Add delay and maximum change rate for commission

pallets/parachain-staking/src/lib.rs

@@ -337,6 +337,14 @@ pub mod pallet {
 
 		/// Weight information for extrinsics in this pallet.
 		type WeightInfo: WeightInfo;
+
+		/// The maximum permill that a commission can change in one go.
+		#[pallet::constant]
+		type MaxCommissionChange: Get<Permill>;
+
+		/// The minimum interval between two commission changes.
+		#[pallet::constant]
+		type CommissionChangeInterval: Get<BlockNumberFor<Self>>;
 	}
 
 	#[pallet::error]
@@ -432,6 +440,10 @@ pub mod pallet {
 		CommissionTooHigh,
 		/// Sudo cannot force new round if payouts are ongoing
 		PayoutsOngoing,
+		/// The commission change is too high.
+		CommissionChangeTooHigh,
+		/// The commission change is too frequent.
+		CommissionChangeTooEarly,
 	}
 
 	#[pallet::event]
@@ -677,6 +689,11 @@ pub mod pallet {
 	pub(crate) type DelayedPayoutInfo<T: Config> =
 		StorageValue<_, DelayedPayoutInfoT<SessionIndex, BalanceOf<T>>, OptionQuery>;
 
+	#[pallet::storage]
+	#[pallet::getter(fn last_commission_change)]
+	pub type LastCommissionChange<T: Config> =
+		StorageMap<_, Blake2_128Concat, T::AccountId, BlockNumberFor<T>, ValueQuery>;
+
 	#[pallet::genesis_config]
 	pub struct GenesisConfig<T: Config> {
 		pub stakers: GenesisStaker<T>,
@@ -1969,21 +1986,36 @@ pub mod pallet {
 		))]
 		pub fn set_commission(origin: OriginFor<T>, commission: Permill) -> DispatchResult {
 			let collator = ensure_signed(origin)?;
-			CandidatePool::<T>::get(&collator).ok_or(Error::<T>::CandidateNotFound)?;
-			if commission > Permill::from_percent(100) {
-				return Err(Error::<T>::CommissionTooHigh.into())
-			}
+			let current_block = <frame_system::Pallet<T>>::block_number();
 
-			<crate::pallet::CandidatePool<T>>::mutate(&collator, |maybe_candidate| {
-				if let Some(candidate) = maybe_candidate {
-					candidate.set_commission(commission);
-				}
-			});
+			// Check if the collator exists
+			let mut candidate =
+				CandidatePool::<T>::get(&collator).ok_or(Error::<T>::CandidateNotFound)?;
 
-			// Emit an event that the commission was updated.
-			Self::deposit_event(crate::pallet::Event::CollatorCommissionChanged(
-				collator, commission,
-			));
+			// Check the time since the last commission change
+			let last_change = LastCommissionChange::<T>::get(&collator);
+			ensure!(
+				current_block >= last_change + T::CommissionChangeInterval::get(),
+				Error::<T>::CommissionChangeTooEarly
+			);
+
+			// Check the maximum change commission
+			let max_change = T::MaxCommissionChange::get();
+			let current_commission = candidate.commission;
+			let change = if commission > current_commission {
+				commission - current_commission
+			} else {
+				current_commission - commission
+			};
+			ensure!(change <= max_change, Error::<T>::CommissionChangeTooHigh);
+
+			// Update the commission and the last change time
+			candidate.set_commission(commission);
+			CandidatePool::<T>::insert(&collator, candidate);
+			LastCommissionChange::<T>::insert(&collator, current_block);
+
+			// Emit an event that the commission was updated
+			Self::deposit_event(Event::CollatorCommissionChanged(collator, commission));
 			Ok(())
 		}
 	}

pallets/parachain-staking/src/mock.rs

@@ -32,7 +32,7 @@ use sp_runtime::{
 	impl_opaque_keys,
 	testing::UintAuthorityId,
 	traits::{BlakeTwo256, ConvertInto, IdentityLookup, OpaqueKeys},
-	BuildStorage, Perbill,
+	BuildStorage, Perbill, Permill,
 };
 use sp_std::fmt::Debug;
 
@@ -154,6 +154,9 @@ parameter_types! {
 	pub const MinDelegatorStake: Balance = 5;
 	pub const MinDelegation: Balance = 3;
 	pub const MaxUnstakeRequests: u32 = 6;
+	pub const MaxCommissionChange: Permill = Permill::from_percent(10);
+	pub const CommissionChangeInterval: BlockNumber = 1;
+
 }
 
 impl Config for Test {
@@ -177,6 +180,8 @@ impl Config for Test {
 	type MaxUnstakeRequests = MaxUnstakeRequests;
 	type PotId = PotId;
 	type WeightInfo = crate::weights::WeightInfo<Test>;
+	type CommissionChangeInterval = CommissionChangeInterval;
+	type MaxCommissionChange = MaxCommissionChange;
 }
 
 impl_opaque_keys! {

pallets/parachain-staking/src/tests.rs

@@ -3990,3 +3990,122 @@ fn check_snapshot_is_cleared() {
 			assert_eq!(at_stake.len(), 0);
 		});
 }
+
+#[test]
+fn change_commission_too_frequently() {
+	ExtBuilder::default()
+		.with_balances(vec![(1, 1000), (2, 1000), (3, 1000)])
+		.with_collators(vec![(1, 500)])
+		.with_delegators(vec![(2, 1, 600), (3, 1, 400)])
+		.build()
+		.execute_with(|| {
+			assert!(System::events().is_empty());
+
+			assert_ok!(Balances::force_set_balance(
+				RawOrigin::Root.into(),
+				StakePallet::account_id(),
+				1000,
+			));
+
+			assert_ok!(StakePallet::set_commission(
+				RuntimeOrigin::signed(1),
+				Permill::from_percent(10)
+			));
+			let state = CandidatePool::<Test>::get(1).unwrap();
+			assert_eq!(state.commission, Permill::from_percent(10));
+			assert_eq!(
+				StakePallet::candidate_pool(1).unwrap().commission,
+				Permill::from_percent(10)
+			);
+
+			// change commission too frequently
+			assert_noop!(
+				StakePallet::set_commission(RuntimeOrigin::signed(1), Permill::from_percent(20)),
+				Error::<Test>::CommissionChangeTooEarly
+			);
+			// change commission too frequently
+			assert_noop!(
+				StakePallet::set_commission(RuntimeOrigin::signed(1), Permill::from_percent(30)),
+				Error::<Test>::CommissionChangeTooEarly
+			);
+		});
+}
+
+#[test]
+fn change_commission_after_while() {
+	ExtBuilder::default()
+		.with_balances(vec![(1, 1000), (2, 1000), (3, 1000)])
+		.with_collators(vec![(1, 500)])
+		.with_delegators(vec![(2, 1, 600), (3, 1, 400)])
+		.build()
+		.execute_with(|| {
+			assert!(System::events().is_empty());
+
+			assert_ok!(Balances::force_set_balance(
+				RawOrigin::Root.into(),
+				StakePallet::account_id(),
+				1000,
+			));
+
+			assert_ok!(StakePallet::set_commission(
+				RuntimeOrigin::signed(1),
+				Permill::from_percent(10)
+			));
+			let state = CandidatePool::<Test>::get(1).unwrap();
+			assert_eq!(state.commission, Permill::from_percent(10));
+			assert_eq!(
+				StakePallet::candidate_pool(1).unwrap().commission,
+				Permill::from_percent(10)
+			);
+
+			// change commission after a while
+			roll_to(10, vec![]);
+			assert_ok!(StakePallet::set_commission(
+				RuntimeOrigin::signed(1),
+				Permill::from_percent(20)
+			));
+			let state = CandidatePool::<Test>::get(1).unwrap();
+			assert_eq!(state.commission, Permill::from_percent(20));
+			assert_eq!(
+				StakePallet::candidate_pool(1).unwrap().commission,
+				Permill::from_percent(20)
+			);
+		});
+}
+
+#[test]
+fn change_commission_by_too_much() {
+	ExtBuilder::default()
+		.with_balances(vec![(1, 1000), (2, 1000), (3, 1000)])
+		.with_collators(vec![(1, 500)])
+		.with_delegators(vec![(2, 1, 600), (3, 1, 400)])
+		.build()
+		.execute_with(|| {
+			assert!(System::events().is_empty());
+
+			assert_ok!(Balances::force_set_balance(
+				RawOrigin::Root.into(),
+				StakePallet::account_id(),
+				1000,
+			));
+
+			assert_ok!(StakePallet::set_commission(
+				RuntimeOrigin::signed(1),
+				Permill::from_percent(10)
+			));
+			let state = CandidatePool::<Test>::get(1).unwrap();
+			assert_eq!(state.commission, Permill::from_percent(10));
+			assert_eq!(
+				StakePallet::candidate_pool(1).unwrap().commission,
+				Permill::from_percent(10)
+			);
+
+			roll_to(10, vec![]);
+
+			// change commission by too much
+			assert_noop!(
+				StakePallet::set_commission(RuntimeOrigin::signed(1), Permill::from_percent(30)),
+				Error::<Test>::CommissionChangeTooHigh
+			);
+		});
+}

precompiles/parachain-staking/src/mock.rs

@@ -34,7 +34,7 @@ use sp_runtime::{
 	impl_opaque_keys,
 	testing::UintAuthorityId,
 	traits::{BlakeTwo256, ConvertInto, IdentityLookup, OpaqueKeys},
-	BuildStorage, Perbill,
+	BuildStorage, Perbill, Permill,
 };
 use sp_std::fmt::Debug;
 
@@ -206,6 +206,8 @@ parameter_types! {
 	pub const MinDelegatorStake: Balance = 5;
 	pub const MinDelegation: Balance = 3;
 	pub const MaxUnstakeRequests: u32 = 6;
+	pub const MaxCommissionChange: Permill = Permill::from_percent(10);
+	pub const CommissionChangeInterval: BlockNumber = 1;
 }
 
 impl parachain_staking::Config for Test {
@@ -229,6 +231,8 @@ impl parachain_staking::Config for Test {
 	type MaxUnstakeRequests = MaxUnstakeRequests;
 	type PotId = PotId;
 	type WeightInfo = parachain_staking::weights::WeightInfo<Test>;
+	type CommissionChangeInterval = CommissionChangeInterval;
+	type MaxCommissionChange = MaxCommissionChange;
 }
 
 impl_opaque_keys! {

runtime/krest/src/lib.rs

@@ -825,6 +825,8 @@ pub mod staking {
 			pub const MaxCollatorCandidates: u32 = 128;
 			/// Maximum number of concurrent requests to unlock unstaked balance
 			pub const MaxUnstakeRequests: u32 = 10;
+			pub const MaxCommissionChange: Permill = Permill::from_percent(10); // Maximum 10% change
+			pub const CommissionChangeInterval: BlockNumber = DAYS; // 24 hours
 	}
 }
 
@@ -851,6 +853,8 @@ impl parachain_staking::Config for Runtime {
 	type MaxUnstakeRequests = staking::MaxUnstakeRequests;
 
 	type WeightInfo = parachain_staking::weights::WeightInfo<Runtime>;
+	type CommissionChangeInterval = staking::CommissionChangeInterval;
+	type MaxCommissionChange = staking::MaxCommissionChange;
 }
 
 /// Implements the adapters for depositing unbalanced tokens on pots

runtime/peaq-dev/src/lib.rs

@@ -831,6 +831,9 @@ pub mod staking {
 			pub const MaxCollatorCandidates: u32 = 64;
 			/// Maximum number of concurrent requests to unlock unstaked balance
 			pub const MaxUnstakeRequests: u32 = 10;
+
+			pub const MaxCommissionChange: Permill = Permill::from_percent(10); // Maximum 10% change
+			pub const CommissionChangeInterval: BlockNumber = DAYS; // 24 hours
 	}
 }
 
@@ -857,6 +860,8 @@ impl parachain_staking::Config for Runtime {
 	type MaxUnstakeRequests = staking::MaxUnstakeRequests;
 
 	type WeightInfo = parachain_staking::weights::WeightInfo<Runtime>;
+	type CommissionChangeInterval = staking::CommissionChangeInterval;
+	type MaxCommissionChange = staking::MaxCommissionChange;
 }
 
 /// Implements the adapters for depositing unbalanced tokens on pots

runtime/peaq/src/lib.rs

@@ -848,6 +848,8 @@ pub mod staking {
 			pub const MaxCollatorCandidates: u32 = 64;
 			/// Maximum number of concurrent requests to unlock unstaked balance
 			pub const MaxUnstakeRequests: u32 = 10;
+			pub const MaxCommissionChange: Permill = Permill::from_percent(10); // Maximum 10% change
+			pub const CommissionChangeInterval: BlockNumber = DAYS; // 24 hours
 	}
 }
 
@@ -874,6 +876,8 @@ impl parachain_staking::Config for Runtime {
 	type MaxUnstakeRequests = staking::MaxUnstakeRequests;
 
 	type WeightInfo = parachain_staking::weights::WeightInfo<Runtime>;
+	type CommissionChangeInterval = staking::CommissionChangeInterval;
+	type MaxCommissionChange = staking::MaxCommissionChange;
 }
 
 /// Implements the adapters for depositing unbalanced tokens on pots