Offences Weight for OnInitialize (#5961)

* Weight accounting for on_offence.

* Try to compute weight.

* Guesstimate upper bounds on db read/writes for slashing

* greater than or equal to

* add new trait

* Update mock.rs

* Add basic weight test

* one more test

* Update frame/staking/src/lib.rs

Co-authored-by: thiolliere <gui.thiolliere@gmail.com>

* Update frame/staking/src/lib.rs

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Add test for offences queue

Co-authored-by: Tomasz Drwięga <tomasz@parity.io>
Co-authored-by: thiolliere <gui.thiolliere@gmail.com>
Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

substrate/frame/offences/src/lib.rs

@@ -28,9 +28,10 @@ mod tests;
 use sp_std::vec::Vec;
 use frame_support::{
 	decl_module, decl_event, decl_storage, Parameter, debug,
+	traits::Get,
 	weights::Weight,
 };
-use sp_runtime::{traits::Hash, Perbill};
+use sp_runtime::{traits::{Hash, Zero}, Perbill};
 use sp_staking::{
 	SessionIndex,
 	offence::{Offence, ReportOffence, Kind, OnOffenceHandler, OffenceDetails, OffenceError},
@@ -58,7 +59,11 @@ pub trait Trait: frame_system::Trait {
 	/// Full identification of the validator.
 	type IdentificationTuple: Parameter + Ord;
 	/// A handler called for every offence report.
-	type OnOffenceHandler: OnOffenceHandler<Self::AccountId, Self::IdentificationTuple>;
+	type OnOffenceHandler: OnOffenceHandler<Self::AccountId, Self::IdentificationTuple, Weight>;
+	/// The a soft limit on maximum weight that may be consumed while dispatching deferred offences in
+	/// `on_initialize`.
+	/// Note it's going to be exceeded before we stop adding to it, so it has to be set conservatively.
+	type WeightSoftLimit: Get<Weight>;
 }
 
 decl_storage! {
@@ -102,23 +107,39 @@ decl_module! {
 
 		fn on_initialize(now: T::BlockNumber) -> Weight {
 			// only decode storage if we can actually submit anything again.
-			if T::OnOffenceHandler::can_report() {
-				<DeferredOffences<T>>::mutate(|deferred| {
-					// keep those that fail to be reported again. An error log is emitted here; this
-					// should not happen if staking's `can_report` is implemented properly.
-					deferred.retain(|(o, p, s)| {
-						T::OnOffenceHandler::on_offence(&o, &p, *s).map_err(|_| {
-							debug::native::error!(
-								target: "pallet-offences",
-								"re-submitting a deferred slash returned Err at {}. This should not happen with pallet-staking",
-								now,
-							);
-						}).is_err()
-					})
-				})
+			if !T::OnOffenceHandler::can_report() {
+				return 0;
 			}
 
-			0
+			let limit = T::WeightSoftLimit::get();
+			let mut consumed = Weight::zero();
+
+			<DeferredOffences<T>>::mutate(|deferred| {
+				deferred.retain(|(offences, perbill, session)| {
+					if consumed >= limit {
+						true
+					} else {
+						// keep those that fail to be reported again. An error log is emitted here; this
+						// should not happen if staking's `can_report` is implemented properly.
+						match T::OnOffenceHandler::on_offence(&offences, &perbill, *session) {
+							Ok(weight) => {
+								consumed += weight;
+								false
+							},
+							Err(_) => {
+								debug::native::error!(
+									target: "pallet-offences",
+									"re-submitting a deferred slash returned Err at {}. This should not happen with pallet-staking",
+									now,
+								);
+								true
+							},
+						}
+					}
+				})
+			});
+
+			consumed
 		}
 	}
 }

substrate/frame/offences/src/mock.rs

@@ -32,7 +32,7 @@ use sp_runtime::traits::{IdentityLookup, BlakeTwo256};
 use sp_core::H256;
 use frame_support::{
 	impl_outer_origin, impl_outer_event, parameter_types, StorageMap, StorageDoubleMap,
-	weights::Weight,
+	weights::{Weight, constants::{WEIGHT_PER_SECOND, RocksDbWeight}},
 };
 use frame_system as system;
 
@@ -45,20 +45,23 @@ pub struct OnOffenceHandler;
 thread_local! {
 	pub static ON_OFFENCE_PERBILL: RefCell<Vec<Perbill>> = RefCell::new(Default::default());
 	pub static CAN_REPORT: RefCell<bool> = RefCell::new(true);
+	pub static OFFENCE_WEIGHT: RefCell<Weight> = RefCell::new(Default::default());
 }
 
-impl<Reporter, Offender> offence::OnOffenceHandler<Reporter, Offender> for OnOffenceHandler {
+impl<Reporter, Offender>
+	offence::OnOffenceHandler<Reporter, Offender, Weight> for OnOffenceHandler
+{
 	fn on_offence(
 		_offenders: &[OffenceDetails<Reporter, Offender>],
 		slash_fraction: &[Perbill],
 		_offence_session: SessionIndex,
-	) -> Result<(), ()> {
-		if <Self as offence::OnOffenceHandler<Reporter, Offender>>::can_report() {
+	) -> Result<Weight, ()> {
+		if <Self as offence::OnOffenceHandler<Reporter, Offender, Weight>>::can_report() {
 			ON_OFFENCE_PERBILL.with(|f| {
 				*f.borrow_mut() = slash_fraction.to_vec();
 			});
 
-			Ok(())
+			Ok(OFFENCE_WEIGHT.with(|w| *w.borrow()))
 		} else {
 			Err(())
 		}
@@ -79,12 +82,16 @@ pub fn with_on_offence_fractions<R, F: FnOnce(&mut Vec<Perbill>) -> R>(f: F) ->
 	})
 }
 
+pub fn set_offence_weight(new: Weight) {
+	OFFENCE_WEIGHT.with(|w| *w.borrow_mut() = new);
+}
+
 // Workaround for https://github.com/rust-lang/rust/issues/26925 . Remove when sorted.
 #[derive(Clone, PartialEq, Eq, Debug)]
 pub struct Runtime;
 parameter_types! {
 	pub const BlockHashCount: u64 = 250;
-	pub const MaximumBlockWeight: Weight = 1024;
+	pub const MaximumBlockWeight: Weight = 2 * WEIGHT_PER_SECOND;
 	pub const MaximumBlockLength: u32 = 2 * 1024;
 	pub const AvailableBlockRatio: Perbill = Perbill::one();
 }
@@ -101,7 +108,7 @@ impl frame_system::Trait for Runtime {
 	type Event = TestEvent;
 	type BlockHashCount = BlockHashCount;
 	type MaximumBlockWeight = MaximumBlockWeight;
-	type DbWeight = ();
+	type DbWeight = RocksDbWeight;
 	type BlockExecutionWeight = ();
 	type ExtrinsicBaseWeight = ();
 	type MaximumExtrinsicWeight = MaximumBlockWeight;
@@ -114,10 +121,15 @@ impl frame_system::Trait for Runtime {
 	type OnKilledAccount = ();
 }
 
+parameter_types! {
+	pub const OffencesWeightSoftLimit: Weight = Perbill::from_percent(60) * MaximumBlockWeight::get();
+}
+
 impl Trait for Runtime {
 	type Event = TestEvent;
 	type IdentificationTuple = u64;
 	type OnOffenceHandler = OnOffenceHandler;
+	type WeightSoftLimit = OffencesWeightSoftLimit;
 }
 
 mod offences {

substrate/frame/offences/src/tests.rs

@@ -22,7 +22,7 @@
 use super::*;
 use crate::mock::{
 	Offences, System, Offence, TestEvent, KIND, new_test_ext, with_on_offence_fractions,
-	offence_reports, set_can_report,
+	offence_reports, set_can_report, set_offence_weight,
 };
 use sp_runtime::Perbill;
 use frame_support::traits::OnInitialize;
@@ -265,3 +265,48 @@ fn should_queue_and_resubmit_rejected_offence() {
 		assert_eq!(Offences::deferred_offences().len(), 0);
 	})
 }
+
+#[test]
+fn weight_soft_limit_is_used() {
+	new_test_ext().execute_with(|| {
+		set_can_report(false);
+		// Only 2 can fit in one block
+		set_offence_weight(<mock::Runtime as Trait>::WeightSoftLimit::get() / 2);
+
+		// Queue 3 offences
+		// #1
+		let offence = Offence {
+			validator_set_count: 5,
+			time_slot: 42,
+			offenders: vec![5],
+		};
+		Offences::report_offence(vec![], offence).unwrap();
+		// #2
+		let offence = Offence {
+			validator_set_count: 5,
+			time_slot: 62,
+			offenders: vec![5],
+		};
+		Offences::report_offence(vec![], offence).unwrap();
+		// #3
+		let offence = Offence {
+			validator_set_count: 5,
+			time_slot: 72,
+			offenders: vec![5],
+		};
+		Offences::report_offence(vec![], offence).unwrap();
+		// 3 are queued
+		assert_eq!(Offences::deferred_offences().len(), 3);
+
+		// Allow reporting
+		set_can_report(true);
+
+		Offences::on_initialize(3);
+		// Two are completed, one is left in the queue
+		assert_eq!(Offences::deferred_offences().len(), 1);
+
+		Offences::on_initialize(4);
+		// All are done now
+		assert_eq!(Offences::deferred_offences().len(), 0);
+	})
+}