path: root/eth/gasprice.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 eth

import (
    "math/big"
    "math/rand"
    "sync"

    "github.com/ethereum/go-ethereum/core"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/logger"
    "github.com/ethereum/go-ethereum/logger/glog"
)

const (
    gpoProcessPastBlocks = 100

    // for testing
    gpoDefaultBaseCorrectionFactor = 110
    gpoDefaultMinGasPrice          = 10000000000000
)

type blockPriceInfo struct {
    baseGasPrice *big.Int
}

// GasPriceOracle recommends gas prices based on the content of recent
// blocks.
type GasPriceOracle struct {
    eth           *Ethereum
    initOnce      sync.Once
    minPrice      *big.Int
    lastBaseMutex sync.Mutex
    lastBase      *big.Int

    // state of listenLoop
    blocks                        map[uint64]*blockPriceInfo
    firstProcessed, lastProcessed uint64
    minBase                       *big.Int
}

// NewGasPriceOracle returns a new oracle.
func NewGasPriceOracle(eth *Ethereum) *GasPriceOracle {
    minprice := eth.GpoMinGasPrice
    if minprice == nil {
        minprice = big.NewInt(gpoDefaultMinGasPrice)
    }
    minbase := new(big.Int).Mul(minprice, big.NewInt(100))
    if eth.GpobaseCorrectionFactor > 0 {
        minbase = minbase.Div(minbase, big.NewInt(int64(eth.GpobaseCorrectionFactor)))
    }
    return &GasPriceOracle{
        eth:      eth,
        blocks:   make(map[uint64]*blockPriceInfo),
        minBase:  minbase,
        minPrice: minprice,
        lastBase: minprice,
    }
}

func (gpo *GasPriceOracle) init() {
    gpo.initOnce.Do(func() {
        gpo.processPastBlocks(gpo.eth.BlockChain())
        go gpo.listenLoop()
    })
}

func (self *GasPriceOracle) processPastBlocks(chain *core.BlockChain) {
    last := int64(-1)
    cblock := chain.CurrentBlock()
    if cblock != nil {
        last = int64(cblock.NumberU64())
    }
    first := int64(0)
    if last > gpoProcessPastBlocks {
        first = last - gpoProcessPastBlocks
    }
    self.firstProcessed = uint64(first)
    for i := first; i <= last; i++ {
        block := chain.GetBlockByNumber(uint64(i))
        if block != nil {
            self.processBlock(block)
        }
    }

}

func (self *GasPriceOracle) listenLoop() {
    events := self.eth.EventMux().Subscribe(core.ChainEvent{}, core.ChainSplitEvent{})
    defer events.Unsubscribe()

    for event := range events.Chan() {
        switch event := event.Data.(type) {
        case core.ChainEvent:
            self.processBlock(event.Block)
        case core.ChainSplitEvent:
            self.processBlock(event.Block)
        }
    }
}

func (self *GasPriceOracle) processBlock(block *types.Block) {
    i := block.NumberU64()
    if i > self.lastProcessed {
        self.lastProcessed = i
    }

    lastBase := self.minPrice
    bpl := self.blocks[i-1]
    if bpl != nil {
        lastBase = bpl.baseGasPrice
    }
    if lastBase == nil {
        return
    }

    var corr int
    lp := self.lowestPrice(block)
    if lp == nil {
        return
    }

    if lastBase.Cmp(lp) < 0 {
        corr = self.eth.GpobaseStepUp
    } else {
        corr = -self.eth.GpobaseStepDown
    }

    crand := int64(corr * (900 + rand.Intn(201)))
    newBase := new(big.Int).Mul(lastBase, big.NewInt(1000000+crand))
    newBase.Div(newBase, big.NewInt(1000000))

    if newBase.Cmp(self.minBase) < 0 {
        newBase = self.minBase
    }

    bpi := self.blocks[i]
    if bpi == nil {
        bpi = &blockPriceInfo{}
        self.blocks[i] = bpi
    }
    bpi.baseGasPrice = newBase
    self.lastBaseMutex.Lock()
    self.lastBase = newBase
    self.lastBaseMutex.Unlock()

    glog.V(logger.Detail).Infof("Processed block #%v, base price is %v\n", block.NumberU64(), newBase.Int64())
}

// returns the lowers possible price with which a tx was or could have been included
func (self *GasPriceOracle) lowestPrice(block *types.Block) *big.Int {
    gasUsed := big.NewInt(0)

    receipts := core.GetBlockReceipts(self.eth.ChainDb(), block.Hash())
    if len(receipts) > 0 {
        if cgu := receipts[len(receipts)-1].CumulativeGasUsed; cgu != nil {
            gasUsed = receipts[len(receipts)-1].CumulativeGasUsed
        }
    }

    if new(big.Int).Mul(gasUsed, big.NewInt(100)).Cmp(new(big.Int).Mul(block.GasLimit(),
        big.NewInt(int64(self.eth.GpoFullBlockRatio)))) < 0 {
        // block is not full, could have posted a tx with MinGasPrice
        return big.NewInt(0)
    }

    txs := block.Transactions()
    if len(txs) == 0 {
        return big.NewInt(0)
    }
    // block is full, 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
        }
    }
    return minPrice
}

// SuggestPrice returns the recommended gas price.
func (self *GasPriceOracle) SuggestPrice() *big.Int {
    self.init()
    self.lastBaseMutex.Lock()
    price := new(big.Int).Set(self.lastBase)
    self.lastBaseMutex.Unlock()

    price.Mul(price, big.NewInt(int64(self.eth.GpobaseCorrectionFactor)))
    price.Div(price, big.NewInt(100))
    if price.Cmp(self.minPrice) < 0 {
        price.Set(self.minPrice)
    } else if self.eth.GpoMaxGasPrice != nil && price.Cmp(self.eth.GpoMaxGasPrice) > 0 {
        price.Set(self.eth.GpoMaxGasPrice)
    }
    return price
}