Log before and after Event processing calls

At various points we've had issues where `Event` processing for a
user possibly is taking a long time, causing other things to stall.
However, due to lack of logging during `Event` processing itself
this can be rather difficult to debug. In
85eb814 we attempted to add
logging for this, but in doing so ended up with more verbose
logging than we were comfortable with.

Instead, here, we log only when we actually process an `Event`,
directly in the callsite passing the `Event` to the user.

Fixes #3331

Author: TheBlueMatt

lightning/src/chain/chainmonitor.rs

@@ -573,7 +573,7 @@ where C::Target: chain::Filter,
 		for funding_txo in mons_to_process {
 			let mut ev;
 			match super::channelmonitor::process_events_body!(
-				self.monitors.read().unwrap().get(&funding_txo).map(|m| &m.monitor), ev, handler(ev).await) {
+				self.monitors.read().unwrap().get(&funding_txo).map(|m| &m.monitor), self.logger, ev, handler(ev).await) {
 				Ok(()) => {},
 				Err(ReplayEvent ()) => {
 					self.event_notifier.notify();
@@ -909,7 +909,7 @@ impl<ChannelSigner: EcdsaChannelSigner, C: Deref, T: Deref, F: Deref, L: Deref,
 	/// [`BumpTransaction`]: events::Event::BumpTransaction
 	fn process_pending_events<H: Deref>(&self, handler: H) where H::Target: EventHandler {
 		for monitor_state in self.monitors.read().unwrap().values() {
-			match monitor_state.monitor.process_pending_events(&handler) {
+			match monitor_state.monitor.process_pending_events(&handler, &self.logger) {
 				Ok(()) => {},
 				Err(ReplayEvent ()) => {
 					self.event_notifier.notify();

lightning/src/chain/channelmonitor.rs

@@ -1236,7 +1236,7 @@ impl<Signer: EcdsaChannelSigner> Writeable for ChannelMonitorImpl<Signer> {
 }
 
 macro_rules! _process_events_body {
-	($self_opt: expr, $event_to_handle: expr, $handle_event: expr) => {
+	($self_opt: expr, $logger: expr, $event_to_handle: expr, $handle_event: expr) => {
 		loop {
 			let mut handling_res = Ok(());
 			let (pending_events, repeated_events);
@@ -1253,8 +1253,11 @@ macro_rules! _process_events_body {
 
 			let mut num_handled_events = 0;
 			for event in pending_events {
+				log_trace!($logger, "Handling event {:?}...", event);
 				$event_to_handle = event;
-				match $handle_event {
+				let event_handling_result = $handle_event;
+				log_trace!($logger, "Done handling event, result: {:?}", event_handling_result);
+				match event_handling_result {
 					Ok(()) => num_handled_events += 1,
 					Err(e) => {
 						// If we encounter an error we stop handling events and make sure to replay
@@ -1614,19 +1617,23 @@ impl<Signer: EcdsaChannelSigner> ChannelMonitor<Signer> {
 	///
 	/// [`SpendableOutputs`]: crate::events::Event::SpendableOutputs
 	/// [`BumpTransaction`]: crate::events::Event::BumpTransaction
-	pub fn process_pending_events<H: Deref>(&self, handler: &H) -> Result<(), ReplayEvent> where H::Target: EventHandler {
+	pub fn process_pending_events<H: Deref, L: Deref>(&self, handler: &H, logger: &L)
+	-> Result<(), ReplayEvent> where H::Target: EventHandler, L::Target: Logger {
 		let mut ev;
-		process_events_body!(Some(self), ev, handler.handle_event(ev))
+		process_events_body!(Some(self), logger, ev, handler.handle_event(ev))
 	}
 
 	/// Processes any events asynchronously.
 	///
 	/// See [`Self::process_pending_events`] for more information.
-	pub async fn process_pending_events_async<Future: core::future::Future<Output = Result<(), ReplayEvent>>, H: Fn(Event) -> Future>(
-		&self, handler: &H
-	) -> Result<(), ReplayEvent> {
+	pub async fn process_pending_events_async<
+		Future: core::future::Future<Output = Result<(), ReplayEvent>>, H: Fn(Event) -> Future,
+		L: Deref,
+	>(
+		&self, handler: &H, logger: &L,
+	) -> Result<(), ReplayEvent> where L::Target: Logger {
 		let mut ev;
-		process_events_body!(Some(self), ev, { handler(ev).await })
+		process_events_body!(Some(self), logger, ev, { handler(ev).await })
 	}
 
 	#[cfg(test)]

lightning/src/ln/channelmanager.rs

@@ -3321,8 +3321,11 @@ macro_rules! process_events_body {
 
 			let mut num_handled_events = 0;
 			for (event, action_opt) in pending_events {
+				log_trace!($self.logger, "Handling event {:?}...", event);
 				$event_to_handle = event;
-				match $handle_event {
+				let event_handling_result = $handle_event;
+				log_trace!($self.logger, "Done handling event, result: {:?}", event_handling_result);
+				match event_handling_result {
 					Ok(()) => {
 						if let Some(action) = action_opt {
 							post_event_actions.push(action);

lightning/src/onion_message/messenger.rs

@@ -1427,7 +1427,9 @@ where
 			for (node_id, recipient) in self.message_recipients.lock().unwrap().iter_mut() {
 				if let OnionMessageRecipient::PendingConnection(_, addresses, _) = recipient {
 					if let Some(addresses) = addresses.take() {
-						let future = ResultFuture::Pending(handler(Event::ConnectionNeeded { node_id: *node_id, addresses }));
+						let event = Event::ConnectionNeeded { node_id: *node_id, addresses };
+						log_trace!(self.logger, "Handling event {:?} async...", event);
+						let future = ResultFuture::Pending(handler(event));
 						futures.push(future);
 					}
 				}
@@ -1439,11 +1441,13 @@ where
 
 			for ev in intercepted_msgs {
 				if let Event::OnionMessageIntercepted { .. } = ev {} else { debug_assert!(false); }
+				log_trace!(self.logger, "Handling event {:?} async...", ev);
 				let future = ResultFuture::Pending(handler(ev));
 				futures.push(future);
 			}
 			// Let the `OnionMessageIntercepted` events finish before moving on to peer_connecteds
 			let res = MultiResultFuturePoller::new(futures).await;
+			log_trace!(self.logger, "Done handling events async, results: {:?}", res);
 			let mut res_iter = res.iter().skip(intercepted_msgs_offset);
 			drop_handled_events_and_abort!(self, res_iter, self.pending_intercepted_msgs_events);
 		}
@@ -1464,10 +1468,12 @@ where
 			} else {
 				let mut futures = Vec::new();
 				for event in peer_connecteds {
+					log_trace!(self.logger, "Handling event {:?} async...", event);
 					let future = ResultFuture::Pending(handler(event));
 					futures.push(future);
 				}
 				let res = MultiResultFuturePoller::new(futures).await;
+				log_trace!(self.logger, "Done handling events async, results: {:?}", res);
 				let mut res_iter = res.iter();
 				drop_handled_events_and_abort!(self, res_iter, self.pending_peer_connected_events);
 			}
@@ -1520,7 +1526,10 @@ where
 		for (node_id, recipient) in self.message_recipients.lock().unwrap().iter_mut() {
 			if let OnionMessageRecipient::PendingConnection(_, addresses, _) = recipient {
 				if let Some(addresses) = addresses.take() {
-					let _ = handler.handle_event(Event::ConnectionNeeded { node_id: *node_id, addresses });
+					let event = Event::ConnectionNeeded { node_id: *node_id, addresses };
+					log_trace!(self.logger, "Handling event {:?}...", event);
+					let res = handler.handle_event(event);
+					log_trace!(self.logger, "Done handling event, ignoring result: {:?}", res);
 				}
 			}
 		}
@@ -1544,7 +1553,10 @@ where
 		let mut handling_intercepted_msgs_failed = false;
 		let mut num_handled_intercepted_events = 0;
 		for ev in intercepted_msgs {
-			match handler.handle_event(ev) {
+			log_trace!(self.logger, "Handling event {:?}...", ev);
+			let res = handler.handle_event(ev);
+			log_trace!(self.logger, "Done handling event, result: {:?}", res);
+			match res {
 				Ok(()) => num_handled_intercepted_events += 1,
 				Err(ReplayEvent ()) => {
 					handling_intercepted_msgs_failed = true;
@@ -1566,7 +1578,10 @@ where
 
 		let mut num_handled_peer_connecteds = 0;
 		for ev in peer_connecteds {
-			match handler.handle_event(ev) {
+			log_trace!(self.logger, "Handling event {:?}...", ev);
+			let res = handler.handle_event(ev);
+			log_trace!(self.logger, "Done handling event, result: {:?}", res);
+			match res {
 				Ok(()) => num_handled_peer_connecteds += 1,
 				Err(ReplayEvent ()) => {
 					self.event_notifier.notify();