Add a bounded fallback on failed elections (#10988)

* Allow `pallet-election-provider` to accept smaller solutions, issue #9478 * Fixing a typo * Adding some more tests Removing a seemingly outdated comment * making it a URL * Updating test name as per suggestion Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com> * Updating documentation to be more explicit And to follow the general guidelines Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com> * Fixing formatting * `Fallback` now of type `InstantElectionProvider` Some cleanups * Allow `pallet-election-provider` to accept smaller solutions, issue #9478 * Fixing a typo * Adding some more tests Removing a seemingly outdated comment * making it a URL * Updating test name as per suggestion Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com> * Updating documentation to be more explicit And to follow the general guidelines Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com> * Fixing formatting * `Fallback` now of type `InstantElectionProvider` Some cleanups * Merging types into one type with generics * Removing `ConstUSize` and use `ConstU32` * cleaning up the code * deprecating `OnChainSequentialPhragmen` Renaming it to `UnboundedSequentialPhragmen` which should only be used at genesis and for testing. Use preferrably `BoundedOnChainSequentialPhragmen` * Amending docs * Adding some explicit imports * Implementing generic `BoundedOnchainExecution` Removing the deprecated `OnChainSequentialPhragmen` * Use the right Balancing strategy * Refactoring `onchain::Config` Creating `onchain::ExecutionConfig` * Merge master * fmt * Name cleanups after review suggestions * cosmetics * renaming `instant_elect` to `elect_with_bounds` Other corresponding changes as per @kianenigma feedback * `BoundedOnchainExecution` -> `BoundedExecution` And `UnboundedOnchainExecution` -> `UnboundedExecution` * feedback from kian * fmt + unneeded import Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com> Co-authored-by: kianenigma <kian@parity.io>
2026-05-30 05:51:02 +00:00 · 2022-03-25 20:15:50 +00:00
parent cbfb1f0e3b
commit e9bfdd9a0d
11 changed files with 225 additions and 137 deletions
@@ -242,7 +242,7 @@ use frame_support::{
 use frame_system::{ensure_none, offchain::SendTransactionTypes};
 use scale_info::TypeInfo;
 use sp_arithmetic::{
-	traits::{CheckedAdd, Saturating, Zero},
+	traits::{Bounded, CheckedAdd, Saturating, Zero},
 	UpperOf,
 };
 use sp_npos_elections::{
@@ -323,10 +323,7 @@ impl<T: Config> ElectionProvider for NoFallback<T> {
 }

 impl<T: Config> InstantElectionProvider for NoFallback<T> {
-	fn instant_elect(
-		_: Option<usize>,
-		_: Option<usize>,
-	) -> Result<Supports<T::AccountId>, Self::Error> {
+	fn elect_with_bounds(_: usize, _: usize) -> Result<Supports<T::AccountId>, Self::Error> {
 		Err("NoFallback.")
 	}
 }
@@ -683,7 +680,7 @@ pub mod pallet {
 			+ TypeInfo;

 		/// Configuration for the fallback.
-		type Fallback: ElectionProvider<
+		type Fallback: InstantElectionProvider<
 			AccountId = Self::AccountId,
 			BlockNumber = Self::BlockNumber,
 			DataProvider = Self::DataProvider,
@@ -692,7 +689,7 @@ pub mod pallet {
 		/// Configuration of the governance-only fallback.
 		///
 		/// As a side-note, it is recommend for test-nets to use `type ElectionProvider =
-		/// OnChainSeqPhragmen<_>` if the test-net is not expected to have thousands of nominators.
+		/// BoundedExecution<_>` if the test-net is not expected to have thousands of nominators.
 		type GovernanceFallback: InstantElectionProvider<
 			AccountId = Self::AccountId,
 			BlockNumber = Self::BlockNumber,
@@ -1040,13 +1037,14 @@ pub mod pallet {
 			let maybe_max_voters = maybe_max_voters.map(|x| x as usize);
 			let maybe_max_targets = maybe_max_targets.map(|x| x as usize);

-			let supports =
-				T::GovernanceFallback::instant_elect(maybe_max_voters, maybe_max_targets).map_err(
-					|e| {
-						log!(error, "GovernanceFallback failed: {:?}", e);
-						Error::<T>::FallbackFailed
-					},
-				)?;
+			let supports = T::GovernanceFallback::elect_with_bounds(
+				maybe_max_voters.unwrap_or(Bounded::max_value()),
+				maybe_max_targets.unwrap_or(Bounded::max_value()),
+			)
+			.map_err(|e| {
+				log!(error, "GovernanceFallback failed: {:?}", e);
+				Error::<T>::FallbackFailed
+			})?;

 			let solution = ReadySolution {
 				supports,
@@ -272,11 +272,13 @@ parameter_types! {
 	pub static MaxElectableTargets: TargetIndex = TargetIndex::max_value();

 	pub static EpochLength: u64 = 30;
-	pub static OnChianFallback: bool = true;
+	pub static OnChainFallback: bool = true;
 }

-impl onchain::Config for Runtime {
-	type Accuracy = sp_runtime::Perbill;
+pub struct OnChainSeqPhragmen;
+impl onchain::ExecutionConfig for OnChainSeqPhragmen {
+	type System = Runtime;
+	type Solver = SequentialPhragmen<AccountId, SolutionAccuracyOf<Runtime>, Balancing>;
 	type DataProvider = StakingMock;
 }

@@ -288,11 +290,23 @@ impl ElectionProvider for MockFallback {
 	type DataProvider = StakingMock;

 	fn elect() -> Result<Supports<AccountId>, Self::Error> {
-		if OnChianFallback::get() {
-			onchain::OnChainSequentialPhragmen::<Runtime>::elect()
-				.map_err(|_| "OnChainSequentialPhragmen failed")
+		Self::elect_with_bounds(Bounded::max_value(), Bounded::max_value())
+	}
+}
+
+impl InstantElectionProvider for MockFallback {
+	fn elect_with_bounds(
+		max_voters: usize,
+		max_targets: usize,
+	) -> Result<Supports<Self::AccountId>, Self::Error> {
+		if OnChainFallback::get() {
+			onchain::UnboundedExecution::<OnChainSeqPhragmen>::elect_with_bounds(
+				max_voters,
+				max_targets,
+			)
+			.map_err(|_| "UnboundedExecution failed")
 		} else {
-			super::NoFallback::<Runtime>::elect()
+			super::NoFallback::<Runtime>::elect_with_bounds(max_voters, max_targets)
 		}
 	}
 }
@@ -532,7 +546,7 @@ impl ExtBuilder {
 		self
 	}
 	pub fn onchain_fallback(self, onchain: bool) -> Self {
-		<OnChianFallback>::set(onchain);
+		<OnChainFallback>::set(onchain);
 		self
 	}
 	pub fn miner_weight(self, weight: Weight) -> Self {