git.delta.rocks / unique-network / refs/commits / 4f4018846dc9

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	#[pallet::generate_store(pub(super) trait Store)]165	pub struct Pallet<T>(_);166167	/// The invulnerable, fixed collators.168	#[pallet::storage]169	#[pallet::getter(fn invulnerables)]170	pub type Invulnerables<T: Config> =171		StorageValue<_, BoundedVec<T::AccountId, T::MaxCollators>, ValueQuery>;172173	/// The (community) collation license holders.174	#[pallet::storage]175	#[pallet::getter(fn license_deposit_of)]176	pub type LicenseDepositOf<T: Config> =177		StorageMap<_, Blake2_128Concat, T::AccountId, BalanceOf<T>, ValueQuery>;178179	/// The (community, limited) collation candidates.180	#[pallet::storage]181	#[pallet::getter(fn candidates)]182	pub type Candidates<T: Config> =183		StorageValue<_, BoundedVec<T::AccountId, T::MaxCollators>, ValueQuery>;184185	/// Last block authored by collator.186	#[pallet::storage]187	#[pallet::getter(fn last_authored_block)]188	pub type LastAuthoredBlock<T: Config> =189		StorageMap<_, Twox64Concat, T::AccountId, T::BlockNumber, ValueQuery>;190191	#[pallet::genesis_config]192	pub struct GenesisConfig<T: Config> {193		pub invulnerables: Vec<T::AccountId>,194	}195196	#[cfg(feature = "std")]197	impl<T: Config> Default for GenesisConfig<T> {198		fn default() -> Self {199			Self {200				invulnerables: Default::default(),201			}202		}203	}204205	#[pallet::genesis_build]206	impl<T: Config> GenesisBuild<T> for GenesisConfig<T> {207		fn build(&self) {208			let duplicate_invulnerables = self209				.invulnerables210				.iter()211				.collect::<std::collections::BTreeSet<_>>();212			assert!(213				duplicate_invulnerables.len() == self.invulnerables.len(),214				"duplicate invulnerables in genesis."215			);216217			let bounded_invulnerables =218				BoundedVec::<_, T::MaxCollators>::try_from(self.invulnerables.clone())219					.expect("genesis invulnerables are more than T::MaxCollators");220221			<Invulnerables<T>>::put(bounded_invulnerables);222		}223	}224225	#[pallet::event]226	#[pallet::generate_deposit(pub(super) fn deposit_event)]227	pub enum Event<T: Config> {228		InvulnerableAdded {229			invulnerable: T::AccountId,230		},231		InvulnerableRemoved {232			invulnerable: T::AccountId,233		},234		LicenseObtained {235			account_id: T::AccountId,236			deposit: BalanceOf<T>,237		},238		LicenseReleased {239			account_id: T::AccountId,240			deposit_returned: BalanceOf<T>,241		},242		CandidateAdded {243			account_id: T::AccountId,244		},245		CandidateRemoved {246			account_id: T::AccountId,247		},248	}249250	// Errors inform users that something went wrong.251	#[pallet::error]252	pub enum Error<T> {253		/// Too many candidates254		TooManyCandidates,255		/// Unknown error256		Unknown,257		/// Permission issue258		Permission,259		/// User already holds license to collate260		AlreadyHoldingLicense,261		/// User does not hold a license to collate262		NoLicense,263		/// User is already a candidate264		AlreadyCandidate,265		/// User is not a candidate266		NotCandidate,267		/// Too many invulnerables268		TooManyInvulnerables,269		/// Too few invulnerables270		TooFewInvulnerables,271		/// User is already an Invulnerable272		AlreadyInvulnerable,273		/// User is not an Invulnerable274		NotInvulnerable,275		/// Account has no associated validator ID276		NoAssociatedValidatorId,277		/// Validator ID is not yet registered278		ValidatorNotRegistered,279	}280281	#[pallet::hooks]282	impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {}283284	#[pallet::call]285	impl<T: Config> Pallet<T> {286		/// Add a collator to the list of invulnerable (fixed) collators.287		#[pallet::call_index(0)]288		#[pallet::weight(<T as Config>::WeightInfo::add_invulnerable(T::MaxCollators::get()))]289		pub fn add_invulnerable(290			origin: OriginFor<T>,291			new: T::AccountId,292		) -> DispatchResultWithPostInfo {293			T::UpdateOrigin::ensure_origin(origin)?;294295			// check if the new invulnerable has associated validator keys before it is added296			let validator_key = T::ValidatorIdOf::convert(new.clone())297				.ok_or(Error::<T>::NoAssociatedValidatorId)?;298			ensure!(299				T::ValidatorRegistration::is_registered(&validator_key),300				Error::<T>::ValidatorNotRegistered301			);302			if Self::invulnerables().contains(&new) {303				return Ok(().into());304			}305306			<Invulnerables<T>>::try_append(new.clone())307				.map_err(|_| Error::<T>::TooManyInvulnerables)?;308309			// try to offboard the new invulnerable if it was a collator candidate before310			let _ = Self::try_remove_candidate(&new);311312			Self::deposit_event(Event::InvulnerableAdded { invulnerable: new });313			Ok(().into())314		}315316		/// Remove a collator from the list of invulnerable (fixed) collators.317		#[pallet::call_index(1)]318		#[pallet::weight(<T as Config>::WeightInfo::remove_invulnerable(T::MaxCollators::get()))]319		pub fn remove_invulnerable(320			origin: OriginFor<T>,321			who: T::AccountId,322		) -> DispatchResultWithPostInfo {323			T::UpdateOrigin::ensure_origin(origin)?;324325			<Invulnerables<T>>::try_mutate(|invulnerables| -> DispatchResult {326				if invulnerables.len() <= 1 {327					return Err(Error::<T>::TooFewInvulnerables.into());328				}329330				let index = invulnerables331					.into_iter()332					.position(|r| *r == who)333					.ok_or(Error::<T>::NotInvulnerable)?;334				invulnerables.remove(index);335				Ok(())336			})?;337			Self::deposit_event(Event::InvulnerableRemoved { invulnerable: who });338			Ok(().into())339		}340341		/// Purchase a license on block collation for this account.342		/// It does not make it a collator candidate, use `onboard` afterward. The account must343		/// (a) already have registered session keys and (b) be able to reserve the `LicenseBond`.344		///345		/// This call is not available to `Invulnerable` collators.346		#[pallet::call_index(2)]347		#[pallet::weight(<T as Config>::WeightInfo::get_license(T::MaxCollators::get()))]348		pub fn get_license(origin: OriginFor<T>) -> DispatchResultWithPostInfo {349			// register_as_candidate350			let who = ensure_signed(origin)?;351352			if LicenseDepositOf::<T>::contains_key(&who) {353				return Err(Error::<T>::AlreadyHoldingLicense.into());354			}355356			let validator_key = T::ValidatorIdOf::convert(who.clone())357				.ok_or(Error::<T>::NoAssociatedValidatorId)?;358			ensure!(359				T::ValidatorRegistration::is_registered(&validator_key),360				Error::<T>::ValidatorNotRegistered361			);362363			let deposit = <LicenseBond<T>>::get();364365			T::Currency::reserve(&who, deposit)?;366			LicenseDepositOf::<T>::insert(who.clone(), deposit);367368			Self::deposit_event(Event::LicenseObtained {369				account_id: who,370				deposit,371			});372			Ok(().into()) // Some(T::WeightInfo::register_as_candidate(current_count as u32)).into())373		}374375		/// Register this account as a candidate for collators for next sessions.376		/// The account must already hold a license, and cannot offboard immediately during a session.377		///378		/// This call is not available to `Invulnerable` collators.379		#[pallet::call_index(3)]380		#[pallet::weight(<T as Config>::WeightInfo::onboard(T::MaxCollators::get()))]381		pub fn onboard(origin: OriginFor<T>) -> DispatchResultWithPostInfo {382			// register_as_candidate383			let who = ensure_signed(origin)?;384385			// ensure the user obtained the license.386			ensure!(387				LicenseDepositOf::<T>::contains_key(&who),388				Error::<T>::NoLicense389			);390			// ensure we are below limit.391			let length = <Candidates<T>>::decode_len().unwrap_or_default()392				+ <Invulnerables<T>>::decode_len().unwrap_or_default();393			ensure!(394				(length as u32) < <DesiredCollators<T>>::get(),395				Error::<T>::TooManyCandidates396			);397			ensure!(398				!Self::invulnerables().contains(&who),399				Error::<T>::AlreadyInvulnerable400			);401402			let current_count =403				<Candidates<T>>::try_mutate(|candidates| -> Result<usize, DispatchError> {404					if candidates.iter().any(|candidate| *candidate == who) {405						Err(Error::<T>::AlreadyCandidate)?406					} else {407						candidates408							.try_push(who.clone())409							.map_err(|_| Error::<T>::TooManyCandidates)?;410						// First authored block is current block plus kick threshold to handle session delay411						<LastAuthoredBlock<T>>::insert(412							who.clone(),413							frame_system::Pallet::<T>::block_number() + <KickThreshold<T>>::get(),414						);415						Ok(candidates.len())416					}417				})?;418419			Self::deposit_event(Event::CandidateAdded { account_id: who });420			Ok(Some(<T as Config>::WeightInfo::onboard(current_count as u32)).into())421		}422423		/// Deregister `origin` as a collator candidate. Note that the collator can only leave on424		/// session change. The license to `onboard` later at any other time will remain.425		#[pallet::call_index(4)]426		#[pallet::weight(<T as Config>::WeightInfo::offboard(T::MaxCollators::get()))]427		pub fn offboard(origin: OriginFor<T>) -> DispatchResultWithPostInfo {428			// leave_intent429			let who = ensure_signed(origin)?;430			let current_count = Self::try_remove_candidate(&who)?;431432			Ok(Some(<T as Config>::WeightInfo::offboard(current_count as u32)).into())433		}434435		/// Forfeit `origin`'s own license. The `LicenseBond` will be unreserved immediately.436		///437		/// This call is not available to `Invulnerable` collators.438		#[pallet::call_index(5)]439		#[pallet::weight(<T as Config>::WeightInfo::release_license(T::MaxCollators::get()))]440		pub fn release_license(origin: OriginFor<T>) -> DispatchResultWithPostInfo {441			// leave_intent442			let who = ensure_signed(origin)?;443444			let current_count = Self::try_remove_candidate_and_release_license(&who, false, true)?;445446			Ok(Some(<T as Config>::WeightInfo::release_license(447				current_count as u32,448			))449			.into())450		}451452		/// Force deregister `origin` as a collator candidate as a governing authority, and revoke its license.453		/// Note that the collator can only leave on session change.454		/// The `LicenseBond` will be unreserved and returned immediately.455		///456		/// This call is, of course, not applicable to `Invulnerable` collators.457		#[pallet::call_index(6)]458		#[pallet::weight(<T as Config>::WeightInfo::force_release_license(T::MaxCollators::get()))]459		pub fn force_release_license(460			origin: OriginFor<T>,461			who: T::AccountId,462		) -> DispatchResultWithPostInfo {463			// leave_intent464			T::UpdateOrigin::ensure_origin(origin)?;465466			let current_count = Self::try_remove_candidate_and_release_license(&who, false, true)?;467468			Ok(Some(<T as Config>::WeightInfo::force_release_license(469				current_count as u32,470			))471			.into())472		}473	}474475	impl<T: Config> Pallet<T> {476		/// Get a unique, inaccessible account id from the `PotId`.477		pub fn account_id() -> T::AccountId {478			T::PotId::get().into_account_truncating()479		}480481		/// Removes a candidate and their license, optionally slashed and optionally ignoring,482		/// whether or not they actually are a candidate.483		fn try_remove_candidate_and_release_license(484			who: &T::AccountId,485			should_slash: bool,486			ignore_if_not_candidate: bool,487		) -> Result<usize, DispatchError> {488			let current_count = Self::try_remove_candidate(who);489			let current_count = if ignore_if_not_candidate490				&& current_count == Err(Error::<T>::NotCandidate.into())491			{492				<Candidates<T>>::decode_len().unwrap_or_default()493			} else {494				current_count?495			};496			Self::try_release_license(who, should_slash)?;497			Ok(current_count)498		}499500		/// Removes a candidate from the collator pool for the next session if they exist.501		fn try_remove_candidate(who: &T::AccountId) -> Result<usize, DispatchError> {502			let current_count =503				<Candidates<T>>::try_mutate(|candidates| -> Result<usize, DispatchError> {504					let index = candidates505						.iter()506						.position(|candidate| *candidate == *who)507						.ok_or(Error::<T>::NotCandidate)?;508					candidates.remove(index);509					<LastAuthoredBlock<T>>::remove(who.clone());510					Ok(candidates.len())511				})?;512			Self::deposit_event(Event::CandidateRemoved {513				account_id: who.clone(),514			});515			Ok(current_count)516		}517518		/// Removes a candidate if they exist and sends them back their deposit, optionally slashed.519		fn try_release_license(who: &T::AccountId, should_slash: bool) -> DispatchResult {520			let mut deposit_returned = BalanceOf::<T>::default();521			LicenseDepositOf::<T>::try_mutate_exists(who, |deposit| -> DispatchResult {522				if let Some(deposit) = deposit.take() {523					if should_slash {524						let slashed = T::SlashRatio::get() * deposit;525						let remaining = deposit - slashed;526527						let (imbalance, _) = T::Currency::slash_reserved(who, slashed);528						//T::Currency::unreserve(who, remaining);529						deposit_returned = remaining;530531						T::Currency::resolve_creating(&T::TreasuryAccountId::get(), imbalance);532					} else {533						//T::Currency::unreserve(who, deposit);534						deposit_returned = deposit;535					}536537					T::Currency::unreserve(who, deposit_returned);538					Ok(())539				} else {540					Err(Error::<T>::NoLicense.into())541				}542			})?;543			Self::deposit_event(Event::LicenseReleased {544				account_id: who.clone(),545				deposit_returned,546			});547			Ok(())548		}549550		/// Assemble the current set of candidates and invulnerables into the next collator set.551		///552		/// This is done on the fly, as frequent as we are told to do so, as the session manager.553		pub fn assemble_collators(554			candidates: BoundedVec<T::AccountId, T::MaxCollators>,555		) -> Vec<T::AccountId> {556			let mut collators = Self::invulnerables().to_vec();557			collators.extend(candidates);558			collators559		}560561		/// Kicks out candidates that did not produce a block in the kick threshold562		/// and **confiscates** their deposits to the treasury.563		pub fn kick_stale_candidates(564			candidates: BoundedVec<T::AccountId, T::MaxCollators>,565		) -> BoundedVec<T::AccountId, T::MaxCollators> {566			let now = frame_system::Pallet::<T>::block_number();567			let kick_threshold = <KickThreshold<T>>::get();568			candidates569				.into_iter()570				.filter_map(|c| {571					let last_block = <LastAuthoredBlock<T>>::get(c.clone());572					let since_last = now.saturating_sub(last_block);573					if since_last < kick_threshold {574						Some(c)575					} else {576						let outcome = Self::try_remove_candidate_and_release_license(&c, true, false);577						if let Err(why) = outcome {578							log::warn!("Failed to kick collator and release license {:?}", why);579							debug_assert!(false, "failed to kick collator and release license {why:?}");580						}581						None582					}583				})584				.collect::<Vec<_>>()585				.try_into()586				.expect("filter_map operation can't result in a bounded vec larger than its original; qed")587		}588	}589590	/// Keep track of number of authored blocks per authority, uncles are counted as well since591	/// they're a valid proof of being online.592	impl<T: Config + pallet_authorship::Config>593		pallet_authorship::EventHandler<T::AccountId, T::BlockNumber> for Pallet<T>594	{595		fn note_author(author: T::AccountId) {596			let pot = Self::account_id();597			// assumes an ED will be sent to pot.598			let reward = T::Currency::free_balance(&pot)599				.checked_sub(&T::Currency::minimum_balance())600				.unwrap_or_else(Zero::zero)601				.div(2u32.into());602			// `reward` is half of pot account minus ED, this should never fail.603			let _success = T::Currency::transfer(&pot, &author, reward, KeepAlive);604			debug_assert!(_success.is_ok());605			<LastAuthoredBlock<T>>::insert(author, frame_system::Pallet::<T>::block_number());606607			frame_system::Pallet::<T>::register_extra_weight_unchecked(608				<T as Config>::WeightInfo::note_author(),609				DispatchClass::Mandatory,610			);611		}612613		fn note_uncle(_author: T::AccountId, _age: T::BlockNumber) {614			//TODO can we ignore this?615		}616	}617618	/// Play the role of the session manager.619	impl<T: Config> SessionManager<T::AccountId> for Pallet<T> {620		fn new_session(index: SessionIndex) -> Option<Vec<T::AccountId>> {621			log::info!(622				"assembling new collators for new session {} at #{:?}",623				index,624				<frame_system::Pallet<T>>::block_number(),625			);626627			let candidates = Self::candidates();628			let candidates_len_before = candidates.len();629			let active_candidates = Self::kick_stale_candidates(candidates);630			let removed = candidates_len_before - active_candidates.len();631			let result = Self::assemble_collators(active_candidates);632633			frame_system::Pallet::<T>::register_extra_weight_unchecked(634				<T as Config>::WeightInfo::new_session(635					candidates_len_before as u32,636					removed as u32,637				),638				DispatchClass::Mandatory,639			);640			Some(result)641		}642		fn start_session(_: SessionIndex) {643			// we don't care.644		}645		fn end_session(_: SessionIndex) {646			// we don't care.647		}648	}649}