git.delta.rocks / unique-network / refs/commits / 37e76bc01ac1

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::traits::{AccountIdConversion, CheckedSub, Saturating, Zero},102		traits::{103			Currency, EnsureOrigin, ExistenceRequirement::KeepAlive, ReservableCurrency,104			ValidatorRegistration,105		},106		BoundedVec, PalletId,107	};108	use frame_system::pallet_prelude::*;109	use pallet_session::SessionManager;110	use sp_runtime::{Perbill, traits::Convert};111	use pallet_configuration::{112		CollatorSelectionDesiredCollatorsOverride as DesiredCollators,113		CollatorSelectionLicenseBondOverride as LicenseBond,114		CollatorSelectionKickThresholdOverride as KickThreshold, BalanceOf,115	};116	use sp_staking::SessionIndex;117118	/// A convertor from collators id. Since this pallet does not have stash/controller, this is119	/// just identity.120	pub struct IdentityCollator;121	impl<T> sp_runtime::traits::Convert<T, Option<T>> for IdentityCollator {122		fn convert(t: T) -> Option<T> {123			Some(t)124		}125	}126127	/// Configure the pallet by specifying the parameters and types on which it depends.128	#[pallet::config]129	pub trait Config: frame_system::Config + pallet_configuration::Config {130		/// Overarching event type.131		type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;132133		/// Origin that can dictate updating parameters of this pallet.134		type UpdateOrigin: EnsureOrigin<Self::RuntimeOrigin>;135136		/// Account Identifier that holds the chain's treasury.137		type TreasuryAccountId: Get<Self::AccountId>;138139		/// Account Identifier from which the internal Pot is generated.140		type PotId: Get<PalletId>;141142		/// Maximum number of candidates and invulnerables that we should have. This is enforced in code.143		type MaxCollators: Get<u32>;144145		/// If kicked, how much of the collator's deposit will be slashed and sent to the slash destination.146		type SlashRatio: Get<Perbill>;147148		/// A stable ID for a validator.149		type ValidatorId: Member + Parameter;150151		/// A conversion from account ID to validator ID.152		///153		/// Its cost must be at most one storage read.154		type ValidatorIdOf: Convert<Self::AccountId, Option<Self::ValidatorId>>;155156		/// Validate a user is registered157		type ValidatorRegistration: ValidatorRegistration<Self::ValidatorId>;158159		/// The weight information of this pallet.160		type WeightInfo: WeightInfo;161	}162163	#[pallet::pallet]164	pub struct Pallet<T>(_);165166	/// The invulnerable, fixed collators.167	#[pallet::storage]168	#[pallet::getter(fn invulnerables)]169	pub type Invulnerables<T: Config> =170		StorageValue<_, BoundedVec<T::AccountId, T::MaxCollators>, ValueQuery>;171172	/// The (community) collation license holders.173	#[pallet::storage]174	#[pallet::getter(fn license_deposit_of)]175	pub type LicenseDepositOf<T: Config> =176		StorageMap<_, Blake2_128Concat, T::AccountId, BalanceOf<T>, ValueQuery>;177178	/// The (community, limited) collation candidates.179	#[pallet::storage]180	#[pallet::getter(fn candidates)]181	pub type Candidates<T: Config> =182		StorageValue<_, BoundedVec<T::AccountId, T::MaxCollators>, ValueQuery>;183184	/// Last block authored by collator.185	#[pallet::storage]186	#[pallet::getter(fn last_authored_block)]187	pub type LastAuthoredBlock<T: Config> =188		StorageMap<_, Twox64Concat, T::AccountId, T::BlockNumber, ValueQuery>;189190	#[pallet::genesis_config]191	pub struct GenesisConfig<T: Config> {192		pub invulnerables: Vec<T::AccountId>,193	}194195	#[cfg(feature = "std")]196	impl<T: Config> Default for GenesisConfig<T> {197		fn default() -> Self {198			Self {199				invulnerables: Default::default(),200			}201		}202	}203204	#[pallet::genesis_build]205	impl<T: Config> GenesisBuild<T> for GenesisConfig<T> {206		fn build(&self) {207			let duplicate_invulnerables = self208				.invulnerables209				.iter()210				.collect::<std::collections::BTreeSet<_>>();211			assert!(212				duplicate_invulnerables.len() == self.invulnerables.len(),213				"duplicate invulnerables in genesis."214			);215216			let bounded_invulnerables =217				BoundedVec::<_, T::MaxCollators>::try_from(self.invulnerables.clone())218					.expect("genesis invulnerables are more than T::MaxCollators");219220			<Invulnerables<T>>::put(bounded_invulnerables);221		}222	}223224	#[pallet::event]225	#[pallet::generate_deposit(pub(super) fn deposit_event)]226	pub enum Event<T: Config> {227		InvulnerableAdded {228			invulnerable: T::AccountId,229		},230		InvulnerableRemoved {231			invulnerable: T::AccountId,232		},233		LicenseObtained {234			account_id: T::AccountId,235			deposit: BalanceOf<T>,236		},237		LicenseReleased {238			account_id: T::AccountId,239			deposit_returned: BalanceOf<T>,240		},241		CandidateAdded {242			account_id: T::AccountId,243		},244		CandidateRemoved {245			account_id: T::AccountId,246		},247	}248249	// Errors inform users that something went wrong.250	#[pallet::error]251	pub enum Error<T> {252		/// Too many candidates253		TooManyCandidates,254		/// Unknown error255		Unknown,256		/// Permission issue257		Permission,258		/// User already holds license to collate259		AlreadyHoldingLicense,260		/// User does not hold a license to collate261		NoLicense,262		/// User is already a candidate263		AlreadyCandidate,264		/// User is not a candidate265		NotCandidate,266		/// Too many invulnerables267		TooManyInvulnerables,268		/// Too few invulnerables269		TooFewInvulnerables,270		/// User is already an Invulnerable271		AlreadyInvulnerable,272		/// User is not an Invulnerable273		NotInvulnerable,274		/// Account has no associated validator ID275		NoAssociatedValidatorId,276		/// Validator ID is not yet registered277		ValidatorNotRegistered,278	}279280	#[pallet::hooks]281	impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {}282283	#[pallet::call]284	impl<T: Config> Pallet<T> {285		/// Add a collator to the list of invulnerable (fixed) collators.286		#[pallet::call_index(0)]287		#[pallet::weight(<T as Config>::WeightInfo::add_invulnerable(T::MaxCollators::get()))]288		pub fn add_invulnerable(289			origin: OriginFor<T>,290			new: T::AccountId,291		) -> DispatchResultWithPostInfo {292			T::UpdateOrigin::ensure_origin(origin)?;293294			// check if the new invulnerable has associated validator keys before it is added295			let validator_key = T::ValidatorIdOf::convert(new.clone())296				.ok_or(Error::<T>::NoAssociatedValidatorId)?;297			ensure!(298				T::ValidatorRegistration::is_registered(&validator_key),299				Error::<T>::ValidatorNotRegistered300			);301			if Self::invulnerables().contains(&new) {302				return Ok(().into());303			}304305			<Invulnerables<T>>::try_append(new.clone())306				.map_err(|_| Error::<T>::TooManyInvulnerables)?;307308			// try to offboard the new invulnerable if it was a collator candidate before309			let _ = Self::try_remove_candidate(&new);310311			Self::deposit_event(Event::InvulnerableAdded { invulnerable: new });312			Ok(().into())313		}314315		/// Remove a collator from the list of invulnerable (fixed) collators.316		#[pallet::call_index(1)]317		#[pallet::weight(<T as Config>::WeightInfo::remove_invulnerable(T::MaxCollators::get()))]318		pub fn remove_invulnerable(319			origin: OriginFor<T>,320			who: T::AccountId,321		) -> DispatchResultWithPostInfo {322			T::UpdateOrigin::ensure_origin(origin)?;323324			<Invulnerables<T>>::try_mutate(|invulnerables| -> DispatchResult {325				if invulnerables.len() <= 1 {326					return Err(Error::<T>::TooFewInvulnerables.into());327				}328329				let index = invulnerables330					.into_iter()331					.position(|r| *r == who)332					.ok_or(Error::<T>::NotInvulnerable)?;333				invulnerables.remove(index);334				Ok(())335			})?;336			Self::deposit_event(Event::InvulnerableRemoved { invulnerable: who });337			Ok(().into())338		}339340		/// Purchase a license on block collation for this account.341		/// It does not make it a collator candidate, use `onboard` afterward. The account must342		/// (a) already have registered session keys and (b) be able to reserve the `LicenseBond`.343		///344		/// This call is not available to `Invulnerable` collators.345		#[pallet::call_index(2)]346		#[pallet::weight(<T as Config>::WeightInfo::get_license(T::MaxCollators::get()))]347		pub fn get_license(origin: OriginFor<T>) -> DispatchResultWithPostInfo {348			// register_as_candidate349			let who = ensure_signed(origin)?;350351			if LicenseDepositOf::<T>::contains_key(&who) {352				return Err(Error::<T>::AlreadyHoldingLicense.into());353			}354355			let validator_key = T::ValidatorIdOf::convert(who.clone())356				.ok_or(Error::<T>::NoAssociatedValidatorId)?;357			ensure!(358				T::ValidatorRegistration::is_registered(&validator_key),359				Error::<T>::ValidatorNotRegistered360			);361362			let deposit = <LicenseBond<T>>::get();363364			T::Currency::reserve(&who, deposit)?;365			LicenseDepositOf::<T>::insert(who.clone(), deposit);366367			Self::deposit_event(Event::LicenseObtained {368				account_id: who,369				deposit,370			});371			Ok(().into()) // Some(T::WeightInfo::register_as_candidate(current_count as u32)).into())372		}373374		/// Register this account as a candidate for collators for next sessions.375		/// The account must already hold a license, and cannot offboard immediately during a session.376		///377		/// This call is not available to `Invulnerable` collators.378		#[pallet::call_index(3)]379		#[pallet::weight(<T as Config>::WeightInfo::onboard(T::MaxCollators::get()))]380		pub fn onboard(origin: OriginFor<T>) -> DispatchResultWithPostInfo {381			// register_as_candidate382			let who = ensure_signed(origin)?;383384			// ensure the user obtained the license.385			ensure!(386				LicenseDepositOf::<T>::contains_key(&who),387				Error::<T>::NoLicense388			);389			// ensure we are below limit.390			let length = <Candidates<T>>::decode_len().unwrap_or_default()391				+ <Invulnerables<T>>::decode_len().unwrap_or_default();392			ensure!(393				(length as u32) < <DesiredCollators<T>>::get(),394				Error::<T>::TooManyCandidates395			);396			ensure!(397				!Self::invulnerables().contains(&who),398				Error::<T>::AlreadyInvulnerable399			);400401			let current_count =402				<Candidates<T>>::try_mutate(|candidates| -> Result<usize, DispatchError> {403					if candidates.iter().any(|candidate| *candidate == who) {404						Err(Error::<T>::AlreadyCandidate)?405					} else {406						candidates407							.try_push(who.clone())408							.map_err(|_| Error::<T>::TooManyCandidates)?;409						// First authored block is current block plus kick threshold to handle session delay410						<LastAuthoredBlock<T>>::insert(411							who.clone(),412							frame_system::Pallet::<T>::block_number() + <KickThreshold<T>>::get(),413						);414						Ok(candidates.len())415					}416				})?;417418			Self::deposit_event(Event::CandidateAdded { account_id: who });419			Ok(Some(<T as Config>::WeightInfo::onboard(current_count as u32)).into())420		}421422		/// Deregister `origin` as a collator candidate. Note that the collator can only leave on423		/// session change. The license to `onboard` later at any other time will remain.424		#[pallet::call_index(4)]425		#[pallet::weight(<T as Config>::WeightInfo::offboard(T::MaxCollators::get()))]426		pub fn offboard(origin: OriginFor<T>) -> DispatchResultWithPostInfo {427			// leave_intent428			let who = ensure_signed(origin)?;429			let current_count = Self::try_remove_candidate(&who)?;430431			Ok(Some(<T as Config>::WeightInfo::offboard(current_count as u32)).into())432		}433434		/// Forfeit `origin`'s own license. The `LicenseBond` will be unreserved immediately.435		///436		/// This call is not available to `Invulnerable` collators.437		#[pallet::call_index(5)]438		#[pallet::weight(<T as Config>::WeightInfo::release_license(T::MaxCollators::get()))]439		pub fn release_license(origin: OriginFor<T>) -> DispatchResultWithPostInfo {440			// leave_intent441			let who = ensure_signed(origin)?;442443			let current_count = Self::try_remove_candidate_and_release_license(&who, false, true)?;444445			Ok(Some(<T as Config>::WeightInfo::release_license(446				current_count as u32,447			))448			.into())449		}450451		/// Force deregister `origin` as a collator candidate as a governing authority, and revoke its license.452		/// Note that the collator can only leave on session change.453		/// The `LicenseBond` will be unreserved and returned immediately.454		///455		/// This call is, of course, not applicable to `Invulnerable` collators.456		#[pallet::call_index(6)]457		#[pallet::weight(<T as Config>::WeightInfo::force_release_license(T::MaxCollators::get()))]458		pub fn force_release_license(459			origin: OriginFor<T>,460			who: T::AccountId,461		) -> DispatchResultWithPostInfo {462			// leave_intent463			T::UpdateOrigin::ensure_origin(origin)?;464465			let current_count = Self::try_remove_candidate_and_release_license(&who, false, true)?;466467			Ok(Some(<T as Config>::WeightInfo::force_release_license(468				current_count as u32,469			))470			.into())471		}472	}473474	impl<T: Config> Pallet<T> {475		/// Get a unique, inaccessible account id from the `PotId`.476		pub fn account_id() -> T::AccountId {477			T::PotId::get().into_account_truncating()478		}479480		/// Removes a candidate and their license, optionally slashed and optionally ignoring,481		/// whether or not they actually are a candidate.482		fn try_remove_candidate_and_release_license(483			who: &T::AccountId,484			should_slash: bool,485			ignore_if_not_candidate: bool,486		) -> Result<usize, DispatchError> {487			let current_count = Self::try_remove_candidate(who);488			let current_count = if ignore_if_not_candidate489				&& current_count == Err(Error::<T>::NotCandidate.into())490			{491				<Candidates<T>>::decode_len().unwrap_or_default()492			} else {493				current_count?494			};495			Self::try_release_license(who, should_slash)?;496			Ok(current_count)497		}498499		/// Removes a candidate from the collator pool for the next session if they exist.500		fn try_remove_candidate(who: &T::AccountId) -> Result<usize, DispatchError> {501			let current_count =502				<Candidates<T>>::try_mutate(|candidates| -> Result<usize, DispatchError> {503					let index = candidates504						.iter()505						.position(|candidate| *candidate == *who)506						.ok_or(Error::<T>::NotCandidate)?;507					candidates.remove(index);508					<LastAuthoredBlock<T>>::remove(who.clone());509					Ok(candidates.len())510				})?;511			Self::deposit_event(Event::CandidateRemoved {512				account_id: who.clone(),513			});514			Ok(current_count)515		}516517		/// Removes a candidate if they exist and sends them back their deposit, optionally slashed.518		fn try_release_license(who: &T::AccountId, should_slash: bool) -> DispatchResult {519			let mut deposit_returned = BalanceOf::<T>::default();520			LicenseDepositOf::<T>::try_mutate_exists(who, |deposit| -> DispatchResult {521				if let Some(deposit) = deposit.take() {522					if should_slash {523						let slashed = T::SlashRatio::get() * deposit;524						let remaining = deposit - slashed;525526						let (imbalance, _) = T::Currency::slash_reserved(who, slashed);527						//T::Currency::unreserve(who, remaining);528						deposit_returned = remaining;529530						T::Currency::resolve_creating(&T::TreasuryAccountId::get(), imbalance);531					} else {532						//T::Currency::unreserve(who, deposit);533						deposit_returned = deposit;534					}535536					T::Currency::unreserve(who, deposit_returned);537					Ok(())538				} else {539					Err(Error::<T>::NoLicense.into())540				}541			})?;542			Self::deposit_event(Event::LicenseReleased {543				account_id: who.clone(),544				deposit_returned,545			});546			Ok(())547		}548549		/// Assemble the current set of candidates and invulnerables into the next collator set.550		///551		/// This is done on the fly, as frequent as we are told to do so, as the session manager.552		pub fn assemble_collators(553			candidates: BoundedVec<T::AccountId, T::MaxCollators>,554		) -> Vec<T::AccountId> {555			let mut collators = Self::invulnerables().to_vec();556			collators.extend(candidates);557			collators558		}559560		/// Kicks out candidates that did not produce a block in the kick threshold561		/// and **confiscates** their deposits to the treasury.562		pub fn kick_stale_candidates(563			candidates: BoundedVec<T::AccountId, T::MaxCollators>,564		) -> BoundedVec<T::AccountId, T::MaxCollators> {565			let now = frame_system::Pallet::<T>::block_number();566			let kick_threshold = <KickThreshold<T>>::get();567			candidates568				.into_iter()569				.filter_map(|c| {570					let last_block = <LastAuthoredBlock<T>>::get(c.clone());571					let since_last = now.saturating_sub(last_block);572					if since_last < kick_threshold {573						Some(c)574					} else {575						let outcome = Self::try_remove_candidate_and_release_license(&c, true, false);576						if let Err(why) = outcome {577							log::warn!("Failed to kick collator and release license {:?}", why);578							debug_assert!(false, "failed to kick collator and release license {why:?}");579						}580						None581					}582				})583				.collect::<Vec<_>>()584				.try_into()585				.expect("filter_map operation can't result in a bounded vec larger than its original; qed")586		}587	}588589	/// Keep track of number of authored blocks per authority, uncles are counted as well since590	/// they're a valid proof of being online.591	impl<T: Config + pallet_authorship::Config>592		pallet_authorship::EventHandler<T::AccountId, T::BlockNumber> for Pallet<T>593	{594		fn note_author(author: T::AccountId) {595			let pot = Self::account_id();596			// assumes an ED will be sent to pot.597			let reward = T::Currency::free_balance(&pot)598				.checked_sub(&T::Currency::minimum_balance())599				.unwrap_or_else(Zero::zero)600				.div(2u32.into());601			// `reward` is half of pot account minus ED, this should never fail.602			let _success = T::Currency::transfer(&pot, &author, reward, KeepAlive);603			debug_assert!(_success.is_ok());604			<LastAuthoredBlock<T>>::insert(author, frame_system::Pallet::<T>::block_number());605606			frame_system::Pallet::<T>::register_extra_weight_unchecked(607				<T as Config>::WeightInfo::note_author(),608				DispatchClass::Mandatory,609			);610		}611	}612613	/// Play the role of the session manager.614	impl<T: Config> SessionManager<T::AccountId> for Pallet<T> {615		fn new_session(index: SessionIndex) -> Option<Vec<T::AccountId>> {616			log::info!(617				"assembling new collators for new session {} at #{:?}",618				index,619				<frame_system::Pallet<T>>::block_number(),620			);621622			let candidates = Self::candidates();623			let candidates_len_before = candidates.len();624			let active_candidates = Self::kick_stale_candidates(candidates);625			let removed = candidates_len_before - active_candidates.len();626			let result = Self::assemble_collators(active_candidates);627628			frame_system::Pallet::<T>::register_extra_weight_unchecked(629				<T as Config>::WeightInfo::new_session(630					candidates_len_before as u32,631					removed as u32,632				),633				DispatchClass::Mandatory,634			);635			Some(result)636		}637		fn start_session(_: SessionIndex) {638			// we don't care.639		}640		fn end_session(_: SessionIndex) {641			// we don't care.642		}643	}644}