// Copyright 2016 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 detailct.
//
// 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 les
import (
"encoding/binary"
"math"
"sync"
"sync/atomic"
"time"
"github.com/ethereum/go-ethereum/common/mclock"
"github.com/ethereum/go-ethereum/eth"
"github.com/ethereum/go-ethereum/ethdb"
"github.com/ethereum/go-ethereum/les/flowcontrol"
"github.com/ethereum/go-ethereum/log"
)
const makeCostStats = false // make request cost statistics during operation
var (
// average request cost estimates based on serving time
reqAvgTimeCost = requestCostTable{
GetBlockHeadersMsg: {150000, 30000},
GetBlockBodiesMsg: {0, 700000},
GetReceiptsMsg: {0, 1000000},
GetCodeMsg: {0, 450000},
GetProofsV2Msg: {0, 600000},
GetHelperTrieProofsMsg: {0, 1000000},
SendTxV2Msg: {0, 450000},
GetTxStatusMsg: {0, 250000},
}
// maximum incoming message size estimates
reqMaxInSize = requestCostTable{
GetBlockHeadersMsg: {40, 0},
GetBlockBodiesMsg: {0, 40},
GetReceiptsMsg: {0, 40},
GetCodeMsg: {0, 80},
GetProofsV2Msg: {0, 80},
GetHelperTrieProofsMsg: {0, 20},
SendTxV2Msg: {0, 66000},
GetTxStatusMsg: {0, 50},
}
// maximum outgoing message size estimates
reqMaxOutSize = requestCostTable{
GetBlockHeadersMsg: {0, 556},
GetBlockBodiesMsg: {0, 100000},
GetReceiptsMsg: {0, 200000},
GetCodeMsg: {0, 50000},
GetProofsV2Msg: {0, 4000},
GetHelperTrieProofsMsg: {0, 4000},
SendTxV2Msg: {0, 100},
GetTxStatusMsg: {0, 100},
}
minBufLimit = uint64(50000000 * maxCostFactor) // minimum buffer limit allowed for a client
minCapacity = (minBufLimit-1)/bufLimitRatio + 1 // minimum capacity allowed for a client
)
const (
maxCostFactor = 2 // ratio of maximum and average cost estimates
gfInitWeight = time.Second * 10
gfMaxWeight = time.Hour
gfUsageThreshold = 0.5
gfUsageTC = time.Second
gfDbKey = "_globalCostFactor"
)
// costTracker is responsible for calculating costs and cost estimates on the
// server side. It continuously updates the global cost factor which is defined
// as the number of cost units per nanosecond of serving time in a single thread.
// It is based on statistics collected during serving requests in high-load periods
// and practically acts as a one-dimension request price scaling factor over the
// pre-defined cost estimate table. Instead of scaling the cost values, the real
// value of cost units is changed by applying the factor to the serving times. This
// is more convenient because the changes in the cost factor can be applied immediately
// without always notifying the clients about the changed cost tables.
type costTracker struct {
db ethdb.Database
stopCh chan chan struct{}
inSizeFactor, outSizeFactor float64
gf, utilTarget float64
gfUpdateCh chan gfUpdate
gfLock sync.RWMutex
totalRechargeCh chan uint64
stats map[uint64][]uint64
}
// newCostTracker creates a cost tracker and loads the cost factor statistics from the database
func newCostTracker(db ethdb.Database, config *eth.Config) *costTracker {
utilTarget := float64(config.LightServ) * flowcontrol.FixedPointMultiplier / 100
ct := &costTracker{
db: db,
stopCh: make(chan chan struct{}),
utilTarget: utilTarget,
}
if config.LightBandwidthIn > 0 {
ct.inSizeFactor = utilTarget / float64(config.LightBandwidthIn)
}
if config.LightBandwidthOut > 0 {
ct.outSizeFactor = utilTarget / float64(config.LightBandwidthOut)
}
if makeCostStats {
ct.stats = make(map[uint64][]uint64)
for code := range reqAvgTimeCost {
ct.stats[code] = make([]uint64, 10)
}
}
ct.gfLoop()
return ct
}
// stop stops the cost tracker and saves the cost factor statistics to the database
func (ct *costTracker) stop() {
stopCh := make(chan struct{})
ct.stopCh <- stopCh
<-stopCh
if makeCostStats {
ct.printStats()
}
}
// makeCostList returns upper cost estimates based on the hardcoded cost estimate
// tables and the optionally specified incoming/outgoing bandwidth limits
func (ct *costTracker) makeCostList() RequestCostList {
maxCost := func(avgTime, inSize, outSize uint64) uint64 {
globalFactor := ct.globalFactor()
cost := avgTime * maxCostFactor
inSizeCost := uint64(float64(inSize) * ct.inSizeFactor * globalFactor * maxCostFactor)
if inSizeCost > cost {
cost = inSizeCost
}
outSizeCost := uint64(float64(outSize) * ct.outSizeFactor * globalFactor * maxCostFactor)
if outSizeCost > cost {
cost = outSizeCost
}
return cost
}
var list RequestCostList
for code, data := range reqAvgTimeCost {
list = append(list, requestCostListItem{
MsgCode: code,
BaseCost: maxCost(data.baseCost, reqMaxInSize[code].baseCost, reqMaxOutSize[code].baseCost),
ReqCost: maxCost(data.reqCost, reqMaxInSize[code].reqCost, reqMaxOutSize[code].reqCost),
})
}
return list
}
type gfUpdate struct {
avgTime, servingTime float64
}
// gfLoop starts an event loop which updates the global cost factor which is
// calculated as a weighted average of the average estimate / serving time ratio.
// The applied weight equals the serving time if gfUsage is over a threshold,
// zero otherwise. gfUsage is the recent average serving time per time unit in
// an exponential moving window. This ensures that statistics are collected only
// under high-load circumstances where the measured serving times are relevant.
// The total recharge parameter of the flow control system which controls the
// total allowed serving time per second but nominated in cost units, should
// also be scaled with the cost factor and is also updated by this loop.
func (ct *costTracker) gfLoop() {
var gfUsage, gfSum, gfWeight float64
lastUpdate := mclock.Now()
expUpdate := lastUpdate
data, _ := ct.db.Get([]byte(gfDbKey))
if len(data) == 16 {
gfSum = math.Float64frombits(binary.BigEndian.Uint64(data[0:8]))
gfWeight = math.Float64frombits(binary.BigEndian.Uint64(data[8:16]))
}
if gfWeight < float64(gfInitWeight) {
gfSum = float64(gfInitWeight)
gfWeight = float64(gfInitWeight)
}
gf := gfSum / gfWeight
ct.gf = gf
ct.gfUpdateCh = make(chan gfUpdate, 100)
go func() {
for {
select {
case r := <-ct.gfUpdateCh:
now := mclock.Now()
max := r.servingTime * gf
if r.avgTime > max {
max = r.avgTime
}
dt := float64(now - expUpdate)
expUpdate = now
gfUsage = gfUsage*math.Exp(-dt/float64(gfUsageTC)) + max*1000000/float64(gfUsageTC)
if gfUsage >= gfUsageThreshold*ct.utilTarget*gf {
gfSum += r.avgTime
gfWeight += r.servingTime
if time.Duration(now-lastUpdate) > time.Second {
gf = gfSum / gfWeight
if gfWeight >= float64(gfMaxWeight) {
gfSum = gf * float64(gfMaxWeight)
gfWeight = float64(gfMaxWeight)
}
lastUpdate = now
ct.gfLock.Lock()
ct.gf = gf
ch := ct.totalRechargeCh
ct.gfLock.Unlock()
if ch != nil {
select {
case ct.totalRechargeCh <- uint64(ct.utilTarget * gf):
default:
}
}
log.Debug("global cost factor updated", "gf", gf, "weight", time.Duration(gfWeight))
}
}
case stopCh := <-ct.stopCh:
var data [16]byte
binary.BigEndian.PutUint64(data[0:8], math.Float64bits(gfSum))
binary.BigEndian.PutUint64(data[8:16], math.Float64bits(gfWeight))
ct.db.Put([]byte(gfDbKey), data[:])
log.Debug("global cost factor saved", "sum", time.Duration(gfSum), "weight", time.Duration(gfWeight))
close(stopCh)
return
}
}
}()
}
// globalFactor returns the current value of the global cost factor
func (ct *costTracker) globalFactor() float64 {
ct.gfLock.RLock()
defer ct.gfLock.RUnlock()
return ct.gf
}
// totalRecharge returns the current total recharge parameter which is used by
// flowcontrol.ClientManager and is scaled by the global cost factor
func (ct *costTracker) totalRecharge() uint64 {
ct.gfLock.RLock()
defer ct.gfLock.RUnlock()
return uint64(ct.gf * ct.utilTarget)
}
// subscribeTotalRecharge returns all future updates to the total recharge value
// through a channel and also returns the current value
func (ct *costTracker) subscribeTotalRecharge(ch chan uint64) uint64 {
ct.gfLock.Lock()
defer ct.gfLock.Unlock()
ct.totalRechargeCh = ch
return uint64(ct.gf * ct.utilTarget)
}
// updateStats updates the global cost factor and (if enabled) the real cost vs.
// average estimate statistics
func (ct *costTracker) updateStats(code, amount, servingTime, realCost uint64) {
avg := reqAvgTimeCost[code]
avgTime := avg.baseCost + amount*avg.reqCost
select {
case ct.gfUpdateCh <- gfUpdate{float64(avgTime), float64(servingTime)}:
default:
}
if makeCostStats {
realCost <<= 4
l := 0
for l < 9 && realCost > avgTime {
l++
realCost >>= 1
}
atomic.AddUint64(&ct.stats[code][l], 1)
}
}
// realCost calculates the final cost of a request based on actual serving time,
// incoming and outgoing message size
//
// Note: message size is only taken into account if bandwidth limitation is applied
// and the cost based on either message size is greater than the cost based on
// serving time. A maximum of the three costs is applied instead of their sum
// because the three limited resources (serving thread time and i/o bandwidth) can
// also be maxed out simultaneously.
func (ct *costTracker) realCost(servingTime uint64, inSize, outSize uint32) uint64 {
cost := float64(servingTime)
inSizeCost := float64(inSize) * ct.inSizeFactor
if inSizeCost > cost {
cost = inSizeCost
}
outSizeCost := float64(outSize) * ct.outSizeFactor
if outSizeCost > cost {
cost = outSizeCost
}
return uint64(cost * ct.globalFactor())
}
// printStats prints the distribution of real request cost relative to the average estimates
func (ct *costTracker) printStats() {
if ct.stats == nil {
return
}
for code, arr := range ct.stats {
log.Info("Request cost statistics", "code", code, "1/16", arr[0], "1/8", arr[1], "1/4", arr[2], "1/2", arr[3], "1", arr[4], "2", arr[5], "4", arr[6], "8", arr[7], "16", arr[8], ">16", arr[9])
}
}
type (
// requestCostTable assigns a cost estimate function to each request type
// which is a linear function of the requested amount
// (cost = baseCost + reqCost * amount)
requestCostTable map[uint64]*requestCosts
requestCosts struct {
baseCost, reqCost uint64
}
// RequestCostList is a list representation of request costs which is used for
// database storage and communication through the network
RequestCostList []requestCostListItem
requestCostListItem struct {
MsgCode, BaseCost, ReqCost uint64
}
)
// getCost calculates the estimated cost for a given request type and amount
func (table requestCostTable) getCost(code, amount uint64) uint64 {
costs := table[code]
return costs.baseCost + amount*costs.reqCost
}
// decode converts a cost list to a cost table
func (list RequestCostList) decode(protocolLength uint64) requestCostTable {
table := make(requestCostTable)
for _, e := range list {
if e.MsgCode < protocolLength {
table[e.MsgCode] = &requestCosts{
baseCost: e.BaseCost,
reqCost: e.ReqCost,
}
}
}
return table
}
// testCostList returns a dummy request cost list used by tests
func testCostList() RequestCostList {
cl := make(RequestCostList, len(reqAvgTimeCost))
var max uint64
for code := range reqAvgTimeCost {
if code > max {
max = code
}
}
i := 0
for code := uint64(0); code <= max; code++ {
if _, ok := reqAvgTimeCost[code]; ok {
cl[i].MsgCode = code
cl[i].BaseCost = 0
cl[i].ReqCost = 0
i++
}
}
return cl
}
