[Manual] Marking offline collators not producing blocks during X rounds

pallets/parachain-staking/src/benchmarks.rs

@@ -19,8 +19,8 @@
 //! Benchmarking
 use crate::{
 	AwardedPts, BalanceOf, BottomDelegations, Call, CandidateBondLessRequest, Config,
-	DelegationAction, Pallet, ParachainBondConfig, ParachainBondInfo, Points, Range, RewardPayment,
-	Round, ScheduledRequest, Staked, TopDelegations,
+	DelegationAction, EnableMarkingOffline, Pallet, ParachainBondConfig, ParachainBondInfo, Points,
+	Range, RewardPayment, Round, ScheduledRequest, Staked, TopDelegations,
 };
 use frame_benchmarking::{account, benchmarks, impl_benchmark_test_suite};
 use frame_support::traits::{Currency, Get, OnFinalize, OnInitialize};
@@ -2192,6 +2192,71 @@ benchmarks! {
 	verify {
 		assert_eq!(T::Currency::free_balance(&collator), original_free_balance + 50u32.into());
 	}
+
+	notify_inactive_collator {
+		use crate::{AtStake, CollatorSnapshot, AwardedPts};
+
+		// Blocks per-round must be greater than TotalSelected
+		Pallet::<T>::set_blocks_per_round(RawOrigin::Root.into(), 101u32)?;
+		Pallet::<T>::set_total_selected(RawOrigin::Root.into(), 100u32)?;
+
+		let mut candidate_count = 1u32;
+		let mut seed = USER_SEED;
+
+		// Create 100 collators
+		for i in 0..100 {
+			seed += i;
+			let collator = create_funded_collator::<T>(
+				"collator",
+				seed,
+				min_candidate_stk::<T>() * 1_000_000u32.into(),
+				true,
+				candidate_count
+			)?;
+			candidate_count += 1;
+		}
+
+		// Create two collators more: the one that will be marked as inactive
+		// and the one that will act as the caller of the extrinsic.
+		seed += 1;
+		let inactive_collator: T::AccountId = create_funded_collator::<T>(
+			"collator",
+			seed,
+			min_candidate_stk::<T>() * 1_000_000u32.into(),
+			true,
+			candidate_count
+		)?;
+		candidate_count += 1;
+
+		seed += 1;
+		let caller: T::AccountId = create_funded_collator::<T>(
+			"collator",
+			seed,
+			min_candidate_stk::<T>() * 1_000_000u32.into(),
+			true,
+			candidate_count
+		)?;
+
+		// Roll to round 2 and call to select_top_candidates.
+		// We do this to be able to have more than 66% of TotalSelected.
+		roll_to_and_author::<T>(2, caller.clone());
+		Pallet::<T>::select_top_candidates(2);
+
+		// Manually change these values for inactive_collator,
+		// so that it can be marked as inactive.
+		<AtStake<T>>::insert(1, &inactive_collator, CollatorSnapshot::default());
+		<AwardedPts<T>>::insert(1, &inactive_collator, 0);
+
+		<AtStake<T>>::insert(2, &inactive_collator, CollatorSnapshot::default());
+		<AwardedPts<T>>::insert(2, &inactive_collator, 0);
+
+		// Enable killswitch
+		<EnableMarkingOffline<T>>::set(true);
+
+	}: _(RawOrigin::Signed(caller), inactive_collator.clone())
+	verify {
+		assert!(!Pallet::<T>::candidate_info(&inactive_collator).expect("must exist").is_active());
+	}
 }
 
 #[cfg(test)]

pallets/parachain-staking/src/lib.rs

@@ -126,6 +126,9 @@ pub mod pallet {
 		/// Minimum number of blocks per round
 		#[pallet::constant]
 		type MinBlocksPerRound: Get<u32>;
+		/// If a collator doesn't produce any block on this number of rounds, it is notified as inactive
+		#[pallet::constant]
+		type MaxOfflineRounds: Get<u32>;
 		/// Number of rounds that candidates remain bonded before exit request is executable
 		#[pallet::constant]
 		type LeaveCandidatesDelay: Get<RoundIndex>;
@@ -170,6 +173,10 @@ pub mod pallet {
 		/// Handler to distribute a collator's reward.
 		/// To use the default implementation of minting rewards, specify the type `()`.
 		type PayoutCollatorReward: PayoutCollatorReward<Self>;
+		/// Handler to notify the runtime when a collator is inactive.
+		/// The default behavior is to mark the collator as offline.
+		/// If you need to use the default implementation, specify the type `()`.
+		type OnInactiveCollator: OnInactiveCollator<Self>;
 		/// Handler to notify the runtime when a new round begin.
 		/// If you don't need it, you can specify the type `()`.
 		type OnNewRound: OnNewRound;
@@ -227,12 +234,15 @@ pub mod pallet {
 		TooLowDelegationCountToAutoCompound,
 		TooLowCandidateAutoCompoundingDelegationCountToAutoCompound,
 		TooLowCandidateAutoCompoundingDelegationCountToDelegate,
+		TooLowCollatorCountToNotifyAsInactive,
+		CannotBeNotifiedAsInactive,
 		TooLowCandidateAutoCompoundingDelegationCountToLeaveCandidates,
 		TooLowCandidateCountWeightHint,
 		TooLowCandidateCountWeightHintGoOffline,
 		CandidateLimitReached,
 		CannotSetAboveMaxCandidates,
 		RemovedCall,
+		MarkingOfflineNotEnabled,
 	}
 
 	#[pallet::event]
@@ -608,7 +618,7 @@ pub mod pallet {
 		Twox64Concat,
 		T::AccountId,
 		CollatorSnapshot<T::AccountId, BalanceOf<T>>,
-		ValueQuery,
+		OptionQuery,
 	>;
 
 	#[pallet::storage]
@@ -645,6 +655,11 @@ pub mod pallet {
 		ValueQuery,
 	>;
 
+	#[pallet::storage]
+	#[pallet::getter(fn marking_offline)]
+	/// Killswitch to enable/disable marking offline feature.
+	pub type EnableMarkingOffline<T: Config> = StorageValue<_, bool, ValueQuery>;
+
 	#[pallet::genesis_config]
 	pub struct GenesisConfig<T: Config> {
 		/// Initialize balance and register all as collators: `(collator AccountId, balance Amount)`
@@ -1375,6 +1390,73 @@ pub mod pallet {
 
 			Ok(().into())
 		}
+
+		/// Notify a collator is inactive during MaxOfflineRounds
+		#[pallet::call_index(29)]
+		#[pallet::weight(
+			// TODO: add the proper benchmark function once it is available
+			T::DbWeight::get().reads_writes(0 as u64, 0 as u64)
+		)]
+		pub fn notify_inactive_collator(
+			origin: OriginFor<T>,
+			collator: T::AccountId,
+		) -> DispatchResult {
+			ensure!(
+				<EnableMarkingOffline<T>>::get(),
+				<Error<T>>::MarkingOfflineNotEnabled
+			);
+			ensure_signed(origin)?;
+
+			let collators = <SelectedCandidates<T>>::get();
+			let max_collators = <TotalSelected<T>>::get();
+
+			// Check collators length is not below or eq to 66% of max_collators.
+			// We use saturating logic here with (2/3)
+			// as it is dangerous to use floating point numbers directly.
+			ensure!(
+				collators.len() * 3 > (max_collators * 2) as usize,
+				<Error<T>>::TooLowCollatorCountToNotifyAsInactive
+			);
+
+			let round_info = <Round<T>>::get();
+			let max_offline_rounds = T::MaxOfflineRounds::get();
+
+			// Take last round to have rounds_to_check = [7,8,9]
+			// in case we are in round 10 for instance
+			let round = round_info.current.saturating_sub(1);
+
+			let mut rounds_to_check: Vec<RoundIndex> = vec![];
+			for round_index in (0..max_offline_rounds).rev() {
+				rounds_to_check.push(round.saturating_sub(round_index));
+			}
+
+			// If this counter is eq to max_offline_rounds,
+			// the collator should be notified as inactive
+			let mut inactive_counter: RoundIndex = 0u32;
+
+			// Iter rounds to check
+			//
+			// - The collator has AtStake associated and their AwardedPts are zero
+			//
+			// If the previous condition is met in all rounds of rounds_to_check,
+			// the collator is notified as inactive
+			for r in rounds_to_check {
+				let stake = <AtStake<T>>::get(r, &collator);
+				let pts = <AwardedPts<T>>::get(r, &collator);
+
+				if stake.is_some() && pts.is_zero() {
+					inactive_counter = inactive_counter.saturating_add(1);
+				}
+			}
+
+			if inactive_counter == max_offline_rounds {
+				let _ = T::OnInactiveCollator::on_inactive_collator(collator.clone(), round);
+			} else {
+				return Err(<Error<T>>::CannotBeNotifiedAsInactive.into());
+			}
+
+			Ok(().into())
+		}
 	}
 
 	/// Represents a payout made via `pay_one_collator_reward`.

pallets/parachain-staking/src/mock.rs

@@ -20,6 +20,7 @@ use crate::{
 	pallet, AwardedPts, Config, Event as ParachainStakingEvent, InflationInfo, Points, Range,
 	COLLATOR_LOCK_ID, DELEGATOR_LOCK_ID,
 };
+use block_author::BlockAuthor as BlockAuthorMap;
 use frame_support::{
 	construct_runtime, parameter_types,
 	traits::{Everything, GenesisBuild, LockIdentifier, OnFinalize, OnInitialize},
@@ -111,6 +112,7 @@ const GENESIS_PARACHAIN_BOND_RESERVE_PERCENT: Percent = Percent::from_percent(30
 const GENESIS_NUM_SELECTED_CANDIDATES: u32 = 5;
 parameter_types! {
 	pub const MinBlocksPerRound: u32 = 3;
+	pub const MaxOfflineRounds: u32 = 1;
 	pub const LeaveCandidatesDelay: u32 = 2;
 	pub const CandidateBondLessDelay: u32 = 2;
 	pub const LeaveDelegatorsDelay: u32 = 2;
@@ -130,6 +132,7 @@ impl Config for Test {
 	type Currency = Balances;
 	type MonetaryGovernanceOrigin = frame_system::EnsureRoot<AccountId>;
 	type MinBlocksPerRound = MinBlocksPerRound;
+	type MaxOfflineRounds = MaxOfflineRounds;
 	type LeaveCandidatesDelay = LeaveCandidatesDelay;
 	type CandidateBondLessDelay = CandidateBondLessDelay;
 	type LeaveDelegatorsDelay = LeaveDelegatorsDelay;
@@ -145,6 +148,7 @@ impl Config for Test {
 	type BlockAuthor = BlockAuthor;
 	type OnCollatorPayout = ();
 	type PayoutCollatorReward = ();
+	type OnInactiveCollator = ();
 	type OnNewRound = ();
 	type WeightInfo = ();
 	type MaxCandidates = MaxCandidates;
@@ -515,6 +519,11 @@ pub(crate) fn set_author(round: BlockNumber, acc: u64, pts: u32) {
 	<AwardedPts<Test>>::mutate(round, acc, |p| *p += pts);
 }
 
+// Allows to change the block author (default is always 0)
+pub(crate) fn set_block_author(acc: u64) {
+	<BlockAuthorMap<Test>>::set(acc);
+}
+
 /// fn to query the lock amount
 pub(crate) fn query_lock_amount(account_id: u64, id: LockIdentifier) -> Option<Balance> {
 	for lock in Balances::locks(&account_id) {