session, staking: introduce static limit on the number of validators

bin/node/cli/src/chain_spec.rs

@@ -317,7 +317,12 @@ pub fn testnet_genesis(
 		staking: StakingConfig {
 			validator_count: initial_authorities.len() as u32,
 			minimum_validator_count: initial_authorities.len() as u32,
-			invulnerables: initial_authorities.iter().map(|x| x.0.clone()).collect(),
+			invulnerables: initial_authorities
+				.iter()
+				.map(|x| x.0.clone())
+				.collect::<Vec<_>>()
+				.try_into()
+				.unwrap(),
 			slash_reward_fraction: Perbill::from_percent(10),
 			stakers,
 			..Default::default()

bin/node/runtime/src/lib.rs

@@ -495,6 +495,10 @@ impl_opaque_keys! {
 	}
 }
 
+parameter_types! {
+	pub const MaxValidators: u32 = 3072;
+}
+
 impl pallet_session::Config for Runtime {
 	type Event = Event;
 	type ValidatorId = <Self as frame_system::Config>::AccountId;
@@ -505,6 +509,7 @@ impl pallet_session::Config for Runtime {
 	type SessionHandler = <SessionKeys as OpaqueKeys>::KeyTypeIdProviders;
 	type Keys = SessionKeys;
 	type WeightInfo = pallet_session::weights::SubstrateWeight<Runtime>;
+	type MaxValidators = MaxValidators;
 }
 
 impl pallet_session::historical::Config for Runtime {
@@ -569,6 +574,7 @@ impl pallet_staking::Config for Runtime {
 	type OnStakerSlash = NominationPools;
 	type WeightInfo = pallet_staking::weights::SubstrateWeight<Runtime>;
 	type BenchmarkingConfig = StakingBenchmarkingConfig;
+	type MaxValidators = MaxValidators;
 }
 
 parameter_types! {

bin/node/testing/src/genesis.rs

@@ -72,7 +72,7 @@ pub fn config_endowed(code: Option<&[u8]>, extra_endowed: Vec<AccountId>) -> Gen
 			validator_count: 3,
 			minimum_validator_count: 0,
 			slash_reward_fraction: Perbill::from_percent(10),
-			invulnerables: vec![alice(), bob(), charlie()],
+			invulnerables: vec![alice(), bob(), charlie()].try_into().unwrap(),
 			..Default::default()
 		},
 		babe: BabeConfig { authorities: vec![], epoch_config: Some(BABE_GENESIS_EPOCH_CONFIG) },

frame/authority-discovery/src/lib.rs

@@ -214,6 +214,7 @@ mod tests {
 		type ValidatorIdOf = ConvertInto;
 		type NextSessionRotation = pallet_session::PeriodicSessions<Period, Offset>;
 		type WeightInfo = ();
+		type MaxValidators = ConstU32<3072>;
 	}
 
 	impl pallet_session::historical::Config for Test {

frame/babe/src/mock.rs

@@ -110,6 +110,10 @@ impl_opaque_keys! {
 	}
 }
 
+parameter_types! {
+	pub const MaxValidators: u32 = 3072;
+}
+
 impl pallet_session::Config for Test {
 	type Event = Event;
 	type ValidatorId = <Self as frame_system::Config>::AccountId;
@@ -120,6 +124,7 @@ impl pallet_session::Config for Test {
 	type SessionHandler = <MockSessionKeys as OpaqueKeys>::KeyTypeIdProviders;
 	type Keys = MockSessionKeys;
 	type WeightInfo = ();
+	type MaxValidators = MaxValidators;
 }
 
 impl pallet_session::historical::Config for Test {
@@ -206,6 +211,7 @@ impl pallet_staking::Config for Test {
 	type OnStakerSlash = ();
 	type BenchmarkingConfig = pallet_staking::TestBenchmarkingConfig;
 	type WeightInfo = ();
+	type MaxValidators = MaxValidators;
 }
 
 impl pallet_offences::Config for Test {
@@ -403,7 +409,7 @@ pub fn new_test_ext_raw_authorities(authorities: Vec<AuthorityId>) -> sp_io::Tes
 		validator_count: 8,
 		force_era: pallet_staking::Forcing::ForceNew,
 		minimum_validator_count: 0,
-		invulnerables: vec![],
+		invulnerables: vec![].try_into().unwrap(),
 		..Default::default()
 	};
 

frame/beefy-mmr/src/mock.rs

@@ -99,6 +99,7 @@ impl pallet_session::Config for Test {
 	type SessionHandler = <MockSessionKeys as OpaqueKeys>::KeyTypeIdProviders;
 	type Keys = MockSessionKeys;
 	type WeightInfo = ();
+	type MaxValidators = ConstU32<3072>;
 }
 
 pub type MmrLeaf = beefy_primitives::mmr::MmrLeaf<

frame/beefy/src/mock.rs

@@ -104,6 +104,7 @@ impl pallet_session::Config for Test {
 	type SessionHandler = <MockSessionKeys as OpaqueKeys>::KeyTypeIdProviders;
 	type Keys = MockSessionKeys;
 	type WeightInfo = ();
+	type MaxValidators = ConstU32<3072>;
 }
 
 pub struct MockSessionManager;

frame/grandpa/src/mock.rs

@@ -112,6 +112,7 @@ where
 parameter_types! {
 	pub const Period: u64 = 1;
 	pub const Offset: u64 = 0;
+	pub const MaxValidators: u32 = 3072;
 }
 
 /// Custom `SessionHandler` since we use `TestSessionKeys` as `Keys`.
@@ -125,6 +126,7 @@ impl pallet_session::Config for Test {
 	type SessionHandler = <TestSessionKeys as OpaqueKeys>::KeyTypeIdProviders;
 	type Keys = TestSessionKeys;
 	type WeightInfo = ();
+	type MaxValidators = MaxValidators;
 }
 
 impl pallet_session::historical::Config for Test {
@@ -210,6 +212,7 @@ impl pallet_staking::Config for Test {
 	type OnStakerSlash = ();
 	type BenchmarkingConfig = pallet_staking::TestBenchmarkingConfig;
 	type WeightInfo = ();
+	type MaxValidators = MaxValidators;
 }
 
 impl pallet_offences::Config for Test {
@@ -304,7 +307,7 @@ pub fn new_test_ext_raw_authorities(authorities: AuthorityList) -> sp_io::TestEx
 		validator_count: 8,
 		force_era: pallet_staking::Forcing::ForceNew,
 		minimum_validator_count: 0,
-		invulnerables: vec![],
+		invulnerables: vec![].try_into().unwrap(),
 		..Default::default()
 	};
 

frame/im-online/src/mock.rs

@@ -169,6 +169,7 @@ impl pallet_session::Config for Runtime {
 	type Event = Event;
 	type NextSessionRotation = pallet_session::PeriodicSessions<Period, Offset>;
 	type WeightInfo = ();
+	type MaxValidators = ConstU32<3072>;
 }
 
 impl pallet_session::historical::Config for Runtime {

frame/im-online/src/tests.rs

@@ -91,7 +91,8 @@ fn should_report_offline_validators() {
 
 		// should not report when heartbeat is sent
 		for (idx, v) in validators.into_iter().take(4).enumerate() {
-			let _ = heartbeat(block, 3, idx as u32, v.into(), Session::validators()).unwrap();
+			let _ = heartbeat(block, 3, idx as u32, v.into(), Session::validators().into_inner())
+				.unwrap();
 		}
 		advance_session();
 
@@ -162,15 +163,15 @@ fn should_mark_online_validator_when_heartbeat_is_received() {
 		assert!(!ImOnline::is_online(2));
 
 		// when
-		let _ = heartbeat(1, 2, 0, 1.into(), Session::validators()).unwrap();
+		let _ = heartbeat(1, 2, 0, 1.into(), Session::validators().into_inner()).unwrap();
 
 		// then
 		assert!(ImOnline::is_online(0));
 		assert!(!ImOnline::is_online(1));
 		assert!(!ImOnline::is_online(2));
 
 		// and when
-		let _ = heartbeat(1, 2, 2, 3.into(), Session::validators()).unwrap();
+		let _ = heartbeat(1, 2, 2, 3.into(), Session::validators().into_inner()).unwrap();
 
 		// then
 		assert!(ImOnline::is_online(0));
@@ -194,11 +195,11 @@ fn late_heartbeat_and_invalid_keys_len_should_fail() {
 
 		// when
 		assert_noop!(
-			heartbeat(1, 3, 0, 1.into(), Session::validators()),
+			heartbeat(1, 3, 0, 1.into(), Session::validators().into_inner()),
 			"Transaction is outdated"
 		);
 		assert_noop!(
-			heartbeat(1, 1, 0, 1.into(), Session::validators()),
+			heartbeat(1, 1, 0, 1.into(), Session::validators().into_inner()),
 			"Transaction is outdated"
 		);
 
@@ -272,7 +273,7 @@ fn should_cleanup_received_heartbeats_on_session_end() {
 		assert_eq!(Session::validators(), vec![1, 2, 3]);
 
 		// send an heartbeat from authority id 0 at session 2
-		let _ = heartbeat(1, 2, 0, 1.into(), Session::validators()).unwrap();
+		let _ = heartbeat(1, 2, 0, 1.into(), Session::validators().into_inner()).unwrap();
 
 		// the heartbeat is stored
 		assert!(!ImOnline::received_heartbeats(&2, &0).is_none());

frame/nomination-pools/benchmarking/src/mock.rs

@@ -116,6 +116,7 @@ impl pallet_staking::Config for Runtime {
 	type OnStakerSlash = Pools;
 	type BenchmarkingConfig = pallet_staking::TestBenchmarkingConfig;
 	type WeightInfo = ();
+	type MaxValidators = ConstU32<3072>;
 }
 
 parameter_types! {

frame/nomination-pools/test-staking/src/mock.rs

@@ -131,6 +131,7 @@ impl pallet_staking::Config for Runtime {
 	type OnStakerSlash = Pools;
 	type BenchmarkingConfig = pallet_staking::TestBenchmarkingConfig;
 	type WeightInfo = ();
+	type MaxValidators = ConstU32<3072>;
 }
 
 parameter_types! {

frame/offences/benchmarking/src/mock.rs

@@ -118,6 +118,7 @@ impl pallet_session::SessionHandler<AccountId> for TestSessionHandler {
 parameter_types! {
 	pub const Period: u64 = 1;
 	pub const Offset: u64 = 0;
+	pub const MaxValidators: u32 = 3072;
 }
 
 impl pallet_session::Config for Test {
@@ -130,6 +131,7 @@ impl pallet_session::Config for Test {
 	type ValidatorId = AccountId;
 	type ValidatorIdOf = pallet_staking::StashOf<Test>;
 	type WeightInfo = ();
+	type MaxValidators = MaxValidators;
 }
 
 pallet_staking_reward_curve::build! {
@@ -182,6 +184,7 @@ impl pallet_staking::Config for Test {
 	type OnStakerSlash = ();
 	type BenchmarkingConfig = pallet_staking::TestBenchmarkingConfig;
 	type WeightInfo = ();
+	type MaxValidators = MaxValidators;
 }
 
 impl pallet_im_online::Config for Test {

frame/session/benchmarking/src/mock.rs

@@ -119,6 +119,10 @@ impl pallet_session::SessionHandler<AccountId> for TestSessionHandler {
 	fn on_disabled(_: u32) {}
 }
 
+parameter_types! {
+	pub const MaxValidators: u32 = 3072;
+}
+
 impl pallet_session::Config for Test {
 	type SessionManager = pallet_session::historical::NoteHistoricalRoot<Test, Staking>;
 	type Keys = SessionKeys;
@@ -129,6 +133,7 @@ impl pallet_session::Config for Test {
 	type ValidatorId = AccountId;
 	type ValidatorIdOf = pallet_staking::StashOf<Test>;
 	type WeightInfo = ();
+	type MaxValidators = MaxValidators;
 }
 pallet_staking_reward_curve::build! {
 	const I_NPOS: sp_runtime::curve::PiecewiseLinear<'static> = curve!(
@@ -178,6 +183,7 @@ impl pallet_staking::Config for Test {
 	type OnStakerSlash = ();
 	type BenchmarkingConfig = pallet_staking::TestBenchmarkingConfig;
 	type WeightInfo = ();
+	type MaxValidators = MaxValidators;
 }
 
 impl crate::Config for Test {}

frame/session/src/historical/mod.rs

@@ -130,7 +130,7 @@ impl<T: Config> ValidatorSet<T::AccountId> for Pallet<T> {
 	}
 
 	fn validators() -> Vec<Self::ValidatorId> {
-		super::Pallet::<T>::validators()
+		super::Pallet::<T>::validators().into_inner()
 	}
 }
 

frame/session/src/lib.rs

@@ -95,7 +95,7 @@
 //! use pallet_session as session;
 //!
 //! fn validators<T: pallet_session::Config>() -> Vec<<T as pallet_session::Config>::ValidatorId> {
-//! 	<pallet_session::Pallet<T>>::validators()
+//! 	<pallet_session::Pallet<T>>::validators().into_inner()
 //! }
 //! # fn main(){}
 //! ```
@@ -124,7 +124,7 @@ use frame_support::{
 		ValidatorRegistration, ValidatorSet,
 	},
 	weights::Weight,
-	Parameter,
+	Parameter, WeakBoundedVec,
 };
 use sp_runtime::{
 	traits::{AtLeast32BitUnsigned, Convert, Member, One, OpaqueKeys, Zero},
@@ -412,6 +412,10 @@ pub mod pallet {
 
 		/// Weight information for extrinsics in this pallet.
 		type WeightInfo: WeightInfo;
+
+		// Maximum number of validators.
+		#[pallet::constant]
+		type MaxValidators: Get<u32>;
 	}
 
 	#[pallet::genesis_config]
@@ -466,6 +470,8 @@ pub mod pallet {
 					);
 					self.keys.iter().map(|x| x.1.clone()).collect()
 				});
+			let initial_validators: WeakBoundedVec<T::ValidatorId, T::MaxValidators> =
+				initial_validators_0.clone().try_into().expect("Too many initial validators");
 			assert!(
 				!initial_validators_0.is_empty(),
 				"Empty validator set for session 0 in genesis block!"
@@ -492,7 +498,7 @@ pub mod pallet {
 			// Tell everyone about the genesis session keys
 			T::SessionHandler::on_genesis_session::<T::Keys>(&queued_keys);
 
-			Validators::<T>::put(initial_validators_0);
+			Validators::<T>::put(initial_validators);
 			<QueuedKeys<T>>::put(queued_keys);
 
 			T::SessionManager::start_session(0);
@@ -502,7 +508,8 @@ pub mod pallet {
 	/// The current set of validators.
 	#[pallet::storage]
 	#[pallet::getter(fn validators)]
-	pub type Validators<T: Config> = StorageValue<_, Vec<T::ValidatorId>, ValueQuery>;
+	pub type Validators<T: Config> =
+		StorageValue<_, WeakBoundedVec<T::ValidatorId, T::MaxValidators>, ValueQuery>;
 
 	/// Current index of the session.
 	#[pallet::storage]
@@ -527,7 +534,8 @@ pub mod pallet {
 	/// a new set of identities.
 	#[pallet::storage]
 	#[pallet::getter(fn disabled_validators)]
-	pub type DisabledValidators<T> = StorageValue<_, Vec<u32>, ValueQuery>;
+	pub type DisabledValidators<T: Config> =
+		StorageValue<_, BoundedVec<u32, T::MaxValidators>, ValueQuery>;
 
 	/// The next session keys for a validator.
 	#[pallet::storage]
@@ -647,7 +655,10 @@ impl<T: Config> Pallet<T> {
 		let session_keys = <QueuedKeys<T>>::get();
 		let validators =
 			session_keys.iter().map(|(validator, _)| validator.clone()).collect::<Vec<_>>();
-		Validators::<T>::put(&validators);
+
+		let bounded_validator_set: WeakBoundedVec<T::ValidatorId, T::MaxValidators> =
+			validators.clone().try_into().expect("Max validators reached");
+		Validators::<T>::put(bounded_validator_set);
 
 		if changed {
 			// reset disabled validators
@@ -669,7 +680,7 @@ impl<T: Config> Pallet<T> {
 				// same as before, as underlying economic conditions may have changed.
 				(validators, true)
 			} else {
-				(Validators::<T>::get(), false)
+				(Validators::<T>::get().into_inner(), false)
 			};
 
 		// Queue next session keys.
@@ -722,7 +733,7 @@ impl<T: Config> Pallet<T> {
 
 		<DisabledValidators<T>>::mutate(|disabled| {
 			if let Err(index) = disabled.binary_search(&i) {
-				disabled.insert(index, i);
+				disabled.try_insert(index, i).expect("Limit reached");
 				T::SessionHandler::on_disabled(i);
 				return true
 			}
@@ -911,7 +922,7 @@ impl<T: Config> ValidatorSet<T::AccountId> for Pallet<T> {
 	}
 
 	fn validators() -> Vec<Self::ValidatorId> {
-		Pallet::<T>::validators()
+		Pallet::<T>::validators().into_inner()
 	}
 }
 

frame/session/src/mock.rs

@@ -301,6 +301,7 @@ impl Config for Test {
 	type Event = Event;
 	type NextSessionRotation = ();
 	type WeightInfo = ();
+	type MaxValidators = ConstU32<3072>;
 }
 
 #[cfg(feature = "historical")]