plugeth/eth/gasprice/lightprice.go
Felix Lange be3865211c core/types: remove header accessors
These accessors were introduced by light client changes, but
the only method that is actually used is GetNumberU64. This
commit replaces all uses of .GetNumberU64 with .Number.Uint64.
2016-11-09 02:19:07 +01:00

161 lines
4.0 KiB
Go

// 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 (
"math/big"
"sort"
"sync"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/internal/ethapi"
"github.com/ethereum/go-ethereum/rpc"
"golang.org/x/net/context"
)
const (
LpoAvgCount = 5
LpoMinCount = 3
LpoMaxBlocks = 20
LpoSelect = 50
LpoDefaultPrice = 20000000000
)
// LightPriceOracle recommends gas prices based on the content of recent
// blocks. Suitable for both light and full clients.
type LightPriceOracle struct {
backend ethapi.Backend
lastHead common.Hash
lastPrice *big.Int
cacheLock sync.RWMutex
fetchLock sync.Mutex
}
// NewLightPriceOracle returns a new oracle.
func NewLightPriceOracle(backend ethapi.Backend) *LightPriceOracle {
return &LightPriceOracle{
backend: backend,
lastPrice: big.NewInt(LpoDefaultPrice),
}
}
// SuggestPrice returns the recommended gas price.
func (self *LightPriceOracle) SuggestPrice(ctx context.Context) (*big.Int, error) {
self.cacheLock.RLock()
lastHead := self.lastHead
lastPrice := self.lastPrice
self.cacheLock.RUnlock()
head, _ := self.backend.HeaderByNumber(ctx, rpc.LatestBlockNumber)
headHash := head.Hash()
if headHash == lastHead {
return lastPrice, nil
}
self.fetchLock.Lock()
defer self.fetchLock.Unlock()
// try checking the cache again, maybe the last fetch fetched what we need
self.cacheLock.RLock()
lastHead = self.lastHead
lastPrice = self.lastPrice
self.cacheLock.RUnlock()
if headHash == lastHead {
return lastPrice, nil
}
blockNum := head.Number.Uint64()
chn := make(chan lpResult, LpoMaxBlocks)
sent := 0
exp := 0
var lps bigIntArray
for sent < LpoAvgCount && blockNum > 0 {
go self.getLowestPrice(ctx, blockNum, chn)
sent++
exp++
blockNum--
}
maxEmpty := LpoAvgCount - LpoMinCount
for exp > 0 {
res := <-chn
if res.err != nil {
return nil, res.err
}
exp--
if res.price != nil {
lps = append(lps, res.price)
} else {
if maxEmpty > 0 {
maxEmpty--
} else {
if blockNum > 0 && sent < LpoMaxBlocks {
go self.getLowestPrice(ctx, blockNum, chn)
sent++
exp++
blockNum--
}
}
}
}
price := lastPrice
if len(lps) > 0 {
sort.Sort(lps)
price = lps[(len(lps)-1)*LpoSelect/100]
}
self.cacheLock.Lock()
self.lastHead = headHash
self.lastPrice = price
self.cacheLock.Unlock()
return price, nil
}
type lpResult struct {
price *big.Int
err error
}
// getLowestPrice calculates the lowest transaction gas price in a given block
// and sends it to the result channel. If the block is empty, price is nil.
func (self *LightPriceOracle) getLowestPrice(ctx context.Context, blockNum uint64, chn chan lpResult) {
block, err := self.backend.BlockByNumber(ctx, rpc.BlockNumber(blockNum))
if block == nil {
chn <- lpResult{nil, err}
return
}
txs := block.Transactions()
if len(txs) == 0 {
chn <- lpResult{nil, nil}
return
}
// find smallest gasPrice
minPrice := txs[0].GasPrice()
for i := 1; i < len(txs); i++ {
price := txs[i].GasPrice()
if price.Cmp(minPrice) < 0 {
minPrice = price
}
}
chn <- lpResult{minPrice, nil}
}
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] }