Coretime: Add request revenue info (paritytech#3940)

Enables the `request_revenue` and `notify_revenue` parts of [RFC 5 -
Coretime
Interface](https://polkadot-fellows.github.io/RFCs/approved/0005-coretime-interface.html)

TODO:
- [x] Finish first pass at implementation
- [x] ~~Need to explicitly burn uncollected and dropped revenue~~
Accumulate it instead
- [x] Confirm working on zombienet
- [x] Tests 
- [ ] Enable XCM `request_revenue` sending on Coretime chain on Kusama
and Polkadot

Fixes: paritytech#2209

---------

Co-authored-by: Dmitry Sinyavin <[email protected]>
Co-authored-by: command-bot <>
Co-authored-by: s0me0ne-unkn0wn <[email protected]>
Co-authored-by: Dónal Murray <[email protected]>
Co-authored-by: Bastian Köcher <[email protected]>

cumulus/parachains/runtimes/coretime/coretime-rococo/Cargo.toml

@@ -199,4 +199,6 @@ try-runtime = [
 	"sp-runtime/try-runtime",
 ]
 
-fast-runtime = []
+fast-runtime = [
+	"rococo-runtime-constants/fast-runtime",
+]

cumulus/parachains/runtimes/coretime/coretime-rococo/src/coretime.rs

@@ -21,22 +21,65 @@ use cumulus_primitives_core::relay_chain;
 use frame_support::{
 	parameter_types,
 	traits::{
-		fungible::{Balanced, Credit},
-		OnUnbalanced,
+		fungible::{Balanced, Credit, Inspect},
+		tokens::{Fortitude, Preservation},
+		DefensiveResult, OnUnbalanced,
 	},
 };
+use frame_system::Pallet as System;
 use pallet_broker::{CoreAssignment, CoreIndex, CoretimeInterface, PartsOf57600, RCBlockNumberOf};
-use parachains_common::{AccountId, Balance, BlockNumber};
+use parachains_common::{AccountId, Balance};
+use rococo_runtime_constants::system_parachain::coretime;
+use sp_runtime::traits::AccountIdConversion;
 use xcm::latest::prelude::*;
+use xcm_executor::traits::TransactAsset;
 
-pub struct CreditToCollatorPot;
-impl OnUnbalanced<Credit<AccountId, Balances>> for CreditToCollatorPot {
-	fn on_nonzero_unbalanced(credit: Credit<AccountId, Balances>) {
-		let staking_pot = CollatorSelection::account_id();
-		let _ = <Balances as Balanced<_>>::resolve(&staking_pot, credit);
+pub struct BurnCoretimeRevenue;
+impl OnUnbalanced<Credit<AccountId, Balances>> for BurnCoretimeRevenue {
+	fn on_nonzero_unbalanced(amount: Credit<AccountId, Balances>) {
+		let acc = RevenueAccumulationAccount::get();
+		if !System::<Runtime>::account_exists(&acc) {
+			System::<Runtime>::inc_providers(&acc);
+		}
+		Balances::resolve(&acc, amount).defensive_ok();
 	}
 }
 
+type AssetTransactor = <xcm_config::XcmConfig as xcm_executor::Config>::AssetTransactor;
+
+fn burn_at_relay(stash: &AccountId, value: Balance) -> Result<(), XcmError> {
+	let dest = Location::parent();
+	let stash_location =
+		Junction::AccountId32 { network: None, id: stash.clone().into() }.into_location();
+	let asset = Asset { id: AssetId(Location::parent()), fun: Fungible(value) };
+	let dummy_xcm_context = XcmContext { origin: None, message_id: [0; 32], topic: None };
+
+	let withdrawn = AssetTransactor::withdraw_asset(&asset, &stash_location, None)?;
+
+	AssetTransactor::can_check_out(&dest, &asset, &dummy_xcm_context)?;
+
+	let parent_assets = Into::<Assets>::into(withdrawn)
+		.reanchored(&dest, &Here.into())
+		.defensive_map_err(|_| XcmError::ReanchorFailed)?;
+
+	PolkadotXcm::send_xcm(
+		Here,
+		Location::parent(),
+		Xcm(vec![
+			Instruction::UnpaidExecution {
+				weight_limit: WeightLimit::Unlimited,
+				check_origin: None,
+			},
+			ReceiveTeleportedAsset(parent_assets.clone()),
+			BurnAsset(parent_assets),
+		]),
+	)?;
+
+	AssetTransactor::check_out(&dest, &asset, &dummy_xcm_context);
+
+	Ok(())
+}
+
 /// A type containing the encoding of the coretime pallet in the Relay chain runtime. Used to
 /// construct any remote calls. The codec index must correspond to the index of `Coretime` in the
 /// `construct_runtime` of the Relay chain.
@@ -66,11 +109,7 @@ enum CoretimeProviderCalls {
 
 parameter_types! {
 	pub const BrokerPalletId: PalletId = PalletId(*b"py/broke");
-}
-
-parameter_types! {
-	pub storage CoreCount: Option<CoreIndex> = None;
-	pub storage CoretimeRevenue: Option<(BlockNumber, Balance)> = None;
+	pub RevenueAccumulationAccount: AccountId = BrokerPalletId::get().into_sub_account_truncating(b"burnstash");
 }
 
 /// Type that implements the `CoretimeInterface` for the allocation of Coretime. Meant to operate
@@ -205,26 +244,30 @@ impl CoretimeInterface for CoretimeAllocator {
 		}
 	}
 
-	fn check_notify_revenue_info() -> Option<(RCBlockNumberOf<Self>, Self::Balance)> {
-		let revenue = CoretimeRevenue::get();
-		CoretimeRevenue::set(&None);
-		revenue
-	}
+	fn on_new_timeslice(_t: pallet_broker::Timeslice) {
+		let stash = RevenueAccumulationAccount::get();
+		let value =
+			Balances::reducible_balance(&stash, Preservation::Expendable, Fortitude::Polite);
 
-	#[cfg(feature = "runtime-benchmarks")]
-	fn ensure_notify_revenue_info(when: RCBlockNumberOf<Self>, revenue: Self::Balance) {
-		CoretimeRevenue::set(&Some((when, revenue)));
+		if value > 0 {
+			log::debug!(target: "runtime::coretime", "Going to burn {value} stashed tokens at RC");
+			match burn_at_relay(&stash, value) {
+				Ok(()) => {
+					log::debug!(target: "runtime::coretime", "Succesfully burnt {value} tokens");
+				},
+				Err(err) => {
+					log::error!(target: "runtime::coretime", "burn_at_relay failed: {err:?}");
+				},
+			}
+		}
 	}
 }
 
 impl pallet_broker::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type Currency = Balances;
-	type OnRevenue = CreditToCollatorPot;
-	#[cfg(feature = "fast-runtime")]
-	type TimeslicePeriod = ConstU32<10>;
-	#[cfg(not(feature = "fast-runtime"))]
-	type TimeslicePeriod = ConstU32<80>;
+	type OnRevenue = BurnCoretimeRevenue;
+	type TimeslicePeriod = ConstU32<{ coretime::TIMESLICE_PERIOD }>;
 	type MaxLeasedCores = ConstU32<50>;
 	type MaxReservedCores = ConstU32<10>;
 	type Coretime = CoretimeAllocator;

cumulus/parachains/runtimes/coretime/coretime-rococo/src/lib.rs

@@ -117,6 +117,7 @@ pub type Migrations = (
 	cumulus_pallet_xcmp_queue::migration::v5::MigrateV4ToV5<Runtime>,
 	pallet_broker::migration::MigrateV0ToV1<Runtime>,
 	pallet_broker::migration::MigrateV1ToV2<Runtime>,
+	pallet_broker::migration::MigrateV2ToV3<Runtime>,
 	// permanent
 	pallet_xcm::migration::MigrateToLatestXcmVersion<Runtime>,
 );