Rework Transaction Priority calculation

bin/node-template/runtime/src/lib.rs

@@ -258,13 +258,13 @@ impl pallet_balances::Config for Runtime {
 
 parameter_types! {
 	pub const TransactionByteFee: Balance = 1;
-	pub OperationalVirtualTip: Balance = ExistentialDeposit::get();
+	pub OperationalFeeMultiplier: u8 = 5;
 }
 
 impl pallet_transaction_payment::Config for Runtime {
 	type OnChargeTransaction = CurrencyAdapter<Balances, ()>;
 	type TransactionByteFee = TransactionByteFee;
-	type OperationalVirtualTip = OperationalVirtualTip;
+	type OperationalFeeMultiplier = OperationalFeeMultiplierBalance;
 	type WeightToFee = IdentityFee<Balance>;
 	type FeeMultiplierUpdate = ();
 }

bin/node/runtime/src/lib.rs

@@ -413,7 +413,7 @@ impl pallet_balances::Config for Runtime {
 
 parameter_types! {
 	pub const TransactionByteFee: Balance = 10 * MILLICENTS;
-	pub const OperationalVirtualTip: Balance = 1 * DOLLARS;
+	pub const OperationalFeeMultiplier: u8 = 5;
 	pub const TargetBlockFullness: Perquintill = Perquintill::from_percent(25);
 	pub AdjustmentVariable: Multiplier = Multiplier::saturating_from_rational(1, 100_000);
 	pub MinimumMultiplier: Multiplier = Multiplier::saturating_from_rational(1, 1_000_000_000u128);
@@ -422,7 +422,8 @@ parameter_types! {
 impl pallet_transaction_payment::Config for Runtime {
 	type OnChargeTransaction = CurrencyAdapter<Balances, DealWithFees>;
 	type TransactionByteFee = TransactionByteFee;
-	type OperationalVirtualTip = OperationalVirtualTip;
+	type OperationalFeeMultiplier = OperationalFeeMultiplier;
+
 	type WeightToFee = IdentityFee<Balance>;
 	type FeeMultiplierUpdate =
 		TargetedFeeAdjustment<Self, TargetBlockFullness, AdjustmentVariable, MinimumMultiplier>;

frame/balances/src/tests_composite.rs

@@ -76,12 +76,12 @@ impl frame_system::Config for Test {
 }
 parameter_types! {
 	pub const TransactionByteFee: u64 = 1;
-	pub const OperationalVirtualTip: u64 = 1;
+	pub const OperationalFeeMultiplier: u8 = 5;
 }
 impl pallet_transaction_payment::Config for Test {
 	type OnChargeTransaction = CurrencyAdapter<Pallet<Test>, ()>;
 	type TransactionByteFee = TransactionByteFee;
-	type OperationalVirtualTip = OperationalVirtualTip;
+	type OperationalFeeMultiplier = OperationalFeeMultiplier;
 	type WeightToFee = IdentityFee<u64>;
 	type FeeMultiplierUpdate = ();
 }

frame/balances/src/tests_local.rs

@@ -78,12 +78,12 @@ impl frame_system::Config for Test {
 }
 parameter_types! {
 	pub const TransactionByteFee: u64 = 1;
-	pub const OperationalVirtualTip: u64 = 1;
+	pub const OperationalFeeMultiplier: u8 = 5;
 }
 impl pallet_transaction_payment::Config for Test {
 	type OnChargeTransaction = CurrencyAdapter<Pallet<Test>, ()>;
 	type TransactionByteFee = TransactionByteFee;
-	type OperationalVirtualTip = OperationalVirtualTip;
+	type OperationalFeeMultiplier = OperationalFeeMultiplier;
 	type WeightToFee = IdentityFee<u64>;
 	type FeeMultiplierUpdate = ();
 }

frame/balances/src/tests_reentrancy.rs

@@ -80,12 +80,12 @@ impl frame_system::Config for Test {
 }
 parameter_types! {
 	pub const TransactionByteFee: u64 = 1;
-	pub const OperationalVirtualTip: u64 = 1;
+	pub const OperationalFeeMultiplier: u8 = 5;
 }
 impl pallet_transaction_payment::Config for Test {
 	type OnChargeTransaction = CurrencyAdapter<Pallet<Test>, ()>;
 	type TransactionByteFee = TransactionByteFee;
-	type OperationalVirtualTip = OperationalVirtualTip;
+	type OperationalFeeMultiplier = OperationalFeeMultiplier;
 	type WeightToFee = IdentityFee<u64>;
 	type FeeMultiplierUpdate = ();
 }

frame/executive/src/lib.rs

@@ -800,12 +800,12 @@ mod tests {
 
 	parameter_types! {
 		pub const TransactionByteFee: Balance = 0;
-		pub const OperationalVirtualTip: Balance = 1;
+		pub const OperationalFeeMultiplier: u8 = 5;
 	}
 	impl pallet_transaction_payment::Config for Runtime {
 		type OnChargeTransaction = CurrencyAdapter<Balances, ()>;
 		type TransactionByteFee = TransactionByteFee;
-		type OperationalVirtualTip = OperationalVirtualTip;
+		type OperationalFeeMultiplier = OperationalFeeMultiplier;
 		type WeightToFee = IdentityFee<Balance>;
 		type FeeMultiplierUpdate = ();
 	}

frame/transaction-payment/src/lib.rs

@@ -264,13 +264,29 @@ pub mod pallet {
 		#[pallet::constant]
 		type TransactionByteFee: Get<BalanceOf<Self>>;
 
-		/// A virtual (not payed) tip added to `Operational` extrinsics to boost their `priority`.
+		/// A fee mulitplier for `Operational` extrinsics to compute "virtual tip" to boost their
+		/// `priority`
 		///
-		/// This value is simply included to a tip component in regular `priority` calculations.
+		/// This value is multipled by the `final_fee` to obtain a "virtual tip" that is later
+		/// added to a tip component in regular `priority` calculations.
 		/// It means that a `Normal` transaction can front-run a similarly-sized `Operational`
-		/// extrinsic (with no tip), by including a tip value greater than this.
+		/// extrinsic (with no tip), by including a tip value greater than the virtual tip.
+		///
+		/// ```rust,ignore
+		/// // For `Normal`
+		/// let priority = priority_calc(tip);
+		///
+		/// // For `Operational`
+		/// let virtual_tip = (inclusion_fee + tip) * OperationalFeeMultiplier;
+		/// let priority = priority_calc(tip + virtual_tip);
+		/// ```
+		///
+		/// Note that since we use `final_fee` the multiplier applies also to the regular `tip`
+		/// sent with the transaction. So not only the transaction get's a priority bump based
+		/// on the `inclusion_fee` but also we amplify the impact of tips applied to `Operational`
+		/// transactions.
 		#[pallet::constant]
-		type OperationalVirtualTip: Get<BalanceOf<Self>>;
+		type OperationalFeeMultiplier: Get<u8>;
 
 		/// Convert a weight value into a deductible fee based on the currency type.
 		type WeightToFee: WeightToFeePolynomial<Balance = BalanceOf<Self>>;
@@ -595,10 +611,11 @@ where
 	/// `tip * (max_block_{weight|length} / bounded_{weight|length})`, since given current
 	/// state of-the-art blockchains, number of per-block transactions is expected to be in a
 	/// range reasonable enough to not saturate the `Balance` type while multiplying by the tip.
-	fn get_priority(
+	pub fn get_priority(
 		info: &DispatchInfoOf<T::Call>,
 		len: usize,
 		tip: BalanceOf<T>,
+		final_fee: BalanceOf<T>,
 	) -> TransactionPriority {
 		// Calculate how many such extrinsics we could fit into an empty block and take
 		// the limitting factor.
@@ -640,7 +657,8 @@ where
 				// to get in even during congestion period, but at the same time low
 				// enough to prevent a possible spam attack by sending invalid operational
 				// extrinsics which push away regular transactions from the pool.
-				let virtual_tip = T::OperationalVirtualTip::get();
+				let fee_multiplier = T::OperationalFeeMultiplier::get().saturated_into();
+				let virtual_tip = final_fee.saturating_mul(fee_multiplier);
 				let scaled_virtual_tip = max_reward(virtual_tip);
 
 				scaled_tip.saturating_add(scaled_virtual_tip)
@@ -689,9 +707,12 @@ where
 		info: &DispatchInfoOf<Self::Call>,
 		len: usize,
 	) -> TransactionValidity {
-		let (_fee, _) = self.withdraw_fee(who, call, info, len)?;
+		let (final_fee, _) = self.withdraw_fee(who, call, info, len)?;
 		let tip = self.0;
-		Ok(ValidTransaction { priority: Self::get_priority(info, len, tip), ..Default::default() })
+		Ok(ValidTransaction {
+			priority: Self::get_priority(info, len, tip, final_fee),
+			..Default::default()
+		})
 	}
 
 	fn pre_dispatch(
@@ -804,7 +825,7 @@ mod tests {
 		pub const BlockHashCount: u64 = 250;
 		pub static TransactionByteFee: u64 = 1;
 		pub static WeightToFee: u64 = 1;
-		pub static OperationalVirtualTip: u64 = 5 * 5;
+		pub static OperationalFeeMultiplier: u8 = 5;
 	}
 
 	impl frame_system::Config for Runtime {
@@ -884,7 +905,7 @@ mod tests {
 	impl Config for Runtime {
 		type OnChargeTransaction = CurrencyAdapter<Balances, DealWithFees>;
 		type TransactionByteFee = TransactionByteFee;
-		type OperationalVirtualTip = OperationalVirtualTip;
+		type OperationalFeeMultiplier = OperationalFeeMultiplier;
 		type WeightToFee = WeightToFee;
 		type FeeMultiplierUpdate = ();
 	}
@@ -1431,13 +1452,13 @@ mod tests {
 				.validate(&2, CALL, &op, len)
 				.unwrap()
 				.priority;
-			assert_eq!(priority, 300);
+			assert_eq!(priority, 5800);
 
 			let priority = ChargeTransactionPayment::<Runtime>(2 * tip)
 				.validate(&2, CALL, &op, len)
 				.unwrap()
 				.priority;
-			assert_eq!(priority, 350);
+			assert_eq!(priority, 6100);
 		});
 	}
 
@@ -1467,7 +1488,7 @@ mod tests {
 				.validate(&2, CALL, &op, len)
 				.unwrap()
 				.priority;
-			assert_eq!(priority, 260);
+			assert_eq!(priority, 5510);
 		});
 	}