git.delta.rocks / unique-network / refs/commits / 3e6399dacf51

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	use super::*;96	pub use crate::weights::WeightInfo;97	use core::ops::Div;98	use frame_support::{99		dispatch::{DispatchClass, DispatchResultWithPostInfo},100		inherent::Vec,101		pallet_prelude::*,102		sp_runtime::traits::{AccountIdConversion, CheckedSub, Saturating, Zero},103		traits::{104			EnsureOrigin,105			fungible::{Balanced, BalancedHold, Inspect, InspectHold, Mutate, MutateHold},106			ValidatorRegistration,107			tokens::{Precision, Preservation},108		},109		BoundedVec, PalletId,110	};111	use frame_system::pallet_prelude::*;112	use pallet_session::SessionManager;113	use sp_runtime::{Perbill, traits::Convert};114	use pallet_configuration::{115		CollatorSelectionDesiredCollatorsOverride as DesiredCollators,116		CollatorSelectionLicenseBondOverride as LicenseBond,117		CollatorSelectionKickThresholdOverride as KickThreshold, BalanceOf,118	};119	use sp_staking::SessionIndex;120121	/// A convertor from collators id. Since this pallet does not have stash/controller, this is122	/// just identity.123	pub struct IdentityCollator;124	impl<T> sp_runtime::traits::Convert<T, Option<T>> for IdentityCollator {125		fn convert(t: T) -> Option<T> {126			Some(t)127		}128	}129130	/// Configure the pallet by specifying the parameters and types on which it depends.131	#[pallet::config]132	pub trait Config: frame_system::Config + pallet_configuration::Config {133		/// Overarching event type.134		type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;135136		/// Origin that can dictate updating parameters of this pallet.137		type UpdateOrigin: EnsureOrigin<Self::RuntimeOrigin>;138139		/// Account Identifier that holds the chain's treasury.140		type TreasuryAccountId: Get<Self::AccountId>;141142		/// Account Identifier from which the internal Pot is generated.143		type PotId: Get<PalletId>;144145		/// Maximum number of candidates and invulnerables that we should have. This is enforced in code.146		type MaxCollators: Get<u32>;147148		/// If kicked, how much of the collator's deposit will be slashed and sent to the slash destination.149		type SlashRatio: Get<Perbill>;150151		/// A stable ID for a validator.152		type ValidatorId: Member + Parameter;153154		/// A conversion from account ID to validator ID.155		///156		/// Its cost must be at most one storage read.157		type ValidatorIdOf: Convert<Self::AccountId, Option<Self::ValidatorId>>;158159		/// Validate a user is registered160		type ValidatorRegistration: ValidatorRegistration<Self::ValidatorId>;161162		/// The weight information of this pallet.163		type WeightInfo: WeightInfo;164165		#[pallet::constant]166		type LicenceBondIdentifier: Get<<<Self as pallet_configuration::Config>::Currency as InspectHold<Self::AccountId>>::Reason>;167	}168169	#[pallet::pallet]170	pub struct Pallet<T>(_);171172	/// The invulnerable, fixed collators.173	#[pallet::storage]174	#[pallet::getter(fn invulnerables)]175	pub type Invulnerables<T: Config> =176		StorageValue<_, BoundedVec<T::AccountId, T::MaxCollators>, ValueQuery>;177178	/// The (community) collation license holders.179	#[pallet::storage]180	#[pallet::getter(fn license_deposit_of)]181	pub type LicenseDepositOf<T: Config> =182		StorageMap<_, Blake2_128Concat, T::AccountId, BalanceOf<T>, ValueQuery>;183184	/// The (community, limited) collation candidates.185	#[pallet::storage]186	#[pallet::getter(fn candidates)]187	pub type Candidates<T: Config> =188		StorageValue<_, BoundedVec<T::AccountId, T::MaxCollators>, ValueQuery>;189190	/// Last block authored by collator.191	#[pallet::storage]192	#[pallet::getter(fn last_authored_block)]193	pub type LastAuthoredBlock<T: Config> =194		StorageMap<_, Twox64Concat, T::AccountId, T::BlockNumber, ValueQuery>;195196	#[pallet::genesis_config]197	pub struct GenesisConfig<T: Config> {198		pub invulnerables: Vec<T::AccountId>,199	}200201	#[cfg(feature = "std")]202	impl<T: Config> Default for GenesisConfig<T> {203		fn default() -> Self {204			Self {205				invulnerables: Default::default(),206			}207		}208	}209210	#[pallet::genesis_build]211	impl<T: Config> GenesisBuild<T> for GenesisConfig<T> {212		fn build(&self) {213			let duplicate_invulnerables = self214				.invulnerables215				.iter()216				.collect::<std::collections::BTreeSet<_>>();217			assert!(218				duplicate_invulnerables.len() == self.invulnerables.len(),219				"duplicate invulnerables in genesis."220			);221222			let bounded_invulnerables =223				BoundedVec::<_, T::MaxCollators>::try_from(self.invulnerables.clone())224					.expect("genesis invulnerables are more than T::MaxCollators");225226			<Invulnerables<T>>::put(bounded_invulnerables);227		}228	}229230	#[pallet::event]231	#[pallet::generate_deposit(pub(super) fn deposit_event)]232	pub enum Event<T: Config> {233		InvulnerableAdded {234			invulnerable: T::AccountId,235		},236		InvulnerableRemoved {237			invulnerable: T::AccountId,238		},239		LicenseObtained {240			account_id: T::AccountId,241			deposit: BalanceOf<T>,242		},243		LicenseReleased {244			account_id: T::AccountId,245			deposit_returned: BalanceOf<T>,246		},247		CandidateAdded {248			account_id: T::AccountId,249		},250		CandidateRemoved {251			account_id: T::AccountId,252		},253	}254255	// Errors inform users that something went wrong.256	#[pallet::error]257	pub enum Error<T> {258		/// Too many candidates259		TooManyCandidates,260		/// Unknown error261		Unknown,262		/// Permission issue263		Permission,264		/// User already holds license to collate265		AlreadyHoldingLicense,266		/// User does not hold a license to collate267		NoLicense,268		/// User is already a candidate269		AlreadyCandidate,270		/// User is not a candidate271		NotCandidate,272		/// Too many invulnerables273		TooManyInvulnerables,274		/// Too few invulnerables275		TooFewInvulnerables,276		/// User is already an Invulnerable277		AlreadyInvulnerable,278		/// User is not an Invulnerable279		NotInvulnerable,280		/// Account has no associated validator ID281		NoAssociatedValidatorId,282		/// Validator ID is not yet registered283		ValidatorNotRegistered,284	}285286	#[pallet::hooks]287	impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {}288289	#[pallet::call]290	impl<T: Config> Pallet<T> {291		/// Add a collator to the list of invulnerable (fixed) collators.292		#[pallet::call_index(0)]293		#[pallet::weight(<T as Config>::WeightInfo::add_invulnerable(T::MaxCollators::get()))]294		pub fn add_invulnerable(295			origin: OriginFor<T>,296			new: T::AccountId,297		) -> DispatchResultWithPostInfo {298			T::UpdateOrigin::ensure_origin(origin)?;299300			// check if the new invulnerable has associated validator keys before it is added301			let validator_key = T::ValidatorIdOf::convert(new.clone())302				.ok_or(Error::<T>::NoAssociatedValidatorId)?;303			ensure!(304				T::ValidatorRegistration::is_registered(&validator_key),305				Error::<T>::ValidatorNotRegistered306			);307			if Self::invulnerables().contains(&new) {308				return Ok(().into());309			}310311			<Invulnerables<T>>::try_append(new.clone())312				.map_err(|_| Error::<T>::TooManyInvulnerables)?;313314			// try to offboard the new invulnerable if it was a collator candidate before315			let _ = Self::try_remove_candidate(&new);316317			Self::deposit_event(Event::InvulnerableAdded { invulnerable: new });318			Ok(().into())319		}320321		/// Remove a collator from the list of invulnerable (fixed) collators.322		#[pallet::call_index(1)]323		#[pallet::weight(<T as Config>::WeightInfo::remove_invulnerable(T::MaxCollators::get()))]324		pub fn remove_invulnerable(325			origin: OriginFor<T>,326			who: T::AccountId,327		) -> DispatchResultWithPostInfo {328			T::UpdateOrigin::ensure_origin(origin)?;329330			<Invulnerables<T>>::try_mutate(|invulnerables| -> DispatchResult {331				if invulnerables.len() <= 1 {332					return Err(Error::<T>::TooFewInvulnerables.into());333				}334335				let index = invulnerables336					.into_iter()337					.position(|r| *r == who)338					.ok_or(Error::<T>::NotInvulnerable)?;339				invulnerables.remove(index);340				Ok(())341			})?;342			Self::deposit_event(Event::InvulnerableRemoved { invulnerable: who });343			Ok(().into())344		}345346		/// Purchase a license on block collation for this account.347		/// It does not make it a collator candidate, use `onboard` afterward. The account must348		/// (a) already have registered session keys and (b) be able to reserve the `LicenseBond`.349		///350		/// This call is not available to `Invulnerable` collators.351		#[pallet::call_index(2)]352		#[pallet::weight(<T as Config>::WeightInfo::get_license(T::MaxCollators::get()))]353		pub fn get_license(origin: OriginFor<T>) -> DispatchResultWithPostInfo {354			// register_as_candidate355			let who = ensure_signed(origin)?;356357			if LicenseDepositOf::<T>::contains_key(&who) {358				return Err(Error::<T>::AlreadyHoldingLicense.into());359			}360361			let validator_key = T::ValidatorIdOf::convert(who.clone())362				.ok_or(Error::<T>::NoAssociatedValidatorId)?;363			ensure!(364				T::ValidatorRegistration::is_registered(&validator_key),365				Error::<T>::ValidatorNotRegistered366			);367368			let deposit = <LicenseBond<T>>::get();369370			T::Currency::hold(&T::LicenceBondIdentifier::get(), &who, deposit)?;371			LicenseDepositOf::<T>::insert(who.clone(), deposit);372373			Self::deposit_event(Event::LicenseObtained {374				account_id: who,375				deposit,376			});377			Ok(().into()) // Some(T::WeightInfo::register_as_candidate(current_count as u32)).into())378		}379380		/// Register this account as a candidate for collators for next sessions.381		/// The account must already hold a license, and cannot offboard immediately during a session.382		///383		/// This call is not available to `Invulnerable` collators.384		#[pallet::call_index(3)]385		#[pallet::weight(<T as Config>::WeightInfo::onboard(T::MaxCollators::get()))]386		pub fn onboard(origin: OriginFor<T>) -> DispatchResultWithPostInfo {387			// register_as_candidate388			let who = ensure_signed(origin)?;389390			// ensure the user obtained the license.391			ensure!(392				LicenseDepositOf::<T>::contains_key(&who),393				Error::<T>::NoLicense394			);395			// ensure we are below limit.396			let length = <Candidates<T>>::decode_len().unwrap_or_default()397				+ <Invulnerables<T>>::decode_len().unwrap_or_default();398			ensure!(399				(length as u32) < <DesiredCollators<T>>::get(),400				Error::<T>::TooManyCandidates401			);402			ensure!(403				!Self::invulnerables().contains(&who),404				Error::<T>::AlreadyInvulnerable405			);406407			let current_count =408				<Candidates<T>>::try_mutate(|candidates| -> Result<usize, DispatchError> {409					if candidates.iter().any(|candidate| *candidate == who) {410						Err(Error::<T>::AlreadyCandidate)?411					} else {412						candidates413							.try_push(who.clone())414							.map_err(|_| Error::<T>::TooManyCandidates)?;415						// First authored block is current block plus kick threshold to handle session delay416						<LastAuthoredBlock<T>>::insert(417							who.clone(),418							frame_system::Pallet::<T>::block_number() + <KickThreshold<T>>::get(),419						);420						Ok(candidates.len())421					}422				})?;423424			Self::deposit_event(Event::CandidateAdded { account_id: who });425			Ok(Some(<T as Config>::WeightInfo::onboard(current_count as u32)).into())426		}427428		/// Deregister `origin` as a collator candidate. Note that the collator can only leave on429		/// session change. The license to `onboard` later at any other time will remain.430		#[pallet::call_index(4)]431		#[pallet::weight(<T as Config>::WeightInfo::offboard(T::MaxCollators::get()))]432		pub fn offboard(origin: OriginFor<T>) -> DispatchResultWithPostInfo {433			// leave_intent434			let who = ensure_signed(origin)?;435			let current_count = Self::try_remove_candidate(&who)?;436437			Ok(Some(<T as Config>::WeightInfo::offboard(current_count as u32)).into())438		}439440		/// Forfeit `origin`'s own license. The `LicenseBond` will be unreserved immediately.441		///442		/// This call is not available to `Invulnerable` collators.443		#[pallet::call_index(5)]444		#[pallet::weight(<T as Config>::WeightInfo::release_license(T::MaxCollators::get()))]445		pub fn release_license(origin: OriginFor<T>) -> DispatchResultWithPostInfo {446			// leave_intent447			let who = ensure_signed(origin)?;448449			let current_count = Self::try_remove_candidate_and_release_license(&who, false, true)?;450451			Ok(Some(<T as Config>::WeightInfo::release_license(452				current_count as u32,453			))454			.into())455		}456457		/// Force deregister `origin` as a collator candidate as a governing authority, and revoke its license.458		/// Note that the collator can only leave on session change.459		/// The `LicenseBond` will be unreserved and returned immediately.460		///461		/// This call is, of course, not applicable to `Invulnerable` collators.462		#[pallet::call_index(6)]463		#[pallet::weight(<T as Config>::WeightInfo::force_release_license(T::MaxCollators::get()))]464		pub fn force_release_license(465			origin: OriginFor<T>,466			who: T::AccountId,467		) -> DispatchResultWithPostInfo {468			// leave_intent469			T::UpdateOrigin::ensure_origin(origin)?;470471			let current_count = Self::try_remove_candidate_and_release_license(&who, false, true)?;472473			Ok(Some(<T as Config>::WeightInfo::force_release_license(474				current_count as u32,475			))476			.into())477		}478	}479480	impl<T: Config> Pallet<T> {481		/// Get a unique, inaccessible account id from the `PotId`.482		pub fn account_id() -> T::AccountId {483			T::PotId::get().into_account_truncating()484		}485486		/// Removes a candidate and their license, optionally slashed and optionally ignoring,487		/// whether or not they actually are a candidate.488		fn try_remove_candidate_and_release_license(489			who: &T::AccountId,490			should_slash: bool,491			ignore_if_not_candidate: bool,492		) -> Result<usize, DispatchError> {493			let current_count = Self::try_remove_candidate(who);494			let current_count = if ignore_if_not_candidate495				&& current_count == Err(Error::<T>::NotCandidate.into())496			{497				<Candidates<T>>::decode_len().unwrap_or_default()498			} else {499				current_count?500			};501			Self::try_release_license(who, should_slash)?;502			Ok(current_count)503		}504505		/// Removes a candidate from the collator pool for the next session if they exist.506		fn try_remove_candidate(who: &T::AccountId) -> Result<usize, DispatchError> {507			let current_count =508				<Candidates<T>>::try_mutate(|candidates| -> Result<usize, DispatchError> {509					let index = candidates510						.iter()511						.position(|candidate| *candidate == *who)512						.ok_or(Error::<T>::NotCandidate)?;513					candidates.remove(index);514					<LastAuthoredBlock<T>>::remove(who.clone());515					Ok(candidates.len())516				})?;517			Self::deposit_event(Event::CandidateRemoved {518				account_id: who.clone(),519			});520			Ok(current_count)521		}522523		/// Removes a candidate if they exist and sends them back their deposit, optionally slashed.524		fn try_release_license(who: &T::AccountId, should_slash: bool) -> DispatchResult {525			let mut deposit_returned = BalanceOf::<T>::default();526			LicenseDepositOf::<T>::try_mutate_exists(who, |deposit| -> DispatchResult {527				if let Some(deposit) = deposit.take() {528					if should_slash {529						let slashed = T::SlashRatio::get() * deposit;530						let remaining = deposit - slashed;531532						let (imbalance, _) =533							T::Currency::slash(&T::LicenceBondIdentifier::get(), who, slashed);534						deposit_returned = remaining;535536						T::Currency::resolve(&T::TreasuryAccountId::get(), imbalance)537							.map_err(|_| DispatchError::Other("Failed to deposit imbalance"))?;538					} else {539						deposit_returned = deposit;540					}541542					T::Currency::release(543						&T::LicenceBondIdentifier::get(),544						who,545						deposit_returned,546						Precision::Exact,547					)?;548					Ok(())549				} else {550					Err(Error::<T>::NoLicense.into())551				}552			})?;553			Self::deposit_event(Event::LicenseReleased {554				account_id: who.clone(),555				deposit_returned,556			});557			Ok(())558		}559560		/// Assemble the current set of candidates and invulnerables into the next collator set.561		///562		/// This is done on the fly, as frequent as we are told to do so, as the session manager.563		pub fn assemble_collators(564			candidates: BoundedVec<T::AccountId, T::MaxCollators>,565		) -> Vec<T::AccountId> {566			let mut collators = Self::invulnerables().to_vec();567			collators.extend(candidates);568			collators569		}570571		/// Kicks out candidates that did not produce a block in the kick threshold572		/// and **confiscates** their deposits to the treasury.573		pub fn kick_stale_candidates(574			candidates: BoundedVec<T::AccountId, T::MaxCollators>,575		) -> BoundedVec<T::AccountId, T::MaxCollators> {576			let now = frame_system::Pallet::<T>::block_number();577			let kick_threshold = <KickThreshold<T>>::get();578			candidates579				.into_iter()580				.filter_map(|c| {581					let last_block = <LastAuthoredBlock<T>>::get(c.clone());582					let since_last = now.saturating_sub(last_block);583					if since_last < kick_threshold {584						Some(c)585					} else {586						let outcome = Self::try_remove_candidate_and_release_license(&c, true, false);587						if let Err(why) = outcome {588							log::warn!("Failed to kick collator and release license {:?}", why);589							debug_assert!(false, "failed to kick collator and release license {why:?}");590						}591						None592					}593				})594				.collect::<Vec<_>>()595				.try_into()596				.expect("filter_map operation can't result in a bounded vec larger than its original; qed")597		}598	}599600	/// Keep track of number of authored blocks per authority, uncles are counted as well since601	/// they're a valid proof of being online.602	impl<T: Config + pallet_authorship::Config>603		pallet_authorship::EventHandler<T::AccountId, T::BlockNumber> for Pallet<T>604	{605		fn note_author(author: T::AccountId) {606			let pot = Self::account_id();607			// assumes an ED will be sent to pot.608			let reward = T::Currency::balance(&pot)609				.checked_sub(&T::Currency::minimum_balance())610				.unwrap_or_else(Zero::zero)611				.div(2u32.into());612613			if !reward.is_zero() {614				// `reward` is half of pot account minus ED, this should never fail.615				let _success = T::Currency::transfer(&pot, &author, reward, Preservation::Preserve);616				debug_assert!(_success.is_ok());617			}618			<LastAuthoredBlock<T>>::insert(author, frame_system::Pallet::<T>::block_number());619620			frame_system::Pallet::<T>::register_extra_weight_unchecked(621				<T as Config>::WeightInfo::note_author(),622				DispatchClass::Mandatory,623			);624		}625	}626627	/// Play the role of the session manager.628	impl<T: Config> SessionManager<T::AccountId> for Pallet<T> {629		fn new_session(index: SessionIndex) -> Option<Vec<T::AccountId>> {630			log::info!(631				"assembling new collators for new session {} at #{:?}",632				index,633				<frame_system::Pallet<T>>::block_number(),634			);635636			let candidates = Self::candidates();637			let candidates_len_before = candidates.len();638			let active_candidates = Self::kick_stale_candidates(candidates);639			let removed = candidates_len_before - active_candidates.len();640			let result = Self::assemble_collators(active_candidates);641642			frame_system::Pallet::<T>::register_extra_weight_unchecked(643				<T as Config>::WeightInfo::new_session(644					candidates_len_before as u32,645					removed as u32,646				),647				DispatchClass::Mandatory,648			);649			Some(result)650		}651		fn start_session(_: SessionIndex) {652			// we don't care.653		}654		fn end_session(_: SessionIndex) {655			// we don't care.656		}657	}658}