Add batching to fast-unstake pallet (#12394)

* implement a brand new batch with all tests passing.

* fix benchmarks as well

* make benchmarks more or less work

* fix migration

* add some testing

* Update frame/fast-unstake/src/benchmarking.rs

Co-authored-by: Roman Useinov <roman.useinov@gmail.com>

* review comments

* some fixes

* fix review comments

* fix build

* fmt

* fix benchmarks

* fmt

* update

Co-authored-by: Roman Useinov <roman.useinov@gmail.com>

substrate/bin/node/runtime/src/lib.rs

@@ -584,6 +584,7 @@ impl pallet_staking::Config for Runtime {
 impl pallet_fast_unstake::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type ControlOrigin = frame_system::EnsureRoot<AccountId>;
+	type BatchSize = ConstU32<128>;
 	type Deposit = ConstU128<{ DOLLARS }>;
 	type Currency = Balances;
 	type Staking = Staking;

substrate/frame/fast-unstake/Cargo.toml

@@ -60,6 +60,7 @@ std = [
 runtime-benchmarks = [
 	"frame-benchmarking/runtime-benchmarks",
 	"frame-system/runtime-benchmarks",
-	"sp-staking/runtime-benchmarks"
+	"sp-staking/runtime-benchmarks",
+	"pallet-staking/runtime-benchmarks"
 ]
 try-runtime = ["frame-support/try-runtime"]

substrate/frame/fast-unstake/src/benchmarking.rs

@@ -36,10 +36,15 @@ const MAX_VALIDATORS: u32 = 128;
 
 type CurrencyOf<T> = <T as Config>::Currency;
 
-fn create_unexposed_nominator<T: Config>() -> T::AccountId {
-	let account = frame_benchmarking::account::<T::AccountId>("nominator_42", 0, USER_SEED);
-	fund_and_bond_account::<T>(&account);
-	account
+fn create_unexposed_nominators<T: Config>() -> Vec<T::AccountId> {
+	(0..T::BatchSize::get())
+		.map(|i| {
+			let account =
+				frame_benchmarking::account::<T::AccountId>("unexposed_nominator", i, USER_SEED);
+			fund_and_bond_account::<T>(&account);
+			account
+		})
+		.collect()
 }
 
 fn fund_and_bond_account<T: Config>(account: &T::AccountId) {
@@ -90,21 +95,27 @@ fn on_idle_full_block<T: Config>() {
 }
 
 benchmarks! {
-	// on_idle, we we don't check anyone, but fully unbond and move them to another pool.
+	// on_idle, we don't check anyone, but fully unbond them.
 	on_idle_unstake {
 		ErasToCheckPerBlock::<T>::put(1);
-		let who = create_unexposed_nominator::<T>();
-		assert_ok!(FastUnstake::<T>::register_fast_unstake(
-			RawOrigin::Signed(who.clone()).into(),
-		));
+		for who in create_unexposed_nominators::<T>() {
+			assert_ok!(FastUnstake::<T>::register_fast_unstake(
+				RawOrigin::Signed(who.clone()).into(),
+			));
+		}
 
 		// run on_idle once. This will check era 0.
 		assert_eq!(Head::<T>::get(), None);
 		on_idle_full_block::<T>();
-		assert_eq!(
+
+		assert!(matches!(
 			Head::<T>::get(),
-			Some(UnstakeRequest { stash: who.clone(), checked: vec![0].try_into().unwrap(), deposit: T::Deposit::get() })
-		);
+			Some(UnstakeRequest {
+				checked,
+				stashes,
+				..
+			}) if checked.len() == 1 && stashes.len() as u32 == T::BatchSize::get()
+		));
 	}
 	: {
 		on_idle_full_block::<T>();
@@ -112,7 +123,7 @@ benchmarks! {
 	verify {
 		assert!(matches!(
 			fast_unstake_events::<T>().last(),
-			Some(Event::Unstaked { .. })
+			Some(Event::BatchFinished)
 		));
 	}
 
@@ -129,10 +140,13 @@ benchmarks! {
 
 		// setup staking with v validators and u eras of data (0..=u)
 		setup_staking::<T>(v, u);
-		let who = create_unexposed_nominator::<T>();
-		assert_ok!(FastUnstake::<T>::register_fast_unstake(
-			RawOrigin::Signed(who.clone()).into(),
-		));
+
+		let stashes = create_unexposed_nominators::<T>().into_iter().map(|s| {
+			assert_ok!(FastUnstake::<T>::register_fast_unstake(
+				RawOrigin::Signed(s.clone()).into(),
+			));
+			(s, T::Deposit::get())
+		}).collect::<Vec<_>>();
 
 		// no one is queued thus far.
 		assert_eq!(Head::<T>::get(), None);
@@ -141,20 +155,19 @@ benchmarks! {
 		on_idle_full_block::<T>();
 	}
 	verify {
-		let checked: frame_support::BoundedVec<_, _> = (1..=u).rev().collect::<Vec<EraIndex>>().try_into().unwrap();
-		assert_eq!(
-			Head::<T>::get(),
-			Some(UnstakeRequest { stash: who.clone(), checked, deposit: T::Deposit::get() })
-		);
+		let checked = (1..=u).rev().collect::<Vec<EraIndex>>();
+		let request = Head::<T>::get().unwrap();
+		assert_eq!(checked, request.checked.into_inner());
 		assert!(matches!(
 			fast_unstake_events::<T>().last(),
-			Some(Event::Checking { .. })
+			Some(Event::BatchChecked { .. })
 		));
+		assert!(stashes.iter().all(|(s, _)| request.stashes.iter().find(|(ss, _)| ss == s).is_some()));
 	}
 
 	register_fast_unstake {
 		ErasToCheckPerBlock::<T>::put(1);
-		let who = create_unexposed_nominator::<T>();
+		let who = create_unexposed_nominators::<T>().get(0).cloned().unwrap();
 		whitelist_account!(who);
 		assert_eq!(Queue::<T>::count(), 0);
 
@@ -166,7 +179,7 @@ benchmarks! {
 
 	deregister {
 		ErasToCheckPerBlock::<T>::put(1);
-		let who = create_unexposed_nominator::<T>();
+		let who = create_unexposed_nominators::<T>().get(0).cloned().unwrap();
 		assert_ok!(FastUnstake::<T>::register_fast_unstake(
 			RawOrigin::Signed(who.clone()).into(),
 		));

substrate/frame/fast-unstake/src/lib.rs

@@ -60,6 +60,7 @@ mod tests;
 // NOTE: enable benchmarking in tests as well.
 #[cfg(feature = "runtime-benchmarks")]
 mod benchmarking;
+pub mod migrations;
 pub mod types;
 pub mod weights;
 
@@ -82,7 +83,7 @@ pub mod pallet {
 	use crate::types::*;
 	use frame_support::{
 		pallet_prelude::*,
-		traits::{Defensive, ReservableCurrency},
+		traits::{Defensive, ReservableCurrency, StorageVersion},
 	};
 	use frame_system::pallet_prelude::*;
 	use sp_runtime::{
@@ -103,7 +104,10 @@ pub mod pallet {
 		}
 	}
 
+	const STORAGE_VERSION: StorageVersion = StorageVersion::new(1);
+
 	#[pallet::pallet]
+	#[pallet::storage_version(STORAGE_VERSION)]
 	pub struct Pallet<T>(_);
 
 	#[pallet::config]
@@ -123,6 +127,11 @@ pub mod pallet {
 		/// The origin that can control this pallet.
 		type ControlOrigin: frame_support::traits::EnsureOrigin<Self::RuntimeOrigin>;
 
+		/// Batch size.
+		///
+		/// This many stashes are processed in each unstake request.
+		type BatchSize: Get<u32>;
+
 		/// The access to staking functionality.
 		type Staking: StakingInterface<Balance = BalanceOf<Self>, AccountId = Self::AccountId>;
 
@@ -132,8 +141,7 @@ pub mod pallet {
 
 	/// The current "head of the queue" being unstaked.
 	#[pallet::storage]
-	pub type Head<T: Config> =
-		StorageValue<_, UnstakeRequest<T::AccountId, MaxChecking<T>, BalanceOf<T>>, OptionQuery>;
+	pub type Head<T: Config> = StorageValue<_, UnstakeRequest<T>, OptionQuery>;
 
 	/// The map of all accounts wishing to be unstaked.
 	///
@@ -158,13 +166,18 @@ pub mod pallet {
 		Unstaked { stash: T::AccountId, result: DispatchResult },
 		/// A staker was slashed for requesting fast-unstake whilst being exposed.
 		Slashed { stash: T::AccountId, amount: BalanceOf<T> },
-		/// A staker was partially checked for the given eras, but the process did not finish.
-		Checking { stash: T::AccountId, eras: Vec<EraIndex> },
 		/// Some internal error happened while migrating stash. They are removed as head as a
 		/// consequence.
 		Errored { stash: T::AccountId },
 		/// An internal error happened. Operations will be paused now.
 		InternalError,
+		/// A batch was partially checked for the given eras, but the process did not finish.
+		BatchChecked { eras: Vec<EraIndex> },
+		/// A batch was terminated.
+		///
+		/// This is always follows by a number of `Unstaked` or `Slashed` events, marking the end
+		/// of the batch. A new batch will be created upon next block.
+		BatchFinished,
 	}
 
 	#[pallet::error]
@@ -225,12 +238,7 @@ pub mod pallet {
 			let stash_account =
 				T::Staking::stash_by_ctrl(&ctrl).map_err(|_| Error::<T>::NotController)?;
 			ensure!(!Queue::<T>::contains_key(&stash_account), Error::<T>::AlreadyQueued);
-			ensure!(
-				Head::<T>::get()
-					.map_or(true, |UnstakeRequest { stash, .. }| stash_account != stash),
-				Error::<T>::AlreadyHead
-			);
-
+			ensure!(!Self::is_head(&stash_account), Error::<T>::AlreadyHead);
 			ensure!(!T::Staking::is_unbonding(&stash_account)?, Error::<T>::NotFullyBonded);
 
 			// chill and fully unstake.
@@ -260,19 +268,13 @@ pub mod pallet {
 			let stash_account =
 				T::Staking::stash_by_ctrl(&ctrl).map_err(|_| Error::<T>::NotController)?;
 			ensure!(Queue::<T>::contains_key(&stash_account), Error::<T>::NotQueued);
-			ensure!(
-				Head::<T>::get()
-					.map_or(true, |UnstakeRequest { stash, .. }| stash_account != stash),
-				Error::<T>::AlreadyHead
-			);
+			ensure!(!Self::is_head(&stash_account), Error::<T>::AlreadyHead);
 			let deposit = Queue::<T>::take(stash_account.clone());
 
 			if let Some(deposit) = deposit.defensive() {
 				let remaining = T::Currency::unreserve(&stash_account, deposit);
 				if !remaining.is_zero() {
-					frame_support::defensive!("`not enough balance to unreserve`");
-					ErasToCheckPerBlock::<T>::put(0);
-					Self::deposit_event(Event::<T>::InternalError)
+					Self::halt("not enough balance to unreserve");
 				}
 			}
 
@@ -291,6 +293,20 @@ pub mod pallet {
 	}
 
 	impl<T: Config> Pallet<T> {
+		/// Returns `true` if `staker` is anywhere to be found in the `head`.
+		pub(crate) fn is_head(staker: &T::AccountId) -> bool {
+			Head::<T>::get().map_or(false, |UnstakeRequest { stashes, .. }| {
+				stashes.iter().any(|(stash, _)| stash == staker)
+			})
+		}
+
+		/// Halt the operations of this pallet.
+		pub(crate) fn halt(reason: &'static str) {
+			frame_support::defensive!(reason);
+			ErasToCheckPerBlock::<T>::put(0);
+			Self::deposit_event(Event::<T>::InternalError)
+		}
+
 		/// process up to `remaining_weight`.
 		///
 		/// Returns the actual weight consumed.
@@ -336,28 +352,30 @@ pub mod pallet {
 				return T::DbWeight::get().reads(2)
 			}
 
-			let UnstakeRequest { stash, mut checked, deposit } =
-				match Head::<T>::take().or_else(|| {
-					// NOTE: there is no order guarantees in `Queue`.
-					Queue::<T>::drain()
-						.map(|(stash, deposit)| UnstakeRequest {
-							stash,
-							deposit,
-							checked: Default::default(),
-						})
-						.next()
-				}) {
-					None => {
-						// There's no `Head` and nothing in the `Queue`, nothing to do here.
-						return T::DbWeight::get().reads(4)
-					},
-					Some(head) => head,
-				};
+			let UnstakeRequest { stashes, mut checked } = match Head::<T>::take().or_else(|| {
+				// NOTE: there is no order guarantees in `Queue`.
+				let stashes: BoundedVec<_, T::BatchSize> = Queue::<T>::drain()
+					.take(T::BatchSize::get() as usize)
+					.collect::<Vec<_>>()
+					.try_into()
+					.expect("take ensures bound is met; qed");
+				if stashes.is_empty() {
+					None
+				} else {
+					Some(UnstakeRequest { stashes, checked: Default::default() })
+				}
+			}) {
+				None => {
+					// There's no `Head` and nothing in the `Queue`, nothing to do here.
+					return T::DbWeight::get().reads(4)
+				},
+				Some(head) => head,
+			};
 
 			log!(
 				debug,
-				"checking {:?}, eras_to_check_per_block = {:?}, remaining_weight = {:?}",
-				stash,
+				"checking {:?} stashes, eras_to_check_per_block = {:?}, remaining_weight = {:?}",
+				stashes.len(),
 				eras_to_check_per_block,
 				remaining_weight
 			);
@@ -365,9 +383,11 @@ pub mod pallet {
 			// the range that we're allowed to check in this round.
 			let current_era = T::Staking::current_era();
 			let bonding_duration = T::Staking::bonding_duration();
+
 			// prune all the old eras that we don't care about. This will help us keep the bound
 			// of `checked`.
 			checked.retain(|e| *e >= current_era.saturating_sub(bonding_duration));
+
 			let unchecked_eras_to_check = {
 				// get the last available `bonding_duration` eras up to current era in reverse
 				// order.
@@ -397,66 +417,75 @@ pub mod pallet {
 				unchecked_eras_to_check
 			);
 
-			if unchecked_eras_to_check.is_empty() {
+			let unstake_stash = |stash: T::AccountId, deposit| {
 				let result = T::Staking::force_unstake(stash.clone());
-
 				let remaining = T::Currency::unreserve(&stash, deposit);
 				if !remaining.is_zero() {
-					frame_support::defensive!("`not enough balance to unreserve`");
-					ErasToCheckPerBlock::<T>::put(0);
-					Self::deposit_event(Event::<T>::InternalError)
+					Self::halt("not enough balance to unreserve");
 				} else {
 					log!(info, "unstaked {:?}, outcome: {:?}", stash, result);
 					Self::deposit_event(Event::<T>::Unstaked { stash, result });
 				}
+			};
 
-				<T as Config>::WeightInfo::on_idle_unstake()
-			} else {
-				// eras remaining to be checked.
-				let mut eras_checked = 0u32;
+			let check_stash = |stash, deposit, eras_checked: &mut u32| {
 				let is_exposed = unchecked_eras_to_check.iter().any(|e| {
 					eras_checked.saturating_inc();
 					T::Staking::is_exposed_in_era(&stash, e)
 				});
 
-				log!(
-					debug,
-					"checked {:?} eras, exposed? {}, (v: {:?}, u: {:?})",
-					eras_checked,
-					is_exposed,
-					validator_count,
-					unchecked_eras_to_check.len()
-				);
-
-				// NOTE: you can be extremely unlucky and get slashed here: You are not exposed in
-				// the last 28 eras, have registered yourself to be unstaked, midway being checked,
-				// you are exposed.
 				if is_exposed {
 					T::Currency::slash_reserved(&stash, deposit);
 					log!(info, "slashed {:?} by {:?}", stash, deposit);
 					Self::deposit_event(Event::<T>::Slashed { stash, amount: deposit });
+					false
 				} else {
-					// Not exposed in these eras.
-					match checked.try_extend(unchecked_eras_to_check.clone().into_iter()) {
-						Ok(_) => {
-							Head::<T>::put(UnstakeRequest {
-								stash: stash.clone(),
-								checked,
-								deposit,
-							});
-							Self::deposit_event(Event::<T>::Checking {
-								stash,
+					true
+				}
+			};
+
+			if unchecked_eras_to_check.is_empty() {
+				// `stash` is not exposed in any era now -- we can let go of them now.
+				stashes.into_iter().for_each(|(stash, deposit)| unstake_stash(stash, deposit));
+				Self::deposit_event(Event::<T>::BatchFinished);
+				<T as Config>::WeightInfo::on_idle_unstake()
+			} else {
+				// eras checked so far.
+				let mut eras_checked = 0u32;
+
+				let pre_length = stashes.len();
+				let stashes: BoundedVec<(T::AccountId, BalanceOf<T>), T::BatchSize> = stashes
+					.into_iter()
+					.filter(|(stash, deposit)| {
+						check_stash(stash.clone(), *deposit, &mut eras_checked)
+					})
+					.collect::<Vec<_>>()
+					.try_into()
+					.expect("filter can only lessen the length; still in bound; qed");
+				let post_length = stashes.len();
+
+				log!(
+					debug,
+					"checked {:?} eras, pre stashes: {:?}, post: {:?}",
+					eras_checked,
+					pre_length,
+					post_length,
+				);
+
+				match checked.try_extend(unchecked_eras_to_check.clone().into_iter()) {
+					Ok(_) =>
+						if stashes.is_empty() {
+							Self::deposit_event(Event::<T>::BatchFinished);
+						} else {
+							Head::<T>::put(UnstakeRequest { stashes, checked });
+							Self::deposit_event(Event::<T>::BatchChecked {
 								eras: unchecked_eras_to_check,
 							});
 						},
-						Err(_) => {
-							// don't put the head back in -- there is an internal error in the
-							// pallet.
-							frame_support::defensive!("`checked is pruned via retain above`");
-							ErasToCheckPerBlock::<T>::put(0);
-							Self::deposit_event(Event::<T>::InternalError);
-						},
-					}
+					Err(_) => {
+						// don't put the head back in -- there is an internal error in the pallet.
+						Self::halt("checked is pruned via retain above")
+					},
 				}
 
 				<T as Config>::WeightInfo::on_idle_check(validator_count * eras_checked)

substrate/frame/fast-unstake/src/migrations.rs

@@ -0,0 +1,77 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2022 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+pub mod v1 {
+	use crate::{types::BalanceOf, *};
+	use frame_support::{
+		storage::unhashed,
+		traits::{Defensive, Get, GetStorageVersion, OnRuntimeUpgrade},
+		weights::Weight,
+	};
+	use sp_staking::EraIndex;
+	use sp_std::prelude::*;
+
+	pub struct MigrateToV1<T>(sp_std::marker::PhantomData<T>);
+	impl<T: Config> OnRuntimeUpgrade for MigrateToV1<T> {
+		fn on_runtime_upgrade() -> Weight {
+			let current = Pallet::<T>::current_storage_version();
+			let onchain = Pallet::<T>::on_chain_storage_version();
+
+			log!(
+				info,
+				"Running migration with current storage version {:?} / onchain {:?}",
+				current,
+				onchain
+			);
+
+			if current == 1 && onchain == 0 {
+				// if a head exists, then we put them back into the queue.
+				if Head::<T>::exists() {
+					if let Some((stash, _, deposit)) =
+						unhashed::take::<(T::AccountId, Vec<EraIndex>, BalanceOf<T>)>(
+							&Head::<T>::hashed_key(),
+						)
+						.defensive()
+					{
+						Queue::<T>::insert(stash, deposit);
+						current.put::<Pallet<T>>();
+					} else {
+						// not much we can do here -- head is already deleted.
+					}
+					T::DbWeight::get().reads_writes(2, 3)
+				} else {
+					T::DbWeight::get().reads(2)
+				}
+			} else {
+				log!(info, "Migration did not execute. This probably should be removed");
+				T::DbWeight::get().reads(1)
+			}
+		}
+
+		#[cfg(feature = "try-runtime")]
+		fn pre_upgrade() -> Result<Vec<u8>, &'static str> {
+			assert_eq!(Pallet::<T>::on_chain_storage_version(), 0);
+			Ok(Default::default())
+		}
+
+		#[cfg(feature = "try-runtime")]
+		fn post_upgrade(_: Vec<u8>) -> Result<(), &'static str> {
+			assert_eq!(Pallet::<T>::on_chain_storage_version(), 1);
+			Ok(())
+		}
+	}
+}

substrate/frame/fast-unstake/src/mock.rs

@@ -16,8 +16,12 @@
 // limitations under the License.
 
 use crate::{self as fast_unstake};
+use frame_benchmarking::frame_support::assert_ok;
 use frame_support::{
-	pallet_prelude::*, parameter_types, traits::ConstU64, weights::constants::WEIGHT_PER_SECOND,
+	pallet_prelude::*,
+	parameter_types,
+	traits::{ConstU64, Currency},
+	weights::constants::WEIGHT_PER_SECOND,
 };
 use sp_runtime::traits::{Convert, IdentityLookup};
 
@@ -168,15 +172,17 @@ impl Convert<sp_core::U256, Balance> for U256ToBalance {
 }
 
 parameter_types! {
-	pub static DepositAmount: u128 = 7;
+	pub static Deposit: u128 = 7;
+	pub static BatchSize: u32 = 1;
 }
 
 impl fast_unstake::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
-	type Deposit = DepositAmount;
+	type Deposit = Deposit;
 	type Currency = Balances;
 	type Staking = Staking;
 	type ControlOrigin = frame_system::EnsureRoot<Self::AccountId>;
+	type BatchSize = BatchSize;
 	type WeightInfo = ();
 }
 
@@ -212,13 +218,13 @@ pub(crate) fn fast_unstake_events_since_last_call() -> Vec<super::Event<Runtime>
 }
 
 pub struct ExtBuilder {
-	exposed_nominators: Vec<(AccountId, AccountId, Balance)>,
+	unexposed: Vec<(AccountId, AccountId, Balance)>,
 }
 
 impl Default for ExtBuilder {
 	fn default() -> Self {
 		Self {
-			exposed_nominators: vec![
+			unexposed: vec![
 				(1, 2, 7 + 100),
 				(3, 4, 7 + 100),
 				(5, 6, 7 + 100),
@@ -255,6 +261,11 @@ impl ExtBuilder {
 			});
 	}
 
+	pub(crate) fn batch(self, size: u32) -> Self {
+		BatchSize::set(size);
+		self
+	}
+
 	pub(crate) fn build(self) -> sp_io::TestExternalities {
 		sp_tracing::try_init_simple();
 		let mut storage =
@@ -266,12 +277,12 @@ impl ExtBuilder {
 
 		let _ = pallet_balances::GenesisConfig::<Runtime> {
 			balances: self
-				.exposed_nominators
+				.unexposed
 				.clone()
 				.into_iter()
 				.map(|(stash, _, balance)| (stash, balance * 2))
 				.chain(
-					self.exposed_nominators
+					self.unexposed
 						.clone()
 						.into_iter()
 						.map(|(_, ctrl, balance)| (ctrl, balance * 2)),
@@ -284,7 +295,7 @@ impl ExtBuilder {
 
 		let _ = pallet_staking::GenesisConfig::<Runtime> {
 			stakers: self
-				.exposed_nominators
+				.unexposed
 				.into_iter()
 				.map(|(x, y, z)| (x, y, z, pallet_staking::StakerStatus::Nominator(vec![42])))
 				.chain(validators_range.map(|x| (x, x, 100, StakerStatus::Validator)))
@@ -307,6 +318,7 @@ impl ExtBuilder {
 			// because we read this value as a measure of how many validators we have.
 			pallet_staking::ValidatorCount::<Runtime>::put(VALIDATORS_PER_ERA as u32);
 		});
+
 		ext
 	}
 
@@ -347,3 +359,20 @@ pub fn assert_unstaked(stash: &AccountId) {
 	assert!(!pallet_staking::Validators::<T>::contains_key(stash));
 	assert!(!pallet_staking::Nominators::<T>::contains_key(stash));
 }
+
+pub fn create_exposed_nominator(exposed: AccountId, era: u32) {
+	// create an exposed nominator in era 1
+	pallet_staking::ErasStakers::<T>::mutate(era, VALIDATORS_PER_ERA, |expo| {
+		expo.others.push(IndividualExposure { who: exposed, value: 0 as Balance });
+	});
+	Balances::make_free_balance_be(&exposed, 100);
+	assert_ok!(Staking::bond(
+		RuntimeOrigin::signed(exposed),
+		exposed,
+		10,
+		pallet_staking::RewardDestination::Staked
+	));
+	assert_ok!(Staking::nominate(RuntimeOrigin::signed(exposed), vec![exposed]));
+	// register the exposed one.
+	assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(exposed)));
+}

substrate/frame/fast-unstake/src/tests.rs

@@ -20,7 +20,7 @@
 use super::*;
 use crate::{mock::*, types::*, weights::WeightInfo, Event};
 use frame_support::{assert_noop, assert_ok, bounded_vec, pallet_prelude::*, traits::Currency};
-use pallet_staking::{CurrentEra, IndividualExposure, RewardDestination};
+use pallet_staking::{CurrentEra, RewardDestination};
 
 use sp_runtime::traits::BadOrigin;
 use sp_staking::StakingInterface;
@@ -107,9 +107,8 @@ fn cannot_register_if_head() {
 		ErasToCheckPerBlock::<T>::put(1);
 		// Insert some Head item for stash
 		Head::<T>::put(UnstakeRequest {
-			stash: 1,
+			stashes: bounded_vec![(1, Deposit::get())],
 			checked: bounded_vec![],
-			deposit: DepositAmount::get(),
 		});
 		// Controller attempts to regsiter
 		assert_noop!(
@@ -142,7 +141,7 @@ fn deregister_works() {
 
 		// Controller account registers for fast unstake.
 		assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(2)));
-		assert_eq!(<T as Config>::Currency::reserved_balance(&1), DepositAmount::get());
+		assert_eq!(<T as Config>::Currency::reserved_balance(&1), Deposit::get());
 
 		// Controller then changes mind and deregisters.
 		assert_ok!(FastUnstake::deregister(RuntimeOrigin::signed(2)));
@@ -191,9 +190,8 @@ fn cannot_deregister_already_head() {
 		assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(2)));
 		// Insert some Head item for stash.
 		Head::<T>::put(UnstakeRequest {
-			stash: 1,
+			stashes: bounded_vec![(1, Deposit::get())],
 			checked: bounded_vec![],
-			deposit: DepositAmount::get(),
 		});
 		// Controller attempts to deregister
 		assert_noop!(FastUnstake::deregister(RuntimeOrigin::signed(2)), Error::<T>::AlreadyHead);
@@ -227,14 +225,14 @@ mod on_idle {
 
 			// set up Queue item
 			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(2)));
-			assert_eq!(Queue::<T>::get(1), Some(DepositAmount::get()));
+			assert_eq!(Queue::<T>::get(1), Some(Deposit::get()));
 
 			// call on_idle with no remaining weight
 			FastUnstake::on_idle(System::block_number(), Weight::from_ref_time(0));
 
 			// assert nothing changed in Queue and Head
 			assert_eq!(Head::<T>::get(), None);
-			assert_eq!(Queue::<T>::get(1), Some(DepositAmount::get()));
+			assert_eq!(Queue::<T>::get(1), Some(Deposit::get()));
 		});
 	}
 
@@ -247,7 +245,7 @@ mod on_idle {
 
 			// given
 			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(2)));
-			assert_eq!(Queue::<T>::get(1), Some(DepositAmount::get()));
+			assert_eq!(Queue::<T>::get(1), Some(Deposit::get()));
 
 			assert_eq!(Queue::<T>::count(), 1);
 			assert_eq!(Head::<T>::get(), None);
@@ -262,13 +260,12 @@ mod on_idle {
 			// then
 			assert_eq!(
 				fast_unstake_events_since_last_call(),
-				vec![Event::Checking { stash: 1, eras: vec![3] }]
+				vec![Event::BatchChecked { eras: vec![3] }]
 			);
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3]
 				})
 			);
@@ -282,13 +279,12 @@ mod on_idle {
 			// then:
 			assert_eq!(
 				fast_unstake_events_since_last_call(),
-				vec![Event::Checking { stash: 1, eras: bounded_vec![2] }]
+				vec![Event::BatchChecked { eras: bounded_vec![2] }]
 			);
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3, 2]
 				})
 			);
@@ -308,13 +304,12 @@ mod on_idle {
 			// then:
 			assert_eq!(
 				fast_unstake_events_since_last_call(),
-				vec![Event::Checking { stash: 1, eras: vec![1, 0] }]
+				vec![Event::BatchChecked { eras: vec![1, 0] }]
 			);
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3, 2, 1, 0]
 				})
 			);
@@ -329,8 +324,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3, 2, 1, 0]
 				})
 			);
@@ -348,7 +342,7 @@ mod on_idle {
 			// then we finish the unbonding:
 			assert_eq!(
 				fast_unstake_events_since_last_call(),
-				vec![Event::Unstaked { stash: 1, result: Ok(()) }]
+				vec![Event::Unstaked { stash: 1, result: Ok(()) }, Event::BatchFinished],
 			);
 			assert_eq!(Head::<T>::get(), None,);
 
@@ -371,7 +365,7 @@ mod on_idle {
 			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(8)));
 			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(10)));
 
-			assert_eq!(<T as Config>::Currency::reserved_balance(&1), DepositAmount::get());
+			assert_eq!(<T as Config>::Currency::reserved_balance(&1), Deposit::get());
 
 			assert_eq!(Queue::<T>::count(), 5);
 			assert_eq!(Head::<T>::get(), None);
@@ -383,8 +377,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3, 2, 1, 0]
 				})
 			);
@@ -404,8 +397,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 5,
+					stashes: bounded_vec![(5, Deposit::get())],
 					checked: bounded_vec![3, 2, 1, 0]
 				}),
 			);
@@ -416,9 +408,10 @@ mod on_idle {
 			assert_eq!(
 				fast_unstake_events_since_last_call(),
 				vec![
-					Event::Checking { stash: 1, eras: vec![3, 2, 1, 0] },
+					Event::BatchChecked { eras: vec![3, 2, 1, 0] },
 					Event::Unstaked { stash: 1, result: Ok(()) },
-					Event::Checking { stash: 5, eras: vec![3, 2, 1, 0] }
+					Event::BatchFinished,
+					Event::BatchChecked { eras: vec![3, 2, 1, 0] }
 				]
 			);
 		});
@@ -432,9 +425,9 @@ mod on_idle {
 
 			// register multi accounts for fast unstake
 			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(2)));
-			assert_eq!(Queue::<T>::get(1), Some(DepositAmount::get()));
+			assert_eq!(Queue::<T>::get(1), Some(Deposit::get()));
 			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(4)));
-			assert_eq!(Queue::<T>::get(3), Some(DepositAmount::get()));
+			assert_eq!(Queue::<T>::get(3), Some(Deposit::get()));
 
 			// assert 2 queue items are in Queue & None in Head to start with
 			assert_eq!(Queue::<T>::count(), 2);
@@ -463,10 +456,12 @@ mod on_idle {
 			assert_eq!(
 				fast_unstake_events_since_last_call(),
 				vec![
-					Event::Checking { stash: 1, eras: vec![3, 2, 1, 0] },
+					Event::BatchChecked { eras: vec![3, 2, 1, 0] },
 					Event::Unstaked { stash: 1, result: Ok(()) },
-					Event::Checking { stash: 3, eras: vec![3, 2, 1, 0] },
+					Event::BatchFinished,
+					Event::BatchChecked { eras: vec![3, 2, 1, 0] },
 					Event::Unstaked { stash: 3, result: Ok(()) },
+					Event::BatchFinished,
 				]
 			);
 
@@ -483,7 +478,7 @@ mod on_idle {
 
 			// register for fast unstake
 			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(2)));
-			assert_eq!(Queue::<T>::get(1), Some(DepositAmount::get()));
+			assert_eq!(Queue::<T>::get(1), Some(Deposit::get()));
 
 			// process on idle
 			next_block(true);
@@ -495,8 +490,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3, 2, 1, 0]
 				})
 			);
@@ -507,8 +501,9 @@ mod on_idle {
 			assert_eq!(
 				fast_unstake_events_since_last_call(),
 				vec![
-					Event::Checking { stash: 1, eras: vec![3, 2, 1, 0] },
-					Event::Unstaked { stash: 1, result: Ok(()) }
+					Event::BatchChecked { eras: vec![3, 2, 1, 0] },
+					Event::Unstaked { stash: 1, result: Ok(()) },
+					Event::BatchFinished
 				]
 			);
 			assert_unstaked(&1);
@@ -525,7 +520,7 @@ mod on_idle {
 
 			// register for fast unstake
 			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(2)));
-			assert_eq!(Queue::<T>::get(1), Some(DepositAmount::get()));
+			assert_eq!(Queue::<T>::get(1), Some(Deposit::get()));
 
 			// process on idle
 			next_block(true);
@@ -537,8 +532,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3, 2, 1, 0]
 				})
 			);
@@ -549,8 +543,9 @@ mod on_idle {
 			assert_eq!(
 				fast_unstake_events_since_last_call(),
 				vec![
-					Event::Checking { stash: 1, eras: vec![3, 2, 1, 0] },
-					Event::Unstaked { stash: 1, result: Ok(()) }
+					Event::BatchChecked { eras: vec![3, 2, 1, 0] },
+					Event::Unstaked { stash: 1, result: Ok(()) },
+					Event::BatchFinished
 				]
 			);
 			assert_unstaked(&1);
@@ -566,7 +561,7 @@ mod on_idle {
 
 			// register for fast unstake
 			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(2)));
-			assert_eq!(Queue::<T>::get(1), Some(DepositAmount::get()));
+			assert_eq!(Queue::<T>::get(1), Some(Deposit::get()));
 
 			// process on idle
 			next_block(true);
@@ -578,8 +573,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3]
 				})
 			);
@@ -589,8 +583,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3, 2]
 				})
 			);
@@ -600,8 +593,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3, 2, 1]
 				})
 			);
@@ -611,8 +603,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3, 2, 1, 0]
 				})
 			);
@@ -624,11 +615,12 @@ mod on_idle {
 			assert_eq!(
 				fast_unstake_events_since_last_call(),
 				vec![
-					Event::Checking { stash: 1, eras: vec![3] },
-					Event::Checking { stash: 1, eras: vec![2] },
-					Event::Checking { stash: 1, eras: vec![1] },
-					Event::Checking { stash: 1, eras: vec![0] },
-					Event::Unstaked { stash: 1, result: Ok(()) }
+					Event::BatchChecked { eras: vec![3] },
+					Event::BatchChecked { eras: vec![2] },
+					Event::BatchChecked { eras: vec![1] },
+					Event::BatchChecked { eras: vec![0] },
+					Event::Unstaked { stash: 1, result: Ok(()) },
+					Event::BatchFinished
 				]
 			);
 			assert_unstaked(&1);
@@ -647,14 +639,13 @@ mod on_idle {
 
 			// register for fast unstake
 			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(2)));
-			assert_eq!(Queue::<T>::get(1), Some(DepositAmount::get()));
+			assert_eq!(Queue::<T>::get(1), Some(Deposit::get()));
 
 			next_block(true);
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3]
 				})
 			);
@@ -663,8 +654,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3, 2]
 				})
 			);
@@ -673,8 +663,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3, 2, 1]
 				})
 			);
@@ -683,8 +672,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3, 2, 1, 0]
 				})
 			);
@@ -698,10 +686,9 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					// note era 0 is pruned to keep the vector length sane.
 					checked: bounded_vec![3, 2, 1, 4],
-					deposit: DepositAmount::get(),
 				})
 			);
 
@@ -711,12 +698,13 @@ mod on_idle {
 			assert_eq!(
 				fast_unstake_events_since_last_call(),
 				vec![
-					Event::Checking { stash: 1, eras: vec![3] },
-					Event::Checking { stash: 1, eras: vec![2] },
-					Event::Checking { stash: 1, eras: vec![1] },
-					Event::Checking { stash: 1, eras: vec![0] },
-					Event::Checking { stash: 1, eras: vec![4] },
-					Event::Unstaked { stash: 1, result: Ok(()) }
+					Event::BatchChecked { eras: vec![3] },
+					Event::BatchChecked { eras: vec![2] },
+					Event::BatchChecked { eras: vec![1] },
+					Event::BatchChecked { eras: vec![0] },
+					Event::BatchChecked { eras: vec![4] },
+					Event::Unstaked { stash: 1, result: Ok(()) },
+					Event::BatchFinished
 				]
 			);
 			assert_unstaked(&1);
@@ -738,8 +726,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3]
 				})
 			);
@@ -748,8 +735,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3, 2]
 				})
 			);
@@ -762,8 +748,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3, 2]
 				})
 			);
@@ -772,8 +757,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3, 2]
 				})
 			);
@@ -788,8 +772,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3, 2, 4]
 				})
 			);
@@ -799,8 +782,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 1,
+					stashes: bounded_vec![(1, Deposit::get())],
 					checked: bounded_vec![3, 2, 4, 1]
 				})
 			);
@@ -812,11 +794,12 @@ mod on_idle {
 			assert_eq!(
 				fast_unstake_events_since_last_call(),
 				vec![
-					Event::Checking { stash: 1, eras: vec![3] },
-					Event::Checking { stash: 1, eras: vec![2] },
-					Event::Checking { stash: 1, eras: vec![4] },
-					Event::Checking { stash: 1, eras: vec![1] },
-					Event::Unstaked { stash: 1, result: Ok(()) }
+					Event::BatchChecked { eras: vec![3] },
+					Event::BatchChecked { eras: vec![2] },
+					Event::BatchChecked { eras: vec![4] },
+					Event::BatchChecked { eras: vec![1] },
+					Event::Unstaked { stash: 1, result: Ok(()) },
+					Event::BatchFinished
 				]
 			);
 
@@ -831,30 +814,15 @@ mod on_idle {
 			CurrentEra::<T>::put(BondingDuration::get());
 
 			// create an exposed nominator in era 1
-			let exposed = 666 as AccountId;
-			pallet_staking::ErasStakers::<T>::mutate(1, VALIDATORS_PER_ERA, |expo| {
-				expo.others.push(IndividualExposure { who: exposed, value: 0 as Balance });
-			});
-			Balances::make_free_balance_be(&exposed, 100);
-			assert_ok!(Staking::bond(
-				RuntimeOrigin::signed(exposed),
-				exposed,
-				10,
-				RewardDestination::Staked
-			));
-			assert_ok!(Staking::nominate(RuntimeOrigin::signed(exposed), vec![exposed]));
-
-			Balances::make_free_balance_be(&exposed, 100_000);
-			// register the exposed one.
-			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(exposed)));
+			let exposed = 666;
+			create_exposed_nominator(exposed, 1);
 
 			// a few blocks later, we realize they are slashed
 			next_block(true);
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: exposed,
+					stashes: bounded_vec![(exposed, Deposit::get())],
 					checked: bounded_vec![3]
 				})
 			);
@@ -862,8 +830,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: exposed,
+					stashes: bounded_vec![(exposed, Deposit::get())],
 					checked: bounded_vec![3, 2]
 				})
 			);
@@ -873,9 +840,10 @@ mod on_idle {
 			assert_eq!(
 				fast_unstake_events_since_last_call(),
 				vec![
-					Event::Checking { stash: exposed, eras: vec![3] },
-					Event::Checking { stash: exposed, eras: vec![2] },
-					Event::Slashed { stash: exposed, amount: DepositAmount::get() }
+					Event::BatchChecked { eras: vec![3] },
+					Event::BatchChecked { eras: vec![2] },
+					Event::Slashed { stash: exposed, amount: Deposit::get() },
+					Event::BatchFinished
 				]
 			);
 		});
@@ -889,30 +857,16 @@ mod on_idle {
 			ErasToCheckPerBlock::<T>::put(2);
 			CurrentEra::<T>::put(BondingDuration::get());
 
-			// create an exposed nominator in era 1
-			let exposed = 666 as AccountId;
-			pallet_staking::ErasStakers::<T>::mutate(0, VALIDATORS_PER_ERA, |expo| {
-				expo.others.push(IndividualExposure { who: exposed, value: 0 as Balance });
-			});
-			Balances::make_free_balance_be(&exposed, DepositAmount::get() + 100);
-			assert_ok!(Staking::bond(
-				RuntimeOrigin::signed(exposed),
-				exposed,
-				10,
-				RewardDestination::Staked
-			));
-			assert_ok!(Staking::nominate(RuntimeOrigin::signed(exposed), vec![exposed]));
-
-			// register the exposed one.
-			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(exposed)));
+			// create an exposed nominator in era 0
+			let exposed = 666;
+			create_exposed_nominator(exposed, 0);
 
 			// a few blocks later, we realize they are slashed
 			next_block(true);
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: exposed,
+					stashes: bounded_vec![(exposed, Deposit::get())],
 					checked: bounded_vec![3, 2]
 				})
 			);
@@ -923,8 +877,9 @@ mod on_idle {
 				fast_unstake_events_since_last_call(),
 				// we slash them
 				vec![
-					Event::Checking { stash: exposed, eras: vec![3, 2] },
-					Event::Slashed { stash: exposed, amount: DepositAmount::get() }
+					Event::BatchChecked { eras: vec![3, 2] },
+					Event::Slashed { stash: exposed, amount: Deposit::get() },
+					Event::BatchFinished
 				]
 			);
 		});
@@ -955,7 +910,7 @@ mod on_idle {
 
 			assert_eq!(
 				fast_unstake_events_since_last_call(),
-				vec![Event::Slashed { stash: 100, amount: DepositAmount::get() }]
+				vec![Event::Slashed { stash: 100, amount: Deposit::get() }, Event::BatchFinished]
 			);
 		});
 	}
@@ -967,7 +922,7 @@ mod on_idle {
 			CurrentEra::<T>::put(BondingDuration::get());
 
 			// create a new validator that 100% not exposed.
-			Balances::make_free_balance_be(&42, 100 + DepositAmount::get());
+			Balances::make_free_balance_be(&42, 100 + Deposit::get());
 			assert_ok!(Staking::bond(RuntimeOrigin::signed(42), 42, 10, RewardDestination::Staked));
 			assert_ok!(Staking::validate(RuntimeOrigin::signed(42), Default::default()));
 
@@ -979,8 +934,7 @@ mod on_idle {
 			assert_eq!(
 				Head::<T>::get(),
 				Some(UnstakeRequest {
-					deposit: DepositAmount::get(),
-					stash: 42,
+					stashes: bounded_vec![(42, Deposit::get())],
 					checked: bounded_vec![3, 2, 1, 0]
 				})
 			);
@@ -990,8 +944,255 @@ mod on_idle {
 			assert_eq!(
 				fast_unstake_events_since_last_call(),
 				vec![
-					Event::Checking { stash: 42, eras: vec![3, 2, 1, 0] },
-					Event::Unstaked { stash: 42, result: Ok(()) }
+					Event::BatchChecked { eras: vec![3, 2, 1, 0] },
+					Event::Unstaked { stash: 42, result: Ok(()) },
+					Event::BatchFinished
+				]
+			);
+		});
+	}
+}
+
+mod batched {
+	use super::*;
+
+	#[test]
+	fn single_block_batched_successful() {
+		ExtBuilder::default().batch(3).build_and_execute(|| {
+			ErasToCheckPerBlock::<T>::put(BondingDuration::get() + 1);
+			CurrentEra::<T>::put(BondingDuration::get());
+
+			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(2)));
+			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(4)));
+			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(6)));
+			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(8)));
+
+			assert_eq!(Queue::<T>::count(), 4);
+			assert_eq!(Head::<T>::get(), None);
+
+			// when
+			next_block(true);
+
+			// then
+			assert_eq!(
+				Head::<T>::get(),
+				Some(UnstakeRequest {
+					stashes: bounded_vec![
+						(1, Deposit::get()),
+						(5, Deposit::get()),
+						(7, Deposit::get())
+					],
+					checked: bounded_vec![3, 2, 1, 0]
+				})
+			);
+			assert_eq!(Queue::<T>::count(), 1);
+
+			// when
+			next_block(true);
+
+			// then
+			assert_eq!(Head::<T>::get(), None);
+			assert_eq!(Queue::<T>::count(), 1);
+
+			assert_eq!(
+				fast_unstake_events_since_last_call(),
+				vec![
+					Event::BatchChecked { eras: vec![3, 2, 1, 0] },
+					Event::Unstaked { stash: 1, result: Ok(()) },
+					Event::Unstaked { stash: 5, result: Ok(()) },
+					Event::Unstaked { stash: 7, result: Ok(()) },
+					Event::BatchFinished
+				]
+			);
+		});
+	}
+
+	#[test]
+	fn multi_block_batched_successful() {
+		ExtBuilder::default().batch(3).build_and_execute(|| {
+			ErasToCheckPerBlock::<T>::put(2);
+			CurrentEra::<T>::put(BondingDuration::get());
+
+			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(2)));
+			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(4)));
+			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(6)));
+			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(8)));
+
+			assert_eq!(Queue::<T>::count(), 4);
+			assert_eq!(Head::<T>::get(), None);
+
+			// when
+			next_block(true);
+
+			// then
+			assert_eq!(
+				Head::<T>::get(),
+				Some(UnstakeRequest {
+					stashes: bounded_vec![
+						(1, Deposit::get()),
+						(5, Deposit::get()),
+						(7, Deposit::get())
+					],
+					checked: bounded_vec![3, 2]
+				})
+			);
+
+			// when
+			next_block(true);
+
+			// then
+			assert_eq!(
+				Head::<T>::get(),
+				Some(UnstakeRequest {
+					stashes: bounded_vec![
+						(1, Deposit::get()),
+						(5, Deposit::get()),
+						(7, Deposit::get())
+					],
+					checked: bounded_vec![3, 2, 1, 0]
+				})
+			);
+
+			// when
+			next_block(true);
+
+			// then
+			assert_eq!(Head::<T>::get(), None);
+
+			assert_eq!(
+				fast_unstake_events_since_last_call(),
+				vec![
+					Event::BatchChecked { eras: vec![3, 2] },
+					Event::BatchChecked { eras: vec![1, 0] },
+					Event::Unstaked { stash: 1, result: Ok(()) },
+					Event::Unstaked { stash: 5, result: Ok(()) },
+					Event::Unstaked { stash: 7, result: Ok(()) },
+					Event::BatchFinished
+				]
+			);
+		});
+	}
+
+	#[test]
+	fn multi_block_batched_some_fail() {
+		ExtBuilder::default().batch(4).build_and_execute(|| {
+			ErasToCheckPerBlock::<T>::put(2);
+			CurrentEra::<T>::put(BondingDuration::get());
+
+			// register two good ones.
+			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(2)));
+			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(4)));
+			create_exposed_nominator(666, 1);
+			create_exposed_nominator(667, 3);
+
+			// then
+			assert_eq!(Queue::<T>::count(), 4);
+			assert_eq!(Head::<T>::get(), None);
+
+			// when
+			next_block(true);
+
+			// then
+			assert_eq!(
+				Head::<T>::get(),
+				Some(UnstakeRequest {
+					stashes: bounded_vec![
+						(1, Deposit::get()),
+						(3, Deposit::get()),
+						(666, Deposit::get())
+					],
+					checked: bounded_vec![3, 2]
+				})
+			);
+
+			// when
+			next_block(true);
+
+			// then
+			assert_eq!(
+				Head::<T>::get(),
+				Some(UnstakeRequest {
+					stashes: bounded_vec![(1, Deposit::get()), (3, Deposit::get()),],
+					checked: bounded_vec![3, 2, 1, 0]
+				})
+			);
+
+			// when
+			next_block(true);
+
+			// then
+			assert_eq!(Head::<T>::get(), None);
+
+			assert_eq!(
+				fast_unstake_events_since_last_call(),
+				vec![
+					Event::Slashed { stash: 667, amount: 7 },
+					Event::BatchChecked { eras: vec![3, 2] },
+					Event::Slashed { stash: 666, amount: 7 },
+					Event::BatchChecked { eras: vec![1, 0] },
+					Event::Unstaked { stash: 1, result: Ok(()) },
+					Event::Unstaked { stash: 3, result: Ok(()) },
+					Event::BatchFinished
+				]
+			);
+		});
+	}
+
+	#[test]
+	fn multi_block_batched_all_fail_early_exit() {
+		ExtBuilder::default().batch(2).build_and_execute(|| {
+			ErasToCheckPerBlock::<T>::put(1);
+			CurrentEra::<T>::put(BondingDuration::get());
+
+			// register two bad ones.
+			create_exposed_nominator(666, 3);
+			create_exposed_nominator(667, 2);
+
+			// then
+			assert_eq!(Queue::<T>::count(), 2);
+			assert_eq!(Head::<T>::get(), None);
+
+			// when we progress a block..
+			next_block(true);
+
+			// ..and register two good ones.
+			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(2)));
+			assert_ok!(FastUnstake::register_fast_unstake(RuntimeOrigin::signed(4)));
+
+			// then one of the bad ones is reaped.
+			assert_eq!(
+				Head::<T>::get(),
+				Some(UnstakeRequest {
+					stashes: bounded_vec![(667, Deposit::get())],
+					checked: bounded_vec![3]
+				})
+			);
+
+			// when we go to next block
+			next_block(true);
+
+			// then the head is empty, we early terminate the batch.
+			assert_eq!(Head::<T>::get(), None);
+
+			// upon next block, we will assemble a new head.
+			next_block(true);
+
+			assert_eq!(
+				Head::<T>::get(),
+				Some(UnstakeRequest {
+					stashes: bounded_vec![(1, Deposit::get()), (3, Deposit::get()),],
+					checked: bounded_vec![3]
+				})
+			);
+
+			assert_eq!(
+				fast_unstake_events_since_last_call(),
+				vec![
+					Event::Slashed { stash: 666, amount: Deposit::get() },
+					Event::BatchChecked { eras: vec![3] },
+					Event::Slashed { stash: 667, amount: Deposit::get() },
+					Event::BatchFinished,
+					Event::BatchChecked { eras: vec![3] }
 				]
 			);
 		});

substrate/frame/fast-unstake/src/types.rs

@@ -17,15 +17,14 @@
 
 //! Types used in the Fast Unstake pallet.
 
-use crate::Config;
+use crate::{Config, MaxChecking};
 use codec::{Decode, Encode, MaxEncodedLen};
 use frame_support::{
-	traits::{Currency, Get},
-	BoundedVec, EqNoBound, PartialEqNoBound, RuntimeDebugNoBound,
+	traits::Currency, BoundedVec, EqNoBound, PartialEqNoBound, RuntimeDebugNoBound,
 };
 use scale_info::TypeInfo;
 use sp_staking::EraIndex;
-use sp_std::{fmt::Debug, prelude::*};
+use sp_std::prelude::*;
 
 pub type BalanceOf<T> =
 	<<T as Config>::Currency as Currency<<T as frame_system::Config>::AccountId>>::Balance;
@@ -33,15 +32,10 @@ pub type BalanceOf<T> =
 #[derive(
 	Encode, Decode, EqNoBound, PartialEqNoBound, Clone, TypeInfo, RuntimeDebugNoBound, MaxEncodedLen,
 )]
-pub struct UnstakeRequest<
-	AccountId: Eq + PartialEq + Debug,
-	MaxChecked: Get<u32>,
-	Balance: PartialEq + Debug,
-> {
-	/// Their stash account.
-	pub(crate) stash: AccountId,
+#[scale_info(skip_type_params(T))]
+pub struct UnstakeRequest<T: Config> {
+	/// This list of stashes being processed in this request, and their corresponding deposit.
+	pub(crate) stashes: BoundedVec<(T::AccountId, BalanceOf<T>), T::BatchSize>,
 	/// The list of eras for which they have been checked.
-	pub(crate) checked: BoundedVec<EraIndex, MaxChecked>,
-	/// Deposit to be slashed if the unstake was unsuccessful.
-	pub(crate) deposit: Balance,
+	pub(crate) checked: BoundedVec<EraIndex, MaxChecking<T>>,
 }