Fix offchain election to respect the weight

.gitignore

@@ -22,3 +22,4 @@ rls*.log
 **/hfuzz_target/
 **/hfuzz_workspace/
 .cargo/
+.cargo-remote.toml

bin/node/runtime/src/lib.rs

@@ -20,10 +20,10 @@
 
 #![cfg_attr(not(feature = "std"), no_std)]
 // `construct_runtime!` does a lot of recursion and requires us to increase the limit to 256.
-#![recursion_limit="256"]
+#![recursion_limit = "256"]
 
-use sp_std::prelude::*;
 
+use sp_std::prelude::*;
 use frame_support::{
 	construct_runtime, parameter_types, debug, RuntimeDebug,
 	weights::{
@@ -441,6 +441,13 @@ parameter_types! {
 	pub const MaxIterations: u32 = 10;
 	// 0.05%. The higher the value, the more strict solution acceptance becomes.
 	pub MinSolutionScoreBump: Perbill = Perbill::from_rational_approximation(5u32, 10_000);
+	// The unsigned solution is mandatory, and this is the absolute maximum weight that we allow for
+	// it.
+	pub OffchainSolutionWeightLimit: Weight =
+		MaximumBlockWeight::get()
+			.saturating_sub(BlockExecutionWeight::get())
+			.saturating_sub(ExtrinsicBaseWeight::get())
+			.saturating_sub(AVERAGE_ON_INITIALIZE_WEIGHT * MaximumBlockWeight::get());
 }
 
 impl pallet_staking::Trait for Runtime {
@@ -469,6 +476,7 @@ impl pallet_staking::Trait for Runtime {
 	type MinSolutionScoreBump = MinSolutionScoreBump;
 	type MaxNominatorRewardedPerValidator = MaxNominatorRewardedPerValidator;
 	type UnsignedPriority = StakingUnsignedPriority;
+	type OffchainSolutionWeightLimit = OffchainSolutionWeightLimit;
 	type WeightInfo = weights::pallet_staking::WeightInfo<Runtime>;
 }
 

frame/babe/src/mock.rs

@@ -218,6 +218,7 @@ impl pallet_staking::Trait for Test {
 	type UnsignedPriority = StakingUnsignedPriority;
 	type MaxIterations = ();
 	type MinSolutionScoreBump = ();
+	type OffchainSolutionWeightLimit = ();
 	type WeightInfo = ();
 }
 

frame/grandpa/src/mock.rs

@@ -233,6 +233,7 @@ impl pallet_staking::Trait for Test {
 	type UnsignedPriority = StakingUnsignedPriority;
 	type MaxIterations = ();
 	type MinSolutionScoreBump = ();
+	type OffchainSolutionWeightLimit = ();
 	type WeightInfo = ();
 }
 

frame/offences/benchmarking/src/mock.rs

@@ -183,6 +183,7 @@ impl pallet_staking::Trait for Test {
 	type UnsignedPriority = ();
 	type MaxIterations = ();
 	type MinSolutionScoreBump = ();
+	type OffchainSolutionWeightLimit = ();
 	type WeightInfo = ();
 }
 

frame/session/benchmarking/src/mock.rs

@@ -190,6 +190,7 @@ impl pallet_staking::Trait for Test {
 	type UnsignedPriority = UnsignedPriority;
 	type MaxIterations = ();
 	type MinSolutionScoreBump = ();
+	type OffchainSolutionWeightLimit = ();
 	type WeightInfo = ();
 }
 

frame/staking/fuzzer/src/mock.rs

@@ -195,5 +195,6 @@ impl pallet_staking::Trait for Test {
 	type MinSolutionScoreBump = ();
 	type MaxNominatorRewardedPerValidator = MaxNominatorRewardedPerValidator;
 	type UnsignedPriority = ();
+	type OffchainSolutionWeightLimit = ();
 	type WeightInfo = ();
 }

frame/staking/src/benchmarking.rs

@@ -494,7 +494,7 @@ benchmarks! {
 			compact,
 			score,
 			size
-		) = offchain_election::prepare_submission::<T>(assignments, winners, false).unwrap();
+		) = offchain_election::prepare_submission::<T>(assignments, winners, false, T::MaximumBlockWeight::get()).unwrap();
 
 		assert_eq!(
 			winners.len(), compact.unique_targets().len(),
@@ -562,7 +562,7 @@ benchmarks! {
 			compact,
 			score,
 			size
-		) = offchain_election::prepare_submission::<T>(assignments, winners, false).unwrap();
+		) = offchain_election::prepare_submission::<T>(assignments, winners, false, T::MaximumBlockWeight::get()).unwrap();
 
 		assert_eq!(
 			winners.len(), compact.unique_targets().len(),

frame/staking/src/lib.rs

@@ -695,7 +695,7 @@ pub enum ElectionStatus<BlockNumber> {
 /// Note that these values must reflect the __total__ number, not only those that are present in the
 /// solution. In short, these should be the same size as the size of the values dumped in
 /// `SnapshotValidators` and `SnapshotNominators`.
-#[derive(PartialEq, Eq, Clone, Encode, Decode, RuntimeDebug, Default)]
+#[derive(PartialEq, Eq, Clone, Copy, Encode, Decode, RuntimeDebug, Default)]
 pub struct ElectionSize {
 	/// Number of validators in the snapshot of the current election round.
 	#[codec(compact)]
@@ -883,6 +883,13 @@ pub trait Trait: frame_system::Trait + SendTransactionTypes<Call<Self>> {
 	/// multiple pallets send unsigned transactions.
 	type UnsignedPriority: Get<TransactionPriority>;
 
+	/// Maximum weight that the unsigned transaction can have.
+	///
+	/// Chose this value with care. On one hand, it should be as high as possible, so the solution
+	/// can contain as many nominators/validators as possible. On the other hand, it should be small
+	/// enough to fit in the block.
+	type OffchainSolutionWeightLimit: Get<Weight>;
+
 	/// Weight information for extrinsics in this pallet.
 	type WeightInfo: WeightInfo;
 }
@@ -1232,6 +1239,8 @@ decl_error! {
 		OffchainElectionBogusScore,
 		/// The election size is invalid.
 		OffchainElectionBogusElectionSize,
+		/// The election weight is invalid.
+		OffchainElectionBogusElectionWeight,
 		/// The call is not allowed at the given time due to restrictions of election period.
 		CallNotAllowed,
 		/// Incorrect previous history depth input provided.
@@ -1339,12 +1348,12 @@ decl_module! {
 			if Self::era_election_status().is_open_at(now) {
 				let offchain_status = set_check_offchain_execution_status::<T>(now);
 				if let Err(why) = offchain_status {
-					log!(debug, "skipping offchain worker in open election window due to [{}]", why);
+					log!(warn, "💸 skipping offchain worker in open election window due to [{}]", why);
 				} else {
 					if let Err(e) = compute_offchain_election::<T>() {
 						log!(error, "💸 Error in election offchain worker: {:?}", e);
 					} else {
-						log!(debug, "Executed offchain worker thread without errors.");
+						log!(debug, "💸 Executed offchain worker thread without errors.");
 					}
 				}
 			}
@@ -2141,14 +2150,15 @@ decl_module! {
 		/// transaction in the block.
 		///
 		/// # <weight>
-		/// See `crate::weight` module.
+		/// The weight of this call is not enforced by the system module and is enforced in this
+		/// module directly.
 		/// # </weight>
-		#[weight = T::WeightInfo::submit_solution_better(
+		#[weight = (T::WeightInfo::submit_solution_better(
 			size.validators.into(),
 			size.nominators.into(),
 			compact.len() as u32,
 			winners.len() as u32,
-		)]
+		), frame_support::weights::DispatchClass::Mandatory)]
 		pub fn submit_election_solution_unsigned(
 			origin,
 			winners: Vec<ValidatorIndex>,
@@ -2158,6 +2168,13 @@ decl_module! {
 			size: ElectionSize,
 		) -> DispatchResultWithPostInfo {
 			ensure_none(origin)?;
+			// The signed solution is `Normal` and the system module checks the weight. But for this
+			// mandatory one, we need to do it.
+			ensure!(
+				Self::check_unsigned_solution_weight(&winners, &compact, &size),
+				Error::<T>::OffchainElectionBogusElectionWeight.with_weight(0),
+			);
+
 			let adjustments = Self::check_and_replace_solution(
 				winners,
 				compact,
@@ -2171,6 +2188,7 @@ decl_module! {
 				effectively depriving the validators from their authoring reward. Hence, this panic
 				is expected."
 			);
+
 			Ok(adjustments)
 		}
 	}
@@ -2190,6 +2208,21 @@ impl<T: Trait> Module<T> {
 		)
 	}
 
+	/// Check the weight of an unsigned solution. Returns true of the weight is below the designated
+	/// limit .
+	pub fn check_unsigned_solution_weight(
+		winners: &Vec<ValidatorIndex>,
+		compact: &CompactAssignments,
+		size: &ElectionSize,
+	) -> bool {
+		T::WeightInfo::submit_solution_better(
+			size.validators.into(),
+			size.nominators.into(),
+			compact.len() as u32,
+			winners.len() as u32,
+		) <= T::OffchainSolutionWeightLimit::get()
+	}
+
 	/// Dump the list of validators and nominators into vectors and keep them on-chain.
 	///
 	/// This data is used to efficiently evaluate election results. returns `true` if the operation
@@ -3082,7 +3115,6 @@ impl<T: Trait> Module<T> {
 	pub fn set_slash_reward_fraction(fraction: Perbill) {
 		SlashRewardFraction::put(fraction);
 	}
-
 }
 
 /// In this implementation `new_session(session)` must be called before `end_session(session-1)`
@@ -3346,11 +3378,11 @@ impl<T: Trait> frame_support::unsigned::ValidateUnsigned for Module<T> {
 	type Call = Call<T>;
 	fn validate_unsigned(source: TransactionSource, call: &Self::Call) -> TransactionValidity {
 		if let Call::submit_election_solution_unsigned(
-			_,
-			_,
+			winners,
+			compact,
 			score,
 			era,
-			_,
+			size,
 		) = call {
 			use offchain_election::DEFAULT_LONGEVITY;
 
@@ -3363,17 +3395,22 @@ impl<T: Trait> frame_support::unsigned::ValidateUnsigned for Module<T> {
 				}
 			}
 
+			// discard solution if it is too big.
+			if !Self::check_unsigned_solution_weight(winners, compact, size) {
+				return Err(InvalidTransaction::ExhaustsResources.into())
+			}
+
 			if let Err(error_with_post_info) = Self::pre_dispatch_checks(*score, *era) {
 				let invalid = to_invalid(error_with_post_info);
 				log!(
 					debug,
-					"validate unsigned pre dispatch checks failed due to error #{:?}.",
+					"💸 validate unsigned pre dispatch checks failed due to error #{:?}.",
 					invalid,
 				);
-				return invalid .into();
+				return invalid.into();
 			}
 
-			log!(debug, "validateUnsigned succeeded for a solution at era {}.", era);
+			log!(debug, "💸 validateUnsigned succeeded for a solution at era {}.", era);
 
 			ValidTransaction::with_tag_prefix("StakingOffchain")
 				// The higher the score[0], the better a solution is.

frame/staking/src/mock.rs

@@ -17,24 +17,29 @@
 
 //! Test utilities
 
-use std::{collections::HashSet, cell::RefCell};
-use sp_runtime::Perbill;
-use sp_runtime::curve::PiecewiseLinear;
-use sp_runtime::traits::{IdentityLookup, Convert, SaturatedConversion, Zero};
-use sp_runtime::testing::{Header, UintAuthorityId, TestXt};
-use sp_staking::{SessionIndex, offence::{OffenceDetails, OnOffenceHandler}};
-use sp_core::H256;
+use crate::*;
 use frame_support::{
-	assert_ok, impl_outer_origin, parameter_types, impl_outer_dispatch, impl_outer_event,
-	StorageValue, StorageMap, StorageDoubleMap, IterableStorageMap,
-	traits::{Currency, Get, FindAuthor, OnFinalize, OnInitialize},
-	weights::{Weight, constants::RocksDbWeight},
+	assert_ok, impl_outer_dispatch, impl_outer_event, impl_outer_origin, parameter_types,
+	traits::{Currency, FindAuthor, Get, OnFinalize, OnInitialize},
+	weights::{constants::RocksDbWeight, Weight},
+	IterableStorageMap, StorageDoubleMap, StorageMap, StorageValue,
 };
+use sp_core::H256;
 use sp_io;
 use sp_npos_elections::{
-	build_support_map, evaluate_support, reduce, ExtendedBalance, StakedAssignment, ElectionScore,
+	build_support_map, evaluate_support, reduce, ElectionScore, ExtendedBalance, StakedAssignment,
 };
-use crate::*;
+use sp_runtime::{
+	curve::PiecewiseLinear,
+	testing::{Header, TestXt, UintAuthorityId},
+	traits::{Convert, IdentityLookup, SaturatedConversion, Zero},
+	Perbill,
+};
+use sp_staking::{
+	offence::{OffenceDetails, OnOffenceHandler},
+	SessionIndex,
+};
+use std::{cell::RefCell, collections::HashSet};
 
 pub const INIT_TIMESTAMP: u64 = 30_000;
 
@@ -194,7 +199,7 @@ pub struct Test;
 
 parameter_types! {
 	pub const BlockHashCount: u64 = 250;
-	pub const MaximumBlockWeight: Weight = 1024;
+	pub const MaximumBlockWeight: Weight = frame_support::weights::constants::WEIGHT_PER_SECOND * 2;
 	pub const MaximumBlockLength: u32 = 2 * 1024;
 	pub const AvailableBlockRatio: Perbill = Perbill::one();
 	pub const MaxLocks: u32 = 1024;
@@ -293,6 +298,7 @@ parameter_types! {
 	pub const MaxNominatorRewardedPerValidator: u32 = 64;
 	pub const UnsignedPriority: u64 = 1 << 20;
 	pub const MinSolutionScoreBump: Perbill = Perbill::zero();
+	pub const OffchainSolutionWeightLimit: Weight = MaximumBlockWeight::get();
 }
 
 thread_local! {
@@ -331,10 +337,12 @@ impl Trait for Test {
 	type MinSolutionScoreBump = MinSolutionScoreBump;
 	type MaxNominatorRewardedPerValidator = MaxNominatorRewardedPerValidator;
 	type UnsignedPriority = UnsignedPriority;
+	type OffchainSolutionWeightLimit = OffchainSolutionWeightLimit;
 	type WeightInfo = ();
 }
 
-impl<LocalCall> frame_system::offchain::SendTransactionTypes<LocalCall> for Test where
+impl<LocalCall> frame_system::offchain::SendTransactionTypes<LocalCall> for Test
+where
 	Call: From<LocalCall>,
 {
 	type OverarchingCall = Call;