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state_changes.go
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state_changes.go
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// Copyright (C) 2019-2024, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.
package executor
import (
"errors"
"fmt"
"time"
"github.com/ava-labs/avalanchego/ids"
"github.com/ava-labs/avalanchego/utils/constants"
"github.com/ava-labs/avalanchego/vms/platformvm/reward"
"github.com/ava-labs/avalanchego/vms/platformvm/state"
"github.com/ava-labs/avalanchego/vms/platformvm/txs"
)
var (
ErrChildBlockAfterStakerChangeTime = errors.New("proposed timestamp later than next staker change time")
ErrChildBlockBeyondSyncBound = errors.New("proposed timestamp is too far in the future relative to local time")
)
// VerifyNewChainTime returns nil if the [newChainTime] is a valid chain time
// given the wall clock time ([now]) and when the next staking set change occurs
// ([nextStakerChangeTime]).
// Requires:
// - [newChainTime] <= [nextStakerChangeTime]: so that no staking set changes
// are skipped.
// - [newChainTime] <= [now] + [SyncBound]: to ensure chain time approximates
// "real" time.
func VerifyNewChainTime(
newChainTime,
nextStakerChangeTime,
now time.Time,
) error {
// Only allow timestamp to move as far forward as the time of the next
// staker set change
if newChainTime.After(nextStakerChangeTime) {
return fmt.Errorf(
"%w, proposed timestamp (%s), next staker change time (%s)",
ErrChildBlockAfterStakerChangeTime,
newChainTime,
nextStakerChangeTime,
)
}
// Only allow timestamp to reasonably far forward
maxNewChainTime := now.Add(SyncBound)
if newChainTime.After(maxNewChainTime) {
return fmt.Errorf(
"%w, proposed time (%s), local time (%s)",
ErrChildBlockBeyondSyncBound,
newChainTime,
now,
)
}
return nil
}
// AdvanceTimeTo applies all state changes to [parentState] resulting from
// advancing the chain time to [newChainTime].
// Returns true iff the validator set changed.
func AdvanceTimeTo(
backend *Backend,
parentState state.Chain,
newChainTime time.Time,
) (bool, error) {
// We promote pending stakers to current stakers first and remove
// completed stakers from the current staker set. We assume that any
// promoted staker will not immediately be removed from the current staker
// set. This is guaranteed by the following invariants.
//
// Invariant: MinStakeDuration > 0 => guarantees [StartTime] != [EndTime]
// Invariant: [newChainTime] <= nextStakerChangeTime.
changes, err := state.NewDiffOn(parentState)
if err != nil {
return false, err
}
pendingStakerIterator, err := parentState.GetPendingStakerIterator()
if err != nil {
return false, err
}
defer pendingStakerIterator.Release()
var changed bool
// Promote any pending stakers to current if [StartTime] <= [newChainTime].
for pendingStakerIterator.Next() {
stakerToRemove := pendingStakerIterator.Value()
if stakerToRemove.StartTime.After(newChainTime) {
break
}
stakerToAdd := *stakerToRemove
stakerToAdd.NextTime = stakerToRemove.EndTime
stakerToAdd.Priority = txs.PendingToCurrentPriorities[stakerToRemove.Priority]
if stakerToRemove.Priority == txs.SubnetPermissionedValidatorPendingPriority {
changes.PutCurrentValidator(&stakerToAdd)
changes.DeletePendingValidator(stakerToRemove)
changed = true
continue
}
supply, err := changes.GetCurrentSupply(stakerToRemove.SubnetID)
if err != nil {
return false, err
}
rewards, err := GetRewardsCalculator(backend, parentState, stakerToRemove.SubnetID)
if err != nil {
return false, err
}
potentialReward := rewards.Calculate(
stakerToRemove.EndTime.Sub(stakerToRemove.StartTime),
stakerToRemove.Weight,
supply,
)
stakerToAdd.PotentialReward = potentialReward
// Invariant: [rewards.Calculate] can never return a [potentialReward]
// such that [supply + potentialReward > maximumSupply].
changes.SetCurrentSupply(stakerToRemove.SubnetID, supply+potentialReward)
switch stakerToRemove.Priority {
case txs.PrimaryNetworkValidatorPendingPriority, txs.SubnetPermissionlessValidatorPendingPriority:
changes.PutCurrentValidator(&stakerToAdd)
changes.DeletePendingValidator(stakerToRemove)
case txs.PrimaryNetworkDelegatorApricotPendingPriority, txs.PrimaryNetworkDelegatorBanffPendingPriority, txs.SubnetPermissionlessDelegatorPendingPriority:
changes.PutCurrentDelegator(&stakerToAdd)
changes.DeletePendingDelegator(stakerToRemove)
default:
return false, fmt.Errorf("expected staker priority got %d", stakerToRemove.Priority)
}
changed = true
}
// Remove any current stakers whose [EndTime] <= [newChainTime].
currentStakerIterator, err := parentState.GetCurrentStakerIterator()
if err != nil {
return false, err
}
defer currentStakerIterator.Release()
for currentStakerIterator.Next() {
stakerToRemove := currentStakerIterator.Value()
if stakerToRemove.EndTime.After(newChainTime) {
break
}
// Invariant: Permissioned stakers are encountered first for a given
// timestamp because their priority is the smallest.
if stakerToRemove.Priority != txs.SubnetPermissionedValidatorCurrentPriority {
// Permissionless stakers are removed by the RewardValidatorTx, not
// an AdvanceTimeTx.
break
}
changes.DeleteCurrentValidator(stakerToRemove)
changed = true
}
if err := changes.Apply(parentState); err != nil {
return false, err
}
parentState.SetTimestamp(newChainTime)
return changed, nil
}
func GetRewardsCalculator(
backend *Backend,
parentState state.Chain,
subnetID ids.ID,
) (reward.Calculator, error) {
if subnetID == constants.PrimaryNetworkID {
return backend.Rewards, nil
}
transformSubnet, err := GetTransformSubnetTx(parentState, subnetID)
if err != nil {
return nil, err
}
return reward.NewCalculator(reward.Config{
MaxConsumptionRate: transformSubnet.MaxConsumptionRate,
MinConsumptionRate: transformSubnet.MinConsumptionRate,
MintingPeriod: backend.Config.RewardConfig.MintingPeriod,
SupplyCap: transformSubnet.MaximumSupply,
}), nil
}