Estimate message fee api (paritytech#600)

* estimate_message_delivery_and_dispatch_fee runtime API

* auto-determine message fees in relay

* remove fee argument from relay calls

* Fix import of weight contant

Co-authored-by: Hernando Castano <castano.ha@gmail.com>

bridges/bin/millau/runtime/src/lib.rs

@@ -30,6 +30,9 @@ include!(concat!(env!("OUT_DIR"), "/wasm_binary.rs"));
 
 pub mod rialto_messages;
 
+use crate::rialto_messages::{ToRialtoMessagePayload, WithRialtoMessageBridge};
+
+use bridge_runtime_common::messages::{source::estimate_message_dispatch_and_delivery_fee, MessageBridge};
 use codec::Decode;
 use pallet_grandpa::{fg_primitives, AuthorityId as GrandpaId, AuthorityList as GrandpaAuthorityList};
 use sp_api::impl_runtime_apis;
@@ -532,7 +535,17 @@ impl_runtime_apis! {
 		}
 	}
 
-	impl bp_rialto::ToRialtoOutboundLaneApi<Block> for Runtime {
+	impl bp_rialto::ToRialtoOutboundLaneApi<Block, Balance, ToRialtoMessagePayload> for Runtime {
+		fn estimate_message_delivery_and_dispatch_fee(
+			_lane_id: bp_message_lane::LaneId,
+			payload: ToRialtoMessagePayload,
+		) -> Option<Balance> {
+			estimate_message_dispatch_and_delivery_fee::<WithRialtoMessageBridge>(
+				&payload,
+				WithRialtoMessageBridge::RELAYER_FEE_PERCENT,
+			).ok()
+		}
+
 		fn messages_dispatch_weight(
 			lane: bp_message_lane::LaneId,
 			begin: bp_message_lane::MessageNonce,

bridges/bin/millau/runtime/src/rialto_messages.rs

@@ -124,9 +124,9 @@ impl MessageBridge for WithRialtoMessageBridge {
 		<crate::Runtime as pallet_transaction_payment::Config>::WeightToFee::calc(&weight) as _
 	}
 
-	fn this_balance_to_bridged_balance(this_balance: bp_millau::Balance) -> bp_rialto::Balance {
+	fn bridged_balance_to_this_balance(bridged_balance: bp_rialto::Balance) -> bp_millau::Balance {
 		// 1:1 conversion that will probably change in the future
-		this_balance as _
+		bridged_balance as _
 	}
 }
 

bridges/bin/rialto/runtime/src/lib.rs

@@ -36,6 +36,9 @@ pub mod kovan;
 pub mod millau_messages;
 pub mod rialto_poa;
 
+use crate::millau_messages::{ToMillauMessagePayload, WithMillauMessageBridge};
+
+use bridge_runtime_common::messages::{source::estimate_message_dispatch_and_delivery_fee, MessageBridge};
 use codec::Decode;
 use pallet_grandpa::{fg_primitives, AuthorityId as GrandpaId, AuthorityList as GrandpaAuthorityList};
 use sp_api::impl_runtime_apis;
@@ -695,7 +698,17 @@ impl_runtime_apis! {
 		}
 	}
 
-	impl bp_millau::ToMillauOutboundLaneApi<Block> for Runtime {
+	impl bp_millau::ToMillauOutboundLaneApi<Block, Balance, ToMillauMessagePayload> for Runtime {
+		fn estimate_message_delivery_and_dispatch_fee(
+			_lane_id: bp_message_lane::LaneId,
+			payload: ToMillauMessagePayload,
+		) -> Option<Balance> {
+			estimate_message_dispatch_and_delivery_fee::<WithMillauMessageBridge>(
+				&payload,
+				WithMillauMessageBridge::RELAYER_FEE_PERCENT,
+			).ok()
+		}
+
 		fn messages_dispatch_weight(
 			lane: bp_message_lane::LaneId,
 			begin: bp_message_lane::MessageNonce,

bridges/bin/rialto/runtime/src/millau_messages.rs

@@ -125,9 +125,9 @@ impl MessageBridge for WithMillauMessageBridge {
 		<crate::Runtime as pallet_transaction_payment::Config>::WeightToFee::calc(&weight) as _
 	}
 
-	fn this_balance_to_bridged_balance(this_balance: bp_rialto::Balance) -> bp_millau::Balance {
+	fn bridged_balance_to_this_balance(bridged_balance: bp_millau::Balance) -> bp_rialto::Balance {
 		// 1:1 conversion that will probably change in the future
-		this_balance as _
+		bridged_balance as _
 	}
 }
 

bridges/bin/runtime-common/src/messages.rs

@@ -81,8 +81,8 @@ pub trait MessageBridge {
 	/// Convert weight of the Bridged chain to the fee (paid in Balance) of the Bridged chain.
 	fn bridged_weight_to_bridged_balance(weight: WeightOf<BridgedChain<Self>>) -> BalanceOf<BridgedChain<Self>>;
 
-	/// Convert This chain Balance into Bridged chain Balance.
-	fn this_balance_to_bridged_balance(this_balance: BalanceOf<ThisChain<Self>>) -> BalanceOf<BridgedChain<Self>>;
+	/// Convert Bridged chain Balance into This chain Balance.
+	fn bridged_balance_to_this_balance(bridged_balance: BalanceOf<BridgedChain<Self>>) -> BalanceOf<ThisChain<Self>>;
 }
 
 /// Chain that has `message-lane` and `call-dispatch` modules.
@@ -170,12 +170,11 @@ pub mod source {
 			// `CallDispatch`, so we verify the message accordingly.
 			pallet_bridge_call_dispatch::verify_message_origin(submitter, payload).map_err(|_| BAD_ORIGIN)?;
 
-			let minimal_fee_in_bridged_tokens =
+			let minimal_fee_in_this_tokens =
 				estimate_message_dispatch_and_delivery_fee::<B>(payload, B::RELAYER_FEE_PERCENT)?;
 
 			// compare with actual fee paid
-			let actual_fee_in_bridged_tokens = B::this_balance_to_bridged_balance(*delivery_and_dispatch_fee);
-			if actual_fee_in_bridged_tokens < minimal_fee_in_bridged_tokens {
+			if *delivery_and_dispatch_fee < minimal_fee_in_this_tokens {
 				return Err(TOO_LOW_FEE);
 			}
 
@@ -225,22 +224,22 @@ pub mod source {
 	pub fn estimate_message_dispatch_and_delivery_fee<B: MessageBridge>(
 		payload: &FromThisChainMessagePayload<B>,
 		relayer_fee_percent: u32,
-	) -> Result<BalanceOf<BridgedChain<B>>, &'static str> {
+	) -> Result<BalanceOf<ThisChain<B>>, &'static str> {
 		// the fee (in Bridged tokens) of all transactions that are made on the Bridged chain
 		let delivery_fee = B::bridged_weight_to_bridged_balance(B::weight_of_delivery_transaction());
 		let dispatch_fee = B::bridged_weight_to_bridged_balance(payload.weight.into());
 		let reward_confirmation_fee =
 			B::bridged_weight_to_bridged_balance(B::weight_of_reward_confirmation_transaction_on_target_chain());
 
-		// the fee (in Bridged tokens) of all transactions that are made on This chain
-		let delivery_confirmation_fee = B::this_balance_to_bridged_balance(B::this_weight_to_this_balance(
-			B::weight_of_delivery_confirmation_transaction_on_this_chain(),
-		));
+		// the fee (in This tokens) of all transactions that are made on This chain
+		let delivery_confirmation_fee =
+			B::this_weight_to_this_balance(B::weight_of_delivery_confirmation_transaction_on_this_chain());
 
-		// minimal fee (in Bridged tokens) is a sum of all required fees
+		// minimal fee (in This tokens) is a sum of all required fees
 		let minimal_fee = delivery_fee
 			.checked_add(&dispatch_fee)
 			.and_then(|fee| fee.checked_add(&reward_confirmation_fee))
+			.map(B::bridged_balance_to_this_balance)
 			.and_then(|fee| fee.checked_add(&delivery_confirmation_fee));
 
 		// before returning, add extra fee that is paid to the relayer (relayer interest)
@@ -563,7 +562,7 @@ mod tests {
 	const REWARD_CONFIRMATION_TRANSACTION_WEIGHT: Weight = 100;
 	const THIS_CHAIN_WEIGHT_TO_BALANCE_RATE: Weight = 2;
 	const BRIDGED_CHAIN_WEIGHT_TO_BALANCE_RATE: Weight = 4;
-	const THIS_CHAIN_TO_BRIDGED_CHAIN_BALANCE_RATE: u32 = 6;
+	const BRIDGED_CHAIN_TO_THIS_CHAIN_BALANCE_RATE: u32 = 6;
 	const BRIDGED_CHAIN_MAX_EXTRINSIC_WEIGHT: Weight = 2048;
 	const BRIDGED_CHAIN_MAX_EXTRINSIC_SIZE: u32 = 1024;
 
@@ -606,8 +605,8 @@ mod tests {
 			BridgedChainBalance(weight as u32 * BRIDGED_CHAIN_WEIGHT_TO_BALANCE_RATE as u32)
 		}
 
-		fn this_balance_to_bridged_balance(this_balance: ThisChainBalance) -> BridgedChainBalance {
-			BridgedChainBalance(this_balance.0 * THIS_CHAIN_TO_BRIDGED_CHAIN_BALANCE_RATE as u32)
+		fn bridged_balance_to_this_balance(bridged_balance: BridgedChainBalance) -> ThisChainBalance {
+			ThisChainBalance(bridged_balance.0 * BRIDGED_CHAIN_TO_THIS_CHAIN_BALANCE_RATE as u32)
 		}
 	}
 
@@ -649,7 +648,7 @@ mod tests {
 			unreachable!()
 		}
 
-		fn this_balance_to_bridged_balance(_this_balance: BridgedChainBalance) -> ThisChainBalance {
+		fn bridged_balance_to_this_balance(_this_balance: ThisChainBalance) -> BridgedChainBalance {
 			unreachable!()
 		}
 	}
@@ -799,7 +798,7 @@ mod tests {
 
 	#[test]
 	fn message_fee_is_checked_by_verifier() {
-		const EXPECTED_MINIMAL_FEE: u32 = 2640;
+		const EXPECTED_MINIMAL_FEE: u32 = 8140;
 
 		// payload of the This -> Bridged chain message
 		let payload = source::FromThisChainMessagePayload::<OnThisChainBridge> {
@@ -815,7 +814,7 @@ mod tests {
 				&payload,
 				OnThisChainBridge::RELAYER_FEE_PERCENT,
 			),
-			Ok(BridgedChainBalance(EXPECTED_MINIMAL_FEE)),
+			Ok(ThisChainBalance(EXPECTED_MINIMAL_FEE)),
 		);
 
 		// and now check that the verifier checks the fee

bridges/primitives/millau/src/lib.rs

@@ -26,7 +26,7 @@ use bp_message_lane::{LaneId, MessageNonce, UnrewardedRelayersState};
 use bp_runtime::Chain;
 use frame_support::{
 	weights::{constants::WEIGHT_PER_SECOND, DispatchClass, Weight},
-	RuntimeDebug,
+	Parameter, RuntimeDebug,
 };
 use frame_system::limits;
 use sp_core::Hasher as HasherT;
@@ -191,6 +191,9 @@ pub const IS_KNOWN_MILLAU_BLOCK_METHOD: &str = "MillauHeaderApi_is_known_block";
 /// Name of the `MillauHeaderApi::incomplete_headers` runtime method.
 pub const INCOMPLETE_MILLAU_HEADERS_METHOD: &str = "MillauHeaderApi_incomplete_headers";
 
+/// Name of the `ToMillauOutboundLaneApi::estimate_message_delivery_and_dispatch_fee` runtime method.
+pub const TO_MILLAU_ESTIMATE_MESSAGE_FEE_METHOD: &str =
+	"ToMillauOutboundLaneApi_estimate_message_delivery_and_dispatch_fee";
 /// Name of the `ToMillauOutboundLaneApi::messages_dispatch_weight` runtime method.
 pub const TO_MILLAU_MESSAGES_DISPATCH_WEIGHT_METHOD: &str = "ToMillauOutboundLaneApi_messages_dispatch_weight";
 /// Name of the `ToMillauOutboundLaneApi::latest_received_nonce` runtime method.
@@ -235,7 +238,20 @@ sp_api::decl_runtime_apis! {
 	///
 	/// This API is implemented by runtimes that are sending messages to Millau chain, not the
 	/// Millau runtime itself.
-	pub trait ToMillauOutboundLaneApi {
+	pub trait ToMillauOutboundLaneApi<OutboundMessageFee: Parameter, OutboundPayload: Parameter> {
+		/// Estimate message delivery and dispatch fee that needs to be paid by the sender on
+		/// this chain.
+		///
+		/// Returns `None` if message is too expensive to be sent to Millau from this chain.
+		///
+		/// Please keep in mind that this method returns lowest message fee required for message
+		/// to be accepted to the lane. It may be good idea to pay a bit over this price to account
+		/// future exchange rate changes and guarantee that relayer would deliver your message
+		/// to the target chain.
+		fn estimate_message_delivery_and_dispatch_fee(
+			lane_id: LaneId,
+			payload: OutboundPayload,
+		) -> Option<OutboundMessageFee>;
 		/// Returns total dispatch weight and encoded payload size of all messages in given inclusive range.
 		///
 		/// If some (or all) messages are missing from the storage, they'll also will

bridges/primitives/rialto/src/lib.rs

@@ -24,7 +24,7 @@ use bp_message_lane::{LaneId, MessageNonce, UnrewardedRelayersState};
 use bp_runtime::Chain;
 use frame_support::{
 	weights::{constants::WEIGHT_PER_SECOND, DispatchClass, Weight},
-	RuntimeDebug,
+	Parameter, RuntimeDebug,
 };
 use frame_system::limits;
 use sp_core::Hasher as HasherT;
@@ -152,6 +152,9 @@ pub const IS_KNOWN_RIALTO_BLOCK_METHOD: &str = "RialtoHeaderApi_is_known_block";
 /// Name of the `RialtoHeaderApi::incomplete_headers` runtime method.
 pub const INCOMPLETE_RIALTO_HEADERS_METHOD: &str = "RialtoHeaderApi_incomplete_headers";
 
+/// Name of the `ToRialtoOutboundLaneApi::estimate_message_delivery_and_dispatch_fee` runtime method.
+pub const TO_RIALTO_ESTIMATE_MESSAGE_FEE_METHOD: &str =
+	"ToRialtoOutboundLaneApi_estimate_message_delivery_and_dispatch_fee";
 /// Name of the `ToRialtoOutboundLaneApi::messages_dispatch_weight` runtime method.
 pub const TO_RIALTO_MESSAGES_DISPATCH_WEIGHT_METHOD: &str = "ToRialtoOutboundLaneApi_messages_dispatch_weight";
 /// Name of the `ToRialtoOutboundLaneApi::latest_generated_nonce` runtime method.
@@ -196,7 +199,20 @@ sp_api::decl_runtime_apis! {
 	///
 	/// This API is implemented by runtimes that are sending messages to Rialto chain, not the
 	/// Rialto runtime itself.
-	pub trait ToRialtoOutboundLaneApi {
+	pub trait ToRialtoOutboundLaneApi<OutboundMessageFee: Parameter, OutboundPayload: Parameter> {
+		/// Estimate message delivery and dispatch fee that needs to be paid by the sender on
+		/// this chain.
+		///
+		/// Returns `None` if message is too expensive to be sent to Rialto from this chain.
+		///
+		/// Please keep in mind that this method returns lowest message fee required for message
+		/// to be accepted to the lane. It may be good idea to pay a bit over this price to account
+		/// future exchange rate changes and guarantee that relayer would deliver your message
+		/// to the target chain.
+		fn estimate_message_delivery_and_dispatch_fee(
+			lane_id: LaneId,
+			payload: OutboundPayload,
+		) -> Option<OutboundMessageFee>;
 		/// Returns total dispatch weight and encoded payload size of all messages in given inclusive range.
 		///
 		/// If some (or all) messages are missing from the storage, they'll also will

bridges/relays/substrate/src/cli.rs

@@ -101,9 +101,9 @@ pub enum Command {
 		/// Hex-encoded lane id.
 		#[structopt(long)]
 		lane: HexLaneId,
-		/// Delivery and dispatch fee.
+		/// Delivery and dispatch fee. If not passed, determined automatically.
 		#[structopt(long)]
-		fee: bp_millau::Balance,
+		fee: Option<bp_millau::Balance>,
 		/// Message type.
 		#[structopt(subcommand)]
 		message: ToRialtoMessage,
@@ -138,9 +138,9 @@ pub enum Command {
 		/// Hex-encoded lane id.
 		#[structopt(long)]
 		lane: HexLaneId,
-		/// Delivery and dispatch fee.
+		/// Delivery and dispatch fee. If not passed, determined automatically.
 		#[structopt(long)]
-		fee: bp_rialto::Balance,
+		fee: Option<bp_rialto::Balance>,
 		/// Message type.
 		#[structopt(subcommand)]
 		message: ToMillauMessage,

bridges/relays/substrate/src/main.rs

@@ -18,13 +18,13 @@
 
 #![warn(missing_docs)]
 
-use codec::Encode;
+use codec::{Decode, Encode};
 use frame_support::weights::GetDispatchInfo;
 use pallet_bridge_call_dispatch::{CallOrigin, MessagePayload};
 use relay_kusama_client::Kusama;
 use relay_millau_client::{Millau, SigningParams as MillauSigningParams};
 use relay_rialto_client::{Rialto, SigningParams as RialtoSigningParams};
-use relay_substrate_client::{ConnectionParams, TransactionSignScheme};
+use relay_substrate_client::{Chain, ConnectionParams, TransactionSignScheme};
 use relay_utils::initialize::initialize_relay;
 use sp_core::{Bytes, Pair};
 use sp_runtime::traits::IdentifyAccount;
@@ -315,8 +315,27 @@ async fn run_command(command: cli::Command) -> Result<(), String> {
 				}
 			};
 
+			let lane = lane.into();
+			let fee = match fee {
+				Some(fee) => fee,
+				None => match estimate_message_delivery_and_dispatch_fee(
+					&millau_client,
+					bp_rialto::TO_RIALTO_ESTIMATE_MESSAGE_FEE_METHOD,
+					lane,
+					payload.clone(),
+				)
+				.await
+				{
+					Ok(Some(fee)) => fee,
+					Ok(None) => return Err("Failed to estimate message fee. Message is too heavy?".into()),
+					Err(error) => return Err(format!("Failed to estimate message fee: {:?}", error)),
+				},
+			};
+
+			log::error!(target: "bridge", "Sending message to Rialto. Fee: {}", fee);
+
 			let millau_call = millau_runtime::Call::BridgeRialtoMessageLane(
-				millau_runtime::MessageLaneCall::send_message(lane.into(), payload, fee),
+				millau_runtime::MessageLaneCall::send_message(lane, payload, fee),
 			);
 
 			let signed_millau_call = Millau::sign_transaction(
@@ -444,8 +463,27 @@ async fn run_command(command: cli::Command) -> Result<(), String> {
 				}
 			};
 
+			let lane = lane.into();
+			let fee = match fee {
+				Some(fee) => fee,
+				None => match estimate_message_delivery_and_dispatch_fee(
+					&rialto_client,
+					bp_millau::TO_MILLAU_ESTIMATE_MESSAGE_FEE_METHOD,
+					lane,
+					payload.clone(),
+				)
+				.await
+				{
+					Ok(Some(fee)) => fee,
+					Ok(None) => return Err("Failed to estimate message fee. Message is too heavy?".into()),
+					Err(error) => return Err(format!("Failed to estimate message fee: {:?}", error)),
+				},
+			};
+
+			log::info!(target: "bridge", "Sending message to Millau. Fee: {}", fee);
+
 			let rialto_call = rialto_runtime::Call::BridgeMillauMessageLane(
-				rialto_runtime::MessageLaneCall::send_message(lane.into(), payload, fee),
+				rialto_runtime::MessageLaneCall::send_message(lane, payload, fee),
 			);
 
 			let signed_rialto_call = Rialto::sign_transaction(
@@ -465,3 +503,17 @@ async fn run_command(command: cli::Command) -> Result<(), String> {
 
 	Ok(())
 }
+
+async fn estimate_message_delivery_and_dispatch_fee<Fee: Decode, C: Chain, P: Encode>(
+	client: &relay_substrate_client::Client<C>,
+	estimate_fee_method: &str,
+	lane: bp_message_lane::LaneId,
+	payload: P,
+) -> Result<Option<Fee>, relay_substrate_client::Error> {
+	let encoded_response = client
+		.state_call(estimate_fee_method.into(), (lane, payload).encode().into(), None)
+		.await?;
+	let decoded_response: Option<Fee> =
+		Decode::decode(&mut &encoded_response.0[..]).map_err(relay_substrate_client::Error::ResponseParseFailed)?;
+	Ok(decoded_response)
+}