[NPoS] Paging reward payouts in order to scale rewardable nominators (p…

…aritytech#1189) helps paritytech#439. closes paritytech#473. PR link in the older substrate repository: paritytech/substrate#13498. # Context Rewards payout is processed today in a single block and limited to `MaxNominatorRewardedPerValidator`. This number is currently 512 on both Kusama and Polkadot. This PR tries to scale the nominators payout to an unlimited count in a multi-block fashion. Exposures are stored in pages, with each page capped to a certain number (`MaxExposurePageSize`). Starting out, this number would be the same as `MaxNominatorRewardedPerValidator`, but eventually, this number can be lowered through new runtime upgrades to limit the rewardeable nominators per dispatched call instruction. The changes in the PR are backward compatible. ## How payouts would work like after this change Staking exposes two calls, 1) the existing `payout_stakers` and 2) `payout_stakers_by_page`. ### payout_stakers This remains backward compatible with no signature change. If for a given era a validator has multiple pages, they can call `payout_stakers` multiple times. The pages are executed in an ascending sequence and the runtime takes care of preventing double claims. ### payout_stakers_by_page Very similar to `payout_stakers` but also accepts an extra param `page_index`. An account can choose to payout rewards only for an explicitly passed `page_index`. **Lets look at an example scenario** Given an active validator on Kusama had 1100 nominators, `MaxExposurePageSize` set to 512 for Era e. In order to pay out rewards to all nominators, the caller would need to call `payout_stakers` 3 times. - `payout_stakers(origin, stash, e)` => will pay the first 512 nominators. - `payout_stakers(origin, stash, e)` => will pay the second set of 512 nominators. - `payout_stakers(origin, stash, e)` => will pay the last set of 76 nominators. ... - `payout_stakers(origin, stash, e)` => calling it the 4th time would return an error `InvalidPage`. The above calls can also be replaced by `payout_stakers_by_page` and passing a `page_index` explicitly. ## Commission note Validator commission is paid out in chunks across all the pages where each commission chunk is proportional to the total stake of the current page. This implies higher the total stake of a page, higher will be the commission. If all the pages of a validator's single era are paid out, the sum of commission paid to the validator across all pages should be equal to what the commission would have been if we had a non-paged exposure. ### Migration Note Strictly speaking, we did not need to bump our storage version since there is no migration of storage in this PR. But it is still useful to mark a storage upgrade for the following reasons: - New storage items are introduced in this PR while some older storage items are deprecated. - For the next `HistoryDepth` eras, the exposure would be incrementally migrated to its corresponding paged storage item. - Runtimes using staking pallet would strictly need to wait at least `HistoryDepth` eras with current upgraded version (14) for the migration to complete. At some era `E` such that `E > era_at_which_V14_gets_into_effect + HistoryDepth`, we will upgrade to version X which will remove the deprecated storage items. In other words, it is a strict requirement that E<sub>x</sub> - E<sub>14</sub> > `HistoryDepth`, where E<sub>x</sub> = Era at which deprecated storages are removed from runtime, E<sub>14</sub> = Era at which runtime is upgraded to version 14. - For Polkadot and Kusama, there is a [tracker ticket](paritytech#433) to clean up the deprecated storage items. ### Storage Changes #### Added - ErasStakersOverview - ClaimedRewards - ErasStakersPaged #### Deprecated The following can be cleaned up after 84 eras which is tracked [here](paritytech#433). - ErasStakers. - ErasStakersClipped. - StakingLedger.claimed_rewards, renamed to StakingLedger.legacy_claimed_rewards. ### Config Changes - Renamed MaxNominatorRewardedPerValidator to MaxExposurePageSize. ### TODO - [x] Tracker ticket for cleaning up the old code after 84 eras. - [x] Add companion. - [x] Redo benchmarks before merge. - [x] Add Changelog for pallet_staking. - [x] Pallet should be configurable to enable/disable paged rewards. - [x] Commission payouts are distributed across pages. - [x] Review documentation thoroughly. - [x] Rename `MaxNominatorRewardedPerValidator` -> `MaxExposurePageSize`. - [x] NMap for `ErasStakersPaged`. - [x] Deprecate ErasStakers. - [x] Integrity tests. ### Followup issues [Runtime api for deprecated ErasStakers storage item](paritytech#426) --------- Co-authored-by: Javier Viola <[email protected]> Co-authored-by: Ross Bulat <[email protected]> Co-authored-by: command-bot <>
duniter · Nov 1, 2023 · 870ce7f · 870ce7f
1 parent 63e2cf1
commit 870ce7f
Show file tree

Hide file tree

Showing 32 changed files with 2,894 additions and 1,652 deletions.
diff --git a/substrate/bin/node/runtime/src/lib.rs b/substrate/bin/node/runtime/src/lib.rs
@@ -485,7 +485,7 @@ impl pallet_babe::Config for Runtime {
 	type DisabledValidators = Session;
 	type WeightInfo = ();
 	type MaxAuthorities = MaxAuthorities;
-	type MaxNominators = MaxNominatorRewardedPerValidator;
+	type MaxNominators = MaxNominators;
 	type KeyOwnerProof =
 		<Historical as KeyOwnerProofSystem<(KeyTypeId, pallet_babe::AuthorityId)>>::Proof;
 	type EquivocationReportSystem =
@@ -628,7 +628,7 @@ parameter_types! {
 	pub const BondingDuration: sp_staking::EraIndex = 24 * 28;
 	pub const SlashDeferDuration: sp_staking::EraIndex = 24 * 7; // 1/4 the bonding duration.
 	pub const RewardCurve: &'static PiecewiseLinear<'static> = &REWARD_CURVE;
-	pub const MaxNominatorRewardedPerValidator: u32 = 256;
+	pub const MaxNominators: u32 = 64;
 	pub const OffendingValidatorsThreshold: Perbill = Perbill::from_percent(17);
 	pub OffchainRepeat: BlockNumber = 5;
 	pub HistoryDepth: u32 = 84;
@@ -663,7 +663,7 @@ impl pallet_staking::Config for Runtime {
 	type SessionInterface = Self;
 	type EraPayout = pallet_staking::ConvertCurve<RewardCurve>;
 	type NextNewSession = Session;
-	type MaxNominatorRewardedPerValidator = MaxNominatorRewardedPerValidator;
+	type MaxExposurePageSize = ConstU32<256>;
 	type OffendingValidatorsThreshold = OffendingValidatorsThreshold;
 	type ElectionProvider = ElectionProviderMultiPhase;
 	type GenesisElectionProvider = onchain::OnChainExecution<OnChainSeqPhragmen>;
@@ -686,8 +686,6 @@ impl pallet_fast_unstake::Config for Runtime {
 	type Currency = Balances;
 	type Staking = Staking;
 	type MaxErasToCheckPerBlock = ConstU32<1>;
-	#[cfg(feature = "runtime-benchmarks")]
-	type MaxBackersPerValidator = MaxNominatorRewardedPerValidator;
 	type WeightInfo = ();
 }
 
@@ -1453,7 +1451,7 @@ impl pallet_grandpa::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type WeightInfo = ();
 	type MaxAuthorities = MaxAuthorities;
-	type MaxNominators = MaxNominatorRewardedPerValidator;
+	type MaxNominators = MaxNominators;
 	type MaxSetIdSessionEntries = MaxSetIdSessionEntries;
 	type KeyOwnerProof = <Historical as KeyOwnerProofSystem<(KeyTypeId, GrandpaId)>>::Proof;
 	type EquivocationReportSystem =
@@ -2392,10 +2390,14 @@ impl_runtime_apis! {
 		}
 	}
 
-	impl pallet_staking_runtime_api::StakingApi<Block, Balance> for Runtime {
+	impl pallet_staking_runtime_api::StakingApi<Block, Balance, AccountId> for Runtime {
 		fn nominations_quota(balance: Balance) -> u32 {
 			Staking::api_nominations_quota(balance)
 		}
+
+		fn eras_stakers_page_count(era: sp_staking::EraIndex, account: AccountId) -> sp_staking::Page {
+			Staking::api_eras_stakers_page_count(era, account)
+		}
 	}
 
 	impl sp_consensus_babe::BabeApi<Block> for Runtime {

diff --git a/substrate/frame/babe/src/mock.rs b/substrate/frame/babe/src/mock.rs
@@ -174,7 +174,7 @@ impl pallet_staking::Config for Test {
 	type SessionInterface = Self;
 	type UnixTime = pallet_timestamp::Pallet<Test>;
 	type EraPayout = pallet_staking::ConvertCurve<RewardCurve>;
-	type MaxNominatorRewardedPerValidator = ConstU32<64>;
+	type MaxExposurePageSize = ConstU32<64>;
 	type OffendingValidatorsThreshold = OffendingValidatorsThreshold;
 	type NextNewSession = Session;
 	type ElectionProvider = onchain::OnChainExecution<OnChainSeqPhragmen>;

diff --git a/substrate/frame/babe/src/tests.rs b/substrate/frame/babe/src/tests.rs
@@ -440,7 +440,7 @@ fn report_equivocation_current_session_works() {
 			assert_eq!(Staking::slashable_balance_of(validator), 10_000);
 
 			assert_eq!(
-				Staking::eras_stakers(1, validator),
+				Staking::eras_stakers(1, &validator),
 				pallet_staking::Exposure { total: 10_000, own: 10_000, others: vec![] },
 			);
 		}
@@ -481,7 +481,7 @@ fn report_equivocation_current_session_works() {
 		assert_eq!(Balances::total_balance(&offending_validator_id), 10_000_000 - 10_000);
 		assert_eq!(Staking::slashable_balance_of(&offending_validator_id), 0);
 		assert_eq!(
-			Staking::eras_stakers(2, offending_validator_id),
+			Staking::eras_stakers(2, &offending_validator_id),
 			pallet_staking::Exposure { total: 0, own: 0, others: vec![] },
 		);
 
@@ -494,7 +494,7 @@ fn report_equivocation_current_session_works() {
 			assert_eq!(Balances::total_balance(validator), 10_000_000);
 			assert_eq!(Staking::slashable_balance_of(validator), 10_000);
 			assert_eq!(
-				Staking::eras_stakers(2, validator),
+				Staking::eras_stakers(2, &validator),
 				pallet_staking::Exposure { total: 10_000, own: 10_000, others: vec![] },
 			);
 		}
@@ -553,7 +553,7 @@ fn report_equivocation_old_session_works() {
 		assert_eq!(Balances::total_balance(&offending_validator_id), 10_000_000 - 10_000);
 		assert_eq!(Staking::slashable_balance_of(&offending_validator_id), 0);
 		assert_eq!(
-			Staking::eras_stakers(3, offending_validator_id),
+			Staking::eras_stakers(3, &offending_validator_id),
 			pallet_staking::Exposure { total: 0, own: 0, others: vec![] },
 		);
 	})

diff --git a/substrate/frame/beefy/src/mock.rs b/substrate/frame/beefy/src/mock.rs
@@ -192,7 +192,7 @@ impl pallet_staking::Config for Test {
 	type SessionInterface = Self;
 	type UnixTime = pallet_timestamp::Pallet<Test>;
 	type EraPayout = pallet_staking::ConvertCurve<RewardCurve>;
-	type MaxNominatorRewardedPerValidator = ConstU32<64>;
+	type MaxExposurePageSize = ConstU32<64>;
 	type OffendingValidatorsThreshold = OffendingValidatorsThreshold;
 	type NextNewSession = Session;
 	type ElectionProvider = onchain::OnChainExecution<OnChainSeqPhragmen>;

diff --git a/substrate/frame/beefy/src/tests.rs b/substrate/frame/beefy/src/tests.rs
@@ -277,7 +277,7 @@ fn report_equivocation_current_set_works() {
 			assert_eq!(Staking::slashable_balance_of(validator), 10_000);
 
 			assert_eq!(
-				Staking::eras_stakers(1, validator),
+				Staking::eras_stakers(1, &validator),
 				pallet_staking::Exposure { total: 10_000, own: 10_000, others: vec![] },
 			);
 		}
@@ -314,7 +314,7 @@ fn report_equivocation_current_set_works() {
 		assert_eq!(Balances::total_balance(&equivocation_validator_id), 10_000_000 - 10_000);
 		assert_eq!(Staking::slashable_balance_of(&equivocation_validator_id), 0);
 		assert_eq!(
-			Staking::eras_stakers(2, equivocation_validator_id),
+			Staking::eras_stakers(2, &equivocation_validator_id),
 			pallet_staking::Exposure { total: 0, own: 0, others: vec![] },
 		);
 
@@ -328,7 +328,7 @@ fn report_equivocation_current_set_works() {
 			assert_eq!(Staking::slashable_balance_of(validator), 10_000);
 
 			assert_eq!(
-				Staking::eras_stakers(2, validator),
+				Staking::eras_stakers(2, &validator),
 				pallet_staking::Exposure { total: 10_000, own: 10_000, others: vec![] },
 			);
 		}
@@ -363,7 +363,7 @@ fn report_equivocation_old_set_works() {
 			assert_eq!(Staking::slashable_balance_of(validator), 10_000);
 
 			assert_eq!(
-				Staking::eras_stakers(2, validator),
+				Staking::eras_stakers(2, &validator),
 				pallet_staking::Exposure { total: 10_000, own: 10_000, others: vec![] },
 			);
 		}
@@ -397,7 +397,7 @@ fn report_equivocation_old_set_works() {
 		assert_eq!(Balances::total_balance(&equivocation_validator_id), 10_000_000 - 10_000);
 		assert_eq!(Staking::slashable_balance_of(&equivocation_validator_id), 0);
 		assert_eq!(
-			Staking::eras_stakers(3, equivocation_validator_id),
+			Staking::eras_stakers(3, &equivocation_validator_id),
 			pallet_staking::Exposure { total: 0, own: 0, others: vec![] },
 		);
 
@@ -411,7 +411,7 @@ fn report_equivocation_old_set_works() {
 			assert_eq!(Staking::slashable_balance_of(validator), 10_000);
 
 			assert_eq!(
-				Staking::eras_stakers(3, validator),
+				Staking::eras_stakers(3, &validator),
 				pallet_staking::Exposure { total: 10_000, own: 10_000, others: vec![] },
 			);
 		}

diff --git a/substrate/frame/election-provider-multi-phase/test-staking-e2e/src/mock.rs b/substrate/frame/election-provider-multi-phase/test-staking-e2e/src/mock.rs
@@ -237,7 +237,6 @@ parameter_types! {
 	pub const SessionsPerEra: sp_staking::SessionIndex = 2;
 	pub const BondingDuration: sp_staking::EraIndex = 28;
 	pub const SlashDeferDuration: sp_staking::EraIndex = 7; // 1/4 the bonding duration.
-	pub const MaxNominatorRewardedPerValidator: u32 = 256;
 	pub const OffendingValidatorsThreshold: Perbill = Perbill::from_percent(40);
 	pub HistoryDepth: u32 = 84;
 }
@@ -269,7 +268,7 @@ impl pallet_staking::Config for Runtime {
 	type SessionInterface = Self;
 	type EraPayout = ();
 	type NextNewSession = Session;
-	type MaxNominatorRewardedPerValidator = MaxNominatorRewardedPerValidator;
+	type MaxExposurePageSize = ConstU32<256>;
 	type OffendingValidatorsThreshold = OffendingValidatorsThreshold;
 	type ElectionProvider = ElectionProviderMultiPhase;
 	type GenesisElectionProvider = onchain::OnChainExecution<OnChainSeqPhragmen>;
@@ -809,7 +808,7 @@ pub(crate) fn on_offence_now(
 pub(crate) fn add_slash(who: &AccountId) {
 	on_offence_now(
 		&[OffenceDetails {
-			offender: (*who, Staking::eras_stakers(active_era(), *who)),
+			offender: (*who, Staking::eras_stakers(active_era(), who)),
 			reporters: vec![],
 		}],
 		&[Perbill::from_percent(10)],

diff --git a/substrate/frame/fast-unstake/src/benchmarking.rs b/substrate/frame/fast-unstake/src/benchmarking.rs
@@ -74,9 +74,9 @@ fn setup_staking<T: Config>(v: u32, until: EraIndex) {
 		.collect::<Vec<_>>();
 
 	for era in 0..=until {
-		let others = (0..T::MaxBackersPerValidator::get())
+		let others = (0..T::Staking::max_exposure_page_size())
 			.map(|s| {
-				let who = frame_benchmarking::account::<T::AccountId>("nominator", era, s);
+				let who = frame_benchmarking::account::<T::AccountId>("nominator", era, s.into());
 				let value = ed;
 				(who, value)
 			})

diff --git a/substrate/frame/fast-unstake/src/lib.rs b/substrate/frame/fast-unstake/src/lib.rs
@@ -203,10 +203,6 @@ pub mod pallet {
 
 		/// The weight information of this pallet.
 		type WeightInfo: WeightInfo;
-
-		/// Use only for benchmarking.
-		#[cfg(feature = "runtime-benchmarks")]
-		type MaxBackersPerValidator: Get<u32>;
 	}
 
 	/// The current "head of the queue" being unstaked.

diff --git a/substrate/frame/fast-unstake/src/mock.rs b/substrate/frame/fast-unstake/src/mock.rs
@@ -134,7 +134,7 @@ impl pallet_staking::Config for Runtime {
 	type EraPayout = pallet_staking::ConvertCurve<RewardCurve>;
 	type NextNewSession = ();
 	type HistoryDepth = ConstU32<84>;
-	type MaxNominatorRewardedPerValidator = ConstU32<64>;
+	type MaxExposurePageSize = ConstU32<64>;
 	type OffendingValidatorsThreshold = ();
 	type ElectionProvider = MockElection;
 	type GenesisElectionProvider = Self::ElectionProvider;
@@ -175,8 +175,6 @@ impl fast_unstake::Config for Runtime {
 	type BatchSize = BatchSize;
 	type WeightInfo = ();
 	type MaxErasToCheckPerBlock = ConstU32<16>;
-	#[cfg(feature = "runtime-benchmarks")]
-	type MaxBackersPerValidator = ConstU32<128>;
 }
 
 type Block = frame_system::mocking::MockBlock<Runtime>;

diff --git a/substrate/frame/grandpa/src/mock.rs b/substrate/frame/grandpa/src/mock.rs
@@ -196,7 +196,7 @@ impl pallet_staking::Config for Test {
 	type SessionInterface = Self;
 	type UnixTime = pallet_timestamp::Pallet<Test>;
 	type EraPayout = pallet_staking::ConvertCurve<RewardCurve>;
-	type MaxNominatorRewardedPerValidator = ConstU32<64>;
+	type MaxExposurePageSize = ConstU32<64>;
 	type OffendingValidatorsThreshold = OffendingValidatorsThreshold;
 	type NextNewSession = Session;
 	type ElectionProvider = onchain::OnChainExecution<OnChainSeqPhragmen>;

diff --git a/substrate/frame/grandpa/src/tests.rs b/substrate/frame/grandpa/src/tests.rs
@@ -333,7 +333,7 @@ fn report_equivocation_current_set_works() {
 			assert_eq!(Staking::slashable_balance_of(validator), 10_000);
 
 			assert_eq!(
-				Staking::eras_stakers(1, validator),
+				Staking::eras_stakers(1, &validator),
 				pallet_staking::Exposure { total: 10_000, own: 10_000, others: vec![] },
 			);
 		}
@@ -371,7 +371,7 @@ fn report_equivocation_current_set_works() {
 		assert_eq!(Balances::total_balance(&equivocation_validator_id), 10_000_000 - 10_000);
 		assert_eq!(Staking::slashable_balance_of(&equivocation_validator_id), 0);
 		assert_eq!(
-			Staking::eras_stakers(2, equivocation_validator_id),
+			Staking::eras_stakers(2, &equivocation_validator_id),
 			pallet_staking::Exposure { total: 0, own: 0, others: vec![] },
 		);
 
@@ -385,7 +385,7 @@ fn report_equivocation_current_set_works() {
 			assert_eq!(Staking::slashable_balance_of(validator), 10_000);
 
 			assert_eq!(
-				Staking::eras_stakers(2, validator),
+				Staking::eras_stakers(2, &validator),
 				pallet_staking::Exposure { total: 10_000, own: 10_000, others: vec![] },
 			);
 		}
@@ -417,7 +417,7 @@ fn report_equivocation_old_set_works() {
 			assert_eq!(Staking::slashable_balance_of(validator), 10_000);
 
 			assert_eq!(
-				Staking::eras_stakers(2, validator),
+				Staking::eras_stakers(2, &validator),
 				pallet_staking::Exposure { total: 10_000, own: 10_000, others: vec![] },
 			);
 		}
@@ -450,7 +450,7 @@ fn report_equivocation_old_set_works() {
 		assert_eq!(Staking::slashable_balance_of(&equivocation_validator_id), 0);
 
 		assert_eq!(
-			Staking::eras_stakers(3, equivocation_validator_id),
+			Staking::eras_stakers(3, &equivocation_validator_id),
 			pallet_staking::Exposure { total: 0, own: 0, others: vec![] },
 		);
 
@@ -464,7 +464,7 @@ fn report_equivocation_old_set_works() {
 			assert_eq!(Staking::slashable_balance_of(validator), 10_000);
 
 			assert_eq!(
-				Staking::eras_stakers(3, validator),
+				Staking::eras_stakers(3, &validator),
 				pallet_staking::Exposure { total: 10_000, own: 10_000, others: vec![] },
 			);
 		}

diff --git a/substrate/frame/nomination-pools/benchmarking/src/mock.rs b/substrate/frame/nomination-pools/benchmarking/src/mock.rs
@@ -110,7 +110,7 @@ impl pallet_staking::Config for Runtime {
 	type SessionInterface = ();
 	type EraPayout = pallet_staking::ConvertCurve<RewardCurve>;
 	type NextNewSession = ();
-	type MaxNominatorRewardedPerValidator = ConstU32<64>;
+	type MaxExposurePageSize = ConstU32<64>;
 	type OffendingValidatorsThreshold = ();
 	type ElectionProvider =
 		frame_election_provider_support::NoElection<(AccountId, BlockNumber, Staking, ())>;

diff --git a/substrate/frame/nomination-pools/src/mock.rs b/substrate/frame/nomination-pools/src/mock.rs
@@ -202,6 +202,11 @@ impl sp_staking::StakingInterface for StakingMock {
 	fn set_current_era(_era: EraIndex) {
 		unimplemented!("method currently not used in testing")
 	}
+
+	#[cfg(feature = "runtime-benchmarks")]
+	fn max_exposure_page_size() -> sp_staking::Page {
+		unimplemented!("method currently not used in testing")
+	}
 }
 
 impl frame_system::Config for Runtime {

diff --git a/substrate/frame/nomination-pools/test-staking/src/mock.rs b/substrate/frame/nomination-pools/test-staking/src/mock.rs
@@ -124,7 +124,7 @@ impl pallet_staking::Config for Runtime {
 	type SessionInterface = ();
 	type EraPayout = pallet_staking::ConvertCurve<RewardCurve>;
 	type NextNewSession = ();
-	type MaxNominatorRewardedPerValidator = ConstU32<64>;
+	type MaxExposurePageSize = ConstU32<64>;
 	type OffendingValidatorsThreshold = ();
 	type ElectionProvider =
 		frame_election_provider_support::NoElection<(AccountId, BlockNumber, Staking, ())>;

diff --git a/substrate/frame/offences/benchmarking/src/mock.rs b/substrate/frame/offences/benchmarking/src/mock.rs
@@ -176,7 +176,7 @@ impl pallet_staking::Config for Test {
 	type SessionInterface = Self;
 	type EraPayout = pallet_staking::ConvertCurve<RewardCurve>;
 	type NextNewSession = Session;
-	type MaxNominatorRewardedPerValidator = ConstU32<64>;
+	type MaxExposurePageSize = ConstU32<64>;
 	type OffendingValidatorsThreshold = ();
 	type ElectionProvider = onchain::OnChainExecution<OnChainSeqPhragmen>;
 	type GenesisElectionProvider = Self::ElectionProvider;

diff --git a/substrate/frame/root-offences/src/lib.rs b/substrate/frame/root-offences/src/lib.rs
@@ -111,7 +111,7 @@ pub mod pallet {
 				.clone()
 				.into_iter()
 				.map(|(o, _)| OffenceDetails::<T> {
-					offender: (o.clone(), Staking::<T>::eras_stakers(now, o)),
+					offender: (o.clone(), Staking::<T>::eras_stakers(now, &o)),
 					reporters: vec![],
 				})
 				.collect())

diff --git a/substrate/frame/root-offences/src/mock.rs b/substrate/frame/root-offences/src/mock.rs
@@ -179,7 +179,7 @@ impl pallet_staking::Config for Test {
 	type SessionInterface = Self;
 	type EraPayout = pallet_staking::ConvertCurve<RewardCurve>;
 	type NextNewSession = Session;
-	type MaxNominatorRewardedPerValidator = ConstU32<64>;
+	type MaxExposurePageSize = ConstU32<64>;
 	type OffendingValidatorsThreshold = OffendingValidatorsThreshold;
 	type ElectionProvider = onchain::OnChainExecution<OnChainSeqPhragmen>;
 	type GenesisElectionProvider = Self::ElectionProvider;

diff --git a/substrate/frame/session/benchmarking/src/mock.rs b/substrate/frame/session/benchmarking/src/mock.rs
@@ -173,7 +173,7 @@ impl pallet_staking::Config for Test {
 	type SessionInterface = Self;
 	type EraPayout = pallet_staking::ConvertCurve<RewardCurve>;
 	type NextNewSession = Session;
-	type MaxNominatorRewardedPerValidator = ConstU32<64>;
+	type MaxExposurePageSize = ConstU32<64>;
 	type OffendingValidatorsThreshold = ();
 	type ElectionProvider = onchain::OnChainExecution<OnChainSeqPhragmen>;
 	type GenesisElectionProvider = Self::ElectionProvider;

diff --git a/substrate/frame/staking/CHANGELOG.md b/substrate/frame/staking/CHANGELOG.md
@@ -0,0 +1,27 @@
+# Changelog
+
+All notable changes and migrations to pallet-staking will be documented in this file.
+
+The format is loosely based
+on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/). We maintain a
+single integer version number for staking pallet to keep track of all storage
+migrations.
+
+## [v14]
+
+### Added
+
+- New item `ErasStakersPaged` that keeps up to `MaxExposurePageSize`
+  individual nominator exposures by era, validator and page.
+- New item `ErasStakersOverview` complementary to `ErasStakersPaged` which keeps
+  state of own and total stake of the validator across pages.
+- New item `ClaimedRewards` to support paged rewards payout.
+
+### Deprecated
+
+- `ErasStakers` and `ErasStakersClipped` is deprecated, will not be used any longer for the exposures of the new era
+  post v14 and can be removed after 84 eras once all the exposures are stale.
+- Field `claimed_rewards` in item `Ledger` is renamed
+  to `legacy_claimed_rewards` and can be removed after 84 eras.
+
+[v14]: https://github.com/paritytech/substrate/pull/13498