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[Westend] Parameterises minimum era inflation to treasury #6165

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[Westend] Parameterises minimum era inflation to treasury #6165

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2125d59
parameterize min treasury era inflation
gpestana Oct 21, 2024
39a3e6b
run era payout tests in test-externalities
gpestana Oct 22, 2024
2199122
Adds prdoc
gpestana Oct 22, 2024
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12 changes: 9 additions & 3 deletions polkadot/runtime/westend/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -257,7 +257,7 @@ pub mod dynamic_params {
use super::*;

/// Parameters used to calculate era payouts, see
/// [`polkadot_runtime_common::impls::EraPayoutParams`].
/// [`polkadot_runtime_common::impls::EraPayoutParams`] and [`crate::EraPayout`].
#[dynamic_pallet_params]
#[codec(index = 0)]
pub mod inflation {
Expand All @@ -281,6 +281,11 @@ pub mod dynamic_params {
/// the `legacy_auction_proportion` of 60% will be used in the calculation of era payouts.
#[codec(index = 4)]
pub static UseAuctionSlots: bool = false;

/// Minimum percentage of the total era inflation that is sent to the treasury. 15% as per
/// Polkadot ref 1139.
#[codec(index = 5)]
pub static MinTreasuryEraInflation: FixedU128 = FixedU128::from_rational(15, 100);
}
}

Expand Down Expand Up @@ -687,6 +692,8 @@ impl pallet_staking::EraPayout<Balance> for EraPayout {
_total_issuance: Balance,
era_duration_millis: u64,
) -> (Balance, Balance) {
use crate::dynamic_params::inflation::MinTreasuryEraInflation;

const MILLISECONDS_PER_YEAR: u64 = (1000 * 3600 * 24 * 36525) / 100;
// A normal-sized era will have 1 / 365.25 here:
let relative_era_len =
Expand All @@ -698,8 +705,7 @@ impl pallet_staking::EraPayout<Balance> for EraPayout {
let yearly_emission = fixed_inflation_rate.saturating_mul_int(fixed_total_issuance);

let era_emission = relative_era_len.saturating_mul_int(yearly_emission);
// 15% to treasury, as per Polkadot ref 1139.
let to_treasury = FixedU128::from_rational(15, 100).saturating_mul_int(era_emission);
let to_treasury = MinTreasuryEraInflation::get().saturating_mul_int(era_emission);
let to_stakers = era_emission.saturating_sub(to_treasury);

(to_stakers.saturated_into(), to_treasury.saturated_into())
Expand Down
158 changes: 89 additions & 69 deletions polkadot/runtime/westend/src/tests.rs
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Expand Up @@ -28,6 +28,12 @@ use xcm_runtime_apis::conversions::LocationToAccountHelper;

const MILLISECONDS_PER_HOUR: u64 = 60 * 60 * 1000;

pub fn new_test_ext() -> sp_io::TestExternalities {
let mut ext = sp_io::TestExternalities::new(Default::default());
ext.execute_with(|| System::set_block_number(1));
ext
}

#[test]
fn remove_keys_weight_is_sensible() {
use polkadot_runtime_common::crowdloan::WeightInfo;
Expand Down Expand Up @@ -318,91 +324,105 @@ fn location_conversion_works() {

#[test]
fn staking_inflation_correct_single_era() {
let (to_stakers, to_treasury) = super::EraPayout::era_payout(
123, // ignored
456, // ignored
MILLISECONDS_PER_HOUR,
);

assert_relative_eq!(to_stakers as f64, (4_046 * CENTS) as f64, max_relative = 0.01);
assert_relative_eq!(to_treasury as f64, (714 * CENTS) as f64, max_relative = 0.01);
// Total per hour is ~47.6 WND
assert_relative_eq!(
(to_stakers as f64 + to_treasury as f64),
(4_760 * CENTS) as f64,
max_relative = 0.001
);
new_test_ext().execute_with(|| {
let (to_stakers, to_treasury) = super::EraPayout::era_payout(
123, // ignored
456, // ignored
MILLISECONDS_PER_HOUR,
);

assert_relative_eq!(to_stakers as f64, (4_046 * CENTS) as f64, max_relative = 0.01);
assert_relative_eq!(to_treasury as f64, (714 * CENTS) as f64, max_relative = 0.01);
// Total per hour is ~47.6 WND
assert_relative_eq!(
(to_stakers as f64 + to_treasury as f64),
(4_760 * CENTS) as f64,
max_relative = 0.001
);
})
}

#[test]
fn staking_inflation_correct_longer_era() {
// Twice the era duration means twice the emission:
let (to_stakers, to_treasury) = super::EraPayout::era_payout(
123, // ignored
456, // ignored
2 * MILLISECONDS_PER_HOUR,
);

assert_relative_eq!(to_stakers as f64, (4_046 * CENTS) as f64 * 2.0, max_relative = 0.001);
assert_relative_eq!(to_treasury as f64, (714 * CENTS) as f64 * 2.0, max_relative = 0.001);
new_test_ext().execute_with(|| {
// Twice the era duration means twice the emission:
let (to_stakers, to_treasury) = super::EraPayout::era_payout(
123, // ignored
456, // ignored
2 * MILLISECONDS_PER_HOUR,
);

assert_relative_eq!(to_stakers as f64, (4_046 * CENTS) as f64 * 2.0, max_relative = 0.001);
assert_relative_eq!(to_treasury as f64, (714 * CENTS) as f64 * 2.0, max_relative = 0.001);
})
}

#[test]
fn staking_inflation_correct_whole_year() {
let (to_stakers, to_treasury) = super::EraPayout::era_payout(
123, // ignored
456, // ignored
(36525 * 24 * MILLISECONDS_PER_HOUR) / 100, // 1 year
);

// Our yearly emissions is about 417k WND:
let yearly_emission = 417_307 * UNITS;
assert_relative_eq!(
to_stakers as f64 + to_treasury as f64,
yearly_emission as f64,
max_relative = 0.001
);

assert_relative_eq!(to_stakers as f64, yearly_emission as f64 * 0.85, max_relative = 0.001);
assert_relative_eq!(to_treasury as f64, yearly_emission as f64 * 0.15, max_relative = 0.001);
new_test_ext().execute_with(|| {
let (to_stakers, to_treasury) = super::EraPayout::era_payout(
123, // ignored
456, // ignored
(36525 * 24 * MILLISECONDS_PER_HOUR) / 100, // 1 year
);

// Our yearly emissions is about 417k WND:
let yearly_emission = 417_307 * UNITS;
assert_relative_eq!(
to_stakers as f64 + to_treasury as f64,
yearly_emission as f64,
max_relative = 0.001
);

assert_relative_eq!(to_stakers as f64, yearly_emission as f64 * 0.85, max_relative = 0.001);
assert_relative_eq!(
to_treasury as f64,
yearly_emission as f64 * 0.15,
max_relative = 0.001
);
})
}

// 10 years into the future, our values do not overflow.
#[test]
fn staking_inflation_correct_not_overflow() {
let (to_stakers, to_treasury) = super::EraPayout::era_payout(
123, // ignored
456, // ignored
(36525 * 24 * MILLISECONDS_PER_HOUR) / 10, // 10 years
);
let initial_ti: i128 = 5_216_342_402_773_185_773;
let projected_total_issuance = (to_stakers as i128 + to_treasury as i128) + initial_ti;

// In 2034, there will be about 9.39 million WND in existence.
assert_relative_eq!(
projected_total_issuance as f64,
(9_390_000 * UNITS) as f64,
max_relative = 0.001
);
new_test_ext().execute_with(|| {
let (to_stakers, to_treasury) = super::EraPayout::era_payout(
123, // ignored
456, // ignored
(36525 * 24 * MILLISECONDS_PER_HOUR) / 10, // 10 years
);
let initial_ti: i128 = 5_216_342_402_773_185_773;
let projected_total_issuance = (to_stakers as i128 + to_treasury as i128) + initial_ti;

// In 2034, there will be about 9.39 million WND in existence.
assert_relative_eq!(
projected_total_issuance as f64,
(9_390_000 * UNITS) as f64,
max_relative = 0.001
);
})
}

// Print percent per year, just as convenience.
#[test]
fn staking_inflation_correct_print_percent() {
let (to_stakers, to_treasury) = super::EraPayout::era_payout(
123, // ignored
456, // ignored
(36525 * 24 * MILLISECONDS_PER_HOUR) / 100, // 1 year
);
let yearly_emission = to_stakers + to_treasury;
let mut ti: i128 = 5_216_342_402_773_185_773;

for y in 0..10 {
let new_ti = ti + yearly_emission as i128;
let inflation = 100.0 * (new_ti - ti) as f64 / ti as f64;
println!("Year {y} inflation: {inflation}%");
ti = new_ti;

assert!(inflation <= 8.0 && inflation > 2.0, "sanity check");
}
new_test_ext().execute_with(|| {
let (to_stakers, to_treasury) = super::EraPayout::era_payout(
123, // ignored
456, // ignored
(36525 * 24 * MILLISECONDS_PER_HOUR) / 100, // 1 year
);
let yearly_emission = to_stakers + to_treasury;
let mut ti: i128 = 5_216_342_402_773_185_773;

for y in 0..10 {
let new_ti = ti + yearly_emission as i128;
let inflation = 100.0 * (new_ti - ti) as f64 / ti as f64;
println!("Year {y} inflation: {inflation}%");
ti = new_ti;

assert!(inflation <= 8.0 && inflation > 2.0, "sanity check");
}
})
}
11 changes: 11 additions & 0 deletions prdoc/pr_6165.prdoc
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Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
title: Parameterises Westend minimum era infaltion to treasury

doc:
- audience: Runtime User
description: |
Parameterises the minimum era inflation percentage that should be automatically minted into
the treasury. This parameterisation exposes the config directly to governance.

crates:
- name: westend-runtime
bump: patch
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