Allow staking miner to use different election algorithms

runtime/common/Cargo.toml

@@ -22,6 +22,7 @@ sp-runtime = { git = "https://github.com/paritytech/substrate", branch = "master
 sp-session = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
 sp-staking = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
 sp-core = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+sp-npos-elections = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
 
 pallet-authorship = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
 pallet-balances = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
@@ -90,6 +91,7 @@ std = [
 	"libsecp256k1/std",
 	"runtime-parachains/std",
 	"xcm/std",
+	"sp-npos-elections/std",
 ]
 runtime-benchmarks = [
 	"libsecp256k1/hmac",

runtime/common/src/elections.rs

@@ -55,3 +55,30 @@ impl pallet_election_provider_multi_phase::BenchmarkingConfig for BenchmarkConfi
 	const MINER_MAXIMUM_VOTERS: u32 = 15_000;
 	const MAXIMUM_TARGETS: u32 = 2000;
 }
+
+/// Maximum number of iterations for balancing that will be executed in the embedded miner of
+/// pallet-election-provider-multi-phase.
+pub const MINER_MAX_ITERATIONS: u32 = 10;
+
+/// A source of random balance for the NPoS Solver, which is meant to be run by the OCW election
+/// miner.
+pub struct OffchainRandomBalancing;
+impl frame_support::pallet_prelude::Get<Option<(usize, sp_npos_elections::ExtendedBalance)>>
+	for OffchainRandomBalancing
+{
+	fn get() -> Option<(usize, sp_npos_elections::ExtendedBalance)> {
+		use sp_runtime::{codec::Decode, traits::TrailingZeroInput};
+		let iters = match MINER_MAX_ITERATIONS {
+			0 => 0,
+			max @ _ => {
+				let seed = sp_io::offchain::random_seed();
+				let random = <u32>::decode(&mut TrailingZeroInput::new(&seed))
+					.expect("input is padded with zeroes; qed") %
+					max.saturating_add(1);
+				random as usize
+			},
+		};
+
+		Some((iters, 0))
+	}
+}

runtime/kusama/src/lib.rs

@@ -356,7 +356,6 @@ parameter_types! {
 	pub SolutionImprovementThreshold: Perbill = Perbill::from_rational(5u32, 10_000);
 
 	// miner configs
-	pub const MinerMaxIterations: u32 = 10;
 	pub OffchainRepeat: BlockNumber = 5;
 }
 
@@ -384,7 +383,6 @@ impl pallet_election_provider_multi_phase::Config for Runtime {
 	type RewardHandler = (); // nothing to do upon rewards
 	type SignedPhase = SignedPhase;
 	type SolutionImprovementThreshold = SolutionImprovementThreshold;
-	type MinerMaxIterations = MinerMaxIterations;
 	type MinerMaxWeight = OffchainSolutionWeightLimit; // For now use the one from staking.
 	type MinerMaxLength = OffchainSolutionLengthLimit;
 	type OffchainRepeat = OffchainRepeat;
@@ -393,6 +391,11 @@ impl pallet_election_provider_multi_phase::Config for Runtime {
 	type Solution = NposCompactSolution24;
 	type OnChainAccuracy = Perbill;
 	type Fallback = Fallback;
+	type Solver = frame_election_provider_support::SequentialPhragmen<
+		AccountId,
+		pallet_election_provider_multi_phase::SolutionAccuracyOf<Runtime>,
+		runtime_common::elections::OffchainRandomBalancing,
+	>;
 	type BenchmarkingConfig = runtime_common::elections::BenchmarkConfig;
 	type ForceOrigin = EnsureOneOf<
 		AccountId,

runtime/polkadot/src/lib.rs

@@ -362,7 +362,6 @@ parameter_types! {
 	pub SolutionImprovementThreshold: Perbill = Perbill::from_rational(5u32, 10_000);
 
 	// miner configs
-	pub const MinerMaxIterations: u32 = 10;
 	pub OffchainRepeat: BlockNumber = 5;
 }
 
@@ -390,7 +389,6 @@ impl pallet_election_provider_multi_phase::Config for Runtime {
 	type SlashHandler = (); // burn slashes
 	type RewardHandler = (); // nothing to do upon rewards
 	type SolutionImprovementThreshold = SolutionImprovementThreshold;
-	type MinerMaxIterations = MinerMaxIterations;
 	type MinerMaxWeight = OffchainSolutionWeightLimit; // For now use the one from staking.
 	type MinerMaxLength = OffchainSolutionLengthLimit;
 	type OffchainRepeat = OffchainRepeat;
@@ -399,6 +397,11 @@ impl pallet_election_provider_multi_phase::Config for Runtime {
 	type OnChainAccuracy = Perbill;
 	type Solution = NposCompactSolution16;
 	type Fallback = Fallback;
+	type Solver = frame_election_provider_support::SequentialPhragmen<
+		AccountId,
+		pallet_election_provider_multi_phase::SolutionAccuracyOf<Runtime>,
+		runtime_common::elections::OffchainRandomBalancing,
+	>;
 	type BenchmarkingConfig = runtime_common::elections::BenchmarkConfig;
 	type ForceOrigin = EnsureOneOf<
 		AccountId,

runtime/westend/src/lib.rs

@@ -342,7 +342,6 @@ parameter_types! {
 	pub SolutionImprovementThreshold: Perbill = Perbill::from_rational(5u32, 10_000);
 
 	// miner configs
-	pub const MinerMaxIterations: u32 = 10;
 	pub OffchainRepeat: BlockNumber = 5;
 }
 
@@ -370,7 +369,6 @@ impl pallet_election_provider_multi_phase::Config for Runtime {
 	type SlashHandler = (); // burn slashes
 	type RewardHandler = (); // nothing to do upon rewards
 	type SolutionImprovementThreshold = SolutionImprovementThreshold;
-	type MinerMaxIterations = MinerMaxIterations;
 	type MinerMaxWeight = OffchainSolutionWeightLimit; // For now use the one from staking.
 	type MinerMaxLength = OffchainSolutionLengthLimit;
 	type OffchainRepeat = OffchainRepeat;
@@ -379,6 +377,11 @@ impl pallet_election_provider_multi_phase::Config for Runtime {
 	type OnChainAccuracy = Perbill;
 	type Solution = NposCompactSolution16;
 	type Fallback = Fallback;
+	type Solver = frame_election_provider_support::SequentialPhragmen<
+		AccountId,
+		pallet_election_provider_multi_phase::SolutionAccuracyOf<Runtime>,
+		runtime_common::elections::OffchainRandomBalancing,
+	>;
 	type BenchmarkingConfig = runtime_common::elections::BenchmarkConfig;
 	type ForceOrigin = EnsureRoot<AccountId>;
 	type WeightInfo = weights::pallet_election_provider_multi_phase::WeightInfo<Runtime>;

utils/staking-miner/Cargo.toml

@@ -22,11 +22,13 @@ sp-core = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sp-version = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sp-io = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sp-runtime = { git = "https://github.com/paritytech/substrate", branch = "master" }
+sp-npos-elections = { git = "https://github.com/paritytech/substrate", branch = "master" }
 sc-transaction-pool-api = { git = "https://github.com/paritytech/substrate", branch = "master" }
 
 
 frame-system = { git = "https://github.com/paritytech/substrate", branch = "master" }
 frame-support = { git = "https://github.com/paritytech/substrate", branch = "master" }
+frame-election-provider-support = { git = "https://github.com/paritytech/substrate", branch = "master" }
 pallet-election-provider-multi-phase = { git = "https://github.com/paritytech/substrate", branch = "master" }
 pallet-staking = { git = "https://github.com/paritytech/substrate", branch = "master" }
 pallet-balances = { git = "https://github.com/paritytech/substrate", branch = "master" }

utils/staking-miner/src/dry_run.rs

@@ -23,7 +23,7 @@ use codec::Encode;
 use frame_support::traits::Currency;
 
 /// Forcefully create the snapshot. This can be used to compute the election at anytime.
-fn force_create_snapshot<T: EPM::Config>(ext: &mut Ext) -> Result<(), Error> {
+fn force_create_snapshot<T: EPM::Config>(ext: &mut Ext) -> Result<(), Error<T>> {
 	ext.execute_with(|| {
 		if <EPM::Snapshot<T>>::exists() {
 			log::info!(target: LOG_TARGET, "snapshot already exists.");
@@ -112,7 +112,7 @@ macro_rules! dry_run_cmd_for { ($runtime:ident) => { paste::paste! {
 		shared: SharedConfig,
 		config: DryRunConfig,
 		signer: Signer,
-	) -> Result<(), Error> {
+	) -> Result<(), Error<$crate::[<$runtime _runtime_exports>]::Runtime>> {
 		use $crate::[<$runtime _runtime_exports>]::*;
 		let mut ext = crate::create_election_ext::<Runtime, Block>(
 			shared.uri.clone(),
@@ -121,7 +121,8 @@ macro_rules! dry_run_cmd_for { ($runtime:ident) => { paste::paste! {
 		).await?;
 		force_create_snapshot::<Runtime>(&mut ext)?;
 
-		let (raw_solution, witness) = crate::mine_unchecked::<Runtime>(&mut ext, config.iterations, false)?;
+		let (raw_solution, witness) = crate::mine_with::<Runtime>(&config.solver, &mut ext)?;
+
 		let nonce = crate::get_account_info::<Runtime>(client, &signer.account, config.at)
 			.await?
 			.map(|i| i.nonce)
@@ -148,7 +149,9 @@ macro_rules! dry_run_cmd_for { ($runtime:ident) => { paste::paste! {
 		});
 		log::info!(target: LOG_TARGET, "dispatch result is {:?}", dispatch_result);
 
-		let outcome = rpc_decode::<sp_runtime::ApplyExtrinsicResult>(client, "system_dryRun", params!{ bytes }).await?;
+		let outcome = rpc_decode::<sp_runtime::ApplyExtrinsicResult>(client, "system_dryRun", params!{ bytes })
+			.await
+			.map_err::<Error<Runtime>, _>(Into::into)?;
 		log::info!(target: LOG_TARGET, "dry-run outcome is {:?}", outcome);
 		Ok(())
 	}

utils/staking-miner/src/emergency_solution.rs

@@ -18,20 +18,22 @@
 
 use crate::{prelude::*, Error, SharedConfig};
 use codec::Encode;
+use frame_election_provider_support::SequentialPhragmen;
 use std::io::Write;
 
 macro_rules! emergency_solution_cmd_for { ($runtime:ident) => { paste::paste! {
 	/// Execute the emergency-solution command.
 	pub(crate) async fn [<emergency_solution_cmd_ $runtime>](
 		shared: SharedConfig,
-	) -> Result<(), Error> {
+	) -> Result<(), Error<$crate::[<$runtime _runtime_exports>]::Runtime>> {
 		use $crate::[<$runtime _runtime_exports>]::*;
 		let mut ext = crate::create_election_ext::<Runtime, Block>(shared.uri.clone(), None, vec![]).await?;
 		ext.execute_with(|| {
 			assert!(EPM::Pallet::<Runtime>::current_phase().is_emergency());
 			// NOTE: this internally calls feasibility_check, but we just re-do it here as an easy way
 			// to get a `ReadySolution`.
-			let (raw_solution, _) = <EPM::Pallet<Runtime>>::mine_solution(50)?;
+			let (raw_solution, _) =
+				<EPM::Pallet<Runtime>>::mine_solution::<SequentialPhragmen<AccountId, sp_runtime::Perbill>>()?;
 			log::info!(target: LOG_TARGET, "mined solution with {:?}", &raw_solution.score);
 			let ready_solution = EPM::Pallet::<Runtime>::feasibility_check(raw_solution, EPM::ElectionCompute::Signed)?;
 			let encoded_ready = ready_solution.encode();