Enable Offchain Equalise (#5683)

* Master.into() * Remove debug stuff * Better license * Migrate away from SimpleDispatchInfo * Fix test * Revert "Migrate away from SimpleDispatchInfo" This reverts commit dbdd27fa19948f16bd17defdc01d3dd32986df11. * Move to offchain randomness * Fix tests * Fix tests more
2026-06-09 20:11:09 +00:00 · 2020-04-27 18:51:46 +02:00
parent 33d00692d8
commit ee54eff488
20 changed files with 635 additions and 373 deletions
@@ -4547,6 +4547,27 @@ dependencies = [
 "substrate-test-utils",
 ]

+[[package]]
+name = "pallet-staking-fuzz"
+version = "0.0.0"
+dependencies = [
+ "frame-support",
+ "frame-system",
+ "honggfuzz",
+ "pallet-balances",
+ "pallet-indices",
+ "pallet-session",
+ "pallet-staking",
+ "pallet-staking-reward-curve",
+ "pallet-timestamp",
+ "parity-scale-codec",
+ "sp-core",
+ "sp-io",
+ "sp-phragmen",
+ "sp-runtime",
+ "sp-std",
+]
+
 [[package]]
 name = "pallet-staking-reward-curve"
 version = "2.0.0-dev"
@@ -95,6 +95,7 @@ members = [
 	"frame/society",
 	"frame/staking",
 	"frame/staking/reward-curve",
+	"frame/staking/fuzzer",
 	"frame/sudo",
 	"frame/support",
 	"frame/support/procedural",
@@ -300,8 +300,9 @@ 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 ElectionLookahead: BlockNumber = 25; // 10 minutes per session => 100 block.
+	pub const ElectionLookahead: BlockNumber = EPOCH_DURATION_IN_BLOCKS / 4;
 	pub const MaxNominatorRewardedPerValidator: u32 = 64;
+	pub const MaxIterations: u32 = 5;
 }

 impl pallet_staking::Trait for Runtime {
@@ -322,6 +323,7 @@ impl pallet_staking::Trait for Runtime {
 	type NextNewSession = Session;
 	type ElectionLookahead = ElectionLookahead;
 	type Call = Call;
+	type MaxIterations = MaxIterations;
 	type MaxNominatorRewardedPerValidator = MaxNominatorRewardedPerValidator;
 	type UnsignedPriority = StakingUnsignedPriority;
 }
@@ -180,6 +180,7 @@ impl pallet_staking::Trait for Test {
 	type Call = Call;
 	type MaxNominatorRewardedPerValidator = MaxNominatorRewardedPerValidator;
 	type UnsignedPriority = UnsignedPriority;
+	type MaxIterations = ();
 }

 impl crate::Trait for Test {}
@@ -1,4 +0,0 @@
-
-target
-corpus
-artifacts
@@ -1,38 +0,0 @@
-[package]
-name = "pallet-staking-fuzz"
-version = "0.0.0"
-authors = ["Automatically generated"]
-publish = false
-edition = "2018"
-
-[package.metadata]
-cargo-fuzz = true
-
-[dependencies]
-libfuzzer-sys = "0.3"
-codec = { package = "parity-scale-codec", version = "1.3.0", default-features = false, features = ["derive"] }
-pallet-staking = { version = "2.0.0-alpha.2", path = "..", features = ["testing-utils"] }
-pallet-staking-reward-curve = { version = "2.0.0-alpha.2",  path = "../reward-curve" }
-pallet-session = { version = "2.0.0-alpha.2", path = "../../session" }
-pallet-indices = { version = "2.0.0-alpha.2", path = "../../indices" }
-pallet-balances = { version = "2.0.0-alpha.2", path = "../../balances" }
-pallet-timestamp = { version = "2.0.0-alpha.2", path = "../../timestamp" }
-frame-system = { version = "2.0.0-alpha.2", path = "../../system" }
-frame-support = { version = "2.0.0-alpha.2", path = "../../support" }
-sp-std = { version = "2.0.0-alpha.2", path = "../../../primitives/std" }
-sp-io ={ version = "2.0.0-alpha.2", path = "../../../primitives/io" }
-sp-core = { version = "2.0.0-alpha.2", path = "../../../primitives/core" }
-sp-phragmen = { version = "2.0.0-alpha.2", path = "../../../primitives/phragmen" }
-sp-runtime = { version = "2.0.0-alpha.2", path = "../../../primitives/runtime" }
-rand = "0.7.3"
-
-# Prevent this from interfering with workspaces
-[workspace]
-members = ["."]
-
-[[bin]]
-name = "submit_solution"
-path = "fuzz_targets/submit_solution.rs"
-
-[package.metadata.docs.rs]
-targets = ["x86_64-unknown-linux-gnu"]
@@ -1,130 +0,0 @@
-// Copyright 2020 Parity Technologies (UK) Ltd.
-// This file is part of Substrate.
-
-// Substrate is free software: you can redistribute it and/or modify
-// it under the terms of the GNU General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-
-// Substrate is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-// GNU General Public License for more details.
-
-// You should have received a copy of the GNU General Public License
-// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
-
-//! Fuzzing for staking pallet.
-
-#![no_main]
-use libfuzzer_sys::fuzz_target;
-use mock::Test;
-use pallet_staking::testing_utils::{
-	self, USER, get_seq_phragmen_solution, get_weak_solution, setup_chain_stakers,
-	set_validator_count, signed_account,
-};
-use frame_support::assert_ok;
-use sp_runtime::{traits::Dispatchable, DispatchError};
-
-mod mock;
-
-#[repr(u32)]
-#[allow(dead_code)]
-#[derive(Debug, Clone, Copy)]
-enum Mode {
-	/// Initial submission. This will be rather cheap.
-	InitialSubmission,
-	/// A better submission that will replace the previous ones. This is the most expensive.
-	StrongerSubmission,
-	/// A weak submission that will be rejected. This will be rather cheap.
-	WeakerSubmission,
-}
-
-pub fn new_test_ext() -> Result<sp_io::TestExternalities, std::string::String> {
-	frame_system::GenesisConfig::default().build_storage::<mock::Test>().map(Into::into)
-}
-
-fuzz_target!(|do_reduce: bool| {
-    let ext = new_test_ext();
-	let mode: Mode = unsafe { std::mem::transmute(testing_utils::random(0, 2)) };
-	let num_validators = testing_utils::random(50, 500);
-	let num_nominators = testing_utils::random(200, 2000);
-	let edge_per_voter = testing_utils::random(1, 16);
-	let to_elect = testing_utils::random(10, num_validators);
-
-	println!("+++ instance with params {} / {} / {} / {:?} / {}",
-		num_nominators,
-		num_validators,
-		edge_per_voter,
-		mode,
-		to_elect,
-	);
-
-	ext.unwrap_or_default().execute_with(|| {
-		// initial setup
-		set_validator_count::<Test>(to_elect);
-		setup_chain_stakers::<Test>(
-			num_validators,
-			num_nominators,
-			edge_per_voter,
-		);
-
-		println!("++ Chain setup done.");
-
-		// stuff to submit
-		let (winners, compact, score) = match mode {
-			Mode::InitialSubmission => {
-				/* No need to setup anything */
-				get_seq_phragmen_solution::<Test>(do_reduce)
-			},
-			Mode::StrongerSubmission => {
-				let (winners, compact, score) = get_weak_solution::<Test>(false);
-				assert_ok!(
-					<pallet_staking::Module<Test>>::submit_election_solution(
-						signed_account::<Test>(USER),
-						winners,
-						compact,
-						score,
-					)
-				);
-				get_seq_phragmen_solution::<Test>(do_reduce)
-			},
-			Mode::WeakerSubmission => {
-				let (winners, compact, score) = get_seq_phragmen_solution::<Test>(do_reduce);
-				assert_ok!(
-					<pallet_staking::Module<Test>>::submit_election_solution(
-						signed_account::<Test>(USER),
-						winners,
-						compact,
-						score,
-					)
-				);
-				get_weak_solution::<Test>(false)
-			}
-		};
-
-		println!("++ Submission ready.");
-
-		// must have chosen correct number of winners.
-		assert_eq!(winners.len() as u32, <pallet_staking::Module<Test>>::validator_count());
-
-		// final call and origin
-		let call = pallet_staking::Call::<Test>::submit_election_solution(
-			winners,
-			compact,
-			score,
-		);
-		let caller = signed_account::<Test>(USER);
-
-		// actually submit
-		match mode {
-			Mode::WeakerSubmission => {
-				assert_eq!(
-					call.dispatch(caller.into()).unwrap_err(),
-					DispatchError::Module { index: 0, error: 11, message: Some("PhragmenWeakSubmission") },
-				);
-			},
-			_ => assert_ok!(call.dispatch(caller.into())),
-		};
-	})
-});
@@ -0,0 +1,2 @@
+hfuzz_target
+hfuzz_workspace
@@ -0,0 +1,34 @@
+[package]
+name = "pallet-staking-fuzz"
+version = "0.0.0"
+authors = ["Automatically generated"]
+publish = false
+edition = "2018"
+license = "GPL-3.0"
+homepage = "https://substrate.dev"
+repository = "https://github.com/paritytech/substrate/"
+description = "FRAME pallet staking fuzzing"
+
+[dependencies]
+honggfuzz = "0.5"
+codec = { package = "parity-scale-codec", version = "1.3.0", default-features = false, features = ["derive"] }
+pallet-staking = { version = "2.0.0-alpha.5", path = "..", features = ["testing-utils"] }
+pallet-staking-reward-curve = { version = "2.0.0-alpha.5",  path = "../reward-curve" }
+pallet-session = { version = "2.0.0-alpha.5", path = "../../session" }
+pallet-indices = { version = "2.0.0-alpha.5", path = "../../indices" }
+pallet-balances = { version = "2.0.0-alpha.5", path = "../../balances" }
+pallet-timestamp = { version = "2.0.0-alpha.5", path = "../../timestamp" }
+frame-system = { version = "2.0.0-alpha.5", path = "../../system" }
+frame-support = { version = "2.0.0-alpha.5", path = "../../support" }
+sp-std = { version = "2.0.0-alpha.5", path = "../../../primitives/std" }
+sp-io ={ version = "2.0.0-alpha.5", path = "../../../primitives/io" }
+sp-core = { version = "2.0.0-alpha.5", path = "../../../primitives/core" }
+sp-phragmen = { version = "2.0.0-alpha.5", path = "../../../primitives/phragmen" }
+sp-runtime = { version = "2.0.0-alpha.5", path = "../../../primitives/runtime" }
+
+[[bin]]
+name = "submit_solution"
+path = "src/submit_solution.rs"
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
@@ -24,11 +24,11 @@ type AccountIndex = u32;
 type BlockNumber = u64;
 type Balance = u64;

-type System = frame_system::Module<Test>;
-type Balances = pallet_balances::Module<Test>;
-type Staking = pallet_staking::Module<Test>;
-type Indices = pallet_indices::Module<Test>;
-type Session = pallet_session::Module<Test>;
+pub type System = frame_system::Module<Test>;
+pub type Balances = pallet_balances::Module<Test>;
+pub type Staking = pallet_staking::Module<Test>;
+pub type Indices = pallet_indices::Module<Test>;
+pub type Session = pallet_session::Module<Test>;

 impl_outer_origin! {
 	pub enum Origin for Test  where system = frame_system {}
@@ -57,6 +57,9 @@ pub struct Test;

 impl frame_system::Trait for Test {
 	type Origin = Origin;
+	type DbWeight = ();
+	type BlockExecutionWeight = ();
+	type ExtrinsicBaseWeight = ();
 	type Index = AccountIndex;
 	type BlockNumber = BlockNumber;
 	type Call = Call;
@@ -150,18 +153,21 @@ pallet_staking_reward_curve::build! {
 parameter_types! {
 	pub const RewardCurve: &'static sp_runtime::curve::PiecewiseLinear<'static> = &I_NPOS;
 	pub const MaxNominatorRewardedPerValidator: u32 = 64;
+	pub const MaxIterations: u32 = 20;
 }

 pub type Extrinsic = sp_runtime::testing::TestXt<Call, ()>;
-type SubmitTransaction = frame_system::offchain::TransactionSubmitter<
-	sp_runtime::testing::UintAuthorityId,
-	Test,
-	Extrinsic,
->;
+
+impl<C> frame_system::offchain::SendTransactionTypes<C> for Test where
+	Call: From<C>,
+{
+	type OverarchingCall = Call;
+	type Extrinsic = Extrinsic;
+}

 impl pallet_staking::Trait for Test {
 	type Currency = Balances;
-	type Time = pallet_timestamp::Module<Self>;
+	type UnixTime = pallet_timestamp::Module<Self>;
 	type CurrencyToVote = CurrencyToVoteHandler;
 	type RewardRemainder = ();
 	type Event = ();
@@ -176,7 +182,7 @@ impl pallet_staking::Trait for Test {
 	type NextNewSession = Session;
 	type ElectionLookahead = ();
 	type Call = Call;
-	type SubmitTransaction = SubmitTransaction;
-	type KeyType = sp_runtime::testing::UintAuthorityId;
+	type MaxIterations = MaxIterations;
 	type MaxNominatorRewardedPerValidator = MaxNominatorRewardedPerValidator;
+	type UnsignedPriority = ();
 }
@@ -0,0 +1,152 @@
+// Copyright 2020 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Fuzzing for staking pallet.
+
+use honggfuzz::fuzz;
+
+use mock::Test;
+use pallet_staking::testing_utils::{
+	USER, get_seq_phragmen_solution, get_weak_solution, setup_chain_stakers,
+	set_validator_count, signed_account,
+};
+use frame_support::assert_ok;
+use sp_runtime::{traits::Dispatchable, DispatchError};
+
+mod mock;
+
+#[repr(u32)]
+#[allow(dead_code)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum Mode {
+	/// Initial submission. This will be rather cheap.
+	InitialSubmission,
+	/// A better submission that will replace the previous ones. This is the most expensive.
+	StrongerSubmission,
+	/// A weak submission that will be rejected. This will be rather cheap.
+	WeakerSubmission,
+}
+
+pub fn new_test_ext() -> Result<sp_io::TestExternalities, std::string::String> {
+	frame_system::GenesisConfig::default().build_storage::<mock::Test>().map(Into::into)
+}
+
+fn main() {
+	let to_range = |x: u32, a: u32, b: u32| {
+		let collapsed = x % b;
+		if collapsed >= a {
+			collapsed
+		} else {
+			collapsed + a
+		}
+	};
+	loop {
+		fuzz!(|data: (u32, u32, u32, u32, u32)| {
+			let (mut num_validators, mut num_nominators, mut edge_per_voter, mut to_elect, mode_u32) = data;
+			let ext = new_test_ext();
+			let mode: Mode = unsafe { std::mem::transmute(mode_u32) };
+			num_validators = to_range(num_validators, 50, 1000);
+			num_nominators = to_range(num_nominators, 50, 2000);
+			edge_per_voter = to_range(edge_per_voter, 1, 16);
+			to_elect = to_range(to_elect, 20, num_validators);
+			let do_reduce = true;
+
+			println!("+++ instance with params {} / {} / {} / {:?}({}) / {}",
+				num_nominators,
+				num_validators,
+				edge_per_voter,
+				mode,
+				mode_u32,
+				to_elect,
+			);
+
+			ext.unwrap_or_default().execute_with(|| {
+				// initial setup
+				set_validator_count::<Test>(to_elect);
+				pallet_staking::testing_utils::init_active_era();
+				setup_chain_stakers::<Test>(
+					num_validators,
+					num_nominators,
+					edge_per_voter,
+				);
+
+				println!("++ Chain setup done.");
+
+				// stuff to submit
+				let (winners, compact, score) = match mode {
+					Mode::InitialSubmission => {
+						/* No need to setup anything */
+						get_seq_phragmen_solution::<Test>(do_reduce)
+					},
+					Mode::StrongerSubmission => {
+						let (winners, compact, score) = get_weak_solution::<Test>(false);
+						println!("Weak on chain score = {:?}", score);
+						assert_ok!(
+							<pallet_staking::Module<Test>>::submit_election_solution(
+								signed_account::<Test>(USER),
+								winners,
+								compact,
+								score,
+								pallet_staking::testing_utils::active_era::<Test>(),
+							)
+						);
+						get_seq_phragmen_solution::<Test>(do_reduce)
+					},
+					Mode::WeakerSubmission => {
+						let (winners, compact, score) = get_seq_phragmen_solution::<Test>(do_reduce);
+						println!("Strong on chain score = {:?}", score);
+						assert_ok!(
+							<pallet_staking::Module<Test>>::submit_election_solution(
+								signed_account::<Test>(USER),
+								winners,
+								compact,
+								score,
+								pallet_staking::testing_utils::active_era::<Test>(),
+							)
+						);
+						get_weak_solution::<Test>(false)
+					}
+				};
+
+				println!("++ Submission ready. Score = {:?}", score);
+
+				// must have chosen correct number of winners.
+				assert_eq!(winners.len() as u32, <pallet_staking::Module<Test>>::validator_count());
+
+				// final call and origin
+				let call = pallet_staking::Call::<Test>::submit_election_solution(
+					winners,
+					compact,
+					score,
+					pallet_staking::testing_utils::active_era::<Test>(),
+				);
+				let caller = signed_account::<Test>(USER);
+
+				// actually submit
+				match mode {
+					Mode::WeakerSubmission => {
+						assert_eq!(
+							call.dispatch(caller.into()).unwrap_err().error,
+							DispatchError::Module { index: 0, error: 15, message: Some("PhragmenWeakSubmission") },
+						);
+					},
+					// NOTE: so exhaustive pattern doesn't work here.. maybe some rust issue? or due to `#[repr(u32)]`?
+					Mode::InitialSubmission | Mode::StrongerSubmission => assert!(call.dispatch(caller.into()).is_ok()),
+				};
+			})
+		});
+	}
+}
@@ -370,7 +370,7 @@ generate_compact_solution_type!(pub GenericCompactAssignments, 16);
 #[derive(Encode, Decode, RuntimeDebug)]
 pub struct ActiveEraInfo {
 	/// Index of era.
-	index: EraIndex,
+	pub index: EraIndex,
 	/// Moment of start expresed as millisecond from `$UNIX_EPOCH`.
 	///
 	/// Start can be none if start hasn't been set for the era yet,
@@ -803,6 +803,10 @@ pub trait Trait: frame_system::Trait + SendTransactionTypes<Call<Self>> {
 	/// The overarching call type.
 	type Call: Dispatchable + From<Call<Self>> + IsSubType<Module<Self>, Self> + Clone;

+	/// Maximum number of equalise iterations to run in the offchain submission. If set to 0,
+	/// equalize will not be executed at all.
+	type MaxIterations: Get<u32>;
+
 	/// The maximum number of nominator rewarded for each validator.
 	///
 	/// For each validator only the `$MaxNominatorRewardedPerValidator` biggest stakers can claim
@@ -64,6 +64,7 @@ thread_local! {
 	static SLASH_DEFER_DURATION: RefCell<EraIndex> = RefCell::new(0);
 	static ELECTION_LOOKAHEAD: RefCell<BlockNumber> = RefCell::new(0);
 	static PERIOD: RefCell<BlockNumber> = RefCell::new(1);
+	static MAX_ITERATIONS: RefCell<u32> = RefCell::new(0);
 }

 /// Another session handler struct to test on_disabled.
@@ -143,6 +144,13 @@ impl Get<EraIndex> for SlashDeferDuration {
 	}
 }

+pub struct MaxIterations;
+impl Get<u32> for MaxIterations {
+	fn get() -> u32 {
+		MAX_ITERATIONS.with(|v| *v.borrow())
+	}
+}
+
 impl_outer_origin! {
 	pub enum Origin for Test  where system = frame_system {}
 }
@@ -310,6 +318,7 @@ impl Trait for Test {
 	type NextNewSession = Session;
 	type ElectionLookahead = ElectionLookahead;
 	type Call = Call;
+	type MaxIterations = MaxIterations;
 	type MaxNominatorRewardedPerValidator = MaxNominatorRewardedPerValidator;
 	type UnsignedPriority = UnsignedPriority;
 }
@@ -337,6 +346,7 @@ pub struct ExtBuilder {
 	num_validators: Option<u32>,
 	invulnerables: Vec<AccountId>,
 	has_stakers: bool,
+	max_offchain_iterations: u32,
 }

 impl Default for ExtBuilder {
@@ -355,6 +365,7 @@ impl Default for ExtBuilder {
 			num_validators: None,
 			invulnerables: vec![],
 			has_stakers: true,
+			max_offchain_iterations: 0,
 		}
 	}
 }
@@ -412,6 +423,10 @@ impl ExtBuilder {
 		self.has_stakers = has;
 		self
 	}
+	pub fn max_offchain_iterations(mut self, iterations: u32) -> Self {
+		self.max_offchain_iterations = iterations;
+		self
+	}
 	pub fn offchain_phragmen_ext(self) -> Self {
 		self.session_per_era(4)
 			.session_length(5)
@@ -423,6 +438,7 @@ impl ExtBuilder {
 		SESSION_PER_ERA.with(|v| *v.borrow_mut() = self.session_per_era);
 		ELECTION_LOOKAHEAD.with(|v| *v.borrow_mut() = self.election_lookahead);
 		PERIOD.with(|v| *v.borrow_mut() = self.session_length);
+		MAX_ITERATIONS.with(|v| *v.borrow_mut() = self.max_offchain_iterations);
 	}
 	pub fn build(self) -> sp_io::TestExternalities {
 		let _ = env_logger::try_init();
@@ -16,17 +16,18 @@

 //! Helpers for offchain worker election.

+use codec::Decode;
 use crate::{
 	Call, CompactAssignments, Module, NominatorIndex, OffchainAccuracy, Trait, ValidatorIndex,
 };
 use frame_system::offchain::SubmitTransaction;
 use sp_phragmen::{
 	build_support_map, evaluate_support, reduce, Assignment, ExtendedBalance, PhragmenResult,
-	PhragmenScore,
+	PhragmenScore, equalize,
 };
 use sp_runtime::offchain::storage::StorageValueRef;
-use sp_runtime::PerThing;
-use sp_runtime::RuntimeDebug;
+use sp_runtime::{PerThing, RuntimeDebug, traits::{TrailingZeroInput, Zero}};
+use frame_support::{debug, traits::Get};
 use sp_std::{convert::TryInto, prelude::*};

 /// Error types related to the offchain election machinery.
@@ -159,10 +160,7 @@ pub fn prepare_submission<T: Trait>(
 	};

 	// Clean winners.
-	let winners = winners
-		.into_iter()
-		.map(|(w, _)| w)
-		.collect::<Vec<T::AccountId>>();
+	let winners = sp_phragmen::to_without_backing(winners);

 	// convert into absolute value and to obtain the reduced version.
 	let mut staked = sp_phragmen::assignment_ratio_to_staked(
@@ -170,10 +168,33 @@ pub fn prepare_submission<T: Trait>(
 		<Module<T>>::slashable_balance_of_vote_weight,
 	);

+	// reduce
 	if do_reduce {
 		reduce(&mut staked);
 	}

+	let (mut support_map, _) = build_support_map::<T::AccountId>(&winners, &staked);
+
+	// equalize a random number of times.
+	let iterations_executed = match T::MaxIterations::get() {
+		0 => {
+			// Don't run equalize at all
+			0
+		}
+		iterations @ _ => {
+			let seed = sp_io::offchain::random_seed();
+			let iterations = <u32>::decode(&mut TrailingZeroInput::new(seed.as_ref()))
+				.expect("input is padded with zeroes; qed") % iterations.saturating_add(1);
+			equalize(
+				&mut staked,
+				&mut support_map,
+				Zero::zero(),
+				iterations as usize,
+			)
+		}
+	};
+
+
 	// Convert back to ratio assignment. This takes less space.
 	let low_accuracy_assignment = sp_phragmen::assignment_staked_to_ratio(staked);

@@ -215,5 +236,12 @@ pub fn prepare_submission<T: Trait>(
 		}
 	}

+	debug::native::debug!(
+		target: "staking",
+		"prepared solution after {} equalization iterations with score {:?}",
+		iterations_executed,
+		score,
+	);
+
 	Ok((winners_indexed, compact, score))
 }
@@ -153,13 +153,13 @@ pub fn get_weak_solution<T: Trait>(
 	let mut backing_stake_of: BTreeMap<T::AccountId, BalanceOf<T>> = BTreeMap::new();

 	// self stake
-	<Validators<T>>::enumerate().for_each(|(who, _p)| {
+	<Validators<T>>::iter().for_each(|(who, _p)| {
 		*backing_stake_of.entry(who.clone()).or_insert(Zero::zero()) +=
 			<Module<T>>::slashable_balance_of(&who)
 	});

 	// add nominator stuff
-	<Nominators<T>>::enumerate().for_each(|(who, nomination)| {
+	<Nominators<T>>::iter().for_each(|(who, nomination)| {
 		nomination.targets.into_iter().for_each(|v| {
 			*backing_stake_of.entry(v).or_insert(Zero::zero()) +=
 				<Module<T>>::slashable_balance_of(&who)
@@ -176,7 +176,7 @@ pub fn get_weak_solution<T: Trait>(
 		.collect();

 	let mut staked_assignments: Vec<StakedAssignment<T::AccountId>> = Vec::new();
-	<Nominators<T>>::enumerate().for_each(|(who, nomination)| {
+	<Nominators<T>>::iter().for_each(|(who, nomination)| {
 		let mut dist: Vec<(T::AccountId, ExtendedBalance)> = Vec::new();
 		nomination.targets.into_iter().for_each(|v| {
 			if winners.iter().find(|&w| *w == v).is_some() {
@@ -325,16 +325,29 @@ pub fn clean<T: Trait>(era: EraIndex)
 		<T as frame_system::Trait>::AccountId: codec::EncodeLike<u32>,
 		u32: codec::EncodeLike<T::AccountId>,
 {
-	<Validators<T>>::enumerate().for_each(|(k, _)| {
+	<Validators<T>>::iter().for_each(|(k, _)| {
 		let ctrl = <Module<T>>::bonded(&k).unwrap();
 		<Bonded<T>>::remove(&k);
 		<Validators<T>>::remove(&k);
 		<Ledger<T>>::remove(&ctrl);
 		<ErasStakers<T>>::remove(k, era);
 	});
-	<Nominators<T>>::enumerate().for_each(|(k, _)| <Nominators<T>>::remove(k));
+	<Nominators<T>>::iter().for_each(|(k, _)| <Nominators<T>>::remove(k));
 	<Ledger<T>>::remove_all();
 	<Bonded<T>>::remove_all();
 	<QueuedElected<T>>::kill();
 	QueuedScore::kill();
 }
+
+/// get the active era.
+pub fn active_era<T: Trait>() -> EraIndex {
+	<Module<T>>::active_era().unwrap().index
+}
+
+/// initialize the first era.
+pub fn init_active_era() {
+	ActiveEra::put(ActiveEraInfo {
+		index: 1,
+		start: None,
+	})
+}
@@ -2901,8 +2901,8 @@ mod offchain_phragmen {

 	#[test]
 	fn signed_result_can_be_submitted() {
-		// should check that we have a new validator set normally,
-		// event says that it comes from offchain.
+		// should check that we have a new validator set normally, event says that it comes from
+		// offchain.
 		ExtBuilder::default()
 			.offchain_phragmen_ext()
 			.build()
@@ -2989,8 +2989,8 @@ mod offchain_phragmen {

 	#[test]
 	fn early_solution_submission_is_rejected() {
-		// should check that we have a new validator set normally,
-		// event says that it comes from offchain.
+		// should check that we have a new validator set normally, event says that it comes from
+		// offchain.
 		ExtBuilder::default()
 			.offchain_phragmen_ext()
 			.build()
@@ -3119,7 +3119,7 @@ mod offchain_phragmen {
 					&inner,
 				),
 				TransactionValidity::Ok(ValidTransaction {
-					priority: (1 << 20) + 1125, // the proposed slot stake.
+					priority: UnsignedPriority::get() + 1125, // the proposed slot stake.
 					requires: vec![],
 					provides: vec![("StakingOffchain", current_era()).encode()],
 					longevity: 3,
@@ -3129,6 +3129,50 @@ mod offchain_phragmen {
 		})
 	}

+	#[test]
+	fn offchain_worker_runs_with_equalise() {
+		// Offchain worker equalises based on the number provided by randomness. See the difference
+		// in the priority, which comes from the computed score.
+		let mut ext = ExtBuilder::default()
+			.offchain_phragmen_ext()
+			.validator_count(2)
+			.max_offchain_iterations(2)
+			.build();
+		let state = offchainify(&mut ext);
+		ext.execute_with(|| {
+			run_to_block(12);
+
+			// local key 11 is in the elected set.
+			assert_eq_uvec!(Session::validators(), vec![11, 21]);
+			assert_eq!(state.read().transactions.len(), 0);
+			Staking::offchain_worker(12);
+			assert_eq!(state.read().transactions.len(), 1);
+
+			let encoded = state.read().transactions[0].clone();
+			let extrinsic: Extrinsic = Decode::decode(&mut &*encoded).unwrap();
+
+			let call = extrinsic.call;
+			let inner = match call {
+				mock::Call::Staking(inner) => inner,
+			};
+
+			assert_eq!(
+				<Staking as sp_runtime::traits::ValidateUnsigned>::validate_unsigned(
+					TransactionSource::Local,
+					&inner,
+				),
+				TransactionValidity::Ok(ValidTransaction {
+					// the proposed slot stake, with equalize.
+					priority: UnsignedPriority::get() + 1250,
+					requires: vec![],
+					provides: vec![("StakingOffchain", active_era()).encode()],
+					longevity: 3,
+					propagate: false,
+				})
+			)
+		})
+	}
+
 	#[test]
 	fn mediocre_submission_from_authority_is_early_rejected() {
 		let mut ext = ExtBuilder::default()
@@ -24,7 +24,7 @@ wasmi = { version = "0.6.2", optional = true }
 hash-db = { version = "0.15.2", default-features = false }
 hash256-std-hasher = { version = "0.15.2", default-features = false }
 base58 = { version = "0.1.0", optional = true }
-rand = { version = "0.7.2", optional = true }
+rand = { version = "0.7.3", optional = true, features = ["small_rng"] }
 substrate-bip39 = { version = "0.4.1", optional = true }
 tiny-bip39 = { version = "0.7", optional = true }
 regex = { version = "1.3.1", optional = true }
@@ -165,7 +165,12 @@ impl offchain::Externalities for TestOffchainExt {
 	}

 	fn random_seed(&mut self) -> [u8; 32] {
-		unimplemented!("not needed in tests so far")
+		use rand::{SeedableRng, RngCore};
+		use rand::rngs::SmallRng;
+		let mut seed = [0u8; 32];
+		let mut small_rng = SmallRng::from_entropy();
+		small_rng.fill_bytes(&mut seed);
+		seed
 	}

 	fn local_storage_set(&mut self, kind: StorageKind, key: &[u8], value: &[u8]) {
@@ -158,7 +158,7 @@ pub struct PhragmenResult<AccountId, T: PerThing> {
 #[derive(RuntimeDebug, Clone, Default)]
 #[cfg_attr(feature = "std", derive(PartialEq, Eq, Encode, Decode))]
 pub struct Assignment<AccountId, T: PerThing> {
-	/// Voter's identifier
+	/// Voter's identifier.
 	pub who: AccountId,
 	/// The distribution of the voter's stake.
 	pub distribution: Vec<(AccountId, T)>,