Add simple collator election mechanism

cumulus/pallets/collator-selection/src/benchmarking.rs

@@ -25,14 +25,11 @@ use codec::Decode;
 use frame_benchmarking::{
 	account, impl_benchmark_test_suite, v2::*, whitelisted_caller, BenchmarkError,
 };
-use frame_support::{
-	dispatch::DispatchResult,
-	traits::{Currency, EnsureOrigin, Get, ReservableCurrency},
-};
+use frame_support::traits::{Currency, EnsureOrigin, Get, ReservableCurrency};
 use frame_system::{pallet_prelude::BlockNumberFor, EventRecord, RawOrigin};
 use pallet_authorship::EventHandler;
 use pallet_session::{self as session, SessionManager};
-use sp_std::prelude::*;
+use sp_std::{cmp, prelude::*};
 
 pub type BalanceOf<T> =
 	<<T as Config>::Currency as Currency<<T as frame_system::Config>::AccountId>>::Balance;
@@ -94,7 +91,7 @@ fn register_candidates<T: Config>(count: u32) {
 	assert!(<CandidacyBond<T>>::get() > 0u32.into(), "Bond cannot be zero!");
 
 	for who in candidates {
-		T::Currency::make_free_balance_be(&who, <CandidacyBond<T>>::get() * 2u32.into());
+		T::Currency::make_free_balance_be(&who, <CandidacyBond<T>>::get() * 3u32.into());
 		<CollatorSelection<T>>::register_as_candidate(RawOrigin::Signed(who).into()).unwrap();
 	}
 }
@@ -107,8 +104,11 @@ fn min_candidates<T: Config>() -> u32 {
 
 fn min_invulnerables<T: Config>() -> u32 {
 	let min_collators = T::MinEligibleCollators::get();
-	let candidates_length = <Candidates<T>>::get().len();
-	min_collators.saturating_sub(candidates_length.try_into().unwrap())
+	let candidates_length = <CandidateList<T>>::decode_len()
+		.unwrap_or_default()
+		.try_into()
+		.unwrap_or_default();
+	min_collators.saturating_sub(candidates_length)
 }
 
 #[benchmarks(where T: pallet_authorship::Config + session::Config)]
@@ -160,22 +160,19 @@ mod benchmarks {
 				.unwrap();
 		}
 		// ... and register them.
-		for (who, _) in candidates {
+		for (who, _) in candidates.iter() {
 			let deposit = <CandidacyBond<T>>::get();
-			T::Currency::make_free_balance_be(&who, deposit * 1000_u32.into());
-			let incoming = CandidateInfo { who: who.clone(), deposit };
-			<Candidates<T>>::try_mutate(|candidates| -> DispatchResult {
-				if !candidates.iter().any(|candidate| candidate.who == who) {
-					T::Currency::reserve(&who, deposit)?;
-					candidates.try_push(incoming).expect("we've respected the bounded vec limit");
-					<LastAuthoredBlock<T>>::insert(
-						who.clone(),
-						frame_system::Pallet::<T>::block_number() + T::KickThreshold::get(),
-					);
-				}
-				Ok(())
+			T::Currency::make_free_balance_be(who, deposit * 1000_u32.into());
+			<CandidateList<T>>::try_mutate(|list| {
+				list.try_push(CandidateInfo { who: who.clone(), deposit }).unwrap();
+				Ok::<(), BenchmarkError>(())
 			})
-			.expect("only returns ok");
+			.unwrap();
+			T::Currency::reserve(who, deposit)?;
+			<LastAuthoredBlock<T>>::insert(
+				who.clone(),
+				frame_system::Pallet::<T>::block_number() + T::KickThreshold::get(),
+			);
 		}
 
 		// now we need to fill up invulnerables
@@ -226,10 +223,27 @@ mod benchmarks {
 	}
 
 	#[benchmark]
-	fn set_candidacy_bond() -> Result<(), BenchmarkError> {
-		let bond_amount: BalanceOf<T> = T::Currency::minimum_balance() * 10u32.into();
+	fn set_candidacy_bond(
+		c: Linear<0, { T::MaxCandidates::get() }>,
+		k: Linear<0, { T::MaxCandidates::get() }>,
+	) -> Result<(), BenchmarkError> {
+		let initial_bond_amount: BalanceOf<T> = T::Currency::minimum_balance() * 2u32.into();
+		<CandidacyBond<T>>::put(initial_bond_amount);
+		register_validators::<T>(c);
+		register_candidates::<T>(c);
+		let kicked = cmp::min(k, c);
 		let origin =
 			T::UpdateOrigin::try_successful_origin().map_err(|_| BenchmarkError::Weightless)?;
+		let bond_amount = if k > 0 {
+			<CandidateList<T>>::mutate(|candidates| {
+				for info in candidates.iter_mut().skip(kicked as usize) {
+					info.deposit = T::Currency::minimum_balance() * 3u32.into();
+				}
+			});
+			T::Currency::minimum_balance() * 3u32.into()
+		} else {
+			T::Currency::minimum_balance()
+		};
 
 		#[extrinsic_call]
 		_(origin as T::RuntimeOrigin, bond_amount);
@@ -238,6 +252,35 @@ mod benchmarks {
 		Ok(())
 	}
 
+	#[benchmark]
+	fn update_bond(
+		c: Linear<{ min_candidates::<T>() + 1 }, { T::MaxCandidates::get() }>,
+	) -> Result<(), BenchmarkError> {
+		<CandidacyBond<T>>::put(T::Currency::minimum_balance());
+		<DesiredCandidates<T>>::put(c);
+
+		register_validators::<T>(c);
+		register_candidates::<T>(c);
+
+		let caller = <CandidateList<T>>::get()[0].who.clone();
+		v2::whitelist!(caller);
+
+		let bond_amount: BalanceOf<T> =
+			T::Currency::minimum_balance() + T::Currency::minimum_balance();
+
+		#[extrinsic_call]
+		_(RawOrigin::Signed(caller.clone()), bond_amount);
+
+		assert_last_event::<T>(
+			Event::CandidateBondUpdated { account_id: caller, deposit: bond_amount }.into(),
+		);
+		assert!(
+			<CandidateList<T>>::get().iter().last().unwrap().deposit ==
+				T::Currency::minimum_balance() * 2u32.into()
+		);
+		Ok(())
+	}
+
 	// worse case is when we have all the max-candidate slots filled except one, and we fill that
 	// one.
 	#[benchmark]
@@ -267,6 +310,36 @@ mod benchmarks {
 		);
 	}
 
+	#[benchmark]
+	fn take_candidate_slot(c: Linear<{ min_candidates::<T>() + 1 }, { T::MaxCandidates::get() }>) {
+		<CandidacyBond<T>>::put(T::Currency::minimum_balance());
+		<DesiredCandidates<T>>::put(1);
+
+		register_validators::<T>(c);
+		register_candidates::<T>(c);
+
+		let caller: T::AccountId = whitelisted_caller();
+		let bond: BalanceOf<T> = T::Currency::minimum_balance() * 10u32.into();
+		T::Currency::make_free_balance_be(&caller, bond);
+
+		<session::Pallet<T>>::set_keys(
+			RawOrigin::Signed(caller.clone()).into(),
+			keys::<T>(c + 1),
+			Vec::new(),
+		)
+		.unwrap();
+
+		let target = <CandidateList<T>>::get().iter().last().unwrap().who.clone();
+
+		#[extrinsic_call]
+		_(RawOrigin::Signed(caller.clone()), bond / 2u32.into(), target.clone());
+
+		assert_last_event::<T>(
+			Event::CandidateReplaced { old: target, new: caller, deposit: bond / 2u32.into() }
+				.into(),
+		);
+	}
+
 	// worse case is the last candidate leaving.
 	#[benchmark]
 	fn leave_intent(c: Linear<{ min_candidates::<T>() + 1 }, { T::MaxCandidates::get() }>) {
@@ -276,7 +349,7 @@ mod benchmarks {
 		register_validators::<T>(c);
 		register_candidates::<T>(c);
 
-		let leaving = <Candidates<T>>::get().last().unwrap().who.clone();
+		let leaving = <CandidateList<T>>::get().iter().last().unwrap().who.clone();
 		v2::whitelist!(leaving);
 
 		#[extrinsic_call]
@@ -323,31 +396,37 @@ mod benchmarks {
 
 		let new_block: BlockNumberFor<T> = 1800u32.into();
 		let zero_block: BlockNumberFor<T> = 0u32.into();
-		let candidates = <Candidates<T>>::get();
+		let candidates: Vec<T::AccountId> = <CandidateList<T>>::get()
+			.iter()
+			.map(|candidate_info| candidate_info.who.clone())
+			.collect();
 
 		let non_removals = c.saturating_sub(r);
 
 		for i in 0..c {
-			<LastAuthoredBlock<T>>::insert(candidates[i as usize].who.clone(), zero_block);
+			<LastAuthoredBlock<T>>::insert(candidates[i as usize].clone(), zero_block);
 		}
 
 		if non_removals > 0 {
 			for i in 0..non_removals {
-				<LastAuthoredBlock<T>>::insert(candidates[i as usize].who.clone(), new_block);
+				<LastAuthoredBlock<T>>::insert(candidates[i as usize].clone(), new_block);
 			}
 		} else {
 			for i in 0..c {
-				<LastAuthoredBlock<T>>::insert(candidates[i as usize].who.clone(), new_block);
+				<LastAuthoredBlock<T>>::insert(candidates[i as usize].clone(), new_block);
 			}
 		}
 
 		let min_candidates = min_candidates::<T>();
-		let pre_length = <Candidates<T>>::get().len();
+		let pre_length = <CandidateList<T>>::decode_len().unwrap_or_default();
 
 		frame_system::Pallet::<T>::set_block_number(new_block);
 
-		assert!(<Candidates<T>>::get().len() == c as usize);
-
+		let current_length: u32 = <CandidateList<T>>::decode_len()
+			.unwrap_or_default()
+			.try_into()
+			.unwrap_or_default();
+		assert!(c == current_length);
 		#[block]
 		{
 			<CollatorSelection<T> as SessionManager<_>>::new_session(0);
@@ -357,16 +436,20 @@ mod benchmarks {
 			// candidates > removals and remaining candidates > min candidates
 			// => remaining candidates should be shorter than before removal, i.e. some were
 			//    actually removed.
-			assert!(<Candidates<T>>::get().len() < pre_length);
+			assert!(<CandidateList<T>>::decode_len().unwrap_or_default() < pre_length);
 		} else if c > r && non_removals < min_candidates {
 			// candidates > removals and remaining candidates would be less than min candidates
 			// => remaining candidates should equal min candidates, i.e. some were removed up to
 			//    the minimum, but then any more were "forced" to stay in candidates.
-			assert!(<Candidates<T>>::get().len() == min_candidates as usize);
+			let current_length: u32 = <CandidateList<T>>::decode_len()
+				.unwrap_or_default()
+				.try_into()
+				.unwrap_or_default();
+			assert!(min_candidates == current_length);
 		} else {
 			// removals >= candidates, non removals must == 0
 			// can't remove more than exist
-			assert!(<Candidates<T>>::get().len() == pre_length);
+			assert!(<CandidateList<T>>::decode_len().unwrap_or_default() == pre_length);
 		}
 	}