Mortal conversion rate updater transactions (#1257)

* merge all similar update_conversion_rate functions

* stall timeout in conversion rate update loop

* fmt

* fix

bridges/relays/bin-substrate/src/chains/kusama_messages_to_polkadot.rs

@@ -16,14 +16,11 @@
 
 //! Kusama-to-Polkadot messages sync entrypoint.
 
-use codec::Encode;
 use frame_support::weights::Weight;
-use sp_core::{Bytes, Pair};
 
 use messages_relay::relay_strategy::MixStrategy;
 use relay_kusama_client::Kusama;
 use relay_polkadot_client::Polkadot;
-use relay_substrate_client::{Client, SignParam, TransactionSignScheme, UnsignedTransaction};
 use substrate_relay_helper::messages_lane::SubstrateMessageLane;
 
 /// Description of Kusama -> Polkadot messages bridge.
@@ -41,6 +38,13 @@ substrate_relay_helper::generate_mocked_receive_message_delivery_proof_call_buil
 	relay_kusama_client::runtime::Call::BridgePolkadotMessages,
 	relay_kusama_client::runtime::BridgePolkadotMessagesCall::receive_messages_delivery_proof
 );
+substrate_relay_helper::generate_mocked_update_conversion_rate_call_builder!(
+	Kusama,
+	KusamaMessagesToPolkadotUpdateConversionRateCallBuilder,
+	relay_kusama_client::runtime::Call::BridgePolkadotMessages,
+	relay_kusama_client::runtime::BridgePolkadotMessagesCall::update_pallet_parameter,
+	relay_kusama_client::runtime::BridgePolkadotMessagesParameter::PolkadotToKusamaConversionRate
+);
 
 impl SubstrateMessageLane for KusamaMessagesToPolkadot {
 	const SOURCE_TO_TARGET_CONVERSION_RATE_PARAMETER_NAME: Option<&'static str> =
@@ -68,42 +72,8 @@ impl SubstrateMessageLane for KusamaMessagesToPolkadot {
 	type ReceiveMessagesDeliveryProofCallBuilder =
 		KusamaMessagesToPolkadotReceiveMessagesDeliveryProofCallBuilder;
 
+	type TargetToSourceChainConversionRateUpdateBuilder =
+		KusamaMessagesToPolkadotUpdateConversionRateCallBuilder;
+
 	type RelayStrategy = MixStrategy;
 }
-
-/// Update Polkadot -> Kusama conversion rate, stored in Kusama runtime storage.
-pub(crate) async fn update_polkadot_to_kusama_conversion_rate(
-	client: Client<Kusama>,
-	signer: <Kusama as TransactionSignScheme>::AccountKeyPair,
-	updated_rate: f64,
-) -> anyhow::Result<()> {
-	let genesis_hash = *client.genesis_hash();
-	let signer_id = (*signer.public().as_array_ref()).into();
-	let (spec_version, transaction_version) = client.simple_runtime_version().await?;
-	client
-		.submit_signed_extrinsic(signer_id, move |_, transaction_nonce| {
-			Ok(Bytes(
-				Kusama::sign_transaction(SignParam {
-					spec_version,
-					transaction_version,
-					genesis_hash,
-					signer,
-					era: relay_substrate_client::TransactionEra::immortal(),
-					unsigned: UnsignedTransaction::new(
-						relay_kusama_client::runtime::Call::BridgePolkadotMessages(
-							relay_kusama_client::runtime::BridgePolkadotMessagesCall::update_pallet_parameter(
-								relay_kusama_client::runtime::BridgePolkadotMessagesParameter::PolkadotToKusamaConversionRate(
-									sp_runtime::FixedU128::from_float(updated_rate),
-								)
-							)
-						).into(),
-						transaction_nonce,
-					),
-				})?
-				.encode(),
-			))
-		})
-		.await
-		.map(drop)
-		.map_err(|err| anyhow::format_err!("{:?}", err))
-}

bridges/relays/bin-substrate/src/chains/millau_messages_to_rialto.rs

@@ -16,13 +16,9 @@
 
 //! Millau-to-Rialto messages sync entrypoint.
 
-use codec::Encode;
-use sp_core::{Bytes, Pair};
-
 use messages_relay::relay_strategy::MixStrategy;
 use relay_millau_client::Millau;
 use relay_rialto_client::Rialto;
-use relay_substrate_client::{Client, SignParam, TransactionSignScheme, UnsignedTransaction};
 use substrate_relay_helper::messages_lane::{
 	DirectReceiveMessagesDeliveryProofCallBuilder, DirectReceiveMessagesProofCallBuilder,
 	SubstrateMessageLane,
@@ -31,6 +27,13 @@ use substrate_relay_helper::messages_lane::{
 /// Description of Millau -> Rialto messages bridge.
 #[derive(Clone, Debug)]
 pub struct MillauMessagesToRialto;
+substrate_relay_helper::generate_direct_update_conversion_rate_call_builder!(
+	Millau,
+	MillauMessagesToRialtoUpdateConversionRateCallBuilder,
+	millau_runtime::Runtime,
+	millau_runtime::WithRialtoMessagesInstance,
+	millau_runtime::rialto_messages::MillauToRialtoMessagesParameter::RialtoToMillauConversionRate
+);
 
 impl SubstrateMessageLane for MillauMessagesToRialto {
 	const SOURCE_TO_TARGET_CONVERSION_RATE_PARAMETER_NAME: Option<&'static str> =
@@ -60,40 +63,8 @@ impl SubstrateMessageLane for MillauMessagesToRialto {
 		millau_runtime::WithRialtoMessagesInstance,
 	>;
 
+	type TargetToSourceChainConversionRateUpdateBuilder =
+		MillauMessagesToRialtoUpdateConversionRateCallBuilder;
+
 	type RelayStrategy = MixStrategy;
 }
-
-/// Update Rialto -> Millau conversion rate, stored in Millau runtime storage.
-pub(crate) async fn update_rialto_to_millau_conversion_rate(
-	client: Client<Millau>,
-	signer: <Millau as TransactionSignScheme>::AccountKeyPair,
-	updated_rate: f64,
-) -> anyhow::Result<()> {
-	let genesis_hash = *client.genesis_hash();
-	let signer_id = (*signer.public().as_array_ref()).into();
-	let (spec_version, transaction_version) = client.simple_runtime_version().await?;
-	client
-		.submit_signed_extrinsic(signer_id, move |_, transaction_nonce| {
-			Ok(Bytes(
-				Millau::sign_transaction(SignParam {
-					spec_version,
-					transaction_version,
-					genesis_hash,
-					signer,
-					era: relay_substrate_client::TransactionEra::immortal(),
-					unsigned: UnsignedTransaction::new(
-						millau_runtime::Call::from(millau_runtime::MessagesCall::update_pallet_parameter {
-							parameter: millau_runtime::rialto_messages::MillauToRialtoMessagesParameter::RialtoToMillauConversionRate(
-								sp_runtime::FixedU128::from_float(updated_rate),
-							),
-						}).into(),
-						transaction_nonce,
-					),
-				})?
-				.encode(),
-			))
-		})
-		.await
-		.map(drop)
-		.map_err(|err| anyhow::format_err!("{:?}", err))
-}

bridges/relays/bin-substrate/src/chains/polkadot_messages_to_kusama.rs

@@ -16,14 +16,10 @@
 
 //! Polkadot-to-Kusama messages sync entrypoint.
 
-use codec::Encode;
-use sp_core::{Bytes, Pair};
-
 use frame_support::weights::Weight;
 use messages_relay::relay_strategy::MixStrategy;
 use relay_kusama_client::Kusama;
 use relay_polkadot_client::Polkadot;
-use relay_substrate_client::{Client, SignParam, TransactionSignScheme, UnsignedTransaction};
 use substrate_relay_helper::messages_lane::SubstrateMessageLane;
 
 /// Description of Polkadot -> Kusama messages bridge.
@@ -41,6 +37,13 @@ substrate_relay_helper::generate_mocked_receive_message_delivery_proof_call_buil
 	relay_polkadot_client::runtime::Call::BridgeKusamaMessages,
 	relay_polkadot_client::runtime::BridgeKusamaMessagesCall::receive_messages_delivery_proof
 );
+substrate_relay_helper::generate_mocked_update_conversion_rate_call_builder!(
+	Polkadot,
+	PolkadotMessagesToKusamaUpdateConversionRateCallBuilder,
+	relay_polkadot_client::runtime::Call::BridgeKusamaMessages,
+	relay_polkadot_client::runtime::BridgeKusamaMessagesCall::update_pallet_parameter,
+	relay_polkadot_client::runtime::BridgeKusamaMessagesParameter::KusamaToPolkadotConversionRate
+);
 
 impl SubstrateMessageLane for PolkadotMessagesToKusama {
 	const SOURCE_TO_TARGET_CONVERSION_RATE_PARAMETER_NAME: Option<&'static str> =
@@ -68,42 +71,8 @@ impl SubstrateMessageLane for PolkadotMessagesToKusama {
 	type ReceiveMessagesDeliveryProofCallBuilder =
 		PolkadotMessagesToKusamaReceiveMessagesDeliveryProofCallBuilder;
 
+	type TargetToSourceChainConversionRateUpdateBuilder =
+		PolkadotMessagesToKusamaUpdateConversionRateCallBuilder;
+
 	type RelayStrategy = MixStrategy;
 }
-
-/// Update Kusama -> Polkadot conversion rate, stored in Polkadot runtime storage.
-pub(crate) async fn update_kusama_to_polkadot_conversion_rate(
-	client: Client<Polkadot>,
-	signer: <Polkadot as TransactionSignScheme>::AccountKeyPair,
-	updated_rate: f64,
-) -> anyhow::Result<()> {
-	let genesis_hash = *client.genesis_hash();
-	let signer_id = (*signer.public().as_array_ref()).into();
-	let (spec_version, transaction_version) = client.simple_runtime_version().await?;
-	client
-		.submit_signed_extrinsic(signer_id, move |_, transaction_nonce| {
-			Ok(Bytes(
-				Polkadot::sign_transaction(SignParam {
-					spec_version,
-					transaction_version,
-					genesis_hash,
-					signer,
-					era: relay_substrate_client::TransactionEra::immortal(),
-					unsigned: UnsignedTransaction::new(
-						relay_polkadot_client::runtime::Call::BridgeKusamaMessages(
-							relay_polkadot_client::runtime::BridgeKusamaMessagesCall::update_pallet_parameter(
-								relay_polkadot_client::runtime::BridgeKusamaMessagesParameter::KusamaToPolkadotConversionRate(
-									sp_runtime::FixedU128::from_float(updated_rate),
-								)
-							)
-						).into(),
-						transaction_nonce,
-					)
-				})?
-				.encode(),
-			))
-		})
-		.await
-		.map(drop)
-		.map_err(|err| anyhow::format_err!("{:?}", err))
-}

bridges/relays/bin-substrate/src/chains/rialto_messages_to_millau.rs

@@ -16,13 +16,9 @@
 
 //! Rialto-to-Millau messages sync entrypoint.
 
-use codec::Encode;
-use sp_core::{Bytes, Pair};
-
 use messages_relay::relay_strategy::MixStrategy;
 use relay_millau_client::Millau;
 use relay_rialto_client::Rialto;
-use relay_substrate_client::{Client, SignParam, TransactionSignScheme, UnsignedTransaction};
 use substrate_relay_helper::messages_lane::{
 	DirectReceiveMessagesDeliveryProofCallBuilder, DirectReceiveMessagesProofCallBuilder,
 	SubstrateMessageLane,
@@ -31,6 +27,13 @@ use substrate_relay_helper::messages_lane::{
 /// Description of Rialto -> Millau messages bridge.
 #[derive(Clone, Debug)]
 pub struct RialtoMessagesToMillau;
+substrate_relay_helper::generate_direct_update_conversion_rate_call_builder!(
+	Rialto,
+	RialtoMessagesToMillauUpdateConversionRateCallBuilder,
+	rialto_runtime::Runtime,
+	rialto_runtime::WithMillauMessagesInstance,
+	rialto_runtime::millau_messages::RialtoToMillauMessagesParameter::MillauToRialtoConversionRate
+);
 
 impl SubstrateMessageLane for RialtoMessagesToMillau {
 	const SOURCE_TO_TARGET_CONVERSION_RATE_PARAMETER_NAME: Option<&'static str> =
@@ -60,40 +63,8 @@ impl SubstrateMessageLane for RialtoMessagesToMillau {
 		rialto_runtime::WithMillauMessagesInstance,
 	>;
 
+	type TargetToSourceChainConversionRateUpdateBuilder =
+		RialtoMessagesToMillauUpdateConversionRateCallBuilder;
+
 	type RelayStrategy = MixStrategy;
 }
-
-/// Update Millau -> Rialto conversion rate, stored in Rialto runtime storage.
-pub(crate) async fn update_millau_to_rialto_conversion_rate(
-	client: Client<Rialto>,
-	signer: <Rialto as TransactionSignScheme>::AccountKeyPair,
-	updated_rate: f64,
-) -> anyhow::Result<()> {
-	let genesis_hash = *client.genesis_hash();
-	let signer_id = (*signer.public().as_array_ref()).into();
-	let (spec_version, transaction_version) = client.simple_runtime_version().await?;
-	client
-		.submit_signed_extrinsic(signer_id, move |_, transaction_nonce| {
-			Ok(Bytes(
-				Rialto::sign_transaction(SignParam {
-					spec_version,
-					transaction_version,
-					genesis_hash,
-					signer,
-					era: relay_substrate_client::TransactionEra::immortal(),
-					unsigned: UnsignedTransaction::new(
-						rialto_runtime::Call::from(rialto_runtime::MessagesCall::update_pallet_parameter {
-							parameter: rialto_runtime::millau_messages::RialtoToMillauMessagesParameter::MillauToRialtoConversionRate(
-								sp_runtime::FixedU128::from_float(updated_rate),
-							),
-						}).into(),
-						transaction_nonce,
-					)
-				})?
-				.encode(),
-			))
-		})
-		.await
-		.map(drop)
-		.map_err(|err| anyhow::format_err!("{:?}", err))
-}

bridges/relays/bin-substrate/src/chains/rococo_messages_to_wococo.rs

@@ -57,5 +57,7 @@ impl SubstrateMessageLane for RococoMessagesToWococo {
 	type ReceiveMessagesDeliveryProofCallBuilder =
 		RococoMessagesToWococoReceiveMessagesDeliveryProofCallBuilder;
 
+	type TargetToSourceChainConversionRateUpdateBuilder = ();
+
 	type RelayStrategy = MixStrategy;
 }

bridges/relays/bin-substrate/src/chains/wococo_messages_to_rococo.rs

@@ -58,5 +58,7 @@ impl SubstrateMessageLane for WococoMessagesToRococo {
 	type ReceiveMessagesDeliveryProofCallBuilder =
 		WococoMessagesToRococoReceiveMessagesDeliveryProofCallBuilder;
 
+	type TargetToSourceChainConversionRateUpdateBuilder = ();
+
 	type RelayStrategy = MixStrategy;
 }

bridges/relays/bin-substrate/src/cli/relay_headers_and_messages.rs

@@ -134,14 +134,8 @@ macro_rules! select_bridge {
 				type RightAccountIdConverter = bp_rialto::AccountIdConverter;
 
 				use crate::chains::{
-					millau_messages_to_rialto::{
+					millau_messages_to_rialto::MillauMessagesToRialto as LeftToRightMessageLane,
-						update_rialto_to_millau_conversion_rate as update_right_to_left_conversion_rate,
+					rialto_messages_to_millau::RialtoMessagesToMillau as RightToLeftMessageLane,
-						MillauMessagesToRialto as LeftToRightMessageLane,
-					},
-					rialto_messages_to_millau::{
-						update_millau_to_rialto_conversion_rate as update_left_to_right_conversion_rate,
-						RialtoMessagesToMillau as RightToLeftMessageLane,
-					},
 				};
 
 				async fn left_create_account(
@@ -181,22 +175,6 @@ macro_rules! select_bridge {
 					wococo_messages_to_rococo::WococoMessagesToRococo as RightToLeftMessageLane,
 				};
 
-				async fn update_right_to_left_conversion_rate(
-					_client: Client<Left>,
-					_signer: <Left as TransactionSignScheme>::AccountKeyPair,
-					_updated_rate: f64,
-				) -> anyhow::Result<()> {
-					Err(anyhow::format_err!("Conversion rate is not supported by this bridge"))
-				}
-
-				async fn update_left_to_right_conversion_rate(
-					_client: Client<Right>,
-					_signer: <Right as TransactionSignScheme>::AccountKeyPair,
-					_updated_rate: f64,
-				) -> anyhow::Result<()> {
-					Err(anyhow::format_err!("Conversion rate is not supported by this bridge"))
-				}
-
 				async fn left_create_account(
 					left_client: Client<Left>,
 					left_sign: <Left as TransactionSignScheme>::AccountKeyPair,
@@ -250,14 +228,8 @@ macro_rules! select_bridge {
 				type RightAccountIdConverter = bp_polkadot::AccountIdConverter;
 
 				use crate::chains::{
-					kusama_messages_to_polkadot::{
+					kusama_messages_to_polkadot::KusamaMessagesToPolkadot as LeftToRightMessageLane,
-						update_polkadot_to_kusama_conversion_rate as update_right_to_left_conversion_rate,
+					polkadot_messages_to_kusama::PolkadotMessagesToKusama as RightToLeftMessageLane,
-						KusamaMessagesToPolkadot as LeftToRightMessageLane,
-					},
-					polkadot_messages_to_kusama::{
-						update_kusama_to_polkadot_conversion_rate as update_left_to_right_conversion_rate,
-						PolkadotMessagesToKusama as RightToLeftMessageLane,
-					},
 				};
 
 				async fn left_create_account(
@@ -354,7 +326,15 @@ impl RelayHeadersAndMessages {
 						Left::NAME
 					)
 				};
-				substrate_relay_helper::conversion_rate_update::run_conversion_rate_update_loop(
+				substrate_relay_helper::conversion_rate_update::run_conversion_rate_update_loop::<
+					LeftToRightMessageLane,
+					Left,
+				>(
+					left_client.clone(),
+					TransactionParams {
+						signer: left_messages_pallet_owner.clone(),
+						mortality: left_transactions_mortality,
+					},
 					left_to_right_metrics
 						.target_to_source_conversion_rate
 						.as_ref()
@@ -371,21 +351,6 @@ impl RelayHeadersAndMessages {
 						.ok_or_else(format_err)?
 						.shared_value_ref(),
 					CONVERSION_RATE_ALLOWED_DIFFERENCE_RATIO,
-					move |new_rate| {
-						log::info!(
-							target: "bridge",
-							"Going to update {} -> {} (on {}) conversion rate to {}.",
-							Right::NAME,
-							Left::NAME,
-							Left::NAME,
-							new_rate,
-						);
-						update_right_to_left_conversion_rate(
-							left_client.clone(),
-							left_messages_pallet_owner.clone(),
-							new_rate,
-						)
-					},
 				);
 			}
 			if let Some(right_messages_pallet_owner) = right_messages_pallet_owner.clone() {
@@ -397,7 +362,15 @@ impl RelayHeadersAndMessages {
 						Right::NAME
 					)
 				};
-				substrate_relay_helper::conversion_rate_update::run_conversion_rate_update_loop(
+				substrate_relay_helper::conversion_rate_update::run_conversion_rate_update_loop::<
+					RightToLeftMessageLane,
+					Right,
+				>(
+					right_client.clone(),
+					TransactionParams {
+						signer: right_messages_pallet_owner.clone(),
+						mortality: right_transactions_mortality,
+					},
 					right_to_left_metrics
 						.target_to_source_conversion_rate
 						.as_ref()
@@ -414,21 +387,6 @@ impl RelayHeadersAndMessages {
 						.ok_or_else(format_err)?
 						.shared_value_ref(),
 					CONVERSION_RATE_ALLOWED_DIFFERENCE_RATIO,
-					move |new_rate| {
-						log::info!(
-							target: "bridge",
-							"Going to update {} -> {} (on {}) conversion rate to {}.",
-							Left::NAME,
-							Right::NAME,
-							Right::NAME,
-							new_rate,
-						);
-						update_left_to_right_conversion_rate(
-							right_client.clone(),
-							right_messages_pallet_owner.clone(),
-							new_rate,
-						)
-					},
 				);
 			}
 

bridges/relays/lib-substrate-relay/src/conversion_rate_update.rs

@@ -16,39 +16,143 @@
 
 //! Tools for updating conversion rate that is stored in the runtime storage.
 
+use crate::{messages_lane::SubstrateMessageLane, TransactionParams};
+
+use codec::Encode;
+use relay_substrate_client::{
+	transaction_stall_timeout, AccountIdOf, AccountKeyPairOf, CallOf, Chain, Client, SignParam,
+	TransactionEra, TransactionSignScheme, UnsignedTransaction,
+};
 use relay_utils::metrics::F64SharedRef;
-use std::{future::Future, time::Duration};
+use sp_core::{Bytes, Pair};
+use std::time::{Duration, Instant};
 
 /// Duration between updater iterations.
 const SLEEP_DURATION: Duration = Duration::from_secs(60);
 
+/// Duration which will almost never expire. Since changing conversion rate may require manual
+/// intervention (e.g. if call is made through `multisig` pallet), we don't want relayer to
+/// resubmit transaction often.
+const ALMOST_NEVER_DURATION: Duration = Duration::from_secs(60 * 60 * 24 * 30);
+
 /// Update-conversion-rate transaction status.
 #[derive(Debug, Clone, Copy, PartialEq)]
 enum TransactionStatus {
 	/// We have not submitted any transaction recently.
 	Idle,
 	/// We have recently submitted transaction that should update conversion rate.
-	Submitted(f64),
+	Submitted(Instant, f64),
+}
+
+/// Different ways of building 'update conversion rate' calls.
+pub trait UpdateConversionRateCallBuilder<C: Chain> {
+	/// Given conversion rate, build call that updates conversion rate in given chain runtime
+	/// storage.
+	fn build_update_conversion_rate_call(conversion_rate: f64) -> anyhow::Result<CallOf<C>>;
+}
+
+impl<C: Chain> UpdateConversionRateCallBuilder<C> for () {
+	fn build_update_conversion_rate_call(_conversion_rate: f64) -> anyhow::Result<CallOf<C>> {
+		Err(anyhow::format_err!("Conversion rate update is not supported at {}", C::NAME))
+	}
+}
+
+/// Macro that generates `UpdateConversionRateCallBuilder` implementation for the case when
+/// you have a direct access to the source chain runtime.
+#[rustfmt::skip]
+#[macro_export]
+macro_rules! generate_direct_update_conversion_rate_call_builder {
+	(
+		$source_chain:ident,
+		$mocked_builder:ident,
+		$runtime:ty,
+		$instance:ty,
+		$parameter:path
+	) => {
+		pub struct $mocked_builder;
+
+		impl $crate::conversion_rate_update::UpdateConversionRateCallBuilder<$source_chain>
+			for $mocked_builder
+		{
+			fn build_update_conversion_rate_call(
+				conversion_rate: f64,
+			) -> anyhow::Result<relay_substrate_client::CallOf<$source_chain>> {
+				Ok(pallet_bridge_messages::Call::update_pallet_parameter::<$runtime, $instance> {
+					parameter: $parameter(sp_runtime::FixedU128::from_float(conversion_rate)),
+				}.into())
+			}
+		}
+	};
+}
+
+/// Macro that generates `UpdateConversionRateCallBuilder` implementation for the case when
+/// you only have an access to the mocked version of source chain runtime. In this case you
+/// should provide "name" of the call variant for the bridge messages calls, the "name" of
+/// the variant for the `update_pallet_parameter` call within that first option and the name
+/// of the conversion rate parameter itself.
+#[rustfmt::skip]
+#[macro_export]
+macro_rules! generate_mocked_update_conversion_rate_call_builder {
+	(
+		$source_chain:ident,
+		$mocked_builder:ident,
+		$bridge_messages:path,
+		$update_pallet_parameter:path,
+		$parameter:path
+	) => {
+		pub struct $mocked_builder;
+
+		impl $crate::conversion_rate_update::UpdateConversionRateCallBuilder<$source_chain>
+			for $mocked_builder
+		{
+			fn build_update_conversion_rate_call(
+				conversion_rate: f64,
+			) -> anyhow::Result<relay_substrate_client::CallOf<$source_chain>> {
+				Ok($bridge_messages($update_pallet_parameter($parameter(
+					sp_runtime::FixedU128::from_float(conversion_rate),
+				))))
+			}
+		}
+	};
 }
 
 /// Run infinite conversion rate updater loop.
 ///
 /// The loop is maintaining the Left -> Right conversion rate, used as `RightTokens = LeftTokens *
 /// Rate`.
-pub fn run_conversion_rate_update_loop<
+pub fn run_conversion_rate_update_loop<Lane, Sign>(
-	SubmitConversionRateFuture: Future<Output = anyhow::Result<()>> + Send + 'static,
+	client: Client<Lane::SourceChain>,
->(
+	transaction_params: TransactionParams<AccountKeyPairOf<Sign>>,
 	left_to_right_stored_conversion_rate: F64SharedRef,
 	left_to_base_conversion_rate: F64SharedRef,
 	right_to_base_conversion_rate: F64SharedRef,
 	max_difference_ratio: f64,
-	submit_conversion_rate: impl Fn(f64) -> SubmitConversionRateFuture + Send + 'static,
+) where
-) {
+	Lane: SubstrateMessageLane,
+	Sign: TransactionSignScheme<Chain = Lane::SourceChain>,
+	AccountIdOf<Lane::SourceChain>: From<<AccountKeyPairOf<Sign> as Pair>::Public>,
+{
+	let stall_timeout = transaction_stall_timeout(
+		transaction_params.mortality,
+		Lane::SourceChain::AVERAGE_BLOCK_INTERVAL,
+		ALMOST_NEVER_DURATION,
+	);
+
+	log::info!(
+		target: "bridge",
+		"Starting {} -> {} conversion rate  (on {}) update loop. Stall timeout: {}s",
+		Lane::TargetChain::NAME,
+		Lane::SourceChain::NAME,
+		Lane::SourceChain::NAME,
+		stall_timeout.as_secs(),
+	);
+
 	async_std::task::spawn(async move {
 		let mut transaction_status = TransactionStatus::Idle;
 		loop {
 			async_std::task::sleep(SLEEP_DURATION).await;
 			let maybe_new_conversion_rate = maybe_select_new_conversion_rate(
+				stall_timeout,
 				&mut transaction_status,
 				&left_to_right_stored_conversion_rate,
 				&left_to_base_conversion_rate,
@@ -57,13 +161,32 @@ pub fn run_conversion_rate_update_loop<
 			)
 			.await;
 			if let Some((prev_conversion_rate, new_conversion_rate)) = maybe_new_conversion_rate {
-				let submit_conversion_rate_future = submit_conversion_rate(new_conversion_rate);
+				log::info!(
-				match submit_conversion_rate_future.await {
+					target: "bridge",
+					"Going to update {} -> {} (on {}) conversion rate to {}.",
+					Lane::TargetChain::NAME,
+					Lane::SourceChain::NAME,
+					Lane::SourceChain::NAME,
+					new_conversion_rate,
+				);
+
+				let result = update_target_to_source_conversion_rate::<Lane, Sign>(
+					client.clone(),
+					transaction_params.clone(),
+					new_conversion_rate,
+				)
+				.await;
+				match result {
 					Ok(()) => {
-						transaction_status = TransactionStatus::Submitted(prev_conversion_rate);
+						transaction_status =
+							TransactionStatus::Submitted(Instant::now(), prev_conversion_rate);
 					},
 					Err(error) => {
-						log::trace!(target: "bridge", "Failed to submit conversion rate update transaction: {:?}", error);
+						log::error!(
+							target: "bridge",
+							"Failed to submit conversion rate update transaction: {:?}",
+							error,
+						);
 					},
 				}
 			}
@@ -73,6 +196,7 @@ pub fn run_conversion_rate_update_loop<
 
 /// Select new conversion rate to submit to the node.
 async fn maybe_select_new_conversion_rate(
+	stall_timeout: Duration,
 	transaction_status: &mut TransactionStatus,
 	left_to_right_stored_conversion_rate: &F64SharedRef,
 	left_to_base_conversion_rate: &F64SharedRef,
@@ -83,7 +207,18 @@ async fn maybe_select_new_conversion_rate(
 		(*left_to_right_stored_conversion_rate.read().await)?;
 	match *transaction_status {
 		TransactionStatus::Idle => (),
-		TransactionStatus::Submitted(previous_left_to_right_stored_conversion_rate) => {
+		TransactionStatus::Submitted(submitted_at, _)
+			if Instant::now() - submitted_at > stall_timeout =>
+		{
+			log::error!(
+				target: "bridge",
+				"Conversion rate update transaction has been lost and loop stalled. Restarting",
+			);
+
+			// we assume that our transaction has been lost
+			*transaction_status = TransactionStatus::Idle;
+		},
+		TransactionStatus::Submitted(_, previous_left_to_right_stored_conversion_rate) => {
 			// we can't compare float values from different sources directly, so we only care
 			// whether the stored rate has been changed or not. If it has been changed, then we
 			// assume that our proposal has been accepted.
@@ -118,11 +253,50 @@ async fn maybe_select_new_conversion_rate(
 	Some((left_to_right_stored_conversion_rate, actual_left_to_right_conversion_rate))
 }
 
+/// Update Target -> Source tokens conversion rate, stored in the Source runtime storage.
+pub async fn update_target_to_source_conversion_rate<Lane, Sign>(
+	client: Client<Lane::SourceChain>,
+	transaction_params: TransactionParams<AccountKeyPairOf<Sign>>,
+	updated_rate: f64,
+) -> anyhow::Result<()>
+where
+	Lane: SubstrateMessageLane,
+	Sign: TransactionSignScheme<Chain = Lane::SourceChain>,
+	AccountIdOf<Lane::SourceChain>: From<<AccountKeyPairOf<Sign> as Pair>::Public>,
+{
+	let genesis_hash = *client.genesis_hash();
+	let signer_id = transaction_params.signer.public().into();
+	let (spec_version, transaction_version) = client.simple_runtime_version().await?;
+	let call =
+		Lane::TargetToSourceChainConversionRateUpdateBuilder::build_update_conversion_rate_call(
+			updated_rate,
+		)?;
+	client
+		.submit_signed_extrinsic(signer_id, move |best_block_id, transaction_nonce| {
+			Ok(Bytes(
+				Sign::sign_transaction(SignParam {
+					spec_version,
+					transaction_version,
+					genesis_hash,
+					signer: transaction_params.signer,
+					era: TransactionEra::new(best_block_id, transaction_params.mortality),
+					unsigned: UnsignedTransaction::new(call.into(), transaction_nonce).into(),
+				})?
+				.encode(),
+			))
+		})
+		.await
+		.map(drop)
+		.map_err(|err| anyhow::format_err!("{:?}", err))
+}
+
 #[cfg(test)]
 mod tests {
 	use super::*;
 	use async_std::sync::{Arc, RwLock};
 
+	const TEST_STALL_TIMEOUT: Duration = Duration::from_secs(60);
+
 	fn test_maybe_select_new_conversion_rate(
 		mut transaction_status: TransactionStatus,
 		stored_conversion_rate: Option<f64>,
@@ -134,6 +308,7 @@ mod tests {
 		let left_to_base_conversion_rate = Arc::new(RwLock::new(left_to_base_conversion_rate));
 		let right_to_base_conversion_rate = Arc::new(RwLock::new(right_to_base_conversion_rate));
 		let result = async_std::task::block_on(maybe_select_new_conversion_rate(
+			TEST_STALL_TIMEOUT,
 			&mut transaction_status,
 			&stored_conversion_rate,
 			&left_to_base_conversion_rate,
@@ -145,15 +320,10 @@ mod tests {
 
 	#[test]
 	fn rate_is_not_updated_when_transaction_is_submitted() {
+		let status = TransactionStatus::Submitted(Instant::now(), 10.0);
 		assert_eq!(
-			test_maybe_select_new_conversion_rate(
+			test_maybe_select_new_conversion_rate(status, Some(10.0), Some(1.0), Some(1.0), 0.0),
-				TransactionStatus::Submitted(10.0),
+			(None, status),
-				Some(10.0),
-				Some(1.0),
-				Some(1.0),
-				0.0
-			),
-			(None, TransactionStatus::Submitted(10.0)),
 		);
 	}
 
@@ -161,7 +331,7 @@ mod tests {
 	fn transaction_state_is_changed_to_idle_when_stored_rate_shanges() {
 		assert_eq!(
 			test_maybe_select_new_conversion_rate(
-				TransactionStatus::Submitted(1.0),
+				TransactionStatus::Submitted(Instant::now(), 1.0),
 				Some(10.0),
 				Some(1.0),
 				Some(1.0),
@@ -252,4 +422,19 @@ mod tests {
 			),
 		);
 	}
+
+	#[test]
+	fn transaction_expires() {
+		let status = TransactionStatus::Submitted(Instant::now() - TEST_STALL_TIMEOUT / 2, 10.0);
+		assert_eq!(
+			test_maybe_select_new_conversion_rate(status, Some(10.0), Some(1.0), Some(1.0), 0.0),
+			(None, status),
+		);
+
+		let status = TransactionStatus::Submitted(Instant::now() - TEST_STALL_TIMEOUT * 2, 10.0);
+		assert_eq!(
+			test_maybe_select_new_conversion_rate(status, Some(10.0), Some(1.0), Some(1.0), 0.0),
+			(Some((10.0, 1.0)), TransactionStatus::Idle),
+		);
+	}
 }

bridges/relays/lib-substrate-relay/src/messages_lane.rs

@@ -17,6 +17,7 @@
 //! Tools for supporting message lanes between two Substrate-based chains.
 
 use crate::{
+	conversion_rate_update::UpdateConversionRateCallBuilder,
 	messages_metrics::StandaloneMessagesMetrics,
 	messages_source::{SubstrateMessagesProof, SubstrateMessagesSource},
 	messages_target::{SubstrateMessagesDeliveryProof, SubstrateMessagesTarget},
@@ -89,6 +90,13 @@ pub trait SubstrateMessageLane: 'static + Clone + Debug + Send + Sync {
 	/// How receive messages delivery proof call is built?
 	type ReceiveMessagesDeliveryProofCallBuilder: ReceiveMessagesDeliveryProofCallBuilder<Self>;
 
+	/// `TargetChain` tokens to `SourceChain` tokens conversion rate update builder.
+	///
+	/// If not applicable to this bridge, you may use `()` here.
+	type TargetToSourceChainConversionRateUpdateBuilder: UpdateConversionRateCallBuilder<
+		Self::SourceChain,
+	>;
+
 	/// Message relay strategy.
 	type RelayStrategy: RelayStrategy;
 }