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proposal_tx_executor.go
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proposal_tx_executor.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/database"
"github.com/ava-labs/avalanchego/ids"
"github.com/ava-labs/avalanchego/utils/constants"
"github.com/ava-labs/avalanchego/utils/math"
"github.com/ava-labs/avalanchego/vms/components/avax"
"github.com/ava-labs/avalanchego/vms/components/verify"
"github.com/ava-labs/avalanchego/vms/platformvm/reward"
"github.com/ava-labs/avalanchego/vms/platformvm/state"
"github.com/ava-labs/avalanchego/vms/platformvm/txs"
"github.com/ava-labs/avalanchego/vms/platformvm/utxo"
)
const (
// Maximum future start time for staking/delegating
MaxFutureStartTime = 24 * 7 * 2 * time.Hour
// SyncBound is the synchrony bound used for safe decision making
SyncBound = 10 * time.Second
MaxValidatorWeightFactor = 5
)
var (
_ txs.Visitor = (*ProposalTxExecutor)(nil)
errChildBlockNotAfterParent = errors.New("proposed timestamp not after current chain time")
errInvalidState = errors.New("generated output isn't valid state")
errShouldBePermissionlessStaker = errors.New("expected permissionless staker")
errWrongTxType = errors.New("wrong transaction type")
errInvalidID = errors.New("invalid ID")
errProposedAddStakerTxAfterBanff = errors.New("staker transaction proposed after Banff")
errAdvanceTimeTxIssuedAfterBanff = errors.New("AdvanceTimeTx issued after Banff")
)
type ProposalTxExecutor struct {
// inputs, to be filled before visitor methods are called
*Backend
Tx *txs.Tx
// [OnCommitState] is the state used for validation.
// In practice, both [OnCommitState] and [onAbortState] are
// identical when passed into this struct, so we could use either.
// [OnCommitState] is modified by this struct's methods to
// reflect changes made to the state if the proposal is committed.
OnCommitState state.Diff
// [OnAbortState] is modified by this struct's methods to
// reflect changes made to the state if the proposal is aborted.
OnAbortState state.Diff
// outputs populated by this struct's methods:
//
// [PrefersCommit] is true iff this node initially prefers to
// commit this block transaction.
PrefersCommit bool
}
func (*ProposalTxExecutor) CreateChainTx(*txs.CreateChainTx) error {
return errWrongTxType
}
func (*ProposalTxExecutor) CreateSubnetTx(*txs.CreateSubnetTx) error {
return errWrongTxType
}
func (*ProposalTxExecutor) ImportTx(*txs.ImportTx) error {
return errWrongTxType
}
func (*ProposalTxExecutor) ExportTx(*txs.ExportTx) error {
return errWrongTxType
}
func (*ProposalTxExecutor) RemoveSubnetValidatorTx(*txs.RemoveSubnetValidatorTx) error {
return errWrongTxType
}
func (*ProposalTxExecutor) TransformSubnetTx(*txs.TransformSubnetTx) error {
return errWrongTxType
}
func (*ProposalTxExecutor) AddPermissionlessValidatorTx(*txs.AddPermissionlessValidatorTx) error {
return errWrongTxType
}
func (*ProposalTxExecutor) AddPermissionlessDelegatorTx(*txs.AddPermissionlessDelegatorTx) error {
return errWrongTxType
}
func (e *ProposalTxExecutor) AddValidatorTx(tx *txs.AddValidatorTx) error {
// AddValidatorTx is a proposal transaction until the Banff fork
// activation. Following the activation, AddValidatorTxs must be issued into
// StandardBlocks.
currentTimestamp := e.OnCommitState.GetTimestamp()
if e.Config.IsBanffActivated(currentTimestamp) {
return fmt.Errorf(
"%w: timestamp (%s) >= Banff fork time (%s)",
errProposedAddStakerTxAfterBanff,
currentTimestamp,
e.Config.BanffTime,
)
}
onAbortOuts, err := verifyAddValidatorTx(
e.Backend,
e.OnCommitState,
e.Tx,
tx,
)
if err != nil {
return err
}
txID := e.Tx.ID()
// Set up the state if this tx is committed
// Consume the UTXOs
utxo.Consume(e.OnCommitState, tx.Ins)
// Produce the UTXOs
utxo.Produce(e.OnCommitState, txID, tx.Outs)
newStaker, err := state.NewPendingStaker(txID, tx)
if err != nil {
return err
}
e.OnCommitState.PutPendingValidator(newStaker)
// Set up the state if this tx is aborted
// Consume the UTXOs
utxo.Consume(e.OnAbortState, tx.Ins)
// Produce the UTXOs
utxo.Produce(e.OnAbortState, txID, onAbortOuts)
e.PrefersCommit = tx.StartTime().After(e.Clk.Time())
return nil
}
func (e *ProposalTxExecutor) AddSubnetValidatorTx(tx *txs.AddSubnetValidatorTx) error {
// AddSubnetValidatorTx is a proposal transaction until the Banff fork
// activation. Following the activation, AddSubnetValidatorTxs must be
// issued into StandardBlocks.
currentTimestamp := e.OnCommitState.GetTimestamp()
if e.Config.IsBanffActivated(currentTimestamp) {
return fmt.Errorf(
"%w: timestamp (%s) >= Banff fork time (%s)",
errProposedAddStakerTxAfterBanff,
currentTimestamp,
e.Config.BanffTime,
)
}
if err := verifyAddSubnetValidatorTx(
e.Backend,
e.OnCommitState,
e.Tx,
tx,
); err != nil {
return err
}
txID := e.Tx.ID()
// Set up the state if this tx is committed
// Consume the UTXOs
utxo.Consume(e.OnCommitState, tx.Ins)
// Produce the UTXOs
utxo.Produce(e.OnCommitState, txID, tx.Outs)
newStaker, err := state.NewPendingStaker(txID, tx)
if err != nil {
return err
}
e.OnCommitState.PutPendingValidator(newStaker)
// Set up the state if this tx is aborted
// Consume the UTXOs
utxo.Consume(e.OnAbortState, tx.Ins)
// Produce the UTXOs
utxo.Produce(e.OnAbortState, txID, tx.Outs)
e.PrefersCommit = tx.StartTime().After(e.Clk.Time())
return nil
}
func (e *ProposalTxExecutor) AddDelegatorTx(tx *txs.AddDelegatorTx) error {
// AddDelegatorTx is a proposal transaction until the Banff fork
// activation. Following the activation, AddDelegatorTxs must be issued into
// StandardBlocks.
currentTimestamp := e.OnCommitState.GetTimestamp()
if e.Config.IsBanffActivated(currentTimestamp) {
return fmt.Errorf(
"%w: timestamp (%s) >= Banff fork time (%s)",
errProposedAddStakerTxAfterBanff,
currentTimestamp,
e.Config.BanffTime,
)
}
onAbortOuts, err := verifyAddDelegatorTx(
e.Backend,
e.OnCommitState,
e.Tx,
tx,
)
if err != nil {
return err
}
txID := e.Tx.ID()
// Set up the state if this tx is committed
// Consume the UTXOs
utxo.Consume(e.OnCommitState, tx.Ins)
// Produce the UTXOs
utxo.Produce(e.OnCommitState, txID, tx.Outs)
newStaker, err := state.NewPendingStaker(txID, tx)
if err != nil {
return err
}
e.OnCommitState.PutPendingDelegator(newStaker)
// Set up the state if this tx is aborted
// Consume the UTXOs
utxo.Consume(e.OnAbortState, tx.Ins)
// Produce the UTXOs
utxo.Produce(e.OnAbortState, txID, onAbortOuts)
e.PrefersCommit = tx.StartTime().After(e.Clk.Time())
return nil
}
func (e *ProposalTxExecutor) AdvanceTimeTx(tx *txs.AdvanceTimeTx) error {
switch {
case tx == nil:
return txs.ErrNilTx
case len(e.Tx.Creds) != 0:
return errWrongNumberOfCredentials
}
// Validate [newChainTime]
newChainTime := tx.Timestamp()
if e.Config.IsBanffActivated(newChainTime) {
return fmt.Errorf(
"%w: proposed timestamp (%s) >= Banff fork time (%s)",
errAdvanceTimeTxIssuedAfterBanff,
newChainTime,
e.Config.BanffTime,
)
}
parentChainTime := e.OnCommitState.GetTimestamp()
if !newChainTime.After(parentChainTime) {
return fmt.Errorf(
"%w, proposed timestamp (%s), chain time (%s)",
errChildBlockNotAfterParent,
parentChainTime,
parentChainTime,
)
}
// Only allow timestamp to move forward as far as the time of next staker
// set change time
nextStakerChangeTime, err := GetNextStakerChangeTime(e.OnCommitState)
if err != nil {
return err
}
now := e.Clk.Time()
if err := VerifyNewChainTime(
newChainTime,
nextStakerChangeTime,
now,
); err != nil {
return err
}
changes, err := AdvanceTimeTo(e.Backend, e.OnCommitState, newChainTime)
if err != nil {
return err
}
// Update the state if this tx is committed
e.OnCommitState.SetTimestamp(newChainTime)
changes.Apply(e.OnCommitState)
e.PrefersCommit = !newChainTime.After(now.Add(SyncBound))
// Note that state doesn't change if this proposal is aborted
return nil
}
func (e *ProposalTxExecutor) RewardValidatorTx(tx *txs.RewardValidatorTx) error {
switch {
case tx == nil:
return txs.ErrNilTx
case tx.TxID == ids.Empty:
return errInvalidID
case len(e.Tx.Creds) != 0:
return errWrongNumberOfCredentials
}
currentStakerIterator, err := e.OnCommitState.GetCurrentStakerIterator()
if err != nil {
return err
}
if !currentStakerIterator.Next() {
return fmt.Errorf("failed to get next staker to remove: %w", database.ErrNotFound)
}
stakerToRemove := currentStakerIterator.Value()
currentStakerIterator.Release()
if stakerToRemove.TxID != tx.TxID {
return fmt.Errorf(
"attempting to remove TxID: %s. Should be removing %s",
tx.TxID,
stakerToRemove.TxID,
)
}
// Verify that the chain's timestamp is the validator's end time
currentChainTime := e.OnCommitState.GetTimestamp()
if !stakerToRemove.EndTime.Equal(currentChainTime) {
return fmt.Errorf(
"attempting to remove TxID: %s before their end time %s",
tx.TxID,
stakerToRemove.EndTime,
)
}
primaryNetworkValidator, err := e.OnCommitState.GetCurrentValidator(
constants.PrimaryNetworkID,
stakerToRemove.NodeID,
)
if err != nil {
// This should never error because the staker set is in memory and
// primary network validators are removed last.
return err
}
stakerTx, _, err := e.OnCommitState.GetTx(stakerToRemove.TxID)
if err != nil {
return fmt.Errorf("failed to get next removed staker tx: %w", err)
}
switch uStakerTx := stakerTx.Unsigned.(type) {
case txs.ValidatorTx:
e.OnCommitState.DeleteCurrentValidator(stakerToRemove)
e.OnAbortState.DeleteCurrentValidator(stakerToRemove)
stake := uStakerTx.Stake()
outputs := uStakerTx.Outputs()
// Invariant: The staked asset must be equal to the reward asset.
stakeAsset := stake[0].Asset
// Refund the stake here
for i, out := range stake {
utxo := &avax.UTXO{
UTXOID: avax.UTXOID{
TxID: tx.TxID,
OutputIndex: uint32(len(outputs) + i),
},
Asset: out.Asset,
Out: out.Output(),
}
e.OnCommitState.AddUTXO(utxo)
e.OnAbortState.AddUTXO(utxo)
}
// Provide the reward here
if stakerToRemove.PotentialReward > 0 {
validationRewardsOwner := uStakerTx.ValidationRewardsOwner()
outIntf, err := e.Fx.CreateOutput(stakerToRemove.PotentialReward, validationRewardsOwner)
if err != nil {
return fmt.Errorf("failed to create output: %w", err)
}
out, ok := outIntf.(verify.State)
if !ok {
return errInvalidState
}
utxo := &avax.UTXO{
UTXOID: avax.UTXOID{
TxID: tx.TxID,
OutputIndex: uint32(len(outputs) + len(stake)),
},
Asset: stakeAsset,
Out: out,
}
e.OnCommitState.AddUTXO(utxo)
e.OnCommitState.AddRewardUTXO(tx.TxID, utxo)
}
// Invariant: A [txs.DelegatorTx] does not also implement the
// [txs.ValidatorTx] interface.
case txs.DelegatorTx:
e.OnCommitState.DeleteCurrentDelegator(stakerToRemove)
e.OnAbortState.DeleteCurrentDelegator(stakerToRemove)
stake := uStakerTx.Stake()
outputs := uStakerTx.Outputs()
stakeAsset := stake[0].Asset
// Refund the stake here
for i, out := range stake {
utxo := &avax.UTXO{
UTXOID: avax.UTXOID{
TxID: tx.TxID,
OutputIndex: uint32(len(outputs) + i),
},
Asset: out.Asset,
Out: out.Output(),
}
e.OnCommitState.AddUTXO(utxo)
e.OnAbortState.AddUTXO(utxo)
}
// We're removing a delegator, so we need to fetch the validator they
// are delegated to.
vdrStaker, err := e.OnCommitState.GetCurrentValidator(
stakerToRemove.SubnetID,
stakerToRemove.NodeID,
)
if err != nil {
return fmt.Errorf(
"failed to get whether %s is a validator: %w",
stakerToRemove.NodeID,
err,
)
}
vdrTxIntf, _, err := e.OnCommitState.GetTx(vdrStaker.TxID)
if err != nil {
return fmt.Errorf(
"failed to get whether %s is a validator: %w",
stakerToRemove.NodeID,
err,
)
}
// Invariant: Delegators must only be able to reference validator
// transactions that implement [txs.ValidatorTx]. All
// validator transactions implement this interface except the
// AddSubnetValidatorTx.
vdrTx, ok := vdrTxIntf.Unsigned.(txs.ValidatorTx)
if !ok {
return errWrongTxType
}
// Calculate split of reward between delegator/delegatee
// The delegator gives stake to the validatee
validatorShares := vdrTx.Shares()
delegatorShares := reward.PercentDenominator - uint64(validatorShares) // parentTx.Shares <= reward.PercentDenominator so no underflow
delegatorReward := delegatorShares * (stakerToRemove.PotentialReward / reward.PercentDenominator) // delegatorShares <= reward.PercentDenominator so no overflow
// Delay rounding as long as possible for small numbers
if optimisticReward, err := math.Mul64(delegatorShares, stakerToRemove.PotentialReward); err == nil {
delegatorReward = optimisticReward / reward.PercentDenominator
}
delegateeReward := stakerToRemove.PotentialReward - delegatorReward // delegatorReward <= reward so no underflow
offset := 0
// Reward the delegator here
if delegatorReward > 0 {
rewardsOwner := uStakerTx.RewardsOwner()
outIntf, err := e.Fx.CreateOutput(delegatorReward, rewardsOwner)
if err != nil {
return fmt.Errorf("failed to create output: %w", err)
}
out, ok := outIntf.(verify.State)
if !ok {
return errInvalidState
}
utxo := &avax.UTXO{
UTXOID: avax.UTXOID{
TxID: tx.TxID,
OutputIndex: uint32(len(outputs) + len(stake)),
},
Asset: stakeAsset,
Out: out,
}
e.OnCommitState.AddUTXO(utxo)
e.OnCommitState.AddRewardUTXO(tx.TxID, utxo)
offset++
}
// Reward the delegatee here
if delegateeReward > 0 {
delegationRewardsOwner := vdrTx.DelegationRewardsOwner()
outIntf, err := e.Fx.CreateOutput(delegateeReward, delegationRewardsOwner)
if err != nil {
return fmt.Errorf("failed to create output: %w", err)
}
out, ok := outIntf.(verify.State)
if !ok {
return errInvalidState
}
utxo := &avax.UTXO{
UTXOID: avax.UTXOID{
TxID: tx.TxID,
OutputIndex: uint32(len(outputs) + len(stake) + offset),
},
Asset: stakeAsset,
Out: out,
}
e.OnCommitState.AddUTXO(utxo)
e.OnCommitState.AddRewardUTXO(tx.TxID, utxo)
}
default:
// Invariant: Permissioned stakers are removed by the advancement of
// time and the current chain timestamp is == this staker's
// EndTime. This means only permissionless stakers should be
// left in the staker set.
return errShouldBePermissionlessStaker
}
// If the reward is aborted, then the current supply should be decreased.
currentSupply, err := e.OnAbortState.GetCurrentSupply(stakerToRemove.SubnetID)
if err != nil {
return err
}
newSupply, err := math.Sub(currentSupply, stakerToRemove.PotentialReward)
if err != nil {
return err
}
e.OnAbortState.SetCurrentSupply(stakerToRemove.SubnetID, newSupply)
var expectedUptimePercentage float64
if stakerToRemove.SubnetID != constants.PrimaryNetworkID {
transformSubnetIntf, err := e.OnCommitState.GetSubnetTransformation(stakerToRemove.SubnetID)
if err != nil {
return err
}
transformSubnet, ok := transformSubnetIntf.Unsigned.(*txs.TransformSubnetTx)
if !ok {
return errIsNotTransformSubnetTx
}
expectedUptimePercentage = float64(transformSubnet.UptimeRequirement) / reward.PercentDenominator
} else {
expectedUptimePercentage = e.Config.UptimePercentage
}
// TODO: calculate subnet uptimes
uptime, err := e.Uptimes.CalculateUptimePercentFrom(
primaryNetworkValidator.NodeID,
constants.PrimaryNetworkID,
primaryNetworkValidator.StartTime,
)
if err != nil {
return fmt.Errorf("failed to calculate uptime: %w", err)
}
e.PrefersCommit = uptime >= expectedUptimePercentage
return nil
}
// GetNextStakerChangeTime returns the next time a staker will be either added
// or removed to/from the current validator set.
func GetNextStakerChangeTime(state state.Chain) (time.Time, error) {
currentStakerIterator, err := state.GetCurrentStakerIterator()
if err != nil {
return time.Time{}, err
}
defer currentStakerIterator.Release()
pendingStakerIterator, err := state.GetPendingStakerIterator()
if err != nil {
return time.Time{}, err
}
defer pendingStakerIterator.Release()
hasCurrentStaker := currentStakerIterator.Next()
hasPendingStaker := pendingStakerIterator.Next()
switch {
case hasCurrentStaker && hasPendingStaker:
nextCurrentTime := currentStakerIterator.Value().NextTime
nextPendingTime := pendingStakerIterator.Value().NextTime
if nextCurrentTime.Before(nextPendingTime) {
return nextCurrentTime, nil
}
return nextPendingTime, nil
case hasCurrentStaker:
return currentStakerIterator.Value().NextTime, nil
case hasPendingStaker:
return pendingStakerIterator.Value().NextTime, nil
default:
return time.Time{}, database.ErrNotFound
}
}
// GetValidator returns information about the given validator, which may be a
// current validator or pending validator.
func GetValidator(state state.Chain, subnetID ids.ID, nodeID ids.NodeID) (*state.Staker, error) {
validator, err := state.GetCurrentValidator(subnetID, nodeID)
if err == nil {
// This node is currently validating the subnet.
return validator, nil
}
if err != database.ErrNotFound {
// Unexpected error occurred.
return nil, err
}
return state.GetPendingValidator(subnetID, nodeID)
}
// canDelegate returns true if [delegator] can be added as a delegator of
// [validator].
//
// A [delegator] can be added if:
// - [delegator]'s start time is not before [validator]'s start time
// - [delegator]'s end time is not after [validator]'s end time
// - the maximum total weight on [validator] will not exceed [weightLimit]
func canDelegate(
state state.Chain,
validator *state.Staker,
weightLimit uint64,
delegator *state.Staker,
) (bool, error) {
if delegator.StartTime.Before(validator.StartTime) {
return false, nil
}
if delegator.EndTime.After(validator.EndTime) {
return false, nil
}
maxWeight, err := GetMaxWeight(state, validator, delegator.StartTime, delegator.EndTime)
if err != nil {
return false, err
}
newMaxWeight, err := math.Add64(maxWeight, delegator.Weight)
if err != nil {
return false, err
}
return newMaxWeight <= weightLimit, nil
}
// GetMaxWeight returns the maximum total weight of the [validator], including
// its own weight, between [startTime] and [endTime].
// The weight changes are applied in the order they will be applied as chain
// time advances.
// Invariant:
// - [validator.StartTime] <= [startTime] < [endTime] <= [validator.EndTime]
func GetMaxWeight(
chainState state.Chain,
validator *state.Staker,
startTime time.Time,
endTime time.Time,
) (uint64, error) {
currentDelegatorIterator, err := chainState.GetCurrentDelegatorIterator(validator.SubnetID, validator.NodeID)
if err != nil {
return 0, err
}
// TODO: We can optimize this by moving the current total weight to be
// stored in the validator state.
//
// Calculate the current total weight on this validator, including the
// weight of the actual validator and the sum of the weights of all of the
// currently active delegators.
currentWeight := validator.Weight
for currentDelegatorIterator.Next() {
currentDelegator := currentDelegatorIterator.Value()
currentWeight, err = math.Add64(currentWeight, currentDelegator.Weight)
if err != nil {
currentDelegatorIterator.Release()
return 0, err
}
}
currentDelegatorIterator.Release()
currentDelegatorIterator, err = chainState.GetCurrentDelegatorIterator(validator.SubnetID, validator.NodeID)
if err != nil {
return 0, err
}
pendingDelegatorIterator, err := chainState.GetPendingDelegatorIterator(validator.SubnetID, validator.NodeID)
if err != nil {
currentDelegatorIterator.Release()
return 0, err
}
delegatorChangesIterator := state.NewStakerDiffIterator(currentDelegatorIterator, pendingDelegatorIterator)
defer delegatorChangesIterator.Release()
// Iterate over the future stake weight changes and calculate the maximum
// total weight on the validator, only including the points in the time
// range [startTime, endTime].
var currentMax uint64
for delegatorChangesIterator.Next() {
delegator, isAdded := delegatorChangesIterator.Value()
// [delegator.NextTime] > [endTime]
if delegator.NextTime.After(endTime) {
// This delegation change (and all following changes) occurs after
// [endTime]. Since we're calculating the max amount staked in
// [startTime, endTime], we can stop.
break
}
// [delegator.NextTime] >= [startTime]
if !delegator.NextTime.Before(startTime) {
// We have advanced time to be at the inside of the delegation
// window. Make sure that the max weight is updated accordingly.
currentMax = math.Max(currentMax, currentWeight)
}
var op func(uint64, uint64) (uint64, error)
if isAdded {
op = math.Add64
} else {
op = math.Sub[uint64]
}
currentWeight, err = op(currentWeight, delegator.Weight)
if err != nil {
return 0, err
}
}
// Because we assume [startTime] < [endTime], we have advanced time to
// be at the end of the delegation window. Make sure that the max weight is
// updated accordingly.
return math.Max(currentMax, currentWeight), nil
}