Keep multiple latest confirmed nonces at source in messages relay (paritytech#719)

* keep multiple latest confirmed nonces at source in messages relay

* post-merge fix

Author: svyatonik

bridges/relays/messages-relay/src/message_race_delivery.rs

@@ -29,7 +29,12 @@ use async_trait::async_trait;
 use bp_message_lane::{MessageNonce, UnrewardedRelayersState, Weight};
 use futures::stream::FusedStream;
 use relay_utils::FailedClient;
-use std::{collections::BTreeMap, marker::PhantomData, ops::RangeInclusive, time::Duration};
+use std::{
+	collections::{BTreeMap, VecDeque},
+	marker::PhantomData,
+	ops::RangeInclusive,
+	time::Duration,
+};
 
 /// Run message delivery race.
 pub async fn run<P: MessageLane>(
@@ -61,7 +66,7 @@ pub async fn run<P: MessageLane>(
 			max_messages_in_single_batch: params.max_messages_in_single_batch,
 			max_messages_weight_in_single_batch: params.max_messages_weight_in_single_batch,
 			max_messages_size_in_single_batch: params.max_messages_size_in_single_batch,
-			latest_confirmed_nonce_at_source: None,
+			latest_confirmed_nonces_at_source: VecDeque::new(),
 			target_nonces: None,
 			strategy: BasicStrategy::new(),
 		},
@@ -164,14 +169,17 @@ where
 	async fn nonces(
 		&self,
 		at_block: TargetHeaderIdOf<P>,
+		update_metrics: bool,
 	) -> Result<(TargetHeaderIdOf<P>, TargetClientNonces<DeliveryRaceTargetNoncesData>), Self::Error> {
 		let (at_block, latest_received_nonce) = self.client.latest_received_nonce(at_block).await?;
 		let (at_block, latest_confirmed_nonce) = self.client.latest_confirmed_received_nonce(at_block).await?;
 		let (at_block, unrewarded_relayers) = self.client.unrewarded_relayers_state(at_block).await?;
 
-		if let Some(metrics_msg) = self.metrics_msg.as_ref() {
-			metrics_msg.update_target_latest_received_nonce::<P>(latest_received_nonce);
-			metrics_msg.update_target_latest_confirmed_nonce::<P>(latest_confirmed_nonce);
+		if update_metrics {
+			if let Some(metrics_msg) = self.metrics_msg.as_ref() {
+				metrics_msg.update_target_latest_received_nonce::<P>(latest_received_nonce);
+				metrics_msg.update_target_latest_confirmed_nonce::<P>(latest_confirmed_nonce);
+			}
 		}
 
 		Ok((
@@ -221,8 +229,8 @@ struct MessageDeliveryStrategy<P: MessageLane> {
 	max_messages_weight_in_single_batch: Weight,
 	/// Maximal messages size in the single delivery transaction.
 	max_messages_size_in_single_batch: usize,
-	/// Latest confirmed nonce at the source client.
-	latest_confirmed_nonce_at_source: Option<MessageNonce>,
+	/// Latest confirmed nonces at the source client + the header id where we have first met this nonce.
+	latest_confirmed_nonces_at_source: VecDeque<(SourceHeaderIdOf<P>, MessageNonce)>,
 	/// Target nonces from the source client.
 	target_nonces: Option<TargetClientNonces<DeliveryRaceTargetNoncesData>>,
 	/// Basic delivery strategy.
@@ -259,8 +267,8 @@ impl<P: MessageLane> std::fmt::Debug for MessageDeliveryStrategy<P> {
 				&self.max_messages_size_in_single_batch,
 			)
 			.field(
-				"latest_confirmed_noncs_at_source",
-				&self.latest_confirmed_nonce_at_source,
+				"latest_confirmed_nonces_at_source",
+				&self.latest_confirmed_nonces_at_source,
 			)
 			.field("target_nonces", &self.target_nonces)
 			.field("strategy", &self.strategy)
@@ -292,17 +300,64 @@ impl<P: MessageLane> RaceStrategy<SourceHeaderIdOf<P>, TargetHeaderIdOf<P>, P::M
 		at_block: SourceHeaderIdOf<P>,
 		nonces: SourceClientNonces<Self::SourceNoncesRange>,
 	) {
-		self.latest_confirmed_nonce_at_source = nonces.confirmed_nonce;
+		if let Some(confirmed_nonce) = nonces.confirmed_nonce {
+			let is_confirmed_nonce_updated = self
+				.latest_confirmed_nonces_at_source
+				.back()
+				.map(|(_, prev_nonce)| *prev_nonce != confirmed_nonce)
+				.unwrap_or(true);
+			if is_confirmed_nonce_updated {
+				self.latest_confirmed_nonces_at_source
+					.push_back((at_block.clone(), confirmed_nonce));
+			}
+		}
 		self.strategy.source_nonces_updated(at_block, nonces)
 	}
 
-	fn target_nonces_updated(
+	fn best_target_nonces_updated(
 		&mut self,
 		nonces: TargetClientNonces<DeliveryRaceTargetNoncesData>,
 		race_state: &mut RaceState<SourceHeaderIdOf<P>, TargetHeaderIdOf<P>, P::MessagesProof>,
 	) {
-		self.target_nonces = Some(nonces.clone());
-		self.strategy.target_nonces_updated(
+		// best target nonces must always be ge than finalized target nonces
+		let mut target_nonces = self.target_nonces.take().unwrap_or_else(|| nonces.clone());
+		target_nonces.nonces_data = nonces.nonces_data.clone();
+		target_nonces.latest_nonce = std::cmp::max(target_nonces.latest_nonce, nonces.latest_nonce);
+		self.target_nonces = Some(target_nonces);
+
+		self.strategy.best_target_nonces_updated(
+			TargetClientNonces {
+				latest_nonce: nonces.latest_nonce,
+				nonces_data: (),
+			},
+			race_state,
+		)
+	}
+
+	fn finalized_target_nonces_updated(
+		&mut self,
+		nonces: TargetClientNonces<DeliveryRaceTargetNoncesData>,
+		race_state: &mut RaceState<SourceHeaderIdOf<P>, TargetHeaderIdOf<P>, P::MessagesProof>,
+	) {
+		if let Some(ref best_finalized_source_header_id_at_best_target) =
+			race_state.best_finalized_source_header_id_at_best_target
+		{
+			let oldest_header_number_to_keep = best_finalized_source_header_id_at_best_target.0;
+			while self
+				.latest_confirmed_nonces_at_source
+				.front()
+				.map(|(id, _)| id.0 < oldest_header_number_to_keep)
+				.unwrap_or(false)
+			{
+				self.latest_confirmed_nonces_at_source.pop_front();
+			}
+		}
+
+		if let Some(ref mut target_nonces) = self.target_nonces {
+			target_nonces.latest_nonce = std::cmp::max(target_nonces.latest_nonce, nonces.latest_nonce);
+		}
+
+		self.strategy.finalized_target_nonces_updated(
 			TargetClientNonces {
 				latest_nonce: nonces.latest_nonce,
 				nonces_data: (),
@@ -315,7 +370,14 @@ impl<P: MessageLane> RaceStrategy<SourceHeaderIdOf<P>, TargetHeaderIdOf<P>, P::M
 		&mut self,
 		race_state: &RaceState<SourceHeaderIdOf<P>, TargetHeaderIdOf<P>, P::MessagesProof>,
 	) -> Option<(RangeInclusive<MessageNonce>, Self::ProofParameters)> {
-		let latest_confirmed_nonce_at_source = self.latest_confirmed_nonce_at_source?;
+		let best_finalized_source_header_id_at_best_target =
+			race_state.best_finalized_source_header_id_at_best_target.clone()?;
+		let latest_confirmed_nonce_at_source = self
+			.latest_confirmed_nonces_at_source
+			.iter()
+			.take_while(|(id, _)| id.0 <= best_finalized_source_header_id_at_best_target.0)
+			.last()
+			.map(|(_, nonce)| *nonce)?;
 		let target_nonces = self.target_nonces.as_ref()?;
 
 		// There's additional condition in the message delivery race: target would reject messages
@@ -509,6 +571,7 @@ mod tests {
 			best_finalized_source_header_id_at_source: Some(header_id(1)),
 			best_finalized_source_header_id_at_best_target: Some(header_id(1)),
 			best_target_header_id: Some(header_id(1)),
+			best_finalized_target_header_id: Some(header_id(1)),
 			nonces_to_submit: None,
 			nonces_submitted: None,
 		};
@@ -519,7 +582,7 @@ mod tests {
 			max_messages_in_single_batch: 4,
 			max_messages_weight_in_single_batch: 4,
 			max_messages_size_in_single_batch: 4,
-			latest_confirmed_nonce_at_source: Some(19),
+			latest_confirmed_nonces_at_source: vec![(header_id(1), 19)].into_iter().collect(),
 			target_nonces: Some(TargetClientNonces {
 				latest_nonce: 19,
 				nonces_data: DeliveryRaceTargetNoncesData {
@@ -548,13 +611,17 @@ mod tests {
 				confirmed_nonce: Some(19),
 			},
 		);
-		race_strategy.strategy.target_nonces_updated(
-			TargetClientNonces {
-				latest_nonce: 19,
-				nonces_data: (),
-			},
-			&mut race_state,
-		);
+
+		let target_nonces = TargetClientNonces {
+			latest_nonce: 19,
+			nonces_data: (),
+		};
+		race_strategy
+			.strategy
+			.best_target_nonces_updated(target_nonces.clone(), &mut race_state);
+		race_strategy
+			.strategy
+			.finalized_target_nonces_updated(target_nonces, &mut race_state);
 
 		(race_state, race_strategy)
 	}
@@ -611,8 +678,12 @@ mod tests {
 
 		// if there are already `max_unconfirmed_nonces_at_target` messages on target,
 		// we need to wait until confirmations will be delivered by receiving race
-		strategy.latest_confirmed_nonce_at_source =
-			Some(strategy.target_nonces.as_ref().unwrap().latest_nonce - strategy.max_unconfirmed_nonces_at_target);
+		strategy.latest_confirmed_nonces_at_source = vec![(
+			header_id(1),
+			strategy.target_nonces.as_ref().unwrap().latest_nonce - strategy.max_unconfirmed_nonces_at_target,
+		)]
+		.into_iter()
+		.collect();
 		assert_eq!(strategy.select_nonces_to_deliver(&state), None);
 	}
 
@@ -622,7 +693,7 @@ mod tests {
 
 		// if there are new confirmed nonces on source, we want to relay this information
 		// to target to prune rewards queue
-		let prev_confirmed_nonce_at_source = strategy.latest_confirmed_nonce_at_source.unwrap();
+		let prev_confirmed_nonce_at_source = strategy.latest_confirmed_nonces_at_source.back().unwrap().1;
 		strategy.target_nonces.as_mut().unwrap().nonces_data.confirmed_nonce = prev_confirmed_nonce_at_source - 1;
 		assert_eq!(
 			strategy.select_nonces_to_deliver(&state),
@@ -650,7 +721,7 @@ mod tests {
 
 		// if there are already `max_unrewarded_relayer_entries_at_target` entries at target,
 		// we need to prove at least `messages_in_oldest_entry` rewards
-		let prev_confirmed_nonce_at_source = strategy.latest_confirmed_nonce_at_source.unwrap();
+		let prev_confirmed_nonce_at_source = strategy.latest_confirmed_nonces_at_source.back().unwrap().1;
 		{
 			let mut nonces_data = &mut strategy.target_nonces.as_mut().unwrap().nonces_data;
 			nonces_data.confirmed_nonce = prev_confirmed_nonce_at_source - 1;
@@ -667,7 +738,7 @@ mod tests {
 
 		// if there are already `max_unrewarded_relayer_entries_at_target` entries at target,
 		// we need to prove at least `messages_in_oldest_entry` rewards
-		let prev_confirmed_nonce_at_source = strategy.latest_confirmed_nonce_at_source.unwrap();
+		let prev_confirmed_nonce_at_source = strategy.latest_confirmed_nonces_at_source.back().unwrap().1;
 		{
 			let mut nonces_data = &mut strategy.target_nonces.as_mut().unwrap().nonces_data;
 			nonces_data.confirmed_nonce = prev_confirmed_nonce_at_source - 3;
@@ -747,12 +818,54 @@ mod tests {
 
 		// 1 delivery confirmation from target to source is still missing, so we may only
 		// relay 3 new messages
-		let prev_confirmed_nonce_at_source = strategy.latest_confirmed_nonce_at_source.unwrap();
-		strategy.latest_confirmed_nonce_at_source = Some(prev_confirmed_nonce_at_source - 1);
+		let prev_confirmed_nonce_at_source = strategy.latest_confirmed_nonces_at_source.back().unwrap().1;
+		strategy.latest_confirmed_nonces_at_source = vec![(header_id(1), prev_confirmed_nonce_at_source - 1)]
+			.into_iter()
+			.collect();
+		strategy.target_nonces.as_mut().unwrap().nonces_data.confirmed_nonce = prev_confirmed_nonce_at_source - 1;
+		assert_eq!(
+			strategy.select_nonces_to_deliver(&state),
+			Some(((20..=22), proof_parameters(false, 3)))
+		);
+	}
+
+	#[test]
+	fn message_delivery_strategy_waits_for_confirmed_nonce_header_to_appear_on_target() {
+		// 1 delivery confirmation from target to source is still missing, so we may deliver
+		// reward confirmation with our message delivery transaction. But the problem is that
+		// the reward has been paid at header 2 && this header is still unknown to target node.
+		//
+		// => so we can't deliver more than 3 messages
+		let (mut state, mut strategy) = prepare_strategy();
+		let prev_confirmed_nonce_at_source = strategy.latest_confirmed_nonces_at_source.back().unwrap().1;
+		strategy.latest_confirmed_nonces_at_source = vec![
+			(header_id(1), prev_confirmed_nonce_at_source - 1),
+			(header_id(2), prev_confirmed_nonce_at_source),
+		]
+		.into_iter()
+		.collect();
 		strategy.target_nonces.as_mut().unwrap().nonces_data.confirmed_nonce = prev_confirmed_nonce_at_source - 1;
+		state.best_finalized_source_header_id_at_best_target = Some(header_id(1));
 		assert_eq!(
 			strategy.select_nonces_to_deliver(&state),
 			Some(((20..=22), proof_parameters(false, 3)))
 		);
+
+		// the same situation, but the header 2 is known to the target node, so we may deliver reward confirmation
+		let (mut state, mut strategy) = prepare_strategy();
+		let prev_confirmed_nonce_at_source = strategy.latest_confirmed_nonces_at_source.back().unwrap().1;
+		strategy.latest_confirmed_nonces_at_source = vec![
+			(header_id(1), prev_confirmed_nonce_at_source - 1),
+			(header_id(2), prev_confirmed_nonce_at_source),
+		]
+		.into_iter()
+		.collect();
+		strategy.target_nonces.as_mut().unwrap().nonces_data.confirmed_nonce = prev_confirmed_nonce_at_source - 1;
+		state.best_finalized_source_header_id_at_source = Some(header_id(2));
+		state.best_finalized_source_header_id_at_best_target = Some(header_id(2));
+		assert_eq!(
+			strategy.select_nonces_to_deliver(&state),
+			Some(((20..=23), proof_parameters(true, 4)))
+		);
 	}
 }