git.delta.rocks / unique-network / refs/commits / 313a9f3da734

1// Copyright 2019-2022 Unique Network (Gibraltar) Ltd.2// This file is part of Unique Network.34// Unique Network is free software: you can redistribute it and/or modify5// it under the terms of the GNU General Public License as published by6// the Free Software Foundation, either version 3 of the License, or7// (at your option) any later version.89// Unique Network is distributed in the hope that it will be useful,10// but WITHOUT ANY WARRANTY; without even the implied warranty of11// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the12// GNU General Public License for more details.1314// You should have received a copy of the GNU General Public License15// along with Unique Network. If not, see <http://www.gnu.org/licenses/>.1617// Original license:18// Copyright (C) 2021 Parity Technologies (UK) Ltd.19// SPDX-License-Identifier: Apache-2.02021// Licensed under the Apache License, Version 2.0 (the "License");22// you may not use this file except in compliance with the License.23// You may obtain a copy of the License at24//25// 	http://www.apache.org/licenses/LICENSE-2.026//27// Unless required by applicable law or agreed to in writing, software28// distributed under the License is distributed on an "AS IS" BASIS,29// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.30// See the License for the specific language governing permissions and31// limitations under the License.3233// todo:collator documentation34//! Collator Selection pallet.35//!36//! A pallet to manage collators in a parachain.37//!38//! ## Overview39//!40//! The Collator Selection pallet manages the collators of a parachain. **Collation is _not_ a41//! secure activity** and this pallet does not implement any game-theoretic mechanisms to meet BFT42//! safety assumptions of the chosen set.43//!44//! ## Terminology45//!46//! - Collator: A parachain block producer.47//! - Bond: An amount of `Balance` _reserved_ for candidate registration.48//! - Invulnerable: An account guaranteed to be in the collator set.49//!50//! ## Implementation51//!52//! The final `Collators` are aggregated from two individual lists:53//!54//! 1. [`Invulnerables`]: a set of collators appointed by governance. These accounts will always be55//!    collators.56//! 2. [`Candidates`]: these are *candidates to the collation task* and may or may not be elected as57//!    a final collator.58//!59//! The current implementation resolves congestion of [`Candidates`] in a first-come-first-serve60//! manner.61//!62//! Candidates will not be allowed to get kicked or leave_intent if the total number of candidates63//! fall below MinCandidates. This is for potential disaster recovery scenarios.64//!65//! ### Rewards66//!67//! The Collator Selection pallet maintains an on-chain account (the "Pot"). In each block, the68//! collator who authored it receives:69//!70//! - Half the value of the Pot.71//! - Half the value of the transaction fees within the block. The other half of the transaction72//!   fees are deposited into the Pot.73//!74//! To initiate rewards an ED needs to be transferred to the pot address.75//!76//! Note: Eventually the Pot distribution may be modified as discussed in77//! [this issue](https://github.com/paritytech/statemint/issues/21#issuecomment-810481073).7879#![cfg_attr(not(feature = "std"), no_std)]8081pub use pallet::*;8283#[cfg(test)]84mod mock;8586#[cfg(test)]87mod tests;8889#[cfg(feature = "runtime-benchmarks")]90mod benchmarking;91pub mod weights;9293#[frame_support::pallet]94pub mod pallet {95	pub use crate::weights::WeightInfo;96	use core::ops::Div;97	use frame_support::{98		dispatch::{DispatchClass, DispatchResultWithPostInfo},99		inherent::Vec,100		pallet_prelude::*,101		sp_runtime::{102			traits::{AccountIdConversion, CheckedSub, Saturating, Zero},103			RuntimeDebug,104		},105		traits::{106			Currency, EnsureOrigin, ExistenceRequirement::KeepAlive, ReservableCurrency,107			ValidatorRegistration,108		},109		BoundedVec, PalletId,110	};111	use frame_system::{pallet_prelude::*, Config as SystemConfig};112	use pallet_session::SessionManager;113	use sp_runtime::{114		Perbill,115		traits::{One, Convert},116	};117	use sp_staking::SessionIndex;118119	type BalanceOf<T> =120		<<T as Config>::Currency as Currency<<T as SystemConfig>::AccountId>>::Balance;121122	/// A convertor from collators id. Since this pallet does not have stash/controller, this is123	/// just identity.124	pub struct IdentityCollator;125	impl<T> sp_runtime::traits::Convert<T, Option<T>> for IdentityCollator {126		fn convert(t: T) -> Option<T> {127			Some(t)128		}129	}130131	/// Configure the pallet by specifying the parameters and types on which it depends.132	#[pallet::config]133	pub trait Config: frame_system::Config {134		/// Overarching event type.135		type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;136137		/// The currency mechanism.138		type Currency: ReservableCurrency<Self::AccountId>;139140		/// Origin that can dictate updating parameters of this pallet.141		type UpdateOrigin: EnsureOrigin<Self::RuntimeOrigin>;142143		/// Account Identifier that holds the chain's treasury.144		type TreasuryAccountId: Get<Self::AccountId>;145146		/// Account Identifier from which the internal Pot is generated.147		type PotId: Get<PalletId>;148149		/// Maximum number of candidates that we should have. This is enforced in code.150		///151		/// This does not take into account the invulnerables.152		type MaxCandidates: Get<u32>;153154		/// Minimum number of candidates that we should have. This is used for disaster recovery.155		///156		/// This does not take into account the invulnerables.157		type MinCandidates: Get<u32>;158159		/// Maximum number of invulnerables. This is enforced in code.160		type MaxInvulnerables: Get<u32>;161162		/// If kicked, how much of the collator's deposit will be slashed and sent to the slash destination.163		type SlashRatio: Get<Perbill>;164165		/// A stable ID for a validator.166		type ValidatorId: Member + Parameter;167168		/// A conversion from account ID to validator ID.169		///170		/// Its cost must be at most one storage read.171		type ValidatorIdOf: Convert<Self::AccountId, Option<Self::ValidatorId>>;172173		/// Validate a user is registered174		type ValidatorRegistration: ValidatorRegistration<Self::ValidatorId>;175176		/// The weight information of this pallet.177		type WeightInfo: WeightInfo;178	}179180	/// Basic information about a collation candidate.181	#[derive(182		PartialEq, Eq, Clone, Encode, Decode, RuntimeDebug, scale_info::TypeInfo, MaxEncodedLen,183	)]184	pub struct CandidateInfo<AccountId, Balance> {185		/// Account identifier.186		pub who: AccountId,187		/// Reserved deposit.188		pub deposit: Balance,189	}190191	#[pallet::pallet]192	#[pallet::generate_store(pub(super) trait Store)]193	pub struct Pallet<T>(_);194195	/// The invulnerable, fixed collators.196	#[pallet::storage]197	#[pallet::getter(fn invulnerables)]198	pub type Invulnerables<T: Config> =199		StorageValue<_, BoundedVec<T::AccountId, T::MaxInvulnerables>, ValueQuery>;200201	/// The (community, limited) collation candidates.202	#[pallet::storage]203	#[pallet::getter(fn candidates)]204	pub type Candidates<T: Config> = StorageValue<205		_,206		BoundedVec<CandidateInfo<T::AccountId, BalanceOf<T>>, T::MaxCandidates>,207		ValueQuery,208	>;209210	/// Collator will be kicked if it does not produce a block within the threshold (does not apply to invulnerables).211	///212	/// Should be a multiple of session or things will get inconsistent. todo:collator reword?213	#[pallet::storage]214	#[pallet::getter(fn kick_threshold)]215	pub type KickThreshold<T: Config> = StorageValue<_, T::BlockNumber, ValueQuery>;216217	/// Last block authored by collator.218	#[pallet::storage]219	#[pallet::getter(fn last_authored_block)]220	pub type LastAuthoredBlock<T: Config> =221		StorageMap<_, Twox64Concat, T::AccountId, T::BlockNumber, ValueQuery>;222223	/// Desired number of candidates.224	///225	/// This should ideally always be less than [`Config::MaxCandidates`] for weights to be correct.226	#[pallet::storage]227	#[pallet::getter(fn desired_candidates)]228	pub type DesiredCandidates<T> = StorageValue<_, u32, ValueQuery>;229230	/// Fixed amount to deposit to become a collator.231	///232	/// When a collator calls `leave_intent` they immediately receive the deposit back.233	#[pallet::storage]234	#[pallet::getter(fn candidacy_bond)]235	pub type CandidacyBond<T> = StorageValue<_, BalanceOf<T>, ValueQuery>;236237	#[pallet::genesis_config]238	pub struct GenesisConfig<T: Config> {239		pub invulnerables: Vec<T::AccountId>,240		pub candidacy_bond: BalanceOf<T>,241		pub kick_threshold: T::BlockNumber,242		pub desired_candidates: u32,243	}244245	#[cfg(feature = "std")]246	impl<T: Config> Default for GenesisConfig<T> {247		fn default() -> Self {248			Self {249				invulnerables: Default::default(),250				candidacy_bond: Default::default(),251				kick_threshold: T::BlockNumber::one(),252				desired_candidates: Default::default(),253			}254		}255	}256257	#[pallet::genesis_build]258	impl<T: Config> GenesisBuild<T> for GenesisConfig<T> {259		fn build(&self) {260			let duplicate_invulnerables = self261				.invulnerables262				.iter()263				.collect::<std::collections::BTreeSet<_>>();264			assert!(265				duplicate_invulnerables.len() == self.invulnerables.len(),266				"duplicate invulnerables in genesis."267			);268269			let bounded_invulnerables =270				BoundedVec::<_, T::MaxInvulnerables>::try_from(self.invulnerables.clone())271					.expect("genesis invulnerables are more than T::MaxInvulnerables");272			assert!(273				T::MaxCandidates::get() >= self.desired_candidates,274				"genesis desired_candidates are more than T::MaxCandidates",275			);276277			<DesiredCandidates<T>>::put(&self.desired_candidates);278			<CandidacyBond<T>>::put(&self.candidacy_bond);279			<KickThreshold<T>>::put(&self.kick_threshold);280			<Invulnerables<T>>::put(bounded_invulnerables);281		}282	}283284	#[pallet::event]285	#[pallet::generate_deposit(pub(super) fn deposit_event)]286	pub enum Event<T: Config> {287		NewDesiredCandidates {288			desired_candidates: u32,289		},290		NewCandidacyBond {291			bond_amount: BalanceOf<T>,292		},293		NewKickThreshold {294			length_in_blocks: T::BlockNumber,295		},296		InvulnerableAdded {297			invulnerable: T::AccountId,298		},299		InvulnerableRemoved {300			invulnerable: T::AccountId,301		},302		CandidateAdded {303			account_id: T::AccountId,304			deposit: BalanceOf<T>,305		},306		CandidateRemoved {307			account_id: T::AccountId,308			deposit_returned: BalanceOf<T>,309		},310	}311312	// Errors inform users that something went wrong.313	#[pallet::error]314	pub enum Error<T> {315		/// Too many candidates316		TooManyCandidates,317		/// Too few candidates318		TooFewCandidates,319		/// Unknown error320		Unknown,321		/// Permission issue322		Permission,323		/// User is already a candidate324		AlreadyCandidate,325		/// User is not a candidate326		NotCandidate,327		/// Too many invulnerables328		TooManyInvulnerables,329		/// Too few invulnerables330		TooFewInvulnerables,331		/// User is already an Invulnerable332		AlreadyInvulnerable,333		/// User is not an Invulnerable334		NotInvulnerable,335		/// Account has no associated validator ID336		NoAssociatedValidatorId,337		/// Validator ID is not yet registered338		ValidatorNotRegistered,339	}340341	#[pallet::hooks]342	impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {}343344	#[pallet::call]345	impl<T: Config> Pallet<T> {346		/// Add a collator to the list of invulnerable (fixed) collators.347		#[pallet::weight(T::WeightInfo::set_invulnerables(1 as u32))] // todo:collator weight348		pub fn add_invulnerable(349			origin: OriginFor<T>,350			new: T::AccountId,351		) -> DispatchResultWithPostInfo {352			T::UpdateOrigin::ensure_origin(origin)?;353354			// check if the new invulnerable has associated validator keys before it is added355			let validator_key = T::ValidatorIdOf::convert(new.clone())356				.ok_or(Error::<T>::NoAssociatedValidatorId)?;357			ensure!(358				T::ValidatorRegistration::is_registered(&validator_key),359				Error::<T>::ValidatorNotRegistered360			);361			// ensure!(!Self::invulnerables().contains(&new), Error::<T>::AlreadyInvulnerable);362			if Self::invulnerables().contains(&new) {363				return Ok(().into());364			}365366			<Invulnerables<T>>::try_append(new.clone())367				.map_err(|_| Error::<T>::TooManyInvulnerables)?;368			Self::deposit_event(Event::InvulnerableAdded { invulnerable: new });369			Ok(().into())370		}371372		/// Remove a collator from the list of invulnerable (fixed) collators.373		#[pallet::weight(T::WeightInfo::set_invulnerables(1))] // todo:collator weight374		pub fn remove_invulnerable(375			origin: OriginFor<T>,376			who: T::AccountId,377		) -> DispatchResultWithPostInfo {378			T::UpdateOrigin::ensure_origin(origin)?;379380			// let index = Self::invulnerables().into_iter().position(|r| r == who).ok_or(Error::<T>::NotInvulnerable)?;381			<Invulnerables<T>>::try_mutate(|invulnerables| -> DispatchResult {382				if invulnerables.len() <= 1 {383					return Err(Error::<T>::TooFewInvulnerables.into());384				}385386				let index = invulnerables387					.into_iter()388					.position(|r| *r == who)389					.ok_or(Error::<T>::NotInvulnerable)?;390				invulnerables.remove(index);391				Ok(())392			})?;393			/*let bounded_invulnerables = BoundedVec::<_, T::MaxInvulnerables>::try_from(new)394				.map_err(|_| Error::<T>::TooManyInvulnerables)?;395396			<Invulnerables<T>>::put(&bounded_invulnerables);*/397			Self::deposit_event(Event::InvulnerableRemoved { invulnerable: who });398			Ok(().into())399		}400401		/// Set the ideal number of collators (not including the invulnerables).402		/// If lowering this number, then the number of running collators could be higher than this figure.403		/// Aside from that edge case, there should be no other way to have more collators than the desired number.404		#[pallet::weight(T::WeightInfo::set_desired_candidates())]405		pub fn set_desired_candidates(406			origin: OriginFor<T>,407			max: u32,408		) -> DispatchResultWithPostInfo {409			T::UpdateOrigin::ensure_origin(origin)?;410			// we trust origin calls, this is just a for more accurate benchmarking411			if max > T::MaxCandidates::get() {412				log::warn!("max > T::MaxCandidates; you might need to run benchmarks again");413			}414			<DesiredCandidates<T>>::put(&max);415			Self::deposit_event(Event::NewDesiredCandidates {416				desired_candidates: max,417			});418			Ok(().into())419		}420421		/// Set the candidacy bond amount.422		#[pallet::weight(T::WeightInfo::set_candidacy_bond())]423		pub fn set_candidacy_bond(424			origin: OriginFor<T>,425			bond: BalanceOf<T>,426		) -> DispatchResultWithPostInfo {427			T::UpdateOrigin::ensure_origin(origin)?;428			<CandidacyBond<T>>::put(&bond);429			Self::deposit_event(Event::NewCandidacyBond { bond_amount: bond });430			Ok(().into())431		}432433		/// Set the length of the kick threshold.434		/// Note that if the length is not a multiple of the session period, it might get inconsistent.435		#[pallet::weight(T::WeightInfo::set_candidacy_bond())] // todo:collator weight436		pub fn set_kick_threshold(437			origin: OriginFor<T>,438			kick_threshold: T::BlockNumber,439		) -> DispatchResultWithPostInfo {440			T::UpdateOrigin::ensure_origin(origin)?;441			// todo:collator insert something to guarantee consistency?442			<KickThreshold<T>>::put(kick_threshold);443			Self::deposit_event(Event::NewKickThreshold {444				length_in_blocks: kick_threshold,445			});446			Ok(().into())447		}448449		/// Register this account as a collator candidate. The account must (a) already have450		/// registered session keys and (b) be able to reserve the `CandidacyBond`.451		///452		/// This call is not available to `Invulnerable` collators.453		#[pallet::weight(T::WeightInfo::register_as_candidate(T::MaxCandidates::get()))]454		pub fn register_as_candidate(origin: OriginFor<T>) -> DispatchResultWithPostInfo {455			let who = ensure_signed(origin)?;456457			// ensure we are below limit.458			let length = <Candidates<T>>::decode_len().unwrap_or_default();459			ensure!(460				(length as u32) < Self::desired_candidates(),461				Error::<T>::TooManyCandidates462			);463			// todo:collator really need it?464			ensure!(465				!Self::invulnerables().contains(&who),466				Error::<T>::AlreadyInvulnerable467			);468469			let validator_key = T::ValidatorIdOf::convert(who.clone())470				.ok_or(Error::<T>::NoAssociatedValidatorId)?;471			ensure!(472				T::ValidatorRegistration::is_registered(&validator_key),473				Error::<T>::ValidatorNotRegistered474			);475476			let deposit = Self::candidacy_bond();477			// First authored block is current block plus kick threshold to handle session delay478			let incoming = CandidateInfo {479				who: who.clone(),480				deposit,481			};482483			let current_count =484				<Candidates<T>>::try_mutate(|candidates| -> Result<usize, DispatchError> {485					if candidates.iter().any(|candidate| candidate.who == who) {486						Err(Error::<T>::AlreadyCandidate)?487					} else {488						T::Currency::reserve(&who, deposit)?;489						candidates490							.try_push(incoming)491							.map_err(|_| Error::<T>::TooManyCandidates)?;492						<LastAuthoredBlock<T>>::insert(493							who.clone(),494							frame_system::Pallet::<T>::block_number() + Self::kick_threshold(),495						);496						Ok(candidates.len())497					}498				})?;499500			Self::deposit_event(Event::CandidateAdded {501				account_id: who,502				deposit,503			});504			Ok(Some(T::WeightInfo::register_as_candidate(current_count as u32)).into())505		}506507		/// Deregister `origin` as a collator candidate. Note that the collator can only leave on508		/// session change. The `CandidacyBond` will be unreserved immediately.509		///510		/// This call will fail if the total number of candidates would drop below `MinCandidates`.511		///512		/// This call is not available to `Invulnerable` collators.513		#[pallet::weight(T::WeightInfo::leave_intent(T::MaxCandidates::get()))]514		pub fn leave_intent(origin: OriginFor<T>) -> DispatchResultWithPostInfo {515			let who = ensure_signed(origin)?;516			// todo:collator invulnerables and candidates should count against min candidates together517			ensure!(518				Self::candidates().len() as u32 > T::MinCandidates::get(),519				Error::<T>::TooFewCandidates520			);521			let current_count = Self::try_remove_candidate(&who, false)?;522523			Ok(Some(T::WeightInfo::leave_intent(current_count as u32)).into())524		}525	}526527	impl<T: Config> Pallet<T> {528		/// Get a unique, inaccessible account id from the `PotId`.529		pub fn account_id() -> T::AccountId {530			T::PotId::get().into_account_truncating()531		}532533		/// Removes a candidate if they exist and sends them back their deposit, optionally slashed.534		fn try_remove_candidate(535			who: &T::AccountId,536			should_slash: bool,537		) -> Result<usize, DispatchError> {538			let mut deposit_returned = BalanceOf::<T>::default();539			let current_count =540				<Candidates<T>>::try_mutate(|candidates| -> Result<usize, DispatchError> {541					let index = candidates542						.iter()543						.position(|candidate| candidate.who == *who)544						.ok_or(Error::<T>::NotCandidate)?;545					let candidate = candidates.remove(index);546					let deposit = candidate.deposit;547548					if should_slash {549						let slashed = T::SlashRatio::get() * deposit;550						let remaining = deposit - slashed;551552						let (imbalance, _) = T::Currency::slash_reserved(who, slashed);553						//T::Currency::unreserve(who, remaining);554						deposit_returned = remaining;555556						T::Currency::resolve_creating(&T::TreasuryAccountId::get(), imbalance);557558					// Self::deposit_event(Event::CandidateSlashed(who.clone()));559					} else {560						//T::Currency::unreserve(who, deposit);561						deposit_returned = deposit;562					}563564					T::Currency::unreserve(who, deposit_returned);565					// candidates.remove(index);566					<LastAuthoredBlock<T>>::remove(who.clone());567					Ok(candidates.len())568				})?;569			Self::deposit_event(Event::CandidateRemoved {570				account_id: who.clone(),571				deposit_returned,572			});573			Ok(current_count)574		}575576		/// Assemble the current set of candidates and invulnerables into the next collator set.577		///578		/// This is done on the fly, as frequent as we are told to do so, as the session manager.579		pub fn assemble_collators(580			candidates: BoundedVec<T::AccountId, T::MaxCandidates>,581		) -> Vec<T::AccountId> {582			let mut collators = Self::invulnerables().to_vec();583			collators.extend(candidates);584			collators585		}586587		/// Kicks out candidates that did not produce a block in the kick threshold588		/// and **confiscates** their deposits to the treasury.589		pub fn kick_stale_candidates(590			candidates: BoundedVec<CandidateInfo<T::AccountId, BalanceOf<T>>, T::MaxCandidates>,591		) -> BoundedVec<T::AccountId, T::MaxCandidates> {592			let now = frame_system::Pallet::<T>::block_number();593			let kick_threshold = Self::kick_threshold();594			candidates595				.into_iter()596				.filter_map(|c| {597					let last_block = <LastAuthoredBlock<T>>::get(c.who.clone());598					let since_last = now.saturating_sub(last_block);599					if since_last < kick_threshold ||600						Self::candidates().len() as u32 <= T::MinCandidates::get()601					{602						Some(c.who)603					} else {604						let outcome = Self::try_remove_candidate(&c.who, true);605						if let Err(why) = outcome {606							log::warn!("Failed to remove candidate {:?}", why);607							debug_assert!(false, "failed to remove candidate {:?}", why);608						}609						None610					}611				})612				.collect::<Vec<_>>()613				.try_into()614				.expect("filter_map operation can't result in a bounded vec larger than its original; qed")615		}616	}617618	/// Keep track of number of authored blocks per authority, uncles are counted as well since619	/// they're a valid proof of being online.620	impl<T: Config + pallet_authorship::Config>621		pallet_authorship::EventHandler<T::AccountId, T::BlockNumber> for Pallet<T>622	{623		fn note_author(author: T::AccountId) {624			let pot = Self::account_id();625			// assumes an ED will be sent to pot.626			let reward = T::Currency::free_balance(&pot)627				.checked_sub(&T::Currency::minimum_balance())628				.unwrap_or_else(Zero::zero)629				.div(2u32.into());630			// `reward` is half of pot account minus ED, this should never fail.631			let _success = T::Currency::transfer(&pot, &author, reward, KeepAlive);632			debug_assert!(_success.is_ok());633			<LastAuthoredBlock<T>>::insert(author, frame_system::Pallet::<T>::block_number());634635			frame_system::Pallet::<T>::register_extra_weight_unchecked(636				T::WeightInfo::note_author(),637				DispatchClass::Mandatory,638			);639		}640641		fn note_uncle(_author: T::AccountId, _age: T::BlockNumber) {642			//TODO can we ignore this?643		}644	}645646	/// Play the role of the session manager.647	impl<T: Config> SessionManager<T::AccountId> for Pallet<T> {648		fn new_session(index: SessionIndex) -> Option<Vec<T::AccountId>> {649			log::info!(650				"assembling new collators for new session {} at #{:?}",651				index,652				<frame_system::Pallet<T>>::block_number(),653			);654655			let candidates = Self::candidates();656			let candidates_len_before = candidates.len();657			let active_candidates = Self::kick_stale_candidates(candidates);658			let removed = candidates_len_before - active_candidates.len();659			let result = Self::assemble_collators(active_candidates);660661			frame_system::Pallet::<T>::register_extra_weight_unchecked(662				T::WeightInfo::new_session(candidates_len_before as u32, removed as u32),663				DispatchClass::Mandatory,664			);665			Some(result)666		}667		fn start_session(_: SessionIndex) {668			// we don't care.669		}670		fn end_session(_: SessionIndex) {671			// we don't care.672		}673	}674}