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Kusama: Make the current inflation formula adjustable. (#364)
This PR does not alter the inflation of Kusama, but instead make the current parameters of the system fully configurable. ## Parameters The parameters are as follows: ```rust /// Minimum inflation rate used to calculate era payouts. pub static MinInflation: Perquintill = Perquintill::from_rational(25u64, 1000); /// Maximum inflation rate used to calculate era payouts. pub static MaxInflation: Perquintill = Perquintill::from_percent(10); /// Ideal stake ratio used to calculate era payouts. pub static IdealStake: Perquintill = Perquintill::from_percent(75); /// Falloff used to calculate era payouts. pub static Falloff: Perquintill = Perquintill::from_percent(5); /// Whether to use auction slots or not in the calculation of era payouts, then we subtract /// `num_auctioned_slots.min(60) / 200` from `ideal_stake`. /// /// That is, we assume up to 60 parachains that are leased can reduce the ideal stake by a /// maximum of 30%. /// /// With the move to agile-coretime, this parameter does not make much sense and should /// generally be set to false. pub static UseAuctionSlots: bool = true; ``` All of the above are exactly the current values in Kusama, and leave everything unchanged, leading to roughly `1kKSM` minted for validators, and around `90KSM` for treasury. All of the above can be changed via the `Root` track only. Given that it is hard to come to consensus, I highly advise this PR (and a similar PR to Polkadot) to NOT alter any parameter and leave that to the token holders. Just to provide one example, if we set `UseAuctionSlots = false` and leave everything else un-changed, the amount minted per era would be: * `807KSM` for staking * `238KSM` for treasury > This, in my opinion, is the most non-controversial change as the incorporation of auctions in the inflation rate is already meaningless with agile-coretime. ## Consideration for UIs This PR is shipped with a new runtime API that is only added to the Kusama runtime: `Inflation_experimental_inflation_info`. I hope this API is used by the UIs to show the inflation parameters of the network, rather than re-creating the Rust logic in the front-end. --------- Signed-off-by: Oliver Tale-Yazdi <[email protected]> Co-authored-by: Oliver Tale-Yazdi <[email protected]> Co-authored-by: s0me0ne-unkn0wn <[email protected]> Co-authored-by: clangenb <[email protected]> Co-authored-by: Dónal Murray <[email protected]> Co-authored-by: Gonçalo Pestana <[email protected]> Co-authored-by: joe petrowski <[email protected]> Co-authored-by: Dónal Murray <[email protected]> Co-authored-by: fellowship-merge-bot[bot] <151052383+fellowship-merge-bot[bot]@users.noreply.github.com>
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| Original file line number | Diff line number | Diff line change |
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| [package] | ||
| authors.workspace = true | ||
| description = "Shared utilities between relay runtimes" | ||
| edition.workspace = true | ||
| license.workspace = true | ||
| name = "relay-common" | ||
| repository.workspace = true | ||
| version.workspace = true | ||
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| [dependencies] | ||
| codec = { features = ["derive", "max-encoded-len"], workspace = true } | ||
| scale-info = { features = ["derive"], workspace = true } | ||
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| sp-api ={ workspace = true } | ||
| sp-runtime = { workspace = true } | ||
| polkadot-primitives = { workspace = true } | ||
| pallet-staking-reward-fn ={ workspace = true } | ||
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| [features] | ||
| default = ["std"] | ||
| std = [ | ||
| "codec/std", | ||
| "scale-info/std", | ||
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| "sp-api/std", | ||
| "sp-runtime/std", | ||
| "polkadot-primitives/std", | ||
| "pallet-staking-reward-fn/std", | ||
| ] |
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| // Copyright (C) Parity Technologies (UK) Ltd. | ||
| // This file is part of Polkadot. | ||
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| // Polkadot 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. | ||
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| // Polkadot 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. | ||
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| // You should have received a copy of the GNU General Public License | ||
| // along with Polkadot. If not, see <http://www.gnu.org/licenses/>. | ||
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| //! Shared code between the Kusama nd Polkadot RC Runtimes. | ||
| #![cfg_attr(not(feature = "std"), no_std)] | ||
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| use polkadot_primitives::Balance; | ||
| use sp_runtime::{Perquintill, Saturating}; | ||
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| /// Extra runtime APIs for kusama runtime. | ||
| pub mod apis { | ||
| /// Information about the current inflation rate of the system. | ||
| /// | ||
| /// Both fields should be treated as best-effort, given that the inflation rate might not be | ||
| /// fully predict-able. | ||
| #[derive(scale_info::TypeInfo, codec::Encode, codec::Decode)] | ||
| pub struct InflationInfo { | ||
| /// The rate of inflation estimated per annum. | ||
| pub inflation: sp_runtime::Perquintill, | ||
| /// Next amount that we anticipate to mint. | ||
| /// | ||
| /// First item is the amount that goes to stakers, second is the leftover that is usually | ||
| /// forwarded to the treasury. | ||
| pub next_mint: (polkadot_primitives::Balance, polkadot_primitives::Balance), | ||
| } | ||
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| sp_api::decl_runtime_apis! { | ||
| pub trait Inflation { | ||
| /// Return the current estimates of the inflation amount. | ||
| /// | ||
| /// This is marked as experimental in light of RFC#89. Nonetheless, its usage is highly | ||
| /// recommended over trying to read-storage, or re-create the onchain logic. | ||
| fn experimental_inflation_prediction_info() -> InflationInfo; | ||
| } | ||
| } | ||
| } | ||
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| // ---- TODO: Below is copy pasted from sdk, remove once we pull the version containing | ||
| // https://github.com/paritytech/polkadot-sdk/pull/4938 | ||
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| #[derive(Debug, Clone)] | ||
| /// Parameters passed into [`relay_era_payout`] function. | ||
| pub struct EraPayoutParams { | ||
| /// Total staked amount. | ||
| pub total_staked: Balance, | ||
| /// Total stakable amount. | ||
| /// | ||
| /// Usually, this is equal to the total issuance, except if a large part of the issuance is | ||
| /// locked in another sub-system. | ||
| pub total_stakable: Balance, | ||
| /// Ideal stake ratio, which is reduced by `legacy_auction_proportion` if not `None`. | ||
| pub ideal_stake: Perquintill, | ||
| /// Maximum inflation rate. | ||
| pub max_annual_inflation: Perquintill, | ||
| /// Minimum inflation rate. | ||
| pub min_annual_inflation: Perquintill, | ||
| /// Falloff used to calculate era payouts. | ||
| pub falloff: Perquintill, | ||
| /// Fraction of the era period used to calculate era payouts. | ||
| pub period_fraction: Perquintill, | ||
| /// Legacy auction proportion, which, if not `None`, is subtracted from `ideal_stake`. | ||
| pub legacy_auction_proportion: Option<Perquintill>, | ||
| } | ||
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| /// A specialized function to compute the inflation of the staking system, tailored for Polkadot | ||
| /// Relay Chains, such as Polkadot, Kusama, and Westend. | ||
| pub fn relay_era_payout(params: EraPayoutParams) -> (Balance, Balance) { | ||
| let EraPayoutParams { | ||
| total_staked, | ||
| total_stakable, | ||
| ideal_stake, | ||
| max_annual_inflation, | ||
| min_annual_inflation, | ||
| falloff, | ||
| period_fraction, | ||
| legacy_auction_proportion, | ||
| } = params; | ||
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| let delta_annual_inflation = max_annual_inflation.saturating_sub(min_annual_inflation); | ||
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| let ideal_stake = ideal_stake.saturating_sub(legacy_auction_proportion.unwrap_or_default()); | ||
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| let stake = Perquintill::from_rational(total_staked, total_stakable); | ||
| let adjustment = pallet_staking_reward_fn::compute_inflation(stake, ideal_stake, falloff); | ||
| let staking_inflation = | ||
| min_annual_inflation.saturating_add(delta_annual_inflation * adjustment); | ||
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| let max_payout = period_fraction * max_annual_inflation * total_stakable; | ||
| let staking_payout = (period_fraction * staking_inflation) * total_stakable; | ||
| let rest = max_payout.saturating_sub(staking_payout); | ||
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| let other_issuance = total_stakable.saturating_sub(total_staked); | ||
| if total_staked > other_issuance { | ||
| let _cap_rest = Perquintill::from_rational(other_issuance, total_staked) * staking_payout; | ||
| // We don't do anything with this, but if we wanted to, we could introduce a cap on the | ||
| // treasury amount with: `rest = rest.min(cap_rest);` | ||
| } | ||
| (staking_payout, rest) | ||
| } | ||
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| // ---- TODO: Above is copy pasted from sdk, remove once we pull the version containing | ||
| // https://github.com/paritytech/polkadot-sdk/pull/4938 |
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