staking: only disable slashed validators and keep them disabled for whole era

bin/node/runtime/src/lib.rs

@@ -444,10 +444,6 @@ impl_opaque_keys! {
 	}
 }
 
-parameter_types! {
-	pub const DisabledValidatorsThreshold: Perbill = Perbill::from_percent(17);
-}
-
 impl pallet_session::Config for Runtime {
 	type Event = Event;
 	type ValidatorId = <Self as frame_system::Config>::AccountId;
@@ -457,7 +453,6 @@ impl pallet_session::Config for Runtime {
 	type SessionManager = pallet_session::historical::NoteHistoricalRoot<Self, Staking>;
 	type SessionHandler = <SessionKeys as OpaqueKeys>::KeyTypeIdProviders;
 	type Keys = SessionKeys;
-	type DisabledValidatorsThreshold = DisabledValidatorsThreshold;
 	type WeightInfo = pallet_session::weights::SubstrateWeight<Runtime>;
 }
 
@@ -483,6 +478,7 @@ parameter_types! {
 	pub const SlashDeferDuration: pallet_staking::EraIndex = 24 * 7; // 1/4 the bonding duration.
 	pub const RewardCurve: &'static PiecewiseLinear<'static> = &REWARD_CURVE;
 	pub const MaxNominatorRewardedPerValidator: u32 = 256;
+	pub const OffendingValidatorsThreshold: Perbill = Perbill::from_percent(17);
 	pub OffchainRepeat: BlockNumber = 5;
 }
 
@@ -509,6 +505,7 @@ impl pallet_staking::Config for Runtime {
 	type EraPayout = pallet_staking::ConvertCurve<RewardCurve>;
 	type NextNewSession = Session;
 	type MaxNominatorRewardedPerValidator = MaxNominatorRewardedPerValidator;
+	type OffendingValidatorsThreshold = OffendingValidatorsThreshold;
 	type ElectionProvider = ElectionProviderMultiPhase;
 	type GenesisElectionProvider = onchain::OnChainSequentialPhragmen<
 		pallet_election_provider_multi_phase::OnChainConfig<Self>,

frame/aura/src/lib.rs

@@ -208,7 +208,7 @@ impl<T: Config> OneSessionHandler<T::AccountId> for Pallet<T> {
 		}
 	}
 
-	fn on_disabled(i: usize) {
+	fn on_disabled(i: u32) {
 		let log: DigestItem<T::Hash> = DigestItem::Consensus(
 			AURA_ENGINE_ID,
 			ConsensusLog::<T::AuthorityId>::OnDisabled(i as AuthorityIndex).encode(),

frame/authority-discovery/src/lib.rs

@@ -131,7 +131,7 @@ impl<T: Config> OneSessionHandler<T::AccountId> for Pallet<T> {
 		}
 	}
 
-	fn on_disabled(_i: usize) {
+	fn on_disabled(_i: u32) {
 		// ignore
 	}
 }
@@ -148,7 +148,7 @@ mod tests {
 	use sp_runtime::{
 		testing::{Header, UintAuthorityId},
 		traits::{ConvertInto, IdentityLookup, OpaqueKeys},
-		KeyTypeId, Perbill,
+		KeyTypeId,
 	};
 
 	type UncheckedExtrinsic = frame_system::mocking::MockUncheckedExtrinsic<Test>;
@@ -168,10 +168,6 @@ mod tests {
 
 	impl Config for Test {}
 
-	parameter_types! {
-		pub const DisabledValidatorsThreshold: Perbill = Perbill::from_percent(33);
-	}
-
 	impl pallet_session::Config for Test {
 		type SessionManager = ();
 		type Keys = UintAuthorityId;
@@ -180,7 +176,6 @@ mod tests {
 		type Event = Event;
 		type ValidatorId = AuthorityId;
 		type ValidatorIdOf = ConvertInto;
-		type DisabledValidatorsThreshold = DisabledValidatorsThreshold;
 		type NextSessionRotation = pallet_session::PeriodicSessions<Period, Offset>;
 		type WeightInfo = ();
 	}
@@ -238,7 +233,7 @@ mod tests {
 		) {
 		}
 
-		fn on_disabled(_validator_index: usize) {}
+		fn on_disabled(_validator_index: u32) {}
 
 		fn on_genesis_session<Ks: OpaqueKeys>(_validators: &[(AuthorityId, Ks)]) {}
 	}

frame/babe/src/lib.rs

@@ -884,8 +884,8 @@ impl<T: Config> OneSessionHandler<T::AccountId> for Pallet<T> {
 		Self::enact_epoch_change(authorities, next_authorities)
 	}
 
-	fn on_disabled(i: usize) {
-		Self::deposit_consensus(ConsensusLog::OnDisabled(i as u32))
+	fn on_disabled(i: u32) {
+		Self::deposit_consensus(ConsensusLog::OnDisabled(i))
 	}
 }
 

frame/babe/src/mock.rs

@@ -68,7 +68,6 @@ frame_support::construct_runtime!(
 
 parameter_types! {
 	pub const BlockHashCount: u64 = 250;
-	pub const DisabledValidatorsThreshold: Perbill = Perbill::from_percent(16);
 	pub BlockWeights: frame_system::limits::BlockWeights =
 		frame_system::limits::BlockWeights::simple_max(1024);
 }
@@ -122,7 +121,6 @@ impl pallet_session::Config for Test {
 	type SessionManager = pallet_session::historical::NoteHistoricalRoot<Self, Staking>;
 	type SessionHandler = <MockSessionKeys as OpaqueKeys>::KeyTypeIdProviders;
 	type Keys = MockSessionKeys;
-	type DisabledValidatorsThreshold = DisabledValidatorsThreshold;
 	type WeightInfo = ();
 }
 
@@ -189,6 +187,7 @@ parameter_types! {
 	pub const MaxNominatorRewardedPerValidator: u32 = 64;
 	pub const ElectionLookahead: u64 = 0;
 	pub const StakingUnsignedPriority: u64 = u64::MAX / 2;
+	pub const OffendingValidatorsThreshold: Perbill = Perbill::from_percent(16);
 }
 
 impl onchain::Config for Test {
@@ -214,6 +213,7 @@ impl pallet_staking::Config for Test {
 	type UnixTime = pallet_timestamp::Pallet<Test>;
 	type EraPayout = pallet_staking::ConvertCurve<RewardCurve>;
 	type MaxNominatorRewardedPerValidator = MaxNominatorRewardedPerValidator;
+	type OffendingValidatorsThreshold = OffendingValidatorsThreshold;
 	type NextNewSession = Session;
 	type ElectionProvider = onchain::OnChainSequentialPhragmen<Self>;
 	type GenesisElectionProvider = Self::ElectionProvider;

frame/grandpa/src/lib.rs

@@ -644,7 +644,7 @@ where
 		SetIdSession::<T>::insert(current_set_id, &session_index);
 	}
 
-	fn on_disabled(i: usize) {
+	fn on_disabled(i: u32) {
 		Self::deposit_log(ConsensusLog::OnDisabled(i as u64))
 	}
 }

frame/grandpa/src/mock.rs

@@ -111,7 +111,6 @@ where
 parameter_types! {
 	pub const Period: u64 = 1;
 	pub const Offset: u64 = 0;
-	pub const DisabledValidatorsThreshold: Perbill = Perbill::from_percent(17);
 }
 
 /// Custom `SessionHandler` since we use `TestSessionKeys` as `Keys`.
@@ -124,7 +123,6 @@ impl pallet_session::Config for Test {
 	type SessionManager = pallet_session::historical::NoteHistoricalRoot<Self, Staking>;
 	type SessionHandler = <TestSessionKeys as OpaqueKeys>::KeyTypeIdProviders;
 	type Keys = TestSessionKeys;
-	type DisabledValidatorsThreshold = DisabledValidatorsThreshold;
 	type WeightInfo = ();
 }
 
@@ -191,6 +189,7 @@ parameter_types! {
 	pub const MaxNominatorRewardedPerValidator: u32 = 64;
 	pub const ElectionLookahead: u64 = 0;
 	pub const StakingUnsignedPriority: u64 = u64::MAX / 2;
+	pub const OffendingValidatorsThreshold: Perbill = Perbill::from_percent(17);
 }
 
 impl onchain::Config for Test {
@@ -216,6 +215,7 @@ impl pallet_staking::Config for Test {
 	type UnixTime = pallet_timestamp::Pallet<Test>;
 	type EraPayout = pallet_staking::ConvertCurve<RewardCurve>;
 	type MaxNominatorRewardedPerValidator = MaxNominatorRewardedPerValidator;
+	type OffendingValidatorsThreshold = OffendingValidatorsThreshold;
 	type NextNewSession = Session;
 	type ElectionProvider = onchain::OnChainSequentialPhragmen<Self>;
 	type GenesisElectionProvider = Self::ElectionProvider;

frame/im-online/src/lib.rs

@@ -814,7 +814,7 @@ impl<T: Config> OneSessionHandler<T::AccountId> for Pallet<T> {
 		}
 	}
 
-	fn on_disabled(_i: usize) {
+	fn on_disabled(_i: u32) {
 		// ignore
 	}
 }

frame/im-online/src/mock.rs

@@ -27,7 +27,7 @@ use sp_core::H256;
 use sp_runtime::{
 	testing::{Header, TestXt, UintAuthorityId},
 	traits::{BlakeTwo256, ConvertInto, IdentityLookup},
-	Perbill, Permill,
+	Permill,
 };
 use sp_staking::{
 	offence::{OffenceError, ReportOffence},
@@ -146,10 +146,6 @@ parameter_types! {
 	pub const Offset: u64 = 0;
 }
 
-parameter_types! {
-	pub const DisabledValidatorsThreshold: Perbill = Perbill::from_percent(33);
-}
-
 impl pallet_session::Config for Runtime {
 	type ShouldEndSession = pallet_session::PeriodicSessions<Period, Offset>;
 	type SessionManager =
@@ -159,7 +155,6 @@ impl pallet_session::Config for Runtime {
 	type ValidatorIdOf = ConvertInto;
 	type Keys = UintAuthorityId;
 	type Event = Event;
-	type DisabledValidatorsThreshold = DisabledValidatorsThreshold;
 	type NextSessionRotation = pallet_session::PeriodicSessions<Period, Offset>;
 	type WeightInfo = ();
 }

frame/offences/benchmarking/src/mock.rs

@@ -112,7 +112,7 @@ impl pallet_session::SessionHandler<AccountId> for TestSessionHandler {
 	) {
 	}
 
-	fn on_disabled(_: usize) {}
+	fn on_disabled(_: u32) {}
 }
 
 parameter_types! {
@@ -129,7 +129,6 @@ impl pallet_session::Config for Test {
 	type Event = Event;
 	type ValidatorId = AccountId;
 	type ValidatorIdOf = pallet_staking::StashOf<Test>;
-	type DisabledValidatorsThreshold = ();
 	type WeightInfo = ();
 }
 
@@ -174,6 +173,7 @@ impl pallet_staking::Config for Test {
 	type EraPayout = pallet_staking::ConvertCurve<RewardCurve>;
 	type NextNewSession = Session;
 	type MaxNominatorRewardedPerValidator = MaxNominatorRewardedPerValidator;
+	type OffendingValidatorsThreshold = ();
 	type ElectionProvider = onchain::OnChainSequentialPhragmen<Self>;
 	type GenesisElectionProvider = Self::ElectionProvider;
 	type WeightInfo = ();

frame/session/benchmarking/src/mock.rs

@@ -117,7 +117,7 @@ impl pallet_session::SessionHandler<AccountId> for TestSessionHandler {
 	) {
 	}
 
-	fn on_disabled(_: usize) {}
+	fn on_disabled(_: u32) {}
 }
 
 impl pallet_session::Config for Test {
@@ -129,7 +129,6 @@ impl pallet_session::Config for Test {
 	type Event = Event;
 	type ValidatorId = AccountId;
 	type ValidatorIdOf = pallet_staking::StashOf<Test>;
-	type DisabledValidatorsThreshold = ();
 	type WeightInfo = ();
 }
 pallet_staking_reward_curve::build! {
@@ -182,6 +181,7 @@ impl pallet_staking::Config for Test {
 	type EraPayout = pallet_staking::ConvertCurve<RewardCurve>;
 	type NextNewSession = Session;
 	type MaxNominatorRewardedPerValidator = MaxNominatorRewardedPerValidator;
+	type OffendingValidatorsThreshold = ();
 	type ElectionProvider = onchain::OnChainSequentialPhragmen<Self>;
 	type GenesisElectionProvider = Self::ElectionProvider;
 	type WeightInfo = ();

frame/session/src/lib.rs

@@ -129,7 +129,7 @@ use frame_support::{
 use frame_system::ensure_signed;
 use sp_runtime::{
 	traits::{AtLeast32BitUnsigned, Convert, Member, One, OpaqueKeys, Zero},
-	KeyTypeId, Perbill, Permill, RuntimeAppPublic,
+	KeyTypeId, Permill, RuntimeAppPublic,
 };
 use sp_staking::SessionIndex;
 use sp_std::{
@@ -297,7 +297,7 @@ pub trait SessionHandler<ValidatorId> {
 	fn on_before_session_ending() {}
 
 	/// A validator got disabled. Act accordingly until a new session begins.
-	fn on_disabled(validator_index: usize);
+	fn on_disabled(validator_index: u32);
 }
 
 #[impl_trait_for_tuples::impl_for_tuples(1, 30)]
@@ -341,7 +341,7 @@ impl<AId> SessionHandler<AId> for Tuple {
 		for_tuples!( #( Tuple::on_before_session_ending(); )* )
 	}
 
-	fn on_disabled(i: usize) {
+	fn on_disabled(i: u32) {
 		for_tuples!( #( Tuple::on_disabled(i); )* )
 	}
 }
@@ -353,7 +353,7 @@ impl<AId> SessionHandler<AId> for TestSessionHandler {
 	fn on_genesis_session<Ks: OpaqueKeys>(_: &[(AId, Ks)]) {}
 	fn on_new_session<Ks: OpaqueKeys>(_: bool, _: &[(AId, Ks)], _: &[(AId, Ks)]) {}
 	fn on_before_session_ending() {}
-	fn on_disabled(_: usize) {}
+	fn on_disabled(_: u32) {}
 }
 
 impl<T: Config> ValidatorRegistration<T::ValidatorId> for Module<T> {
@@ -391,12 +391,6 @@ pub trait Config: frame_system::Config {
 	/// The keys.
 	type Keys: OpaqueKeys + Member + Parameter + Default;
 
-	/// The fraction of validators set that is safe to be disabled.
-	///
-	/// After the threshold is reached `disabled` method starts to return true,
-	/// which in combination with `pallet_staking` forces a new era.
-	type DisabledValidatorsThreshold: Get<Perbill>;
-
 	/// Weight information for extrinsics in this pallet.
 	type WeightInfo: WeightInfo;
 }
@@ -664,42 +658,34 @@ impl<T: Config> Module<T> {
 		T::SessionHandler::on_new_session::<T::Keys>(changed, &session_keys, &queued_amalgamated);
 	}
 
-	/// Disable the validator of index `i`.
-	///
-	/// Returns `true` if this causes a `DisabledValidatorsThreshold` of validators
-	/// to be already disabled.
-	pub fn disable_index(i: usize) -> bool {
-		let (fire_event, threshold_reached) = DisabledValidators::mutate(|disabled| {
-			let i = i as u32;
+	/// Disable the validator of index `i`, returns `false` if the validator was already disabled.
+	pub fn disable_index(i: u32) -> bool {
+		if i >= Validators::<T>::decode_len().unwrap_or(0) as u32 {
+			return false
+		}
+
+		DisabledValidators::mutate(|disabled| {
 			if let Err(index) = disabled.binary_search(&i) {
-				let count = <Validators<T>>::decode_len().unwrap_or(0) as u32;
-				let threshold = T::DisabledValidatorsThreshold::get() * count;
 				disabled.insert(index, i);
-				(true, disabled.len() as u32 > threshold)
-			} else {
-				(false, false)
+				T::SessionHandler::on_disabled(i);
+				return true
 			}
-		});
-
-		if fire_event {
-			T::SessionHandler::on_disabled(i);
-		}
 
-		threshold_reached
+			false
+		})
 	}
 
 	/// Disable the validator identified by `c`. (If using with the staking module,
 	/// this would be their *stash* account.)
 	///
-	/// Returns `Ok(true)` if more than `DisabledValidatorsThreshold` validators in current
-	/// session is already disabled.
-	/// If used with the staking module it allows to force a new era in such case.
-	pub fn disable(c: &T::ValidatorId) -> sp_std::result::Result<bool, ()> {
+	/// Returns `false` either if the validator could not be found or it was already
+	/// disabled.
+	pub fn disable(c: &T::ValidatorId) -> bool {
 		Self::validators()
 			.iter()
 			.position(|i| i == c)
-			.map(Self::disable_index)
-			.ok_or(())
+			.map(|i| Self::disable_index(i as u32))
+			.unwrap_or(false)
 	}
 
 	/// Upgrade the key type from some old type to a new type. Supports adding