Staking: Introduce `MaxBackersPerWinner` #11935

ggwpez · 2022-07-29T12:26:42Z

Draft for @kianenigma
This is a preparation for bounding the Staking, eg #11585

Helps with paritytech/polkadot-sdk#473

Changes:

Add MaxBackersPerWinner and Bounder
Use BoundedSupports in ReadySolution to make it a bit more bounded. The BoundedSupports is still an unbound vector though and would otherwise require a second Get<u32> bound.
Add TruncateIntoBoundedSupports
Feasibility check errors when the input is too long.
elect_with_bounds returns bounded supports.
set_emergency_election_result errors when the input is too long.

Open:

Check if the off-chain miner needs to trim.
Fix score function to not consume self
Tests for trimming in unsigned.rs
From @kianenigma: "[…] once we mine a solution (this code is used by both offchain workers, or by staking-miner binary), we want to do a trim_assignment_backers as well."

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

kianenigma · 2022-07-30T14:25:36Z

bin/node/runtime/src/lib.rs

@@ -658,6 +659,10 @@ impl onchain::Config for OnChainSeqPhragmen {
 	>;
 	type DataProvider = <Runtime as pallet_election_provider_multi_phase::Config>::DataProvider;
 	type WeightInfo = frame_election_provider_support::weights::SubstrateWeight<Runtime>;
+
+	// TODO no idea what to use here
+	type MaxBackersPerWinner = ConstU32<{ u32::MAX }>;


Should be 1024 or something a few orders larger than MaxNominatorRewardedPerValidator.

kianenigma · 2022-07-30T14:27:13Z

frame/election-provider-multi-phase/src/lib.rs

 	/// The final supports of the solution.
 	///
 	/// This is target-major vector, storing each winners, total backing, and each individual
 	/// backer.
-	pub supports: Supports<A>,
+	pub supports: BoundedSupports<AccountId, MaxBackersPerWinner>,


I generally move structs to be <T: Config> once they need more than one generic from T, just a suggestion.

kianenigma · 2022-07-30T14:34:11Z

frame/election-provider-multi-phase/src/lib.rs

+/// Try to convert the supports of a solution into a [`ReadySolution`].
+///
+/// Errors if any of the supports has more than [`MaxBackersPerWinner`] backers.
+impl<AccountId: PartialEq, MaxBackersPerWinner: Get<u32>>


Instead of this, I would implement just impl TryFrom<Supports<AccountId>> for BoundedSupports<..> in election-provider-support/src.

The other two elements of the tuple seems very out of context.

Also, IIRC a lot of such conversions need to re-allocate in safe rust but with unsafe we can circumvent it.

kianenigma · 2022-07-30T14:36:01Z

frame/election-provider-multi-phase/src/lib.rs

+			let solution: ReadySolution<_, _> =
+				(supports, Default::default(), ElectionCompute::Emergency)
+					.try_into()
+					.map_err(|_| Error::<T>::TooManyBackersPerWinner)?;


Suggested change

let solution: ReadySolution<_, _> =

(supports, Default::default(), ElectionCompute::Emergency)

.try_into()

.map_err(|_| Error::<T>::TooManyBackersPerWinner)?;

ReadySolution {

supports: supports.into_iter().map(|s| s.try_into()).collect::<Result<Vec<_>, _>>().map_err(|_| Error::<T>::TooManyBackersPerWinner)?,

score: Default::default(),

ElectionCompute::Emergency,

};

Supplement of https://github.com/paritytech/substrate/pull/11935/files#r933816968

kianenigma · 2022-07-30T14:38:30Z

frame/election-provider-support/src/lib.rs

+	pub voters: BoundedVec<(AccountId, ExtendedBalance), Bound>,
+}
+
+pub type BoundedSupportOf<E> = BoundedSupport<


Suggested change

pub type BoundedSupportOf<E> = BoundedSupport<

/// Same as [`BoundedSupport`], parameterized by something that implements [`ElectionProvider`]

pub type BoundedSupportOf<E> = BoundedSupport<

kianenigma · 2022-07-30T14:38:46Z

frame/election-provider-support/src/lib.rs

+	<E as ElectionProvider>::MaxBackersPerWinner,
+>;
+
+pub type BoundedSupports<AccountId, MaxBackersPerWinner> =


Suggested change

pub type BoundedSupports<AccountId, MaxBackersPerWinner> =

/// Bounded counter-part of [`sp_npos_elections::Supports`].

pub type BoundedSupports<AccountId, MaxBackersPerWinner> =

kianenigma · 2022-07-30T14:39:33Z

frame/election-provider-support/src/lib.rs

+pub type BoundedSupports<AccountId, MaxBackersPerWinner> =
+	Vec<(AccountId, BoundedSupport<AccountId, MaxBackersPerWinner>)>;
+
+/// Convenience to create a [`BoundedSupport`] from a [`ElectionProvider`].


Suggested change

/// Convenience to create a [`BoundedSupport`] from a [`ElectionProvider`].

/// Convenience to create a [`BoundedSupports`] from a [`ElectionProvider`].

I am very open to the idea of not relying on this damn 's' to distinguish Support and Supports. Suggestions?

kianenigma · 2022-07-30T16:27:32Z

From @kianenigma: "[…] once we mine a solution (this code is used by both offchain workers, or by staking-miner binary), we want to do a trim_assignment_backers as well."

This part of this work is quite nasty, deals with a lot of legacy code that I have admittedly not had the time to really re-think since years ago, so I decided to take a stab at it. Feel free to cherry pick this commit if it makes sense, else try your approach if you have one.

only checked things compile, without any test.

https://github.com/paritytech/substrate/compare/kiz-max-backers-per-winner...kiz-max-backers-per-winner-2?expand=1

PS. this is the same as what I meant by

Check if the off-chain miner needs to trim.

So these two TODOs are practically the same.

kianenigma · 2022-09-26T09:21:55Z

cc @Ank4n

kianenigma · 2022-12-05T14:05:47Z

Let's close this for now, and revisit later.

kianenigma and others added 7 commits July 24, 2022 15:00

draft for Oliver

de627ee

Tests compile

adce6cf

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

Benchmarks compile

3a25c09

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

Cleanup

6f5fdb7

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

More cleanup

aa63ebc

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

Cleanup

9cbbe83

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

Review fixes

b21f3ad

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

ggwpez requested review from kianenigma and andresilva as code owners July 29, 2022 12:26

github-actions bot added A0-please_review Pull request needs code review. and removed A3-in_progress Pull request is in progress. No review needed at this stage. labels Jul 29, 2022

ggwpez added A3-in_progress Pull request is in progress. No review needed at this stage. and removed A0-please_review Pull request needs code review. labels Jul 29, 2022

kianenigma reviewed Jul 30, 2022

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kianenigma added this to In progress. in NPoS and Elections 💸 🗳 (NEW: https://github.com/orgs/paritytech/projects/33) via automation Aug 16, 2022

kianenigma mentioned this pull request Aug 23, 2022

Consolidate Nominator Support in Slashing and Rewards paritytech/polkadot-sdk#473

Closed

kianenigma mentioned this pull request Aug 24, 2023

Tracking issue for bounding pallet-staking storage items paritytech/polkadot-sdk#255

Open

kianenigma assigned Ank4n Sep 26, 2022

kianenigma mentioned this pull request Nov 3, 2022

Increase max rewardable nominators paritytech/polkadot#6230

Merged

kianenigma closed this Dec 5, 2022

louismerlin removed the D9-needsaudit 👮 PR contains changes to fund-managing logic that should be properly reviewed and externally audited label May 4, 2023

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Staking: Introduce `MaxBackersPerWinner` #11935

Staking: Introduce `MaxBackersPerWinner` #11935

ggwpez commented Jul 29, 2022 •

edited by kianenigma

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kianenigma commented Sep 26, 2022

kianenigma commented Dec 5, 2022

	pub type BoundedSupportOf<E> = BoundedSupport<
	/// Same as [`BoundedSupport`], parameterized by something that implements [`ElectionProvider`]
	pub type BoundedSupportOf<E> = BoundedSupport<

	pub type BoundedSupports<AccountId, MaxBackersPerWinner> =
	/// Bounded counter-part of [`sp_npos_elections::Supports`].
	pub type BoundedSupports<AccountId, MaxBackersPerWinner> =

	/// Convenience to create a [`BoundedSupport`] from a [`ElectionProvider`].
	/// Convenience to create a [`BoundedSupports`] from a [`ElectionProvider`].

Staking: Introduce MaxBackersPerWinner #11935

Staking: Introduce MaxBackersPerWinner #11935

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Staking: Introduce `MaxBackersPerWinner` #11935

Staking: Introduce `MaxBackersPerWinner` #11935

ggwpez commented Jul 29, 2022 •

edited by kianenigma

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