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Diffstat (limited to 'eth/gasprice/lightprice.go')
| -rw-r--r-- | eth/gasprice/lightprice.go | 160 |
1 files changed, 160 insertions, 0 deletions
diff --git a/eth/gasprice/lightprice.go b/eth/gasprice/lightprice.go new file mode 100644 index 000000000..ce075ff4e --- /dev/null +++ b/eth/gasprice/lightprice.go @@ -0,0 +1,160 @@ +// 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.GetNumberU64() + 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] } |