Add Dynamic Fee support for Moonbeam

runtime/moonbeam/src/lib.rs

@@ -369,25 +369,40 @@ parameter_types! {
 	pub const TargetBlockFullness: Perquintill = Perquintill::from_percent(25);
 	/// The adjustment variable of the runtime. Higher values will cause `TargetBlockFullness` to
 	/// change the fees more rapidly. This low value causes changes to occur slowly over time.
-	pub AdjustmentVariable: Multiplier = Multiplier::saturating_from_rational(3, 100_000);
+	pub AdjustmentVariable: Multiplier = Multiplier::saturating_from_rational(4, 1_000);
 	/// Minimum amount of the multiplier. This value cannot be too low. A test case should ensure
 	/// that combined with `AdjustmentVariable`, we can recover from the minimum.
 	/// See `multiplier_can_grow_from_zero` in integration_tests.rs.
 	/// This value is currently only used by pallet-transaction-payment as an assertion that the
 	/// next multiplier is always > min value.
-	pub MinimumMultiplier: Multiplier = Multiplier::saturating_from_rational(1, 1_000_000u128);
+	pub MinimumMultiplier: Multiplier = Multiplier::from(1u128);
 	/// Maximum multiplier. We pick a value that is expensive but not impossibly so; it should act
 	/// as a safety net.
 	pub MaximumMultiplier: Multiplier = Multiplier::from(100_000u128);
 	pub PrecompilesValue: MoonbeamPrecompiles<Runtime> = MoonbeamPrecompiles::<_>::new();
 	pub WeightPerGas: Weight = Weight::from_ref_time(WEIGHT_PER_GAS);
 }
 
-pub struct FixedGasPrice;
-impl FeeCalculator for FixedGasPrice {
+pub struct TransactionPaymentAsGasPrice;
+impl FeeCalculator for TransactionPaymentAsGasPrice {
 	fn min_gas_price() -> (U256, Weight) {
+		// note: transaction-payment differs from EIP-1559 in that its tip and length fees are not
+		//       scaled by the multiplier, which means its multiplier will be overstated when
+		//       applied to an ethereum transaction
+		// note: transaction-payment uses both a congestion modifier (next_fee_multiplier, which is
+		//       updated once per block in on_finalize) and a 'WeightToFee' implementation. Our
+		//       runtime implements this as a 'ConstantModifier', so we can get away with a simple
+		//       multiplication here.
+		// It is imperative that `saturating_mul_int` be performed as late as possible in the
+		// expression since it involves fixed point multiplication with a division by a fixed
+		// divisor. This leads to truncation and subsequent precision loss if performed too early.
+		// This can lead to min_gas_price being same across blocks even if the multiplier changes.
+		// There's still some precision loss when the final `gas_price` (used_gas * min_gas_price)
+		// is computed in frontier, but that's currently unavoidable.
+		let min_gas_price = TransactionPayment::next_fee_multiplier()
+			.saturating_mul_int(currency::WEIGHT_FEE.saturating_mul(WEIGHT_PER_GAS as u128));
 		(
-			(1 * currency::GIGAWEI * currency::SUPPLY_FACTOR).into(),
+			min_gas_price.into(),
 			<Runtime as frame_system::Config>::DbWeight::get().reads(1),
 		)
 	}
@@ -435,7 +450,7 @@ where
 moonbeam_runtime_common::impl_on_charge_evm_transaction!();
 
 impl pallet_evm::Config for Runtime {
-	type FeeCalculator = FixedGasPrice;
+	type FeeCalculator = TransactionPaymentAsGasPrice;
 	type GasWeightMapping = pallet_evm::FixedGasWeightMapping<Self>;
 	type WeightPerGas = WeightPerGas;
 	type BlockHashMapping = pallet_ethereum::EthereumBlockHashMapping<Self>;

runtime/moonbeam/tests/common/mod.rs

@@ -28,9 +28,9 @@ pub use moonbeam_runtime::{
 	currency::{GIGAWEI, GLMR, SUPPLY_FACTOR, WEI},
 	xcm_config::AssetType,
 	AccountId, AssetId, AssetManager, Assets, AuthorInherent, Balance, Balances, CrowdloanRewards,
-	Ethereum, Executive, FixedGasPrice, InflationInfo, LocalAssets, ParachainStaking, Range,
-	Runtime, RuntimeCall, RuntimeEvent, System, TransactionConverter, UncheckedExtrinsic, HOURS,
-	WEEKS,
+	Ethereum, Executive, InflationInfo, LocalAssets, ParachainStaking, Range, Runtime, RuntimeCall,
+	RuntimeEvent, System, TransactionConverter, TransactionPaymentAsGasPrice, UncheckedExtrinsic,
+	HOURS, WEEKS,
 };
 use nimbus_primitives::{NimbusId, NIMBUS_ENGINE_ID};
 use sp_core::{Encode, H160};
@@ -42,9 +42,9 @@ use fp_rpc::ConvertTransaction;
 
 // A valid signed Alice transfer.
 pub const VALID_ETH_TX: &str =
-	"f8648085174876e8008252089412cb274aad8251c875c0bf6872b67d9983e53fdd01801ba05deb036\
-	17e9c2d82e0f4e897ef8fbb01c91244abfc4bd9c3206bc87f9fc71a01a0719f146637fe2b462ccae80\
-	e462ecefa560635d933257ec117a1f7701b178c93";
+	"02f869820501808085e8d4a51000825208943cd0a705a2dc65e5b1e1205896baa2be8a07c6e00180c\
+	001a061087911e877a5802142a89a40d231d50913db399eb50839bb2d04e612b22ec8a01aa313efdf2\
+	793bea76da6813bda611444af16a6207a8cfef2d9c8aa8f8012f7";
 
 // An invalid signed Alice transfer with a gas limit artifically set to 0.
 pub const INVALID_ETH_TX: &str =

runtime/moonbeam/tests/integration_test.rs

@@ -21,7 +21,7 @@
 mod common;
 use common::*;
 
-use fp_evm::{Context, FeeCalculator};
+use fp_evm::Context;
 use frame_support::{
 	assert_noop, assert_ok,
 	dispatch::{DispatchClass, Dispatchable},
@@ -39,14 +39,15 @@ use moonbeam_runtime::{
 	xcm_config::{CurrencyId, SelfReserve, UnitWeightCost},
 	AccountId, Balances, CouncilCollective, CrowdloanRewards, ParachainStaking, PolkadotXcm,
 	Precompiles, Runtime, RuntimeBlockWeights, RuntimeCall, RuntimeEvent, System,
-	TechCommitteeCollective, TreasuryCouncilCollective, XTokens, XcmTransactor,
+	TechCommitteeCollective, TransactionPayment, TreasuryCouncilCollective, XTokens, XcmTransactor,
 	FOREIGN_ASSET_PRECOMPILE_ADDRESS_PREFIX, LOCAL_ASSET_PRECOMPILE_ADDRESS_PREFIX,
 };
 use nimbus_primitives::NimbusId;
 use pallet_evm::PrecompileSet;
 use pallet_evm_precompileset_assets_erc20::{
 	AccountIdAssetIdConversion, IsLocal, SELECTOR_LOG_APPROVAL, SELECTOR_LOG_TRANSFER,
 };
+use pallet_transaction_payment::Multiplier;
 use pallet_xcm_transactor::{Currency, CurrencyPayment, TransactWeights};
 use parity_scale_codec::Encode;
 use polkadot_parachain::primitives::Sibling;
@@ -76,6 +77,8 @@ type LocalAssetsPCall = pallet_evm_precompileset_assets_erc20::Erc20AssetsPrecom
 type XcmTransactorV2PCall =
 	pallet_evm_precompile_xcm_transactor::v2::XcmTransactorPrecompileV2Call<Runtime>;
 
+const BASE_FEE_GENESIS: u128 = 10000 * GIGAWEI;
+
 #[test]
 fn xcmp_queue_controller_origin_is_root() {
 	// important for the XcmExecutionManager impl of PauseExecution which uses root origin
@@ -496,7 +499,7 @@ fn transfer_through_evm_to_stake() {
 			);
 
 			let gas_limit = 100000u64;
-			let gas_price: U256 = (100 * GIGAWEI).into();
+			let gas_price: U256 = BASE_FEE_GENESIS.into();
 			// Bob transfers 2_000_000 GLMR to Charlie via EVM
 			assert_ok!(RuntimeCall::EVM(pallet_evm::Call::<Runtime>::call {
 				source: H160::from(BOB),
@@ -917,7 +920,7 @@ fn claim_via_precompile() {
 
 			// Alice uses the crowdloan precompile to claim through the EVM
 			let gas_limit = 100000u64;
-			let gas_price: U256 = 100_000_000_000u64.into();
+			let gas_price: U256 = BASE_FEE_GENESIS.into();
 
 			// Construct the call data (selector, amount)
 			let mut call_data = Vec::<u8>::from([0u8; 4]);
@@ -1163,7 +1166,7 @@ fn update_reward_address_via_precompile() {
 
 			// Charlie uses the crowdloan precompile to update address through the EVM
 			let gas_limit = 100000u64;
-			let gas_price: U256 = 100_000_000_000u64.into();
+			let gas_price: U256 = BASE_FEE_GENESIS.into();
 
 			// Construct the input data to check if Bob is a contributor
 			let mut call_data = Vec::<u8>::from([0u8; 36]);
@@ -1282,6 +1285,46 @@ fn ethereum_invalid_transaction() {
 	});
 }
 
+#[test]
+fn initial_gas_fee_is_correct() {
+	use fp_evm::FeeCalculator;
+
+	ExtBuilder::default().build().execute_with(|| {
+		let multiplier = TransactionPayment::next_fee_multiplier();
+		assert_eq!(multiplier, Multiplier::from(1u128));
+
+		assert_eq!(
+			TransactionPaymentAsGasPrice::min_gas_price(),
+			(
+				125_000_000_000u128.into(),
+				Weight::from_ref_time(25_000_000u64)
+			)
+		);
+	});
+}
+
+#[test]
+fn min_gas_fee_is_correct() {
+	use fp_evm::FeeCalculator;
+	use frame_support::traits::Hooks;
+
+	ExtBuilder::default().build().execute_with(|| {
+		pallet_transaction_payment::NextFeeMultiplier::<Runtime>::put(Multiplier::from(0));
+		TransactionPayment::on_finalize(System::block_number()); // should trigger min to kick in
+
+		let multiplier = TransactionPayment::next_fee_multiplier();
+		assert_eq!(multiplier, Multiplier::from(1u128));
+
+		assert_eq!(
+			TransactionPaymentAsGasPrice::min_gas_price(),
+			(
+				125_000_000_000u128.into(),
+				Weight::from_ref_time(25_000_000u64)
+			)
+		);
+	});
+}
+
 #[test]
 fn transfer_ed_0_substrate() {
 	ExtBuilder::default()
@@ -1308,7 +1351,7 @@ fn transfer_ed_0_evm() {
 		.with_balances(vec![
 			(
 				AccountId::from(ALICE),
-				((1 * GLMR) + (21_000 * (100 * GIGAWEI))) + (1 * WEI),
+				((1 * GLMR) + (21_000 * BASE_FEE_GENESIS)) + (1 * WEI),
 			),
 			(AccountId::from(BOB), 0),
 		])
@@ -1321,8 +1364,8 @@ fn transfer_ed_0_evm() {
 				input: Vec::new(),
 				value: (1 * GLMR).into(),
 				gas_limit: 21_000u64,
-				max_fee_per_gas: U256::from(100 * GIGAWEI),
-				max_priority_fee_per_gas: None,
+				max_fee_per_gas: BASE_FEE_GENESIS.into(),
+				max_priority_fee_per_gas: Some(BASE_FEE_GENESIS.into()),
 				nonce: Some(U256::from(0)),
 				access_list: Vec::new(),
 			})
@@ -1338,7 +1381,7 @@ fn refund_ed_0_evm() {
 		.with_balances(vec![
 			(
 				AccountId::from(ALICE),
-				((1 * GLMR) + (21_777 * (100 * GIGAWEI))),
+				((1 * GLMR) + (21_777 * BASE_FEE_GENESIS)),
 			),
 			(AccountId::from(BOB), 0),
 		])
@@ -1351,16 +1394,16 @@ fn refund_ed_0_evm() {
 				input: Vec::new(),
 				value: (1 * GLMR).into(),
 				gas_limit: 21_777u64,
-				max_fee_per_gas: U256::from(100 * GIGAWEI),
-				max_priority_fee_per_gas: None,
+				max_fee_per_gas: BASE_FEE_GENESIS.into(),
+				max_priority_fee_per_gas: Some(BASE_FEE_GENESIS.into()),
 				nonce: Some(U256::from(0)),
 				access_list: Vec::new(),
 			})
 			.dispatch(<Runtime as frame_system::Config>::RuntimeOrigin::root()));
 			// ALICE is refunded
 			assert_eq!(
 				Balances::free_balance(AccountId::from(ALICE)),
-				777 * (100 * GIGAWEI),
+				777 * BASE_FEE_GENESIS,
 			);
 		});
 }
@@ -1440,7 +1483,7 @@ fn total_issuance_after_evm_transaction_without_priority_fee() {
 	ExtBuilder::default()
 		.with_balances(vec![(
 			AccountId::from(BOB),
-			(1 * GLMR) + (21_000 * (200 * GIGAWEI)),
+			(1 * GLMR) + (21_000 * BASE_FEE_GENESIS),
 		)])
 		.build()
 		.execute_with(|| {
@@ -1452,16 +1495,16 @@ fn total_issuance_after_evm_transaction_without_priority_fee() {
 				input: Vec::new(),
 				value: (1 * GLMR).into(),
 				gas_limit: 21_000u64,
-				max_fee_per_gas: U256::from(100 * GIGAWEI),
-				max_priority_fee_per_gas: None,
+				max_fee_per_gas: BASE_FEE_GENESIS.into(),
+				max_priority_fee_per_gas: Some(BASE_FEE_GENESIS.into()),
 				nonce: Some(U256::from(0)),
 				access_list: Vec::new(),
 			})
 			.dispatch(<Runtime as frame_system::Config>::RuntimeOrigin::root()));
 
 			let issuance_after = <Runtime as pallet_evm::Config>::Currency::total_issuance();
 			// Fee is 100 GWEI base fee.
-			let fee = ((100 * GIGAWEI) * 21_000) as f64;
+			let fee = (BASE_FEE_GENESIS * 21_000) as f64;
 			// 80% was burned.
 			let expected_burn = (fee * 0.8) as u128;
 			assert_eq!(issuance_after, issuance_before - expected_burn,);
@@ -2875,15 +2918,6 @@ fn removed_precompiles() {
 	})
 }
 
-#[test]
-fn base_fee_should_default_to_associate_type_value() {
-	ExtBuilder::default().build().execute_with(|| {
-		let (base_fee, _) =
-			<moonbeam_runtime::Runtime as pallet_evm::Config>::FeeCalculator::min_gas_price();
-		assert_eq!(base_fee, (1 * GIGAWEI * SUPPLY_FACTOR).into());
-	});
-}
-
 #[test]
 fn evm_revert_substrate_events() {
 	ExtBuilder::default()
@@ -2907,7 +2941,7 @@ fn evm_revert_substrate_events() {
 				.into(),
 				value: U256::zero(), // No value sent in EVM
 				gas_limit: 500_000,
-				max_fee_per_gas: U256::from(100 * GIGAWEI),
+				max_fee_per_gas: BASE_FEE_GENESIS.into(),
 				max_priority_fee_per_gas: None,
 				nonce: Some(U256::from(0)),
 				access_list: Vec::new(),
@@ -2946,7 +2980,7 @@ fn evm_success_keeps_substrate_events() {
 				.into(),
 				value: U256::zero(), // No value sent in EVM
 				gas_limit: 500_000,
-				max_fee_per_gas: U256::from(100 * GIGAWEI),
+				max_fee_per_gas: BASE_FEE_GENESIS.into(),
 				max_priority_fee_per_gas: None,
 				nonce: Some(U256::from(0)),
 				access_list: Vec::new(),

runtime/moonbeam/tests/runtime_apis.rs

@@ -54,7 +54,10 @@ fn ethereum_runtime_rpc_api_account_basic() {
 #[test]
 fn ethereum_runtime_rpc_api_gas_price() {
 	ExtBuilder::default().build().execute_with(|| {
-		assert_eq!(Runtime::gas_price(), FixedGasPrice::min_gas_price().0);
+		assert_eq!(
+			Runtime::gas_price(),
+			TransactionPaymentAsGasPrice::min_gas_price().0
+		);
 	});
 }
 
@@ -186,7 +189,7 @@ fn ethereum_runtime_rpc_api_create() {
 #[test]
 fn ethereum_runtime_rpc_api_current_transaction_statuses() {
 	let alith = <Runtime as pallet_evm::Config>::AddressMapping::into_account_id(
-		H160::from_str("6be02d1d3665660d22ff9624b7be0551ee1ac91b")
+		H160::from_str("f24FF3a9CF04c71Dbc94D0b566f7A27B94566cac")
 			.expect("internal H160 is valid; qed"),
 	);
 	ExtBuilder::default()
@@ -247,7 +250,7 @@ fn ethereum_runtime_rpc_api_current_block() {
 #[test]
 fn ethereum_runtime_rpc_api_current_receipts() {
 	let alith = <Runtime as pallet_evm::Config>::AddressMapping::into_account_id(
-		H160::from_str("6be02d1d3665660d22ff9624b7be0551ee1ac91b")
+		H160::from_str("f24FF3a9CF04c71Dbc94D0b566f7A27B94566cac")
 			.expect("internal H160 is valid; qed"),
 	);
 	ExtBuilder::default()

tests/smoke-tests/test-dynamic-fees.ts

@@ -116,8 +116,11 @@ describeSmokeSuite(
         this.skip();
       }
 
-      if (specName.toString() == "moonbeam") {
-        debug(`Runtime ${specName.toString()} not supported by these tests, skipping.`);
+      if (specVersion.toNumber() < 2300 && specName.toString() == "moonbeam") {
+        debug(
+          `Runtime ${specName.toString()} version ` +
+            `${specVersion.toString()} is less than 2300, skipping test suite.`
+        );
         this.skip();
       }
 

tests/tests/test-precompile/test-precompile-xcm-utils.ts

@@ -282,7 +282,7 @@ describeDevMoonbeam(
       const { result } = await context.createBlock(
         createTransaction(context, {
           ...ALITH_TRANSACTION_TEMPLATE,
-          gasPrice: 100_000_000_000,
+          gasPrice: 1_000_000_000_000,
           to: PRECOMPILE_XCM_UTILS_ADDRESS,
           data: XCM_UTILSTRANSACTOR_INTERFACE.encodeFunctionData("xcmExecute", [
             receivedMessage.toU8a(),

tests/util/constants.ts

@@ -127,9 +127,9 @@ export const RUNTIME_CONSTANTS = {
     MAX_BASE_FEE_IN_WEI: "125000000000000",
   },
   MOONBEAM: {
-    MIN_FEE_MULTIPLIER: "1000000000000",
-    MAX_FEE_MULTIPLIER: "100000000000000000",
-    MIN_BASE_FEE_IN_WEI: "",
-    MAX_BASE_FEE_IN_WEI: "",
+    MIN_FEE_MULTIPLIER: "1000000000000000000",
+    MAX_FEE_MULTIPLIER: "100000000000000000000000",
+    MIN_BASE_FEE_IN_WEI: "125000000000",
+    MAX_BASE_FEE_IN_WEI: "12500000000000000",
   },
 };