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gasprice.go
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gasprice.go
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// (c) 2019-2020, Ava Labs, Inc.
//
// This file is a derived work, based on the go-ethereum library whose original
// notices appear below.
//
// It is distributed under a license compatible with the licensing terms of the
// original code from which it is derived.
//
// Much love to the original authors for their work.
// **********
// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package gasprice
import (
"context"
"math/big"
"sort"
"sync"
"github.com/ava-labs/avalanchego/utils/timer"
"github.com/ava-labs/coreth/consensus/dummy"
"github.com/ava-labs/coreth/core"
"github.com/ava-labs/coreth/core/types"
"github.com/ava-labs/coreth/params"
"github.com/ava-labs/coreth/rpc"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/event"
"github.com/ethereum/go-ethereum/log"
lru "github.com/hashicorp/golang-lru"
)
var (
DefaultMaxPrice = big.NewInt(150 * params.GWei)
DefaultMinPrice = big.NewInt(0 * params.GWei)
DefaultMinGasUsed = big.NewInt(2_000_000) // block gas limit is 8,000,000
)
type Config struct {
Blocks int
Percentile int
MaxHeaderHistory int
MaxBlockHistory int
MaxPrice *big.Int `toml:",omitempty"`
MinPrice *big.Int `toml:",omitempty"`
MinGasUsed *big.Int `toml:",omitempty"`
}
// OracleBackend includes all necessary background APIs for oracle.
type OracleBackend interface {
HeaderByNumber(ctx context.Context, number rpc.BlockNumber) (*types.Header, error)
BlockByNumber(ctx context.Context, number rpc.BlockNumber) (*types.Block, error)
GetReceipts(ctx context.Context, hash common.Hash) (types.Receipts, error)
PendingBlockAndReceipts() (*types.Block, types.Receipts)
ChainConfig() *params.ChainConfig
SubscribeChainHeadEvent(ch chan<- core.ChainHeadEvent) event.Subscription
MinRequiredTip(ctx context.Context, header *types.Header) (*big.Int, error)
}
// Oracle recommends gas prices based on the content of recent
// blocks. Suitable for both light and full clients.
type Oracle struct {
backend OracleBackend
lastHead common.Hash
lastPrice *big.Int
// [minPrice] ensures we don't get into a positive feedback loop where tips
// sink to 0 during a period of slow block production, such that nobody's
// transactions will be included until the full block fee duration has
// elapsed.
minPrice *big.Int
maxPrice *big.Int
// [minGasUsed] ensures we don't recommend users pay non-zero tips when other
// users are paying a tip to unnecessarily expedite block production.
minGasUsed *big.Int
cacheLock sync.RWMutex
fetchLock sync.Mutex
// clock to decide what set of rules to use when recommending a gas price
clock timer.Clock
checkBlocks, percentile int
maxHeaderHistory, maxBlockHistory int
historyCache *lru.Cache
}
// NewOracle returns a new gasprice oracle which can recommend suitable
// gasprice for newly created transaction.
func NewOracle(backend OracleBackend, config Config) *Oracle {
blocks := config.Blocks
if blocks < 1 {
blocks = 1
log.Warn("Sanitizing invalid gasprice oracle sample blocks", "provided", config.Blocks, "updated", blocks)
}
percent := config.Percentile
if percent < 0 {
percent = 0
log.Warn("Sanitizing invalid gasprice oracle sample percentile", "provided", config.Percentile, "updated", percent)
}
if percent > 100 {
percent = 100
log.Warn("Sanitizing invalid gasprice oracle sample percentile", "provided", config.Percentile, "updated", percent)
}
maxPrice := config.MaxPrice
if maxPrice == nil || maxPrice.Int64() <= 0 {
maxPrice = DefaultMaxPrice
log.Warn("Sanitizing invalid gasprice oracle max price", "provided", config.MaxPrice, "updated", maxPrice)
}
minPrice := config.MinPrice
if minPrice == nil || minPrice.Int64() < 0 {
minPrice = DefaultMinPrice
log.Warn("Sanitizing invalid gasprice oracle min price", "provided", config.MinPrice, "updated", minPrice)
}
minGasUsed := config.MinGasUsed
if minGasUsed == nil || minGasUsed.Int64() < 0 {
minGasUsed = DefaultMinGasUsed
log.Warn("Sanitizing invalid gasprice oracle min gas used", "provided", config.MinGasUsed, "updated", minGasUsed)
}
cache, _ := lru.New(2048)
headEvent := make(chan core.ChainHeadEvent, 1)
backend.SubscribeChainHeadEvent(headEvent)
go func() {
var lastHead common.Hash
for ev := range headEvent {
if ev.Block.ParentHash() != lastHead {
cache.Purge()
}
lastHead = ev.Block.Hash()
}
}()
return &Oracle{
backend: backend,
lastPrice: minPrice,
minPrice: minPrice,
maxPrice: maxPrice,
minGasUsed: minGasUsed,
checkBlocks: blocks,
percentile: percent,
maxHeaderHistory: config.MaxHeaderHistory,
maxBlockHistory: config.MaxBlockHistory,
historyCache: cache,
}
}
// EstiamteBaseFee returns an estimate of what the base fee will be on a block
// produced at the current time. If ApricotPhase3 has not been activated, it may
// return a nil value and a nil error.
func (oracle *Oracle) EstimateBaseFee(ctx context.Context) (*big.Int, error) {
// Fetch the most recent block by number
block, err := oracle.backend.BlockByNumber(ctx, rpc.LatestBlockNumber)
if err != nil {
return nil, err
}
// If the fetched block does not have a base fee, return nil as the base fee
if block.BaseFee() == nil {
return nil, nil
}
// If the block does have a baseFee, calculate the next base fee
// based on the current time and add it to the tip to estimate the
// total gas price estimate.
_, nextBaseFee, err := dummy.CalcBaseFee(oracle.backend.ChainConfig(), block.Header(), oracle.clock.Unix())
return nextBaseFee, err
}
// SuggestPrice returns an estimated price for legacy transactions.
func (oracle *Oracle) SuggestPrice(ctx context.Context) (*big.Int, error) {
// Estimate the effective tip based on recent blocks.
tip, err := oracle.suggestTipCap(ctx)
if err != nil {
return nil, err
}
nextBaseFee, err := oracle.EstimateBaseFee(ctx)
if err != nil {
return nil, err
}
// If [nextBaseFee] is nil, return [tip] without modification.
if nextBaseFee == nil {
return tip, nil
}
return new(big.Int).Add(tip, nextBaseFee), nil
}
// SuggestTipCap returns a tip cap so that newly created transaction can have a
// very high chance to be included in the following blocks.
//
// Note, for legacy transactions and the legacy eth_gasPrice RPC call, it will be
// necessary to add the basefee to the returned number to fall back to the legacy
// behavior.
func (oracle *Oracle) SuggestTipCap(ctx context.Context) (*big.Int, error) {
return oracle.suggestTipCap(ctx)
}
// sugggestTipCap checks the clock to estimate what network rules will be applied to
// new transactions and then suggests a gas tip cap based on the response.
func (oracle *Oracle) suggestTipCap(ctx context.Context) (*big.Int, error) {
bigTimestamp := big.NewInt(oracle.clock.Time().Unix())
switch {
case oracle.backend.ChainConfig().IsApricotPhase4(bigTimestamp):
return oracle.suggestDynamicTipCap(ctx)
case oracle.backend.ChainConfig().IsApricotPhase3(bigTimestamp):
return new(big.Int).Set(common.Big0), nil
case oracle.backend.ChainConfig().IsApricotPhase1(bigTimestamp):
return big.NewInt(params.ApricotPhase1MinGasPrice), nil
default:
return big.NewInt(params.LaunchMinGasPrice), nil
}
}
// suggestDynamicTipCap estimates the gas tip based on a simple sampling method
func (oracle *Oracle) suggestDynamicTipCap(ctx context.Context) (*big.Int, error) {
head, _ := oracle.backend.HeaderByNumber(ctx, rpc.LatestBlockNumber)
headHash := head.Hash()
// If the latest gasprice is still available, return it.
oracle.cacheLock.RLock()
lastHead, lastPrice := oracle.lastHead, oracle.lastPrice
oracle.cacheLock.RUnlock()
if headHash == lastHead {
return new(big.Int).Set(lastPrice), nil
}
oracle.fetchLock.Lock()
defer oracle.fetchLock.Unlock()
// Try checking the cache again, maybe the last fetch fetched what we need
oracle.cacheLock.RLock()
lastHead, lastPrice = oracle.lastHead, oracle.lastPrice
oracle.cacheLock.RUnlock()
if headHash == lastHead {
return new(big.Int).Set(lastPrice), nil
}
var (
sent, exp int
number = head.Number.Uint64()
result = make(chan results, oracle.checkBlocks)
quit = make(chan struct{})
results []*big.Int
)
for sent < oracle.checkBlocks && number > 0 {
go oracle.getBlockTips(ctx, number, result, quit)
sent++
exp++
number--
}
for exp > 0 {
res := <-result
if res.err != nil {
close(quit)
return new(big.Int).Set(lastPrice), res.err
}
exp--
if res.value != nil {
results = append(results, res.value)
} else {
results = append(results, new(big.Int).Set(common.Big0))
}
}
price := lastPrice
if len(results) > 0 {
sort.Sort(bigIntArray(results))
price = results[(len(results)-1)*oracle.percentile/100]
}
if price.Cmp(oracle.maxPrice) > 0 {
price = new(big.Int).Set(oracle.maxPrice)
}
if price.Cmp(oracle.minPrice) < 0 {
price = new(big.Int).Set(oracle.minPrice)
}
oracle.cacheLock.Lock()
oracle.lastHead = headHash
oracle.lastPrice = price
oracle.cacheLock.Unlock()
return new(big.Int).Set(price), nil
}
type results struct {
value *big.Int
err error
}
// getBlockTips calculates the minimum required tip to be included in a given
// block and sends the value to the result channel.
func (oracle *Oracle) getBlockTips(ctx context.Context, blockNum uint64, result chan results, quit chan struct{}) {
header, err := oracle.backend.HeaderByNumber(ctx, rpc.BlockNumber(blockNum))
if header == nil {
select {
case result <- results{nil, err}:
case <-quit:
}
return
}
// Don't bias the estimate with blocks containing a limited number of transactions paying to
// expedite block production.
if header.GasUsed < oracle.minGasUsed.Uint64() {
select {
case result <- results{nil, nil}:
case <-quit:
}
return
}
// Compute minimum required tip to be included in previous block
//
// NOTE: Using this approach, we will never recommend that the caller
// provides a non-zero tip unless some block is produced faster than the
// target rate (which could only occur if some set of callers manually override the
// suggested tip). In the future, we may wish to start suggesting a non-zero
// tip when most blocks are full otherwise callers may observe an unexpected
// delay in transaction inclusion.
minTip, err := oracle.backend.MinRequiredTip(ctx, header)
select {
case result <- results{minTip, err}:
case <-quit:
}
}
type bigIntArray []*big.Int
func (s bigIntArray) Len() int { return len(s) }
func (s bigIntArray) Less(i, j int) bool { return s[i].Cmp(s[j]) < 0 }
func (s bigIntArray) Swap(i, j int) { s[i], s[j] = s[j], s[i] }