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Branislav Kontur
bb8ddc46c1
I started this investigation/issue based on @liamaharon question [here](https://github.com/paritytech/polkadot-sdk/pull/1801#discussion_r1410452499). ## Problem The `pallet_balances` integrity test should correctly detect that the runtime has correct distinct `HoldReasons` variant count. I assume the same situation exists for RuntimeFreezeReason. It is not a critical problem, if we set `MaxHolds` with a sufficiently large value, everything should be ok. However, in this case, the integrity_test check becomes less useful. **Situation for "any" runtime:** - `HoldReason` enums from different pallets: ```rust /// from pallet_nis #[pallet::composite_enum] pub enum HoldReason { NftReceipt, } /// from pallet_preimage #[pallet::composite_enum] pub enum HoldReason { Preimage, } // from pallet_state-trie-migration #[pallet::composite_enum] pub enum HoldReason { SlashForContinueMigrate, SlashForMigrateCustomTop, SlashForMigrateCustomChild, } ``` - generated `RuntimeHoldReason` enum looks like: ```rust pub enum RuntimeHoldReason { #[codec(index = 32u8)] Preimage(pallet_preimage::HoldReason), #[codec(index = 38u8)] Nis(pallet_nis::HoldReason), #[codec(index = 42u8)] StateTrieMigration(pallet_state_trie_migration::HoldReason), } ``` - composite enum `RuntimeHoldReason` variant count is detected as `3` - we set `type MaxHolds = ConstU32<3>` - `pallet_balances::integrity_test` is ok with `3`(at least 3) However, the real problem can occur in a live runtime where some functionality might stop working. This is due to a total of 5 distinct hold reasons (for pallets with multi-instance support, it is even more), and not all of them can be used because of an incorrect `MaxHolds`, which is deemed acceptable according to the `integrity_test`: ``` // pseudo-code - if we try to call all of these: T::Currency::hold(&pallet_nis::HoldReason::NftReceipt.into(), &nft_owner, deposit)?; T::Currency::hold(&pallet_preimage::HoldReason::Preimage.into(), &nft_owner, deposit)?; T::Currency::hold(&pallet_state_trie_migration::HoldReason::SlashForContinueMigrate.into(), &nft_owner, deposit)?; // With `type MaxHolds = ConstU32<3>` these two will fail T::Currency::hold(&pallet_state_trie_migration::HoldReason::SlashForMigrateCustomTop.into(), &nft_owner, deposit)?; T::Currency::hold(&pallet_state_trie_migration::HoldReason::SlashForMigrateCustomChild.into(), &nft_owner, deposit)?; ``` ## Solutions A macro `#[pallet::*]` expansion is extended of `VariantCount` implementation for the `#[pallet::composite_enum]` enum type. This expansion generates the `VariantCount` implementation for pallets' `HoldReason`, `FreezeReason`, `LockId`, and `SlashReason`. Enum variants must be plain enum values without fields to ensure a deterministic count. The composite runtime enum, `RuntimeHoldReason` and `RuntimeFreezeReason`, now sets `VariantCount::VARIANT_COUNT` as the sum of pallets' enum `VariantCount::VARIANT_COUNT`: ```rust #[frame_support::pallet(dev_mode)] mod module_single_instance { #[pallet::composite_enum] pub enum HoldReason { ModuleSingleInstanceReason1, ModuleSingleInstanceReason2, } ... } #[frame_support::pallet(dev_mode)] mod module_multi_instance { #[pallet::composite_enum] pub enum HoldReason<I: 'static = ()> { ModuleMultiInstanceReason1, ModuleMultiInstanceReason2, ModuleMultiInstanceReason3, } ... } impl self::sp_api_hidden_includes_construct_runtime::hidden_include::traits::VariantCount for RuntimeHoldReason { const VARIANT_COUNT: u32 = 0 + module_single_instance::HoldReason::VARIANT_COUNT + module_multi_instance::HoldReason::<module_multi_instance::Instance1>::VARIANT_COUNT + module_multi_instance::HoldReason::<module_multi_instance::Instance2>::VARIANT_COUNT + module_multi_instance::HoldReason::<module_multi_instance::Instance3>::VARIANT_COUNT; } ``` In addition, `MaxHolds` is removed (as suggested [here](https://github.com/paritytech/polkadot-sdk/pull/2657#discussion_r1443324573)) from `pallet_balances`, and its `Holds` are now bounded to `RuntimeHoldReason::VARIANT_COUNT`. Therefore, there is no need to let the runtime specify `MaxHolds`. ## For reviewers Relevant changes can be found here: - `substrate/frame/support/procedural/src/lib.rs` - `substrate/frame/support/procedural/src/pallet/parse/composite.rs` - `substrate/frame/support/procedural/src/pallet/expand/composite.rs` - `substrate/frame/support/procedural/src/construct_runtime/expand/composite_helper.rs` - `substrate/frame/support/procedural/src/construct_runtime/expand/hold_reason.rs` - `substrate/frame/support/procedural/src/construct_runtime/expand/freeze_reason.rs` - `substrate/frame/support/src/traits/misc.rs` And the rest of the files is just about removed `MaxHolds` from `pallet_balances` ## Next steps Do the same for `MaxFreezes` https://github.com/paritytech/polkadot-sdk/issues/2997. --------- Co-authored-by: command-bot <> Co-authored-by: Bastian Köcher <git@kchr.de> Co-authored-by: Dónal Murray <donal.murray@parity.io> Co-authored-by: gupnik <nikhilgupta.iitk@gmail.com>
Scored Pool Module
The module maintains a scored membership pool. Each entity in the
pool can be attributed a Score. From this pool a set Members
is constructed. This set contains the MemberCount highest
scoring entities. Unscored entities are never part of Members.
If an entity wants to be part of the pool a deposit is required. The deposit is returned when the entity withdraws or when it is removed by an entity with the appropriate authority.
Every Period blocks the set of Members is refreshed from the
highest scoring members in the pool and, no matter if changes
occurred, T::MembershipChanged::set_members_sorted is invoked.
On first load T::MembershipInitialized::initialize_members is
invoked with the initial Members set.
It is possible to withdraw candidacy/resign your membership at any
time. If an entity is currently a member, this results in removal
from the Pool and Members; the entity is immediately replaced
by the next highest scoring candidate in the pool, if available.
Interface
Public Functions
submit_candidacy- Submit candidacy to become a member. Requires a deposit.withdraw_candidacy- Withdraw candidacy. Deposit is returned.score- Attribute a quantitative score to an entity.kick- Remove an entity from the pool and members. Deposit is returned.change_member_count- Changes the amount of candidates taken intoMembers.
Usage
use pallet_scored_pool::{self as scored_pool};
#[frame_support::pallet]
pub mod pallet {
use super::*;
use frame_support::pallet_prelude::*;
use frame_system::pallet_prelude::*;
#[pallet::pallet]
pub struct Pallet<T>(_);
#[pallet::config]
pub trait Config: frame_system::Config + scored_pool::Config {}
#[pallet::call]
impl<T: Config> Pallet<T> {
#[pallet::weight(0)]
pub fn candidate(origin: OriginFor<T>) -> DispatchResult {
let who = ensure_signed(origin)?;
let _ = <scored_pool::Pallet<T>>::submit_candidacy(
T::RuntimeOrigin::from(Some(who.clone()).into())
);
Ok(())
}
}
}
Dependencies
This module depends on the System module.
License: Apache-2.0