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state_changes.go
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/
state_changes.go
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// Copyright (C) 2019-2022, 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
}
type StateChanges interface {
Apply(onAccept state.Diff)
Len() int
}
type stateChanges struct {
updatedSupplies map[ids.ID]uint64
currentValidatorsToAdd []*state.Staker
currentDelegatorsToAdd []*state.Staker
pendingValidatorsToRemove []*state.Staker
pendingDelegatorsToRemove []*state.Staker
currentValidatorsToRemove []*state.Staker
}
func (s *stateChanges) Apply(stateDiff state.Diff) {
for subnetID, supply := range s.updatedSupplies {
stateDiff.SetCurrentSupply(subnetID, supply)
}
for _, currentValidatorToAdd := range s.currentValidatorsToAdd {
stateDiff.PutCurrentValidator(currentValidatorToAdd)
}
for _, pendingValidatorToRemove := range s.pendingValidatorsToRemove {
stateDiff.DeletePendingValidator(pendingValidatorToRemove)
}
for _, currentDelegatorToAdd := range s.currentDelegatorsToAdd {
stateDiff.PutCurrentDelegator(currentDelegatorToAdd)
}
for _, pendingDelegatorToRemove := range s.pendingDelegatorsToRemove {
stateDiff.DeletePendingDelegator(pendingDelegatorToRemove)
}
for _, currentValidatorToRemove := range s.currentValidatorsToRemove {
stateDiff.DeleteCurrentValidator(currentValidatorToRemove)
}
}
func (s *stateChanges) Len() int {
return len(s.currentValidatorsToAdd) + len(s.currentDelegatorsToAdd) +
len(s.pendingValidatorsToRemove) + len(s.pendingDelegatorsToRemove) +
len(s.currentValidatorsToRemove)
}
// AdvanceTimeTo does not modify [parentState].
// Instead it returns all the StateChanges caused by advancing the chain time to
// the [newChainTime].
func AdvanceTimeTo(
backend *Backend,
parentState state.Chain,
newChainTime time.Time,
) (StateChanges, error) {
pendingStakerIterator, err := parentState.GetPendingStakerIterator()
if err != nil {
return nil, err
}
defer pendingStakerIterator.Release()
changes := &stateChanges{
updatedSupplies: make(map[ids.ID]uint64),
}
// Add to the staker set any pending stakers whose start time is at or
// before the new timestamp
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 {
// Invariant: [txTimestamp] <= [nextStakerChangeTime].
// Invariant: minimum stake duration is > 0.
//
// Both of the above invariants ensure the staker we are adding here
// should never be attempted to be removed in the following loop.
changes.currentValidatorsToAdd = append(changes.currentValidatorsToAdd, &stakerToAdd)
changes.pendingValidatorsToRemove = append(changes.pendingValidatorsToRemove, stakerToRemove)
continue
}
supply, ok := changes.updatedSupplies[stakerToRemove.SubnetID]
if !ok {
supply, err = parentState.GetCurrentSupply(stakerToRemove.SubnetID)
if err != nil {
return nil, err
}
}
rewards, err := GetRewardsCalculator(backend, parentState, stakerToRemove.SubnetID)
if err != nil {
return nil, 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.updatedSupplies[stakerToRemove.SubnetID] = supply + potentialReward
switch stakerToRemove.Priority {
case txs.PrimaryNetworkValidatorPendingPriority, txs.SubnetPermissionlessValidatorPendingPriority:
changes.currentValidatorsToAdd = append(changes.currentValidatorsToAdd, &stakerToAdd)
changes.pendingValidatorsToRemove = append(changes.pendingValidatorsToRemove, stakerToRemove)
case txs.PrimaryNetworkDelegatorApricotPendingPriority, txs.PrimaryNetworkDelegatorBanffPendingPriority, txs.SubnetPermissionlessDelegatorPendingPriority:
changes.currentDelegatorsToAdd = append(changes.currentDelegatorsToAdd, &stakerToAdd)
changes.pendingDelegatorsToRemove = append(changes.pendingDelegatorsToRemove, stakerToRemove)
default:
return nil, fmt.Errorf("expected staker priority got %d", stakerToRemove.Priority)
}
}
currentStakerIterator, err := parentState.GetCurrentStakerIterator()
if err != nil {
return nil, 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.currentValidatorsToRemove = append(changes.currentValidatorsToRemove, stakerToRemove)
}
return changes, nil
}
func GetRewardsCalculator(
backend *Backend,
parentState state.Chain,
subnetID ids.ID,
) (reward.Calculator, error) {
if subnetID == constants.PrimaryNetworkID {
return backend.Rewards, nil
}
transformSubnetIntf, err := parentState.GetSubnetTransformation(subnetID)
if err != nil {
return nil, err
}
transformSubnet, ok := transformSubnetIntf.Unsigned.(*txs.TransformSubnetTx)
if !ok {
return nil, errIsNotTransformSubnetTx
}
return reward.NewCalculator(reward.Config{
MaxConsumptionRate: transformSubnet.MaxConsumptionRate,
MinConsumptionRate: transformSubnet.MinConsumptionRate,
MintingPeriod: backend.Config.RewardConfig.MintingPeriod,
SupplyCap: transformSubnet.MaximumSupply,
}), nil
}