// 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 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 les implements the Light Ethereum Subprotocol.
package les
import (
"fmt"
"io"
"math"
"math/rand"
"net"
"strconv"
"sync"
"time"
"github.com/ethereum/go-ethereum/common/mclock"
"github.com/ethereum/go-ethereum/ethdb"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/p2p"
"github.com/ethereum/go-ethereum/p2p/discover"
"github.com/ethereum/go-ethereum/p2p/discv5"
"github.com/ethereum/go-ethereum/rlp"
)
const (
// After a connection has been ended or timed out, there is a waiting period
// before it can be selected for connection again.
// waiting period = base delay * (1 + random(1))
// base delay = shortRetryDelay for the first shortRetryCnt times after a
// successful connection, after that longRetryDelay is applied
shortRetryCnt = 5
shortRetryDelay = time.Second * 5
longRetryDelay = time.Minute * 10
// maxNewEntries is the maximum number of newly discovered (never connected) nodes.
// If the limit is reached, the least recently discovered one is thrown out.
maxNewEntries = 1000
// maxKnownEntries is the maximum number of known (already connected) nodes.
// If the limit is reached, the least recently connected one is thrown out.
// (not that unlike new entries, known entries are persistent)
maxKnownEntries = 1000
// target for simultaneously connected servers
targetServerCount = 5
// target for servers selected from the known table
// (we leave room for trying new ones if there is any)
targetKnownSelect = 3
// after dialTimeout, consider the server unavailable and adjust statistics
dialTimeout = time.Second * 30
// targetConnTime is the minimum expected connection duration before a server
// drops a client without any specific reason
targetConnTime = time.Minute * 10
// new entry selection weight calculation based on most recent discovery time:
// unity until discoverExpireStart, then exponential decay with discoverExpireConst
discoverExpireStart = time.Minute * 20
discoverExpireConst = time.Minute * 20
// known entry selection weight is dropped by a factor of exp(-failDropLn) after
// each unsuccessful connection (restored after a successful one)
failDropLn = 0.1
// known node connection success and quality statistics have a long term average
// and a short term value which is adjusted exponentially with a factor of
// pstatRecentAdjust with each dial/connection and also returned exponentially
// to the average with the time constant pstatReturnToMeanTC
pstatRecentAdjust = 0.1
pstatReturnToMeanTC = time.Hour
// node address selection weight is dropped by a factor of exp(-addrFailDropLn) after
// each unsuccessful connection (restored after a successful one)
addrFailDropLn = math.Ln2
// responseScoreTC and delayScoreTC are exponential decay time constants for
// calculating selection chances from response times and block delay times
responseScoreTC = time.Millisecond * 100
delayScoreTC = time.Second * 5
timeoutPow = 10
// peerSelectMinWeight is added to calculated weights at request peer selection
// to give poorly performing peers a little chance of coming back
peerSelectMinWeight = 0.005
// initStatsWeight is used to initialize previously unknown peers with good
// statistics to give a chance to prove themselves
initStatsWeight = 1
)
// serverPool implements a pool for storing and selecting newly discovered and already
// known light server nodes. It received discovered nodes, stores statistics about
// known nodes and takes care of always having enough good quality servers connected.
type serverPool struct {
db ethdb.Database
dbKey []byte
server *p2p.Server
quit chan struct{}
wg *sync.WaitGroup
connWg sync.WaitGroup
topic discv5.Topic
discSetPeriod chan time.Duration
discNodes chan *discv5.Node
discLookups chan bool
entries map[discover.NodeID]*poolEntry
lock sync.Mutex
timeout, enableRetry chan *poolEntry
adjustStats chan poolStatAdjust
knownQueue, newQueue poolEntryQueue
knownSelect, newSelect *weightedRandomSelect
knownSelected, newSelected int
fastDiscover bool
}
// newServerPool creates a new serverPool instance
func newServerPool(db ethdb.Database, quit chan struct{}, wg *sync.WaitGroup) *serverPool {
pool := &serverPool{
db: db,
quit: quit,
wg: wg,
entries: make(map[discover.NodeID]*poolEntry),
timeout: make(chan *poolEntry, 1),
adjustStats: make(chan poolStatAdjust, 100),
enableRetry: make(chan *poolEntry, 1),
knownSelect: newWeightedRandomSelect(),
newSelect: newWeightedRandomSelect(),
fastDiscover: true,
}
pool.knownQueue = newPoolEntryQueue(maxKnownEntries, pool.removeEntry)
pool.newQueue = newPoolEntryQueue(maxNewEntries, pool.removeEntry)
return pool
}
func (pool *serverPool) start(server *p2p.Server, topic discv5.Topic) {
pool.server = server
pool.topic = topic
pool.dbKey = append([]byte("serverPool/"), []byte(topic)...)
pool.wg.Add(1)
pool.loadNodes()
go pool.eventLoop()
pool.checkDial()
if pool.server.DiscV5 != nil {
pool.discSetPeriod = make(chan time.Duration, 1)
pool.discNodes = make(chan *discv5.Node, 100)
pool.discLookups = make(chan bool, 100)
go pool.server.DiscV5.SearchTopic(pool.topic, pool.discSetPeriod, pool.discNodes, pool.discLookups)
}
}
// connect should be called upon any incoming connection. If the connection has been
// dialed by the server pool recently, the appropriate pool entry is returned.
// Otherwise, the connection should be rejected.
// Note that whenever a connection has been accepted and a pool entry has been returned,
// disconnect should also always be called.
func (pool *serverPool) connect(p *peer, ip net.IP, port uint16) *poolEntry {
pool.lock.Lock()
defer pool.lock.Unlock()
entry := pool.entries[p.ID()]
if entry == nil {
entry = pool.findOrNewNode(p.ID(), ip, port)
}
p.Log().Debug("Connecting to new peer", "state", entry.state)
if entry.state == psConnected || entry.state == psRegistered {
return nil
}
pool.connWg.Add(1)
entry.peer = p
entry.state = psConnected
addr := &poolEntryAddress{
ip: ip,
port: port,
lastSeen: mclock.Now(),
}
entry.lastConnected = addr
entry.addr = make(map[string]*poolEntryAddress)
entry.addr[addr.strKey()] = addr
entry.addrSelect = *newWeightedRandomSelect()
entry.addrSelect.update(addr)
return entry
}
// registered should be called after a successful handshake
func (pool *serverPool) registered(entry *poolEntry) {
log.Debug("Registered new entry", "enode", entry.id)
pool.lock.Lock()
defer pool.lock.Unlock()
entry.state = psRegistered
entry.regTime = mclock.Now()
if !entry.known {
pool.newQueue.remove(entry)
entry.known = true
}
pool.knownQueue.setLatest(entry)
entry.shortRetry = shortRetryCnt
}
// disconnect should be called when ending a connection. Service quality statistics
// can be updated optionally (not updated if no registration happened, in this case
// only connection statistics are updated, just like in case of timeout)
func (pool *serverPool) disconnect(entry *poolEntry) {
log.Debug("Disconnected old entry", "enode", entry.id)
pool.lock.Lock()
defer pool.lock.Unlock()
if entry.state == psRegistered {
connTime := mclock.Now() - entry.regTime
connAdjust := float64(connTime) / float64(targetConnTime)
if connAdjust > 1 {
connAdjust = 1
}
stopped := false
select {
case <-pool.quit:
stopped = true
default:
}
if stopped {
entry.connectStats.add(1, connAdjust)
} else {
entry.connectStats.add(connAdjust, 1)
}
}
entry.state = psNotConnected
if entry.knownSelected {
pool.knownSelected--
} else {
pool.newSelected--
}
pool.setRetryDial(entry)
pool.connWg.Done()
}
const (
pseBlockDelay = iota
pseResponseTime
pseResponseTimeout
)
// poolStatAdjust records are sent to adjust peer block delay/response time statistics
type poolStatAdjust struct {
adjustType int
entry *poolEntry
time time.Duration
}
// adjustBlockDelay adjusts the block announce delay statistics of a node
func (pool *serverPool) adjustBlockDelay(entry *poolEntry, time time.Duration) {
if entry == nil {
return
}
pool.adjustStats <- poolStatAdjust{pseBlockDelay, entry, time}
}
// adjustResponseTime adjusts the request response time statistics of a node
func (pool *serverPool) adjustResponseTime(entry *poolEntry, time time.Duration, timeout bool) {
if entry == nil {
return
}
if timeout {
pool.adjustStats <- poolStatAdjust{pseResponseTimeout, entry, time}
} else {
pool.adjustStats <- poolStatAdjust{pseResponseTime, entry, time}
}
}
// eventLoop handles pool events and mutex locking for all internal functions
func (pool *serverPool) eventLoop() {
lookupCnt := 0
var convTime mclock.AbsTime
if pool.discSetPeriod != nil {
pool.discSetPeriod <- time.Millisecond * 100
}
for {
select {
case entry := <-pool.timeout:
pool.lock.Lock()
if !entry.removed {
pool.checkDialTimeout(entry)
}
pool.lock.Unlock()
case entry := <-pool.enableRetry:
pool.lock.Lock()
if !entry.removed {
entry.delayedRetry = false
pool.updateCheckDial(entry)
}
pool.lock.Unlock()
case adj := <-pool.adjustStats:
pool.lock.Lock()
switch adj.adjustType {
case pseBlockDelay:
adj.entry.delayStats.add(float64(adj.time), 1)
case pseResponseTime:
adj.entry.responseStats.add(float64(adj.time), 1)
adj.entry.timeoutStats.add(0, 1)
case pseResponseTimeout:
adj.entry.timeoutStats.add(1, 1)
}
pool.lock.Unlock()
case node := <-pool.discNodes:
pool.lock.Lock()
entry := pool.findOrNewNode(discover.NodeID(node.ID), node.IP, node.TCP)
pool.updateCheckDial(entry)
pool.lock.Unlock()
case conv := <-pool.discLookups:
if conv {
if lookupCnt == 0 {
convTime = mclock.Now()
}
lookupCnt++
if pool.fastDiscover && (lookupCnt == 50 || time.Duration(mclock.Now()-convTime) > time.Minute) {
pool.fastDiscover = false
if pool.discSetPeriod != nil {
pool.discSetPeriod <- time.Minute
}
}
}
case <-pool.quit:
if pool.discSetPeriod != nil {
close(pool.discSetPeriod)
}
pool.connWg.Wait()
pool.saveNodes()
pool.wg.Done()
return
}
}
}
func (pool *serverPool) findOrNewNode(id discover.NodeID, ip net.IP, port uint16) *poolEntry {
now := mclock.Now()
entry := pool.entries[id]
if entry == nil {
log.Debug("Discovered new entry", "id", id)
entry = &poolEntry{
id: id,
addr: make(map[string]*poolEntryAddress),
addrSelect: *newWeightedRandomSelect(),
shortRetry: shortRetryCnt,
}
pool.entries[id] = entry
// initialize previously unknown peers with good statistics to give a chance to prove themselves
entry.connectStats.add(1, initStatsWeight)
entry.delayStats.add(0, initStatsWeight)
entry.responseStats.add(0, initStatsWeight)
entry.timeoutStats.add(0, initStatsWeight)
}
entry.lastDiscovered = now
addr := &poolEntryAddress{
ip: ip,
port: port,
}
if a, ok := entry.addr[addr.strKey()]; ok {
addr = a
} else {
entry.addr[addr.strKey()] = addr
}
addr.lastSeen = now
entry.addrSelect.update(addr)
if !entry.known {
pool.newQueue.setLatest(entry)
}
return entry
}
// loadNodes loads known nodes and their statistics from the database
func (pool *serverPool) loadNodes() {
enc, err := pool.db.Get(pool.dbKey)
if err != nil {
return
}
var list []*poolEntry
err = rlp.DecodeBytes(enc, &list)
if err != nil {
log.Debug("Failed to decode node list", "err", err)
return
}
for _, e := range list {
log.Debug("Loaded server stats", "id", e.id, "fails", e.lastConnected.fails,
"conn", fmt.Sprintf("%v/%v", e.connectStats.avg, e.connectStats.weight),
"delay", fmt.Sprintf("%v/%v", time.Duration(e.delayStats.avg), e.delayStats.weight),
"response", fmt.Sprintf("%v/%v", time.Duration(e.responseStats.avg), e.responseStats.weight),
"timeout", fmt.Sprintf("%v/%v", e.timeoutStats.avg, e.timeoutStats.weight))
pool.entries[e.id] = e
pool.knownQueue.setLatest(e)
pool.knownSelect.update((*knownEntry)(e))
}
}
// saveNodes saves known nodes and their statistics into the database. Nodes are
// ordered from least to most recently connected.
func (pool *serverPool) saveNodes() {
list := make([]*poolEntry, len(pool.knownQueue.queue))
for i := range list {
list[i] = pool.knownQueue.fetchOldest()
}
enc, err := rlp.EncodeToBytes(list)
if err == nil {
pool.db.Put(pool.dbKey, enc)
}
}
// removeEntry removes a pool entry when the entry count limit is reached.
// Note that it is called by the new/known queues from which the entry has already
// been removed so removing it from the queues is not necessary.
func (pool *serverPool) removeEntry(entry *poolEntry) {
pool.newSelect.remove((*discoveredEntry)(entry))
pool.knownSelect.remove((*knownEntry)(entry))
entry.removed = true
delete(pool.entries, entry.id)
}
// setRetryDial starts the timer which will enable dialing a certain node again
func (pool *serverPool) setRetryDial(entry *poolEntry) {
delay := longRetryDelay
if entry.shortRetry > 0 {
entry.shortRetry--
delay = shortRetryDelay
}
delay += time.Duration(rand.Int63n(int64(delay) + 1))
entry.delayedRetry = true
go func() {
select {
case <-pool.quit:
case <-time.After(delay):
select {
case <-pool.quit:
case pool.enableRetry <- entry:
}
}
}()
}
// updateCheckDial is called when an entry can potentially be dialed again. It updates
// its selection weights and checks if new dials can/should be made.
func (pool *serverPool) updateCheckDial(entry *poolEntry) {
pool.newSelect.update((*discoveredEntry)(entry))
pool.knownSelect.update((*knownEntry)(entry))
pool.checkDial()
}
// checkDial checks if new dials can/should be made. It tries to select servers both
// based on good statistics and recent discovery.
func (pool *serverPool) checkDial() {
fillWithKnownSelects := !pool.fastDiscover
for pool.knownSelected < targetKnownSelect {
entry := pool.knownSelect.choose()
if entry == nil {
fillWithKnownSelects = false
break
}
pool.dial((*poolEntry)(entry.(*knownEntry)), true)
}
for pool.knownSelected+pool.newSelected < targetServerCount {
entry := pool.newSelect.choose()
if entry == nil {
break
}
pool.dial((*poolEntry)(entry.(*discoveredEntry)), false)
}
if fillWithKnownSelects {
// no more newly discovered nodes to select and since fast discover period
// is over, we probably won't find more in the near future so select more
// known entries if possible
for pool.knownSelected < targetServerCount {
entry := pool.knownSelect.choose()
if entry == nil {
break
}
pool.dial((*poolEntry)(entry.(*knownEntry)), true)
}
}
}
// dial initiates a new connection
func (pool *serverPool) dial(entry *poolEntry, knownSelected bool) {
if pool.server == nil || entry.state != psNotConnected {
return
}
entry.state = psDialed
entry.knownSelected = knownSelected
if knownSelected {
pool.knownSelected++
} else {
pool.newSelected++
}
addr := entry.addrSelect.choose().(*poolEntryAddress)
log.Debug("Dialing new peer", "lesaddr", entry.id.String()+"@"+addr.strKey(), "set", len(entry.addr), "known", knownSelected)
entry.dialed = addr
go func() {
pool.server.AddPeer(discover.NewNode(entry.id, addr.ip, addr.port, addr.port))
select {
case <-pool.quit:
case <-time.After(dialTimeout):
select {
case <-pool.quit:
case pool.timeout <- entry:
}
}
}()
}
// checkDialTimeout checks if the node is still in dialed state and if so, resets it
// and adjusts connection statistics accordingly.
func (pool *serverPool) checkDialTimeout(entry *poolEntry) {
if entry.state != psDialed {
return
}
log.Debug("Dial timeout", "lesaddr", entry.id.String()+"@"+entry.dialed.strKey())
entry.state = psNotConnected
if entry.knownSelected {
pool.knownSelected--
} else {
pool.newSelected--
}
entry.connectStats.add(0, 1)
entry.dialed.fails++
pool.setRetryDial(entry)
}
const (
psNotConnected = iota
psDialed
psConnected
psRegistered
)
// poolEntry represents a server node and stores its current state and statistics.
type poolEntry struct {
peer *peer
id discover.NodeID
addr map[string]*poolEntryAddress
lastConnected, dialed *poolEntryAddress
addrSelect weightedRandomSelect
lastDiscovered mclock.AbsTime
known, knownSelected bool
connectStats, delayStats poolStats
responseStats, timeoutStats poolStats
state int
regTime mclock.AbsTime
queueIdx int
removed bool
delayedRetry bool
shortRetry int
}
func (e *poolEntry) EncodeRLP(w io.Writer) error {
return rlp.Encode(w, []interface{}{e.id, e.lastConnected.ip, e.lastConnected.port, e.lastConnected.fails, &e.connectStats, &e.delayStats, &e.responseStats, &e.timeoutStats})
}
func (e *poolEntry) DecodeRLP(s *rlp.Stream) error {
var entry struct {
ID discover.NodeID
IP net.IP
Port uint16
Fails uint
CStat, DStat, RStat, TStat poolStats
}
if err := s.Decode(&entry); err != nil {
return err
}
addr := &poolEntryAddress{ip: entry.IP, port: entry.Port, fails: entry.Fails, lastSeen: mclock.Now()}
e.id = entry.ID
e.addr = make(map[string]*poolEntryAddress)
e.addr[addr.strKey()] = addr
e.addrSelect = *newWeightedRandomSelect()
e.addrSelect.update(addr)
e.lastConnected = addr
e.connectStats = entry.CStat
e.delayStats = entry.DStat
e.responseStats = entry.RStat
e.timeoutStats = entry.TStat
e.shortRetry = shortRetryCnt
e.known = true
return nil
}
// discoveredEntry implements wrsItem
type discoveredEntry poolEntry
// Weight calculates random selection weight for newly discovered entries
func (e *discoveredEntry) Weight() int64 {
if e.state != psNotConnected || e.delayedRetry {
return 0
}
t := time.Duration(mclock.Now() - e.lastDiscovered)
if t <= discoverExpireStart {
return 1000000000
} else {
return int64(1000000000 * math.Exp(-float64(t-discoverExpireStart)/float64(discoverExpireConst)))
}
}
// knownEntry implements wrsItem
type knownEntry poolEntry
// Weight calculates random selection weight for known entries
func (e *knownEntry) Weight() int64 {
if e.state != psNotConnected || !e.known || e.delayedRetry {
return 0
}
return int64(1000000000 * e.connectStats.recentAvg() * math.Exp(-float64(e.lastConnected.fails)*failDropLn-e.responseStats.recentAvg()/float64(responseScoreTC)-e.delayStats.recentAvg()/float64(delayScoreTC)) * math.Pow((1-e.timeoutStats.recentAvg()), timeoutPow))
}
// poolEntryAddress is a separate object because currently it is necessary to remember
// multiple potential network addresses for a pool entry. This will be removed after
// the final implementation of v5 discovery which will retrieve signed and serial
// numbered advertisements, making it clear which IP/port is the latest one.
type poolEntryAddress struct {
ip net.IP
port uint16
lastSeen mclock.AbsTime // last time it was discovered, connected or loaded from db
fails uint // connection failures since last successful connection (persistent)
}
func (a *poolEntryAddress) Weight() int64 {
t := time.Duration(mclock.Now() - a.lastSeen)
return int64(1000000*math.Exp(-float64(t)/float64(discoverExpireConst)-float64(a.fails)*addrFailDropLn)) + 1
}
func (a *poolEntryAddress) strKey() string {
return a.ip.String() + ":" + strconv.Itoa(int(a.port))
}
// poolStats implement statistics for a certain quantity with a long term average
// and a short term value which is adjusted exponentially with a factor of
// pstatRecentAdjust with each update and also returned exponentially to the
// average with the time constant pstatReturnToMeanTC
type poolStats struct {
sum, weight, avg, recent float64
lastRecalc mclock.AbsTime
}
// init initializes stats with a long term sum/update count pair retrieved from the database
func (s *poolStats) init(sum, weight float64) {
s.sum = sum
s.weight = weight
var avg float64
if weight > 0 {
avg = s.sum / weight
}
s.avg = avg
s.recent = avg
s.lastRecalc = mclock.Now()
}
// recalc recalculates recent value return-to-mean and long term average
func (s *poolStats) recalc() {
now := mclock.Now()
s.recent = s.avg + (s.recent-s.avg)*math.Exp(-float64(now-s.lastRecalc)/float64(pstatReturnToMeanTC))
if s.sum == 0 {
s.avg = 0
} else {
if s.sum > s.weight*1e30 {
s.avg = 1e30
} else {
s.avg = s.sum / s.weight
}
}
s.lastRecalc = now
}
// add updates the stats with a new value
func (s *poolStats) add(value, weight float64) {
s.weight += weight
s.sum += value * weight
s.recalc()
}
// recentAvg returns the short-term adjusted average
func (s *poolStats) recentAvg() float64 {
s.recalc()
return s.recent
}
func (s *poolStats) EncodeRLP(w io.Writer) error {
return rlp.Encode(w, []interface{}{math.Float64bits(s.sum), math.Float64bits(s.weight)})
}
func (s *poolStats) DecodeRLP(st *rlp.Stream) error {
var stats struct {
SumUint, WeightUint uint64
}
if err := st.Decode(&stats); err != nil {
return err
}
s.init(math.Float64frombits(stats.SumUint), math.Float64frombits(stats.WeightUint))
return nil
}
// poolEntryQueue keeps track of its least recently accessed entries and removes
// them when the number of entries reaches the limit
type poolEntryQueue struct {
queue map[int]*poolEntry // known nodes indexed by their latest lastConnCnt value
newPtr, oldPtr, maxCnt int
removeFromPool func(*poolEntry)
}
// newPoolEntryQueue returns a new poolEntryQueue
func newPoolEntryQueue(maxCnt int, removeFromPool func(*poolEntry)) poolEntryQueue {
return poolEntryQueue{queue: make(map[int]*poolEntry), maxCnt: maxCnt, removeFromPool: removeFromPool}
}
// fetchOldest returns and removes the least recently accessed entry
func (q *poolEntryQueue) fetchOldest() *poolEntry {
if len(q.queue) == 0 {
return nil
}
for {
if e := q.queue[q.oldPtr]; e != nil {
delete(q.queue, q.oldPtr)
q.oldPtr++
return e
}
q.oldPtr++
}
}
// remove removes an entry from the queue
func (q *poolEntryQueue) remove(entry *poolEntry) {
if q.queue[entry.queueIdx] == entry {
delete(q.queue, entry.queueIdx)
}
}
// setLatest adds or updates a recently accessed entry. It also checks if an old entry
// needs to be removed and removes it from the parent pool too with a callback function.
func (q *poolEntryQueue) setLatest(entry *poolEntry) {
if q.queue[entry.queueIdx] == entry {
delete(q.queue, entry.queueIdx)
} else {
if len(q.queue) == q.maxCnt {
e := q.fetchOldest()
q.remove(e)
q.removeFromPool(e)
}
}
entry.queueIdx = q.newPtr
q.queue[entry.queueIdx] = entry
q.newPtr++
}
