Lazy payouts (#4474)

* TODOs

* Remove superfluous:

* partial implementation

* full implementation

* fix preferences

* update comments

* upgrade test WIP

* fix more tests

* fix cutoff

* fix saturation

* comment

* upgrade mock

* upgrade test

* WIP migration

* WIP migration

* remove slot stake stuff

* fix merge

* migration of ledger

* remove equalize from test

* add test

* fix

* update doc

* fix compilation

* improve test readibility

* improve doc

* fix most todo

* fix migration and test

* remove println

* WIP

* add test and spec

* weight

* update doc

* safer end_era

* fix exposure of conversion

* Revert "safer end_era"

This reverts commit 72ff737.

* fix useless put

* exposure clipped

* doc

* fix payout with clipped

* fix node runtime

* add doc

* pluggable and generalized staking module

* remove print

* update doc

* refactor

* improve documentation and implementation

* fix test

* Fix test

* fix test

* fix test

* fix remove lowest stake from exposure, not biggest.

* nomination index arguments in nominator_payout

* add test

* try to fix offence

* apply slashed and bond eras until active era

* doc

* update spec version

* add test upgrade from previous test environment

* Apply suggestions from code review

Co-Authored-By: Shawn Tabrizi <[email protected]>

* nominators upgrade has been cleaned

* dynamic history depth implementation

* make current_era - history_depth included

* Change equality check to start era to less than or equal

* Use era specific validator prefs

* Add print statement and comment about start era if <

* fix next_reward overflow

* make more check for bad era claim for zero cost

* small refactor

* code refactor + fix use of deprecated storage

* fix wasm build

* add comment

* Fix tests

* remove outdated comment

* Apply suggestions from code review

Co-Authored-By: Shawn Tabrizi <[email protected]>

* gather active era information into one storage

Co-authored-by: thiolliere <[email protected]>
Co-authored-by: Shawn Tabrizi <[email protected]>

Author: 3 people

bin/node/cli/src/chain_spec.rs

@@ -247,7 +247,6 @@ pub fn testnet_genesis(
 			}).collect::<Vec<_>>(),
 		}),
 		pallet_staking: Some(StakingConfig {
-			current_era: 0,
 			validator_count: initial_authorities.len() as u32 * 2,
 			minimum_validator_count: initial_authorities.len() as u32,
 			stakers: initial_authorities.iter().map(|x| {

bin/node/runtime/src/lib.rs

@@ -269,6 +269,7 @@ parameter_types! {
 	pub const BondingDuration: pallet_staking::EraIndex = 24 * 28;
 	pub const SlashDeferDuration: pallet_staking::EraIndex = 24 * 7; // 1/4 the bonding duration.
 	pub const RewardCurve: &'static PiecewiseLinear<'static> = &REWARD_CURVE;
+	pub const MaxNominatorRewardedPerValidator: u32 = 64;
 }
 
 impl pallet_staking::Trait for Runtime {
@@ -286,6 +287,7 @@ impl pallet_staking::Trait for Runtime {
 	type SlashCancelOrigin = pallet_collective::EnsureProportionAtLeast<_3, _4, AccountId, CouncilCollective>;
 	type SessionInterface = Self;
 	type RewardCurve = RewardCurve;
+	type MaxNominatorRewardedPerValidator = MaxNominatorRewardedPerValidator;
 }
 
 parameter_types! {

bin/node/testing/src/genesis.rs

@@ -84,7 +84,6 @@ pub fn config_endowed(
 			]
 		}),
 		pallet_staking: Some(StakingConfig {
-			current_era: 0,
 			stakers: vec![
 				(dave(), alice(), 111 * DOLLARS, pallet_staking::StakerStatus::Validator),
 				(eve(), bob(), 100 * DOLLARS, pallet_staking::StakerStatus::Validator),

frame/im-online/src/mock.rs

@@ -49,6 +49,7 @@ impl pallet_session::SessionManager<u64> for TestSessionManager {
 		VALIDATORS.with(|l| l.borrow_mut().take())
 	}
 	fn end_session(_: SessionIndex) {}
+	fn start_session(_: SessionIndex) {}
 }
 
 impl pallet_session::historical::SessionManager<u64, u64> for TestSessionManager {
@@ -62,6 +63,7 @@ impl pallet_session::historical::SessionManager<u64, u64> for TestSessionManager
 		)
 	}
 	fn end_session(_: SessionIndex) {}
+	fn start_session(_: SessionIndex) {}
 }
 
 /// An extrinsic type used for tests.

frame/session/src/historical.rs

@@ -108,6 +108,7 @@ pub trait SessionManager<ValidatorId, FullIdentification>: crate::SessionManager
 	/// If there was a validator set change, its returns the set of new validators along with their
 	/// full identifications.
 	fn new_session(new_index: SessionIndex) -> Option<Vec<(ValidatorId, FullIdentification)>>;
+	fn start_session(start_index: SessionIndex);
 	fn end_session(end_index: SessionIndex);
 }
 
@@ -146,6 +147,9 @@ impl<T: Trait, I> crate::SessionManager<T::ValidatorId> for NoteHistoricalRoot<T
 
 		new_validators
 	}
+	fn start_session(start_index: SessionIndex) {
+		<I as SessionManager<_, _>>::start_session(start_index)
+	}
 	fn end_session(end_index: SessionIndex) {
 		<I as SessionManager<_, _>>::end_session(end_index)
 	}

frame/session/src/lib.rs

@@ -162,10 +162,15 @@ pub trait SessionManager<ValidatorId> {
 	/// Because the session pallet can queue validator set the ending session can be lower than the
 	/// last new session index.
 	fn end_session(end_index: SessionIndex);
+	/// Start the session.
+	///
+	/// The session start to be used for validation
+	fn start_session(start_index: SessionIndex);
 }
 
 impl<A> SessionManager<A> for () {
 	fn new_session(_: SessionIndex) -> Option<Vec<A>> { None }
+	fn start_session(_: SessionIndex) {}
 	fn end_session(_: SessionIndex) {}
 }
 
@@ -423,6 +428,8 @@ decl_storage! {
 
 			<Validators<T>>::put(initial_validators_0);
 			<QueuedKeys<T>>::put(queued_keys);
+
+			T::SessionManager::start_session(0);
 		});
 	}
 }
@@ -520,6 +527,8 @@ impl<T: Trait> Module<T> {
 		// Inform the session handlers that a session is going to end.
 		T::SessionHandler::on_before_session_ending();
 
+		T::SessionManager::end_session(session_index);
+
 		// Get queued session keys and validators.
 		let session_keys = <QueuedKeys<T>>::get();
 		let validators = session_keys.iter()
@@ -532,12 +541,12 @@ impl<T: Trait> Module<T> {
 			DisabledValidators::take();
 		}
 
-		T::SessionManager::end_session(session_index);
-
 		// Increment session index.
 		let session_index = session_index + 1;
 		CurrentIndex::put(session_index);
 
+		T::SessionManager::start_session(session_index);
+
 		// Get next validator set.
 		let maybe_next_validators = T::SessionManager::new_session(session_index + 1);
 		let (next_validators, next_identities_changed)

frame/session/src/mock.rs

@@ -92,6 +92,7 @@ impl SessionHandler<u64> for TestSessionHandler {
 pub struct TestSessionManager;
 impl SessionManager<u64> for TestSessionManager {
 	fn end_session(_: SessionIndex) {}
+	fn start_session(_: SessionIndex) {}
 	fn new_session(_: SessionIndex) -> Option<Vec<u64>> {
 		if !TEST_SESSION_CHANGED.with(|l| *l.borrow()) {
 			VALIDATORS.with(|v| {
@@ -112,6 +113,7 @@ impl SessionManager<u64> for TestSessionManager {
 #[cfg(feature = "historical")]
 impl crate::historical::SessionManager<u64, u64> for TestSessionManager {
 	fn end_session(_: SessionIndex) {}
+	fn start_session(_: SessionIndex) {}
 	fn new_session(new_index: SessionIndex)
 		-> Option<Vec<(u64, u64)>>
 	{