stake: fix collator fee to 20% (paritytech#306)

* done

* bump spec

* fix types

moonbeam-types-bundle/index.ts

@@ -200,14 +200,12 @@ export const moonbeamDefinitions = {
         OrderedSet: "Vec<Bond>",
         Collator: {
           id: "AccountId",
-          fee: "Perbill",
           bond: "Balance",
           nominators: "Vec<Bond>",
           total: "Balance",
           state: "CollatorStatus",
         },
         CollatorSnapshot: {
-          fee: "Perbill",
           bond: "Balance",
           nominators: "Vec<Bond>",
           total: "Balance",

pallets/parachain-staking/src/lib.rs

@@ -131,7 +131,6 @@ pub mod pallet {
 	#[derive(Default, Encode, Decode, RuntimeDebug)]
 	/// Snapshot of collator state at the start of the round for which they are selected
 	pub struct CollatorSnapshot<AccountId, Balance> {
-		pub fee: Perbill,
 		pub bond: Balance,
 		pub nominators: Vec<Bond<AccountId, Balance>>,
 		pub total: Balance,
@@ -141,7 +140,6 @@ pub mod pallet {
 	/// Global collator state with commission fee, bonded stake, and nominations
 	pub struct Collator<AccountId, Balance> {
 		pub id: AccountId,
-		pub fee: Perbill,
 		pub bond: Balance,
 		pub nominators: OrderedSet<Bond<AccountId, Balance>>,
 		pub total: Balance,
@@ -153,11 +151,10 @@ pub mod pallet {
 			B: AtLeast32BitUnsigned + Ord + Copy + sp_std::ops::AddAssign + sp_std::ops::SubAssign,
 		> Collator<A, B>
 	{
-		pub fn new(id: A, fee: Perbill, bond: B) -> Self {
+		pub fn new(id: A, bond: B) -> Self {
 			let total = bond;
 			Collator {
 				id,
-				fee,
 				bond,
 				nominators: OrderedSet::new(),
 				total,
@@ -216,7 +213,6 @@ pub mod pallet {
 	impl<A: Clone, B: Copy> From<Collator<A, B>> for CollatorSnapshot<A, B> {
 		fn from(other: Collator<A, B>) -> CollatorSnapshot<A, B> {
 			CollatorSnapshot {
-				fee: other.fee,
 				bond: other.bond,
 				nominators: other.nominators.0,
 				total: other.total,
@@ -389,8 +385,8 @@ pub mod pallet {
 		type MaxNominatorsPerCollator: Get<u32>;
 		/// Maximum collators per nominator
 		type MaxCollatorsPerNominator: Get<u32>;
-		/// Maximum fee for any collator
-		type MaxFee: Get<Perbill>;
+		/// Commission due to collators, set at genesis
+		type DefaultCollatorCommission: Get<Perbill>;
 		/// Minimum stake required for any account to be in `SelectedCandidates` for the round
 		type MinCollatorStk: Get<BalanceOf<Self>>;
 		/// Minimum stake required for any account to be a collator candidate
@@ -408,7 +404,6 @@ pub mod pallet {
 		CandidateDNE,
 		NominatorExists,
 		CandidateExists,
-		FeeOverMax,
 		ValBondBelowMin,
 		NomBondBelowMin,
 		NominationBelowMin,
@@ -462,6 +457,8 @@ pub mod pallet {
 		StakeExpectationsSet(BalanceOf<T>, BalanceOf<T>, BalanceOf<T>),
 		/// Set total selected candidates to this value [old, new]
 		TotalSelectedSet(u32, u32),
+		/// Set collator commission to this value [old, new]
+		CollatorCommissionSet(Perbill, Perbill),
 		/// Set blocks per round [current_round, first_block, old, new]
 		BlocksPerRoundSet(RoundIndex, T::BlockNumber, u32, u32),
 	}
@@ -493,6 +490,11 @@ pub mod pallet {
 		}
 	}
 
+	#[pallet::storage]
+	#[pallet::getter(fn collator_commission)]
+	/// Commission percent taken off of rewards for all collators
+	type CollatorCommission<T: Config> = StorageValue<_, Perbill, ValueQuery>;
+
 	#[pallet::storage]
 	#[pallet::getter(fn total_selected)]
 	/// The total candidates selected every round
@@ -622,11 +624,12 @@ pub mod pallet {
 				} else {
 					<Pallet<T>>::join_candidates(
 						T::Origin::from(Some(actor.clone()).into()),
-						Perbill::zero(), // default fee for collators registered at genesis is 0%
 						balance,
 					)
 				};
 			}
+			// Set collator commission to default config
+			<CollatorCommission<T>>::put(T::DefaultCollatorCommission::get());
 			// Set total selected candidates to minimum config
 			<TotalSelected<T>>::put(T::MinSelectedCandidates::get());
 			// Choose top TotalSelected collator candidates
@@ -700,6 +703,18 @@ pub mod pallet {
 			Ok(().into())
 		}
 		#[pallet::weight(0)]
+		/// Set the commission for all collators
+		pub fn set_collator_commission(
+			origin: OriginFor<T>,
+			pct: Perbill,
+		) -> DispatchResultWithPostInfo {
+			frame_system::ensure_root(origin)?;
+			let old = <CollatorCommission<T>>::get();
+			<CollatorCommission<T>>::put(pct);
+			Self::deposit_event(Event::CollatorCommissionSet(old, pct));
+			Ok(().into())
+		}
+		#[pallet::weight(0)]
 		/// Set blocks per round
 		/// - if called with `new` less than length of current round, will transition immediately
 		/// in the next block
@@ -720,13 +735,11 @@ pub mod pallet {
 		#[pallet::weight(0)]
 		pub fn join_candidates(
 			origin: OriginFor<T>,
-			fee: Perbill,
 			bond: BalanceOf<T>,
 		) -> DispatchResultWithPostInfo {
 			let acc = ensure_signed(origin)?;
 			ensure!(!Self::is_candidate(&acc), Error::<T>::CandidateExists);
 			ensure!(!Self::is_nominator(&acc), Error::<T>::NominatorExists);
-			ensure!(fee <= T::MaxFee::get(), Error::<T>::FeeOverMax);
 			ensure!(
 				bond >= T::MinCollatorCandidateStk::get(),
 				Error::<T>::ValBondBelowMin
@@ -740,7 +753,7 @@ pub mod pallet {
 				Error::<T>::CandidateExists
 			);
 			T::Currency::reserve(&acc, bond)?;
-			let candidate = Collator::new(acc.clone(), fee, bond);
+			let candidate = Collator::new(acc.clone(), bond);
 			let new_total = <Total<T>>::get() + bond;
 			<Total<T>>::put(new_total);
 			<CollatorState<T>>::insert(&acc, candidate);
@@ -1147,6 +1160,7 @@ pub mod pallet {
 				}
 			};
 			let duration = T::BondDuration::get();
+			let collator_fee = <CollatorCommission<T>>::get();
 			if next > duration {
 				let round_to_payout = next - duration;
 				let total = <Points<T>>::get(round_to_payout);
@@ -1166,7 +1180,7 @@ pub mod pallet {
 					} else {
 						// pay collator first; commission + due_portion
 						let val_pct = Perbill::from_rational(state.bond, state.total);
-						let commission = state.fee * amt_due;
+						let commission = collator_fee * amt_due;
 						let val_due = if commission > T::Currency::minimum_balance() {
 							amt_due -= commission;
 							(val_pct * amt_due) + commission

pallets/parachain-staking/src/mock.rs

@@ -100,7 +100,7 @@ parameter_types! {
 	pub const MinSelectedCandidates: u32 = 5;
 	pub const MaxNominatorsPerCollator: u32 = 4;
 	pub const MaxCollatorsPerNominator: u32 = 4;
-	pub const MaxFee: Perbill = Perbill::from_percent(50);
+	pub const DefaultCollatorCommission: Perbill = Perbill::from_percent(20);
 	pub const MinCollatorStk: u128 = 10;
 	pub const MinNominatorStk: u128 = 5;
 	pub const MinNomination: u128 = 3;
@@ -114,7 +114,7 @@ impl Config for Test {
 	type MinSelectedCandidates = MinSelectedCandidates;
 	type MaxNominatorsPerCollator = MaxNominatorsPerCollator;
 	type MaxCollatorsPerNominator = MaxCollatorsPerNominator;
-	type MaxFee = MaxFee;
+	type DefaultCollatorCommission = DefaultCollatorCommission;
 	type MinCollatorStk = MinCollatorStk;
 	type MinCollatorCandidateStk = MinCollatorStk;
 	type MinNominatorStk = MinNominatorStk;

pallets/parachain-staking/src/tests.rs

@@ -22,7 +22,7 @@ use crate::mock::{
 };
 use crate::{CollatorStatus, Error, Event};
 use frame_support::{assert_noop, assert_ok};
-use sp_runtime::{traits::Zero, DispatchError, Perbill};
+use sp_runtime::{traits::Zero, DispatchError};
 
 #[test]
 fn geneses() {
@@ -131,35 +131,27 @@ fn online_offline_works() {
 fn join_collator_candidates() {
 	two_collators_four_nominators().execute_with(|| {
 		assert_noop!(
-			Stake::join_candidates(Origin::signed(1), Perbill::from_percent(2), 11u128,),
+			Stake::join_candidates(Origin::signed(1), 11u128,),
 			Error::<Test>::CandidateExists
 		);
 		assert_noop!(
-			Stake::join_candidates(Origin::signed(3), Perbill::from_percent(2), 11u128,),
+			Stake::join_candidates(Origin::signed(3), 11u128,),
 			Error::<Test>::NominatorExists
 		);
 		assert_noop!(
-			Stake::join_candidates(Origin::signed(7), Perbill::from_percent(2), 9u128,),
+			Stake::join_candidates(Origin::signed(7), 9u128,),
 			Error::<Test>::ValBondBelowMin
 		);
 		assert_noop!(
-			Stake::join_candidates(Origin::signed(8), Perbill::from_percent(2), 10u128,),
+			Stake::join_candidates(Origin::signed(8), 10u128,),
 			DispatchError::Module {
 				index: 1,
 				error: 3,
 				message: Some("InsufficientBalance")
 			}
 		);
-		assert_noop!(
-			Stake::join_candidates(Origin::signed(7), Perbill::from_percent(51), 10u128,),
-			Error::<Test>::FeeOverMax
-		);
 		assert!(System::events().is_empty());
-		assert_ok!(Stake::join_candidates(
-			Origin::signed(7),
-			Perbill::from_percent(3),
-			10u128,
-		));
+		assert_ok!(Stake::join_candidates(Origin::signed(7), 10u128,));
 		assert_eq!(
 			last_event(),
 			MetaEvent::stake(Event::JoinedCollatorCandidates(7, 10u128, 1110u128))
@@ -225,11 +217,7 @@ fn collator_selection_chooses_top_candidates() {
 			MetaEvent::stake(Event::CollatorScheduledExit(2, 6, 4))
 		);
 		roll_to(21);
-		assert_ok!(Stake::join_candidates(
-			Origin::signed(6),
-			Perbill::from_percent(2),
-			69u128
-		));
+		assert_ok!(Stake::join_candidates(Origin::signed(6), 69u128));
 		assert_eq!(
 			last_event(),
 			MetaEvent::stake(Event::JoinedCollatorCandidates(6, 69u128, 469u128))
@@ -448,11 +436,7 @@ fn collator_commission() {
 			Event::NewRound(5, 2, 1, 40),
 		];
 		assert_eq!(events(), expected);
-		assert_ok!(Stake::join_candidates(
-			Origin::signed(4),
-			Perbill::from_percent(20),
-			20u128
-		));
+		assert_ok!(Stake::join_candidates(Origin::signed(4), 20u128));
 		assert_eq!(
 			last_event(),
 			MetaEvent::stake(Event::JoinedCollatorCandidates(4, 20u128, 60u128))
@@ -783,10 +767,10 @@ fn payouts_follow_nomination_changes() {
 			Event::CollatorChosen(3, 3, 20),
 			Event::CollatorChosen(3, 5, 10),
 			Event::NewRound(10, 3, 5, 140),
-			Event::Rewarded(1, 20),
-			Event::Rewarded(6, 10),
-			Event::Rewarded(7, 10),
-			Event::Rewarded(10, 10),
+			Event::Rewarded(1, 26),
+			Event::Rewarded(6, 8),
+			Event::Rewarded(7, 8),
+			Event::Rewarded(10, 8),
 			Event::CollatorChosen(4, 1, 50),
 			Event::CollatorChosen(4, 2, 40),
 			Event::CollatorChosen(4, 4, 20),
@@ -810,10 +794,10 @@ fn payouts_follow_nomination_changes() {
 		let mut new2 = vec![
 			Event::NominatorLeftCollator(6, 1, 10, 40),
 			Event::NominatorLeft(6, 10),
-			Event::Rewarded(1, 21),
-			Event::Rewarded(6, 10),
-			Event::Rewarded(7, 10),
-			Event::Rewarded(10, 10),
+			Event::Rewarded(1, 27),
+			Event::Rewarded(6, 8),
+			Event::Rewarded(7, 8),
+			Event::Rewarded(10, 8),
 			Event::CollatorChosen(5, 2, 40),
 			Event::CollatorChosen(5, 1, 40),
 			Event::CollatorChosen(5, 4, 20),
@@ -828,10 +812,10 @@ fn payouts_follow_nomination_changes() {
 		roll_to(26);
 		// keep paying 6
 		let mut new3 = vec![
-			Event::Rewarded(1, 22),
-			Event::Rewarded(6, 11),
-			Event::Rewarded(7, 11),
-			Event::Rewarded(10, 11),
+			Event::Rewarded(1, 29),
+			Event::Rewarded(6, 9),
+			Event::Rewarded(7, 9),
+			Event::Rewarded(10, 9),
 			Event::CollatorChosen(6, 2, 40),
 			Event::CollatorChosen(6, 1, 40),
 			Event::CollatorChosen(6, 4, 20),
@@ -845,9 +829,9 @@ fn payouts_follow_nomination_changes() {
 		roll_to(31);
 		// no more paying 6
 		let mut new4 = vec![
-			Event::Rewarded(1, 29),
-			Event::Rewarded(7, 14),
-			Event::Rewarded(10, 14),
+			Event::Rewarded(1, 35),
+			Event::Rewarded(7, 11),
+			Event::Rewarded(10, 11),
 			Event::CollatorChosen(7, 2, 40),
 			Event::CollatorChosen(7, 1, 40),
 			Event::CollatorChosen(7, 4, 20),
@@ -863,9 +847,9 @@ fn payouts_follow_nomination_changes() {
 		// new nomination is not rewarded yet
 		let mut new5 = vec![
 			Event::Nomination(8, 10, 1, 50),
-			Event::Rewarded(1, 30),
-			Event::Rewarded(7, 15),
-			Event::Rewarded(10, 15),
+			Event::Rewarded(1, 36),
+			Event::Rewarded(7, 12),
+			Event::Rewarded(10, 12),
 			Event::CollatorChosen(8, 1, 50),
 			Event::CollatorChosen(8, 2, 40),
 			Event::CollatorChosen(8, 4, 20),
@@ -879,9 +863,9 @@ fn payouts_follow_nomination_changes() {
 		roll_to(41);
 		// new nomination is still not rewarded yet
 		let mut new6 = vec![
-			Event::Rewarded(1, 32),
-			Event::Rewarded(7, 16),
-			Event::Rewarded(10, 16),
+			Event::Rewarded(1, 38),
+			Event::Rewarded(7, 13),
+			Event::Rewarded(10, 13),
 			Event::CollatorChosen(9, 1, 50),
 			Event::CollatorChosen(9, 2, 40),
 			Event::CollatorChosen(9, 4, 20),
@@ -894,10 +878,10 @@ fn payouts_follow_nomination_changes() {
 		roll_to(46);
 		// new nomination is rewarded for first time, 2 rounds after joining (`BondDuration` = 2)
 		let mut new7 = vec![
-			Event::Rewarded(1, 27),
-			Event::Rewarded(7, 13),
-			Event::Rewarded(8, 13),
-			Event::Rewarded(10, 13),
+			Event::Rewarded(1, 35),
+			Event::Rewarded(7, 11),
+			Event::Rewarded(8, 11),
+			Event::Rewarded(10, 11),
 			Event::CollatorChosen(10, 1, 50),
 			Event::CollatorChosen(10, 2, 40),
 			Event::CollatorChosen(10, 4, 20),

runtime/src/lib.rs

@@ -393,8 +393,8 @@ parameter_types! {
 	pub const MaxNominatorsPerCollator: u32 = 10;
 	/// Maximum 25 collators per nominator
 	pub const MaxCollatorsPerNominator: u32 = 25;
-	/// The maximum percent a collator can take off the top of its rewards is 50%
-	pub const MaxFee: Perbill = Perbill::from_percent(50);
+	/// The fixed percent a collator takes off the top of due rewards is 20%
+	pub const DefaultCollatorCommission: Perbill = Perbill::from_percent(20);
 	/// Minimum stake required to be reserved to be a collator is 1_000
 	pub const MinCollatorStk: u128 = 1_000 * GLMR;
 	/// Minimum stake required to be reserved to be a nominator is 5
@@ -409,7 +409,7 @@ impl parachain_staking::Config for Runtime {
 	type MinSelectedCandidates = MinSelectedCandidates;
 	type MaxNominatorsPerCollator = MaxNominatorsPerCollator;
 	type MaxCollatorsPerNominator = MaxCollatorsPerNominator;
-	type MaxFee = MaxFee;
+	type DefaultCollatorCommission = DefaultCollatorCommission;
 	type MinCollatorStk = MinCollatorStk;
 	type MinCollatorCandidateStk = MinCollatorStk;
 	type MinNomination = MinNominatorStk;