Payload
 use crate::util::async_poll::{MultiResultFuturePoller, ResultFuture};
 use crate::util::logger::{Logger, WithContext};
 use crate::util::ser::Writeable;
+use crate::util::wakers::{Future, Notifier};
 
 use core::fmt;
 use core::ops::Deref;
@@ -266,6 +267,9 @@ pub struct OnionMessenger<
 	pending_intercepted_msgs_events: Mutex<Vec<Event>>,
 	pending_peer_connected_events: Mutex<Vec<Event>>,
 	pending_events_processor: AtomicBool,
+	/// A [`Notifier`] used to wake up the background processor in case we have any [`Event`]s for
+	/// it to give to users.
+	event_notifier: Notifier,
 }
 
 /// [`OnionMessage`]s buffered to be sent.
@@ -1037,6 +1041,7 @@ macro_rules! drop_handled_events_and_abort { ($self: expr, $res: expr, $offset:
 		if $res.iter().any(|r| r.is_err()) {
 			// We failed handling some events. Return to have them eventually replayed.
 			$self.pending_events_processor.store(false, Ordering::Release);
+			$self.event_notifier.notify();
 			return;
 		}
 	}
@@ -1119,6 +1124,7 @@ where
 			pending_intercepted_msgs_events: Mutex::new(Vec::new()),
 			pending_peer_connected_events: Mutex::new(Vec::new()),
 			pending_events_processor: AtomicBool::new(false),
+			event_notifier: Notifier::new(),
 		}
 	}
 
@@ -1230,6 +1236,7 @@ where
 				Some(addresses) => {
 					e.insert(OnionMessageRecipient::pending_connection(addresses))
 						.enqueue_message(onion_message);
+					self.event_notifier.notify();
 					Ok(SendSuccess::BufferedAwaitingConnection(first_node_id))
 				},
 			},
@@ -1345,6 +1352,18 @@ where
 			return
 		}
 		pending_intercepted_msgs_events.push(event);
+		self.event_notifier.notify();
+	}
+
+	/// Gets a [`Future`] that completes when an event is available via
+	/// [`EventsProvider::process_pending_events`] or [`Self::process_pending_events_async`].
+	///
+	/// Note that callbacks registered on the [`Future`] MUST NOT call back into this
+	/// [`OnionMessenger`] and should instead register actions to be taken later.
+	///
+	/// [`EventsProvider::process_pending_events`]: crate::events::EventsProvider::process_pending_events
+	pub fn get_update_future(&self) -> Future {
+		self.event_notifier.get_future()
 	}
 
 	/// Processes any events asynchronously using the given handler.
@@ -1616,6 +1635,7 @@ where
 				pending_peer_connected_events.push(
 					Event::OnionMessagePeerConnected { peer_node_id: *their_node_id }
 				);
+				self.event_notifier.notify();
 			}
 		} else {
 			self.message_recipients.lock().unwrap().remove(their_node_id);

lightning/src/util/wakers.rs

@@ -244,10 +244,21 @@ impl Sleeper {
 		Self { notifiers: vec![Arc::clone(&future.state)] }
 	}
 	/// Constructs a new sleeper from two futures, allowing blocking on both at once.
-	// Note that this is the common case - a ChannelManager and ChainMonitor.
 	pub fn from_two_futures(fut_a: &Future, fut_b: &Future) -> Self {
 		Self { notifiers: vec![Arc::clone(&fut_a.state), Arc::clone(&fut_b.state)] }
 	}
+	/// Constructs a new sleeper from three futures, allowing blocking on all three at once.
+	///
+	// Note that this is the common case - a ChannelManager, a ChainMonitor, and an
+	// OnionMessenger.
+	pub fn from_three_futures(fut_a: &Future, fut_b: &Future, fut_c: &Future) -> Self {
+		let notifiers = vec![
+			Arc::clone(&fut_a.state),
+			Arc::clone(&fut_b.state),
+			Arc::clone(&fut_c.state)
+		];
+		Self { notifiers }
+	}
 	/// Constructs a new sleeper on many futures, allowing blocking on all at once.
 	pub fn new(futures: Vec<Future>) -> Self {
 		Self { notifiers: futures.into_iter().map(|f| Arc::clone(&f.state)).collect() }