Enable async backing on asset-hub-rococo (#2826)

The goal is to move all system chains on Rococo (+ other testnets?) to
use async backing.

Starting with `asset-hub-rococo` to get feedback, before I do the rest.

## Related

Example: https://github.com/paritytech/polkadot-sdk/pull/1619/
Guide:
https://github.com/w3f/polkadot-wiki/blob/master/docs/maintain/maintain-guides-async-backing.md

---------

Co-authored-by: Branislav Kontur <bkontur@gmail.com>
Co-authored-by: Dónal Murray <donal.murray@parity.io>

cumulus/parachains/runtimes/assets/asset-hub-rococo/Cargo.toml

@@ -77,6 +77,7 @@ cumulus-pallet-parachain-system = { path = "../../../../pallets/parachain-system
 cumulus-pallet-session-benchmarking = { path = "../../../../pallets/session-benchmarking", default-features = false }
 cumulus-pallet-xcm = { path = "../../../../pallets/xcm", default-features = false }
 cumulus-pallet-xcmp-queue = { path = "../../../../pallets/xcmp-queue", default-features = false, features = ["bridging"] }
+cumulus-primitives-aura = { path = "../../../../primitives/aura", default-features = false }
 cumulus-primitives-core = { path = "../../../../primitives/core", default-features = false }
 cumulus-primitives-utility = { path = "../../../../primitives/utility", default-features = false }
 pallet-collator-selection = { path = "../../../../pallets/collator-selection", default-features = false }
@@ -188,6 +189,7 @@ std = [
 	"cumulus-pallet-session-benchmarking/std",
 	"cumulus-pallet-xcm/std",
 	"cumulus-pallet-xcmp-queue/std",
+	"cumulus-primitives-aura/std",
 	"cumulus-primitives-core/std",
 	"cumulus-primitives-utility/std",
 	"frame-benchmarking?/std",

cumulus/parachains/runtimes/assets/asset-hub-rococo/src/lib.rs

@@ -33,7 +33,7 @@ use assets_common::{
 	matching::{FromNetwork, FromSiblingParachain},
 	AssetIdForTrustBackedAssetsConvert,
 };
-use cumulus_pallet_parachain_system::RelayNumberStrictlyIncreases;
+use cumulus_pallet_parachain_system::RelayNumberMonotonicallyIncreases;
 use cumulus_primitives_core::AggregateMessageOrigin;
 use parachains_common::rococo::snowbridge::EthereumNetwork;
 use sp_api::impl_runtime_apis;
@@ -62,7 +62,7 @@ use frame_support::{
 		ConstU128, ConstU32, ConstU64, ConstU8, EitherOfDiverse, Equals, InstanceFilter,
 		TransformOrigin,
 	},
-	weights::{ConstantMultiplier, Weight},
+	weights::{constants::WEIGHT_REF_TIME_PER_SECOND, ConstantMultiplier, Weight},
 	BoundedVec, PalletId,
 };
 use frame_system::{
@@ -71,14 +71,13 @@ use frame_system::{
 };
 use pallet_asset_conversion_tx_payment::AssetConversionAdapter;
 use pallet_nfts::PalletFeatures;
-pub use parachains_common as common;
 use parachains_common::{
 	impls::DealWithFees,
 	message_queue::{NarrowOriginToSibling, ParaIdToSibling},
 	rococo::{consensus::*, currency::*, fee::WeightToFee},
 	AccountId, AssetIdForTrustBackedAssets, AuraId, Balance, BlockNumber, CollectionId, Hash,
 	Header, ItemId, Nonce, Signature, AVERAGE_ON_INITIALIZE_RATIO, DAYS, HOURS,
-	MAXIMUM_BLOCK_WEIGHT, NORMAL_DISPATCH_RATIO, SLOT_DURATION,
+	NORMAL_DISPATCH_RATIO,
 };
 use sp_runtime::{Perbill, RuntimeDebug};
 use xcm_config::{
@@ -141,6 +140,28 @@ pub fn native_version() -> NativeVersion {
 	NativeVersion { runtime_version: VERSION, can_author_with: Default::default() }
 }
 
+/// We allow for 2 seconds of compute with a 6 second average block.
+const MAXIMUM_BLOCK_WEIGHT: Weight = Weight::from_parts(
+	WEIGHT_REF_TIME_PER_SECOND.saturating_mul(2),
+	cumulus_primitives_core::relay_chain::MAX_POV_SIZE as u64,
+);
+
+/// Maximum number of blocks simultaneously accepted by the Runtime, not yet included
+/// into the relay chain.
+const UNINCLUDED_SEGMENT_CAPACITY: u32 = 3;
+/// How many parachain blocks are processed by the relay chain per parent. Limits the
+/// number of blocks authored per slot.
+const BLOCK_PROCESSING_VELOCITY: u32 = 1;
+
+/// This determines the average expected block time that we are targeting.
+/// Blocks will be produced at a minimum duration defined by `SLOT_DURATION`.
+/// `SLOT_DURATION` is picked up by `pallet_timestamp` which is in turn picked
+/// up by `pallet_aura` to implement `fn slot_duration()`.
+///
+/// Change this to adjust the block time.
+pub const MILLISECS_PER_BLOCK: u64 = 6000;
+pub const SLOT_DURATION: u64 = MILLISECS_PER_BLOCK;
+
 parameter_types! {
 	pub const Version: RuntimeVersion = VERSION;
 	pub RuntimeBlockLength: BlockLength =
@@ -189,6 +210,9 @@ impl pallet_timestamp::Config for Runtime {
 	/// A timestamp: milliseconds since the unix epoch.
 	type Moment = u64;
 	type OnTimestampSet = Aura;
+	#[cfg(feature = "experimental")]
+	type MinimumPeriod = ConstU64<0>;
+	#[cfg(not(feature = "experimental"))]
 	type MinimumPeriod = ConstU64<{ SLOT_DURATION / 2 }>;
 	type WeightInfo = weights::pallet_timestamp::WeightInfo<Runtime>;
 }
@@ -630,15 +654,17 @@ impl cumulus_pallet_parachain_system::Config for Runtime {
 	type OutboundXcmpMessageSource = XcmpQueue;
 	type XcmpMessageHandler = XcmpQueue;
 	type ReservedXcmpWeight = ReservedXcmpWeight;
-	type CheckAssociatedRelayNumber = RelayNumberStrictlyIncreases;
-	type ConsensusHook = cumulus_pallet_aura_ext::FixedVelocityConsensusHook<
-		Runtime,
-		RELAY_CHAIN_SLOT_DURATION_MILLIS,
-		BLOCK_PROCESSING_VELOCITY,
-		UNINCLUDED_SEGMENT_CAPACITY,
-	>;
+	type CheckAssociatedRelayNumber = RelayNumberMonotonicallyIncreases;
+	type ConsensusHook = ConsensusHook;
 }
 
+type ConsensusHook = cumulus_pallet_aura_ext::FixedVelocityConsensusHook<
+	Runtime,
+	RELAY_CHAIN_SLOT_DURATION_MILLIS,
+	BLOCK_PROCESSING_VELOCITY,
+	UNINCLUDED_SEGMENT_CAPACITY,
+>;
+
 parameter_types! {
 	pub MessageQueueServiceWeight: Weight = Perbill::from_percent(35) * RuntimeBlockWeights::get().max_block;
 }
@@ -722,9 +748,9 @@ impl pallet_aura::Config for Runtime {
 	type AuthorityId = AuraId;
 	type DisabledValidators = ();
 	type MaxAuthorities = ConstU32<100_000>;
-	type AllowMultipleBlocksPerSlot = ConstBool<false>;
+	type AllowMultipleBlocksPerSlot = ConstBool<true>;
 	#[cfg(feature = "experimental")]
-	type SlotDuration = pallet_aura::MinimumPeriodTimesTwo<Self>;
+	type SlotDuration = ConstU64<SLOT_DURATION>;
 }
 
 parameter_types! {
@@ -1067,7 +1093,7 @@ mod benches {
 impl_runtime_apis! {
 	impl sp_consensus_aura::AuraApi<Block, AuraId> for Runtime {
 		fn slot_duration() -> sp_consensus_aura::SlotDuration {
-			sp_consensus_aura::SlotDuration::from_millis(Aura::slot_duration())
+			sp_consensus_aura::SlotDuration::from_millis(SLOT_DURATION)
 		}
 
 		fn authorities() -> Vec<AuraId> {
@@ -1075,6 +1101,15 @@ impl_runtime_apis! {
 		}
 	}
 
+	impl cumulus_primitives_aura::AuraUnincludedSegmentApi<Block> for Runtime {
+		fn can_build_upon(
+			included_hash: <Block as BlockT>::Hash,
+			slot: cumulus_primitives_aura::Slot,
+		) -> bool {
+			ConsensusHook::can_build_upon(included_hash, slot)
+		}
+	}
+
 	impl sp_api::Core<Block> for Runtime {
 		fn version() -> RuntimeVersion {
 			VERSION

cumulus/parachains/runtimes/assets/asset-hub-rococo/tests/tests.rs

@@ -28,10 +28,11 @@ use asset_hub_rococo_runtime::{
 	AllPalletsWithoutSystem, AssetConversion, AssetDeposit, Assets, Balances, CollatorSelection,
 	ExistentialDeposit, ForeignAssets, ForeignAssetsInstance, MetadataDepositBase,
 	MetadataDepositPerByte, ParachainSystem, Runtime, RuntimeCall, RuntimeEvent, SessionKeys,
-	ToWestendXcmRouterInstance, TrustBackedAssetsInstance, XcmpQueue,
+	ToWestendXcmRouterInstance, TrustBackedAssetsInstance, XcmpQueue, SLOT_DURATION,
 };
 use asset_test_utils::{
-	test_cases_over_bridge::TestBridgingConfig, CollatorSessionKey, CollatorSessionKeys, ExtBuilder,
+	test_cases_over_bridge::TestBridgingConfig, CollatorSessionKey, CollatorSessionKeys,
+	ExtBuilder, SlotDurations,
 };
 use codec::{Decode, Encode};
 use cumulus_primitives_utility::ChargeWeightInFungibles;
@@ -46,9 +47,10 @@ use frame_support::{
 	weights::{Weight, WeightToFee as WeightToFeeT},
 };
 use parachains_common::{
-	rococo::{currency::UNITS, fee::WeightToFee},
+	rococo::{consensus::RELAY_CHAIN_SLOT_DURATION_MILLIS, currency::UNITS, fee::WeightToFee},
 	AccountId, AssetIdForTrustBackedAssets, AuraId, Balance,
 };
+use sp_consensus_aura::SlotDuration;
 use sp_runtime::traits::MaybeEquivalence;
 use std::convert::Into;
 use xcm::latest::prelude::{Assets as XcmAssets, *};
@@ -78,6 +80,13 @@ fn collator_session_keys() -> CollatorSessionKeys<Runtime> {
 	CollatorSessionKeys::default().add(collator_session_key(ALICE))
 }
 
+fn slot_durations() -> SlotDurations {
+	SlotDurations {
+		relay: SlotDuration::from_millis(RELAY_CHAIN_SLOT_DURATION_MILLIS.into()),
+		para: SlotDuration::from_millis(SLOT_DURATION),
+	}
+}
+
 #[test]
 fn test_buy_and_refund_weight_in_native() {
 	ExtBuilder::<Runtime>::default()
@@ -892,6 +901,7 @@ asset_test_utils::include_teleports_for_native_asset_works!(
 	WeightToFee,
 	ParachainSystem,
 	collator_session_keys(),
+	slot_durations(),
 	ExistentialDeposit::get(),
 	Box::new(|runtime_event_encoded: Vec<u8>| {
 		match RuntimeEvent::decode(&mut &runtime_event_encoded[..]) {
@@ -912,6 +922,7 @@ asset_test_utils::include_teleports_for_foreign_assets_works!(
 	ForeignCreatorsSovereignAccountOf,
 	ForeignAssetsInstance,
 	collator_session_keys(),
+	slot_durations(),
 	ExistentialDeposit::get(),
 	Box::new(|runtime_event_encoded: Vec<u8>| {
 		match RuntimeEvent::decode(&mut &runtime_event_encoded[..]) {
@@ -1023,6 +1034,7 @@ fn limited_reserve_transfer_assets_for_native_asset_over_bridge_works(
 		LocationToAccountId,
 	>(
 		collator_session_keys(),
+		slot_durations(),
 		ExistentialDeposit::get(),
 		AccountId::from(ALICE),
 		Box::new(|runtime_event_encoded: Vec<u8>| {
@@ -1194,6 +1206,7 @@ mod asset_hub_rococo_tests {
 			LocationToAccountId,
 		>(
 			collator_session_keys(),
+			slot_durations(),
 			ExistentialDeposit::get(),
 			AccountId::from(ALICE),
 			Box::new(|runtime_event_encoded: Vec<u8>| {

cumulus/parachains/runtimes/assets/asset-hub-westend/src/lib.rs

@@ -55,7 +55,6 @@ use frame_system::{
 use pallet_asset_conversion_tx_payment::AssetConversionAdapter;
 use pallet_nfts::{DestroyWitness, PalletFeatures};
 use pallet_xcm::EnsureXcm;
-pub use parachains_common as common;
 use parachains_common::{
 	impls::DealWithFees,
 	message_queue::*,

cumulus/parachains/runtimes/assets/asset-hub-westend/tests/tests.rs

@@ -32,7 +32,8 @@ use asset_hub_westend_runtime::{
 };
 pub use asset_hub_westend_runtime::{AssetConversion, AssetDeposit, CollatorSelection, System};
 use asset_test_utils::{
-	test_cases_over_bridge::TestBridgingConfig, CollatorSessionKey, CollatorSessionKeys, ExtBuilder,
+	test_cases_over_bridge::TestBridgingConfig, CollatorSessionKey, CollatorSessionKeys,
+	ExtBuilder, SlotDurations,
 };
 use codec::{Decode, Encode};
 use cumulus_primitives_utility::ChargeWeightInFungibles;
@@ -47,9 +48,10 @@ use frame_support::{
 	weights::{Weight, WeightToFee as WeightToFeeT},
 };
 use parachains_common::{
-	westend::{currency::UNITS, fee::WeightToFee},
-	AccountId, AssetIdForTrustBackedAssets, AuraId, Balance,
+	westend::{consensus::RELAY_CHAIN_SLOT_DURATION_MILLIS, currency::UNITS, fee::WeightToFee},
+	AccountId, AssetIdForTrustBackedAssets, AuraId, Balance, SLOT_DURATION,
 };
+use sp_consensus_aura::SlotDuration;
 use sp_runtime::traits::MaybeEquivalence;
 use std::convert::Into;
 use xcm::latest::prelude::{Assets as XcmAssets, *};
@@ -79,6 +81,13 @@ fn collator_session_keys() -> CollatorSessionKeys<Runtime> {
 	CollatorSessionKeys::default().add(collator_session_key(ALICE))
 }
 
+fn slot_durations() -> SlotDurations {
+	SlotDurations {
+		relay: SlotDuration::from_millis(RELAY_CHAIN_SLOT_DURATION_MILLIS.into()),
+		para: SlotDuration::from_millis(SLOT_DURATION),
+	}
+}
+
 #[test]
 fn test_buy_and_refund_weight_in_native() {
 	ExtBuilder::<Runtime>::default()
@@ -895,6 +904,7 @@ asset_test_utils::include_teleports_for_native_asset_works!(
 	WeightToFee,
 	ParachainSystem,
 	collator_session_keys(),
+	slot_durations(),
 	ExistentialDeposit::get(),
 	Box::new(|runtime_event_encoded: Vec<u8>| {
 		match RuntimeEvent::decode(&mut &runtime_event_encoded[..]) {
@@ -915,6 +925,7 @@ asset_test_utils::include_teleports_for_foreign_assets_works!(
 	ForeignCreatorsSovereignAccountOf,
 	ForeignAssetsInstance,
 	collator_session_keys(),
+	slot_durations(),
 	ExistentialDeposit::get(),
 	Box::new(|runtime_event_encoded: Vec<u8>| {
 		match RuntimeEvent::decode(&mut &runtime_event_encoded[..]) {
@@ -1041,6 +1052,7 @@ fn limited_reserve_transfer_assets_for_native_asset_to_asset_hub_rococo_works()
 		LocationToAccountId,
 	>(
 		collator_session_keys(),
+		slot_durations(),
 		ExistentialDeposit::get(),
 		AccountId::from(ALICE),
 		Box::new(|runtime_event_encoded: Vec<u8>| {
@@ -1208,6 +1220,7 @@ fn reserve_transfer_native_asset_to_non_teleport_para_works() {
 		LocationToAccountId,
 	>(
 		collator_session_keys(),
+		slot_durations(),
 		ExistentialDeposit::get(),
 		AccountId::from(ALICE),
 		Box::new(|runtime_event_encoded: Vec<u8>| {

cumulus/parachains/runtimes/assets/test-utils/src/test_cases.rs

@@ -31,7 +31,7 @@ use frame_system::pallet_prelude::BlockNumberFor;
 use parachains_common::{AccountId, Balance};
 use parachains_runtimes_test_utils::{
 	assert_metadata, assert_total, mock_open_hrmp_channel, AccountIdOf, BalanceOf,
-	CollatorSessionKeys, ExtBuilder, ValidatorIdOf, XcmReceivedFrom,
+	CollatorSessionKeys, ExtBuilder, SlotDurations, ValidatorIdOf, XcmReceivedFrom,
 };
 use sp_runtime::{
 	traits::{MaybeEquivalence, StaticLookup, Zero},
@@ -57,6 +57,7 @@ pub fn teleports_for_native_asset_works<
 	HrmpChannelOpener,
 >(
 	collator_session_keys: CollatorSessionKeys<Runtime>,
+	slot_durations: SlotDurations,
 	existential_deposit: BalanceOf<Runtime>,
 	target_account: AccountIdOf<Runtime>,
 	unwrap_pallet_xcm_event: Box<dyn Fn(Vec<u8>) -> Option<pallet_xcm::Event<Runtime>>>,
@@ -205,6 +206,7 @@ pub fn teleports_for_native_asset_works<
 					None,
 					included_head.clone(),
 					&alice,
+					&slot_durations,
 				));
 
 				// check balances
@@ -257,6 +259,7 @@ pub fn teleports_for_native_asset_works<
 						Some((runtime_para_id, other_para_id)),
 						included_head,
 						&alice,
+						&slot_durations,
 					),
 					Err(DispatchError::Module(sp_runtime::ModuleError {
 						index: 31,
@@ -288,6 +291,7 @@ macro_rules! include_teleports_for_native_asset_works(
 		$weight_to_fee:path,
 		$hrmp_channel_opener:path,
 		$collator_session_key:expr,
+		$slot_durations:expr,
 		$existential_deposit:expr,
 		$unwrap_pallet_xcm_event:expr,
 		$runtime_para_id:expr
@@ -306,6 +310,7 @@ macro_rules! include_teleports_for_native_asset_works(
 				$hrmp_channel_opener
 			>(
 				$collator_session_key,
+				$slot_durations,
 				$existential_deposit,
 				target_account,
 				$unwrap_pallet_xcm_event,
@@ -328,6 +333,7 @@ pub fn teleports_for_foreign_assets_works<
 	ForeignAssetsPalletInstance,
 >(
 	collator_session_keys: CollatorSessionKeys<Runtime>,
+	slot_durations: SlotDurations,
 	target_account: AccountIdOf<Runtime>,
 	existential_deposit: BalanceOf<Runtime>,
 	asset_owner: AccountIdOf<Runtime>,
@@ -592,6 +598,7 @@ pub fn teleports_for_foreign_assets_works<
 					Some((runtime_para_id, foreign_para_id)),
 					included_head,
 					&alice,
+					&slot_durations,
 				));
 
 				// check balances
@@ -644,6 +651,7 @@ macro_rules! include_teleports_for_foreign_assets_works(
 		$sovereign_account_of:path,
 		$assets_pallet_instance:path,
 		$collator_session_key:expr,
+		$slot_durations:expr,
 		$existential_deposit:expr,
 		$unwrap_pallet_xcm_event:expr,
 		$unwrap_xcmp_queue_event:expr
@@ -666,6 +674,7 @@ macro_rules! include_teleports_for_foreign_assets_works(
 				$assets_pallet_instance
 			>(
 				$collator_session_key,
+				$slot_durations,
 				target_account,
 				$existential_deposit,
 				asset_owner,
@@ -1397,6 +1406,7 @@ pub fn reserve_transfer_native_asset_to_non_teleport_para_works<
 	LocationToAccountId,
 >(
 	collator_session_keys: CollatorSessionKeys<Runtime>,
+	slot_durations: SlotDurations,
 	existential_deposit: BalanceOf<Runtime>,
 	alice_account: AccountIdOf<Runtime>,
 	unwrap_pallet_xcm_event: Box<dyn Fn(Vec<u8>) -> Option<pallet_xcm::Event<Runtime>>>,
@@ -1470,6 +1480,7 @@ pub fn reserve_transfer_native_asset_to_non_teleport_para_works<
 				other_para_id.into(),
 				included_head,
 				&alice,
+				&slot_durations,
 			);
 
 			// we calculate exact delivery fees _after_ sending the message by weighing the sent

cumulus/parachains/runtimes/assets/test-utils/src/test_cases_over_bridge.rs

@@ -27,7 +27,7 @@ use frame_system::pallet_prelude::BlockNumberFor;
 use parachains_common::{AccountId, Balance};
 use parachains_runtimes_test_utils::{
 	mock_open_hrmp_channel, AccountIdOf, BalanceOf, CollatorSessionKeys, ExtBuilder, RuntimeHelper,
-	ValidatorIdOf, XcmReceivedFrom,
+	SlotDurations, ValidatorIdOf, XcmReceivedFrom,
 };
 use sp_runtime::{traits::StaticLookup, Saturating};
 use sp_std::ops::Mul;
@@ -52,6 +52,7 @@ pub fn limited_reserve_transfer_assets_for_native_asset_works<
 	LocationToAccountId,
 >(
 	collator_session_keys: CollatorSessionKeys<Runtime>,
+	slot_durations: SlotDurations,
 	existential_deposit: BalanceOf<Runtime>,
 	alice_account: AccountIdOf<Runtime>,
 	unwrap_pallet_xcm_event: Box<dyn Fn(Vec<u8>) -> Option<pallet_xcm::Event<Runtime>>>,
@@ -125,6 +126,7 @@ pub fn limited_reserve_transfer_assets_for_native_asset_works<
 				local_bridge_hub_para_id.into(),
 				included_head,
 				&alice,
+				&slot_durations,
 			);
 
 			// we calculate exact delivery fees _after_ sending the message by weighing the sent