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mining: add halving logic #528

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Oct 13, 2021
Merged

mining: add halving logic #528

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68 changes: 63 additions & 5 deletions pallets/phala/src/mining.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -25,7 +25,10 @@ pub mod pallet {
WorkerPublicKey,
};
use sp_core::U256;
use sp_runtime::{traits::AccountIdConversion, SaturatedConversion};
use sp_runtime::{
traits::{AccountIdConversion, One, Zero},
SaturatedConversion,
};
use sp_std::cmp;

use crate::balance_convert::FixedPointConvert;
Expand Down Expand Up @@ -238,6 +241,14 @@ pub mod pallet {
#[pallet::storage]
pub type NextSessionId<T> = StorageValue<_, u32, ValueQuery>;

/// The block number when the mining starts. Used to calculate halving.
#[pallet::storage]
pub type MiningStartBlock<T: Config> = StorageValue<_, T::BlockNumber>;

/// The interval of halving (75% decay) in block number.
#[pallet::storage]
pub type MiningHalvingInterval<T: Config> = StorageValue<_, T::BlockNumber>;

/// The stakes of miner accounts.
///
/// Only presents for mining and cooling down miners.
Expand Down Expand Up @@ -269,6 +280,10 @@ pub mod pallet {
MinerSettled(T::AccountId, u128, u128),
/// Some internal error happened when settling a miner's ledger. \[worker\]
InternalErrorMinerSettleFailed(WorkerPublicKey),
/// Block subsidy halved by 25%
SubsidyBudgetHalved,
/// Some internal error happened when trying to halve the subsidy
InternalErrorWrongHalvingConfigured,
}

#[pallet::error]
Expand Down Expand Up @@ -384,8 +399,18 @@ pub mod pallet {
where
BalanceOf<T>: FixedPointConvert,
{
fn on_finalize(_n: T::BlockNumber) {
fn on_finalize(n: T::BlockNumber) {
Self::heartbeat_challenge();
if let Some(interval) = MiningHalvingInterval::<T>::get() {
let block_elapsed = n - MiningStartBlock::<T>::get().unwrap_or_default();
// Halve when it reaches the last block in an interval
if interval > Zero::zero() && block_elapsed % interval == interval - One::one() {
let r = Self::trigger_subsidy_halving();
if r.is_err() {
Self::deposit_event(Event::<T>::InternalErrorWrongHalvingConfigured);
}
}
}
}

fn on_runtime_upgrade() -> Weight {
Expand All @@ -401,8 +426,11 @@ pub mod pallet {
// Triggers GK RepairV event (again) to rescure the slashed miners due to
// incorrectly applied tokenomic.
w += migrations::repair_v::<T>();
// Khala-only halving parameters
MiningStartBlock::<T>::put(T::BlockNumber::from(414189u32));
MiningHalvingInterval::<T>::put(T::BlockNumber::from(324000u32));
STORAGE_VERSION.put::<super::Pallet<T>>();
w += T::DbWeight::get().writes(1);
w += T::DbWeight::get().writes(3);
}
w
}
Expand Down Expand Up @@ -432,6 +460,16 @@ pub mod pallet {
Self::push_message(SystemEvent::HeartbeatChallenge(seed_info));
}

fn trigger_subsidy_halving() -> Result<(), ()> {
let mut tokenomic = TokenomicParameters::<T>::get().ok_or(())?;
let budget_per_block = FixedPoint::from_bits(tokenomic.budget_per_block);
let new_budget = budget_per_block * fp!(0.75);
tokenomic.budget_per_block = new_budget.to_bits();
Self::update_tokenomic_parameters(tokenomic);
Self::deposit_event(Event::<T>::SubsidyBudgetHalved);
Ok(())
}

pub fn on_mining_message_received(
message: DecodedMessage<MiningReportEvent>,
) -> DispatchResult {
Expand Down Expand Up @@ -1154,6 +1192,7 @@ pub mod pallet {
#[test]
fn test_tokenomic() {
new_test_ext().execute_with(|| {
set_block_1();
let params = TokenomicParameters::<Test>::get().unwrap();
let tokenomic = Tokenomic::<Test>::new(params);
fn pow(x: FixedPoint, n: u32) -> FixedPoint {
Expand Down Expand Up @@ -1209,13 +1248,32 @@ pub mod pallet {
let rho = FixedPoint::from_bits(tokenomic.params.rho);
assert_eq!(pow(rho, HOUR_BLOCKS), fp!(1.00019999999998037056));
// Budget per day
let budger_per_block = FixedPoint::from_bits(tokenomic.params.budget_per_block);
assert_eq!(budger_per_block * 3600 * 24 / 12, fp!(720000));
let budget_per_block = FixedPoint::from_bits(tokenomic.params.budget_per_block);
assert_eq!(budget_per_block * 3600 * 24 / 12, fp!(720000));
// Cost estimation per year
assert_eq!(
tokenomic.op_cost(2000) / 12 * 3600 * 24 * 365,
fp!(171.71874999975847951583)
);
// Subsidy halving to 75%
let _ = take_messages();
let _ = take_events();
assert_ok!(PhalaMining::trigger_subsidy_halving());
let params = TokenomicParameters::<Test>::get().unwrap();
assert_eq!(FixedPoint::from_bits(params.budget_per_block), fp!(75));
assert_ok!(PhalaMining::trigger_subsidy_halving());
let params = TokenomicParameters::<Test>::get().unwrap();
assert_eq!(FixedPoint::from_bits(params.budget_per_block), fp!(56.25));
let msgs = take_messages();
assert_eq!(msgs.len(), 2);
let ev = take_events();
assert_eq!(
ev,
vec![
TestEvent::PhalaMining(Event::<Test>::SubsidyBudgetHalved),
TestEvent::PhalaMining(Event::<Test>::SubsidyBudgetHalved)
]
);
});
}

Expand Down