use AtStake to dispatch rewards instead of AwardedPts (#1896)

pallets/parachain-staking/src/benchmarks.rs

@@ -19,8 +19,8 @@
 //! Benchmarking
 use crate::{
 	AwardedPts, BalanceOf, Call, CandidateBondLessRequest, Config, DelegationAction, Pallet,
-	ParachainBondConfig, ParachainBondInfo, Points, Range, Round, ScheduledRequest, Staked,
-	TopDelegations,
+	ParachainBondConfig, ParachainBondInfo, Points, Range, RewardPayment, Round, ScheduledRequest,
+	Staked, TopDelegations,
 };
 use frame_benchmarking::{account, benchmarks, impl_benchmark_test_suite, vec};
 use frame_support::traits::{Currency, Get, OnFinalize, OnInitialize};
@@ -1036,7 +1036,8 @@ benchmarks! {
 		// TODO: this is an extra read right here (we should whitelist it?)
 		let payout_info = Pallet::<T>::delayed_payouts(round_for_payout).expect("payout expected");
 		let result = Pallet::<T>::pay_one_collator_reward(round_for_payout, payout_info);
-		assert!(result.0.is_some()); // TODO: how to keep this in scope so it can be done in verify block?
+		// TODO: how to keep this in scope so it can be done in verify block?
+		assert!(matches!(result.0, RewardPayment::Paid));
 	}
 	verify {
 		// collator should have been paid

pallets/parachain-staking/src/lib.rs

@@ -1387,6 +1387,17 @@ pub mod pallet {
 		}
 	}
 
+	/// Represents a payout made via `pay_one_collator_reward`.
+	pub(crate) enum RewardPayment {
+		/// A collator was paid
+		Paid,
+		/// A collator was skipped for payment. This can happen if they haven't been awarded any
+		/// points, that is, they did not produce any blocks.
+		Skipped,
+		/// All collator payments have been processed.
+		Finished,
+	}
+
 	impl<T: Config> Pallet<T> {
 		pub fn is_delegator(acc: &T::AccountId) -> bool {
 			<DelegatorState<T>>::get(acc).is_some()
@@ -1518,22 +1529,13 @@ pub mod pallet {
 
 			if let Some(payout_info) = <DelayedPayouts<T>>::get(paid_for_round) {
 				let result = Self::pay_one_collator_reward(paid_for_round, payout_info);
-				if result.0.is_none() {
-					// result.0 indicates whether or not a payout was made
-					// clean up storage items that we no longer need
+
+				// clean up storage items that we no longer need
+				if matches!(result.0, RewardPayment::Finished) {
 					<DelayedPayouts<T>>::remove(paid_for_round);
 					<Points<T>>::remove(paid_for_round);
-
-					// remove all candidates that did not produce any blocks for
-					// the given round. The weight is added based on the number of backend
-					// items removed.
-					let remove_result = <AtStake<T>>::clear_prefix(paid_for_round, 20, None);
-					result
-						.1
-						.saturating_add(T::DbWeight::get().writes(remove_result.backend as u64))
-				} else {
-					result.1 // weight consumed by pay_one_collator_reward
 				}
+				result.1 // weight consumed by pay_one_collator_reward
 			} else {
 				Weight::from_ref_time(0u64)
 			}
@@ -1546,7 +1548,7 @@ pub mod pallet {
 		pub(crate) fn pay_one_collator_reward(
 			paid_for_round: RoundIndex,
 			payout_info: DelayedPayout<BalanceOf<T>>,
-		) -> (Option<(T::AccountId, BalanceOf<T>)>, Weight) {
+		) -> (RewardPayment, Weight) {
 			// TODO: it would probably be optimal to roll Points into the DelayedPayouts storage
 			// item so that we do fewer reads each block
 			let total_points = <Points<T>>::get(paid_for_round);
@@ -1557,22 +1559,25 @@ pub mod pallet {
 				// 2. we called pay_one_collator_reward when we were actually done with deferred
 				//    payouts
 				log::warn!("pay_one_collator_reward called with no <Points<T>> for the round!");
-				return (None, Weight::zero());
+				return (RewardPayment::Finished, Weight::zero());
 			}
 
 			let collator_fee = payout_info.collator_commission;
 			let collator_issuance = collator_fee * payout_info.round_issuance;
 
-			if let Some((collator, pts)) =
-				<AwardedPts<T>>::iter_prefix(paid_for_round).drain().next()
+			if let Some((collator, state)) =
+				<AtStake<T>>::iter_prefix(paid_for_round).drain().next()
 			{
+				// Take the awarded points for the collator
+				let pts = <AwardedPts<T>>::take(paid_for_round, &collator);
+				if pts == 0 {
+					return (RewardPayment::Skipped, T::DbWeight::get().reads(1));
+				}
+
 				let mut extra_weight = Weight::zero();
 				let pct_due = Perbill::from_rational(pts, total_points);
 				let total_paid = pct_due * payout_info.total_staking_reward;
 				let mut amt_due = total_paid;
-				// Take the snapshot of block author and delegations
-
-				let state = <AtStake<T>>::take(paid_for_round, &collator);
 
 				let num_delegators = state.delegations.len();
 				if state.delegations.is_empty() {
@@ -1619,14 +1624,14 @@ pub mod pallet {
 				}
 
 				(
-					Some((collator, total_paid)),
+					RewardPayment::Paid,
 					T::WeightInfo::pay_one_collator_reward(num_delegators as u32)
 						.saturating_add(extra_weight),
 				)
 			} else {
 				// Note that we don't clean up storage here; it is cleaned up in
 				// handle_delayed_payouts()
-				(None, Weight::from_ref_time(0u64.into()))
+				(RewardPayment::Finished, Weight::from_ref_time(0u64.into()))
 			}
 		}
 

pallets/parachain-staking/src/mock.rs

@@ -249,7 +249,7 @@ impl ExtBuilder {
 }
 
 /// Rolls forward one block. Returns the new block number.
-pub(crate) fn roll_one_block() -> BlockNumber {
+fn roll_one_block() -> BlockNumber {
 	Balances::on_finalize(System::block_number());
 	System::on_finalize(System::block_number());
 	System::set_block_number(System::block_number() + 1);
@@ -261,7 +261,7 @@ pub(crate) fn roll_one_block() -> BlockNumber {
 }
 
 /// Rolls to the desired block. Returns the number of blocks played.
-pub(crate) fn roll_to(n: BlockNumber) -> BlockNumber {
+pub(crate) fn roll_to(n: BlockNumber) -> u32 {
 	let mut num_blocks = 0;
 	let mut block = System::block_number();
 	while block < n {
@@ -271,6 +271,15 @@ pub(crate) fn roll_to(n: BlockNumber) -> BlockNumber {
 	num_blocks
 }
 
+/// Rolls desired number of blocks. Returns the final block.
+pub(crate) fn roll_blocks(num_blocks: u32) -> BlockNumber {
+	let mut block = System::block_number();
+	for _ in 0..num_blocks {
+		block = roll_one_block();
+	}
+	block
+}
+
 /// Rolls block-by-block to the beginning of the specified round.
 /// This will complete the block in which the round change occurs.
 /// Returns the number of blocks played.