plugeth/les/clientpool.go

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// Copyright 2019 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
import (
"io"
"math"
"sync"
"time"
"github.com/ethereum/go-ethereum/common/mclock"
"github.com/ethereum/go-ethereum/common/prque"
"github.com/ethereum/go-ethereum/ethdb"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/p2p/enode"
"github.com/ethereum/go-ethereum/rlp"
)
const (
negBalanceExpTC = time.Hour // time constant for exponentially reducing negative balance
fixedPointMultiplier = 0x1000000 // constant to convert logarithms to fixed point format
connectedBias = time.Minute // this bias is applied in favor of already connected clients in order to avoid kicking them out very soon
lazyQueueRefresh = time.Second * 10 // refresh period of the connected queue
)
var (
clientPoolDbKey = []byte("clientPool")
clientBalanceDbKey = []byte("clientPool-balance")
)
// clientPool implements a client database that assigns a priority to each client
// based on a positive and negative balance. Positive balance is externally assigned
// to prioritized clients and is decreased with connection time and processed
// requests (unless the price factors are zero). If the positive balance is zero
// then negative balance is accumulated. Balance tracking and priority calculation
// for connected clients is done by balanceTracker. connectedQueue ensures that
// clients with the lowest positive or highest negative balance get evicted when
// the total capacity allowance is full and new clients with a better balance want
// to connect. Already connected nodes receive a small bias in their favor in order
// to avoid accepting and instantly kicking out clients.
// Balances of disconnected clients are stored in posBalanceQueue and negBalanceQueue
// and are also saved in the database. Negative balance is transformed into a
// logarithmic form with a constantly shifting linear offset in order to implement
// an exponential decrease. negBalanceQueue has a limited size and drops the smallest
// values when necessary. Positive balances are stored in the database as long as
// they exist, posBalanceQueue only acts as a cache for recently accessed entries.
type clientPool struct {
db ethdb.Database
lock sync.Mutex
clock mclock.Clock
stopCh chan chan struct{}
closed bool
removePeer func(enode.ID)
queueLimit, countLimit int
freeClientCap, capacityLimit, connectedCapacity uint64
connectedMap map[enode.ID]*clientInfo
posBalanceMap map[enode.ID]*posBalance
negBalanceMap map[string]*negBalance
connectedQueue *prque.LazyQueue
posBalanceQueue, negBalanceQueue *prque.Prque
posFactors, negFactors priceFactors
posBalanceAccessCounter int64
startupTime mclock.AbsTime
logOffsetAtStartup int64
}
// clientPeer represents a client in the pool.
// Positive balances are assigned to node key while negative balances are assigned
// to freeClientId. Currently network IP address without port is used because
// clients have a limited access to IP addresses while new node keys can be easily
// generated so it would be useless to assign a negative value to them.
type clientPeer interface {
ID() enode.ID
freeClientId() string
updateCapacity(uint64)
}
// clientInfo represents a connected client
type clientInfo struct {
address string
id enode.ID
capacity uint64
priority bool
pool *clientPool
peer clientPeer
queueIndex int // position in connectedQueue
balanceTracker balanceTracker
}
// connSetIndex callback updates clientInfo item index in connectedQueue
func connSetIndex(a interface{}, index int) {
a.(*clientInfo).queueIndex = index
}
// connPriority callback returns actual priority of clientInfo item in connectedQueue
func connPriority(a interface{}, now mclock.AbsTime) int64 {
c := a.(*clientInfo)
return c.balanceTracker.getPriority(now)
}
// connMaxPriority callback returns estimated maximum priority of clientInfo item in connectedQueue
func connMaxPriority(a interface{}, until mclock.AbsTime) int64 {
c := a.(*clientInfo)
pri := c.balanceTracker.estimatedPriority(until, true)
c.balanceTracker.addCallback(balanceCallbackQueue, pri+1, func() {
c.pool.lock.Lock()
if c.queueIndex != -1 {
c.pool.connectedQueue.Update(c.queueIndex)
}
c.pool.lock.Unlock()
})
return pri
}
// priceFactors determine the pricing policy (may apply either to positive or
// negative balances which may have different factors).
// - timeFactor is cost unit per nanosecond of connection time
// - capacityFactor is cost unit per nanosecond of connection time per 1000000 capacity
// - requestFactor is cost unit per request "realCost" unit
type priceFactors struct {
timeFactor, capacityFactor, requestFactor float64
}
// newClientPool creates a new client pool
func newClientPool(db ethdb.Database, freeClientCap uint64, queueLimit int, clock mclock.Clock, removePeer func(enode.ID)) *clientPool {
pool := &clientPool{
db: db,
clock: clock,
connectedMap: make(map[enode.ID]*clientInfo),
posBalanceMap: make(map[enode.ID]*posBalance),
negBalanceMap: make(map[string]*negBalance),
connectedQueue: prque.NewLazyQueue(connSetIndex, connPriority, connMaxPriority, clock, lazyQueueRefresh),
negBalanceQueue: prque.New(negSetIndex),
posBalanceQueue: prque.New(posSetIndex),
freeClientCap: freeClientCap,
queueLimit: queueLimit,
removePeer: removePeer,
stopCh: make(chan chan struct{}),
}
pool.loadFromDb()
go func() {
for {
select {
case <-clock.After(lazyQueueRefresh):
pool.lock.Lock()
pool.connectedQueue.Refresh()
pool.lock.Unlock()
case stop := <-pool.stopCh:
close(stop)
return
}
}
}()
return pool
}
// stop shuts the client pool down
func (f *clientPool) stop() {
stop := make(chan struct{})
f.stopCh <- stop
<-stop
f.lock.Lock()
f.closed = true
f.saveToDb()
f.lock.Unlock()
}
// connect should be called after a successful handshake. If the connection was
// rejected, there is no need to call disconnect.
func (f *clientPool) connect(peer clientPeer, capacity uint64) bool {
f.lock.Lock()
defer f.lock.Unlock()
// Short circuit is clientPool is already closed.
if f.closed {
return false
}
// Dedup connected peers.
id, freeID := peer.ID(), peer.freeClientId()
if _, ok := f.connectedMap[id]; ok {
clientRejectedMeter.Mark(1)
log.Debug("Client already connected", "address", freeID, "id", peerIdToString(id))
return false
}
// Create a clientInfo but do not add it yet
now := f.clock.Now()
posBalance := f.getPosBalance(id).value
e := &clientInfo{pool: f, peer: peer, address: freeID, queueIndex: -1, id: id, priority: posBalance != 0}
var negBalance uint64
nb := f.negBalanceMap[freeID]
if nb != nil {
negBalance = uint64(math.Exp(float64(nb.logValue-f.logOffset(now)) / fixedPointMultiplier))
}
// If the client is a free client, assign with a low free capacity,
// Otherwise assign with the given value(priority client)
if !e.priority {
capacity = f.freeClientCap
}
// Ensure the capacity will never lower than the free capacity.
if capacity < f.freeClientCap {
capacity = f.freeClientCap
}
e.capacity = capacity
e.balanceTracker.init(f.clock, capacity)
e.balanceTracker.setBalance(posBalance, negBalance)
f.setClientPriceFactors(e)
// If the number of clients already connected in the clientpool exceeds its
// capacity, evict some clients with lowest priority.
//
// If the priority of the newly added client is lower than the priority of
// all connected clients, the client is rejected.
newCapacity := f.connectedCapacity + capacity
newCount := f.connectedQueue.Size() + 1
if newCapacity > f.capacityLimit || newCount > f.countLimit {
var (
kickList []*clientInfo
kickPriority int64
)
f.connectedQueue.MultiPop(func(data interface{}, priority int64) bool {
c := data.(*clientInfo)
kickList = append(kickList, c)
kickPriority = priority
newCapacity -= c.capacity
newCount--
return newCapacity > f.capacityLimit || newCount > f.countLimit
})
if newCapacity > f.capacityLimit || newCount > f.countLimit || (e.balanceTracker.estimatedPriority(now+mclock.AbsTime(connectedBias), false)-kickPriority) > 0 {
// reject client
for _, c := range kickList {
f.connectedQueue.Push(c)
}
clientRejectedMeter.Mark(1)
log.Debug("Client rejected", "address", freeID, "id", peerIdToString(id))
return false
}
// accept new client, drop old ones
for _, c := range kickList {
f.dropClient(c, now, true)
}
}
// client accepted, finish setting it up
if nb != nil {
delete(f.negBalanceMap, freeID)
f.negBalanceQueue.Remove(nb.queueIndex)
}
if e.priority {
e.balanceTracker.addCallback(balanceCallbackZero, 0, func() { f.balanceExhausted(id) })
}
f.connectedMap[id] = e
f.connectedQueue.Push(e)
f.connectedCapacity += e.capacity
totalConnectedGauge.Update(int64(f.connectedCapacity))
if e.capacity != f.freeClientCap {
e.peer.updateCapacity(e.capacity)
}
clientConnectedMeter.Mark(1)
log.Debug("Client accepted", "address", freeID)
return true
}
// disconnect should be called when a connection is terminated. If the disconnection
// was initiated by the pool itself using disconnectFn then calling disconnect is
// not necessary but permitted.
func (f *clientPool) disconnect(p clientPeer) {
f.lock.Lock()
defer f.lock.Unlock()
if f.closed {
return
}
address := p.freeClientId()
id := p.ID()
// Short circuit if the peer hasn't been registered.
e := f.connectedMap[id]
if e == nil {
log.Debug("Client not connected", "address", address, "id", peerIdToString(id))
return
}
f.dropClient(e, f.clock.Now(), false)
}
// dropClient removes a client from the connected queue and finalizes its balance.
// If kick is true then it also initiates the disconnection.
func (f *clientPool) dropClient(e *clientInfo, now mclock.AbsTime, kick bool) {
if _, ok := f.connectedMap[e.id]; !ok {
return
}
f.finalizeBalance(e, now)
f.connectedQueue.Remove(e.queueIndex)
delete(f.connectedMap, e.id)
f.connectedCapacity -= e.capacity
totalConnectedGauge.Update(int64(f.connectedCapacity))
if kick {
clientKickedMeter.Mark(1)
log.Debug("Client kicked out", "address", e.address)
f.removePeer(e.id)
} else {
clientDisconnectedMeter.Mark(1)
log.Debug("Client disconnected", "address", e.address)
}
}
// finalizeBalance stops the balance tracker, retrieves the final balances and
// stores them in posBalanceQueue and negBalanceQueue
func (f *clientPool) finalizeBalance(c *clientInfo, now mclock.AbsTime) {
c.balanceTracker.stop(now)
pos, neg := c.balanceTracker.getBalance(now)
pb := f.getPosBalance(c.id)
pb.value = pos
f.storePosBalance(pb)
if neg < 1 {
neg = 1
}
nb := &negBalance{address: c.address, queueIndex: -1, logValue: int64(math.Log(float64(neg))*fixedPointMultiplier) + f.logOffset(now)}
f.negBalanceMap[c.address] = nb
f.negBalanceQueue.Push(nb, -nb.logValue)
if f.negBalanceQueue.Size() > f.queueLimit {
nn := f.negBalanceQueue.PopItem().(*negBalance)
delete(f.negBalanceMap, nn.address)
}
}
// balanceExhausted callback is called by balanceTracker when positive balance is exhausted.
// It revokes priority status and also reduces the client capacity if necessary.
func (f *clientPool) balanceExhausted(id enode.ID) {
f.lock.Lock()
defer f.lock.Unlock()
c := f.connectedMap[id]
if c == nil || !c.priority {
return
}
c.priority = false
if c.capacity != f.freeClientCap {
f.connectedCapacity += f.freeClientCap - c.capacity
totalConnectedGauge.Update(int64(f.connectedCapacity))
c.capacity = f.freeClientCap
c.peer.updateCapacity(c.capacity)
}
}
// setConnLimit sets the maximum number and total capacity of connected clients,
// dropping some of them if necessary.
func (f *clientPool) setLimits(count int, totalCap uint64) {
f.lock.Lock()
defer f.lock.Unlock()
f.countLimit = count
f.capacityLimit = totalCap
now := mclock.Now()
f.connectedQueue.MultiPop(func(data interface{}, priority int64) bool {
c := data.(*clientInfo)
f.dropClient(c, now, true)
return f.connectedCapacity > f.capacityLimit || f.connectedQueue.Size() > f.countLimit
})
}
// requestCost feeds request cost after serving a request from the given peer.
func (f *clientPool) requestCost(p *peer, cost uint64) {
f.lock.Lock()
defer f.lock.Unlock()
info, exist := f.connectedMap[p.ID()]
if !exist || f.closed {
return
}
info.balanceTracker.requestCost(cost)
}
// logOffset calculates the time-dependent offset for the logarithmic
// representation of negative balance
func (f *clientPool) logOffset(now mclock.AbsTime) int64 {
// Note: fixedPointMultiplier acts as a multiplier here; the reason for dividing the divisor
// is to avoid int64 overflow. We assume that int64(negBalanceExpTC) >> fixedPointMultiplier.
logDecay := int64((time.Duration(now - f.startupTime)) / (negBalanceExpTC / fixedPointMultiplier))
return f.logOffsetAtStartup + logDecay
}
// setPriceFactors changes pricing factors for both positive and negative balances.
// Applies to connected clients and also future connections.
func (f *clientPool) setPriceFactors(posFactors, negFactors priceFactors) {
f.lock.Lock()
defer f.lock.Unlock()
f.posFactors, f.negFactors = posFactors, negFactors
for _, c := range f.connectedMap {
f.setClientPriceFactors(c)
}
}
// setClientPriceFactors sets the pricing factors for an individual connected client
func (f *clientPool) setClientPriceFactors(c *clientInfo) {
c.balanceTracker.setFactors(true, f.negFactors.timeFactor+float64(c.capacity)*f.negFactors.capacityFactor/1000000, f.negFactors.requestFactor)
c.balanceTracker.setFactors(false, f.posFactors.timeFactor+float64(c.capacity)*f.posFactors.capacityFactor/1000000, f.posFactors.requestFactor)
}
// clientPoolStorage is the RLP representation of the pool's database storage
type clientPoolStorage struct {
LogOffset uint64
List []*negBalance
}
// loadFromDb restores pool status from the database storage
// (automatically called at initialization)
func (f *clientPool) loadFromDb() {
enc, err := f.db.Get(clientPoolDbKey)
if err != nil {
return
}
var storage clientPoolStorage
err = rlp.DecodeBytes(enc, &storage)
if err != nil {
log.Error("Failed to decode client list", "err", err)
return
}
f.logOffsetAtStartup = int64(storage.LogOffset)
f.startupTime = f.clock.Now()
for _, e := range storage.List {
log.Debug("Loaded free client record", "address", e.address, "logValue", e.logValue)
f.negBalanceMap[e.address] = e
f.negBalanceQueue.Push(e, -e.logValue)
}
}
// saveToDb saves pool status to the database storage
// (automatically called during shutdown)
func (f *clientPool) saveToDb() {
now := f.clock.Now()
storage := clientPoolStorage{
LogOffset: uint64(f.logOffset(now)),
}
for _, c := range f.connectedMap {
f.finalizeBalance(c, now)
}
i := 0
storage.List = make([]*negBalance, len(f.negBalanceMap))
for _, e := range f.negBalanceMap {
storage.List[i] = e
i++
}
enc, err := rlp.EncodeToBytes(storage)
if err != nil {
log.Error("Failed to encode negative balance list", "err", err)
} else {
f.db.Put(clientPoolDbKey, enc)
}
}
// storePosBalance stores a single positive balance entry in the database
func (f *clientPool) storePosBalance(b *posBalance) {
if b.value == b.lastStored {
return
}
enc, err := rlp.EncodeToBytes(b)
if err != nil {
log.Error("Failed to encode client balance", "err", err)
} else {
f.db.Put(append(clientBalanceDbKey, b.id[:]...), enc)
b.lastStored = b.value
}
}
// getPosBalance retrieves a single positive balance entry from cache or the database
func (f *clientPool) getPosBalance(id enode.ID) *posBalance {
if b, ok := f.posBalanceMap[id]; ok {
f.posBalanceQueue.Remove(b.queueIndex)
f.posBalanceAccessCounter--
f.posBalanceQueue.Push(b, f.posBalanceAccessCounter)
return b
}
balance := &posBalance{}
if enc, err := f.db.Get(append(clientBalanceDbKey, id[:]...)); err == nil {
if err := rlp.DecodeBytes(enc, balance); err != nil {
log.Error("Failed to decode client balance", "err", err)
balance = &posBalance{}
}
}
balance.id = id
balance.queueIndex = -1
if f.posBalanceQueue.Size() >= f.queueLimit {
b := f.posBalanceQueue.PopItem().(*posBalance)
f.storePosBalance(b)
delete(f.posBalanceMap, b.id)
}
f.posBalanceAccessCounter--
f.posBalanceQueue.Push(balance, f.posBalanceAccessCounter)
f.posBalanceMap[id] = balance
return balance
}
// addBalance updates the positive balance of a client.
// If setTotal is false then the given amount is added to the balance.
// If setTotal is true then amount represents the total amount ever added to the
// given ID and positive balance is increased by (amount-lastTotal) while lastTotal
// is updated to amount. This method also allows removing positive balance.
func (f *clientPool) addBalance(id enode.ID, amount uint64, setTotal bool) {
f.lock.Lock()
defer f.lock.Unlock()
pb := f.getPosBalance(id)
c := f.connectedMap[id]
var negBalance uint64
if c != nil {
pb.value, negBalance = c.balanceTracker.getBalance(f.clock.Now())
}
if setTotal {
if pb.value+amount > pb.lastTotal {
pb.value += amount - pb.lastTotal
} else {
pb.value = 0
}
pb.lastTotal = amount
} else {
pb.value += amount
pb.lastTotal += amount
}
f.storePosBalance(pb)
if c != nil {
c.balanceTracker.setBalance(pb.value, negBalance)
if !c.priority && pb.value > 0 {
c.priority = true
c.balanceTracker.addCallback(balanceCallbackZero, 0, func() { f.balanceExhausted(id) })
}
}
}
// posBalance represents a recently accessed positive balance entry
type posBalance struct {
id enode.ID
value, lastStored, lastTotal uint64
queueIndex int // position in posBalanceQueue
}
// EncodeRLP implements rlp.Encoder
func (e *posBalance) EncodeRLP(w io.Writer) error {
return rlp.Encode(w, []interface{}{e.value, e.lastTotal})
}
// DecodeRLP implements rlp.Decoder
func (e *posBalance) DecodeRLP(s *rlp.Stream) error {
var entry struct {
Value, LastTotal uint64
}
if err := s.Decode(&entry); err != nil {
return err
}
e.value = entry.Value
e.lastStored = entry.Value
e.lastTotal = entry.LastTotal
return nil
}
// posSetIndex callback updates posBalance item index in posBalanceQueue
func posSetIndex(a interface{}, index int) {
a.(*posBalance).queueIndex = index
}
// negBalance represents a negative balance entry of a disconnected client
type negBalance struct {
address string
logValue int64
queueIndex int // position in negBalanceQueue
}
// EncodeRLP implements rlp.Encoder
func (e *negBalance) EncodeRLP(w io.Writer) error {
return rlp.Encode(w, []interface{}{e.address, uint64(e.logValue)})
}
// DecodeRLP implements rlp.Decoder
func (e *negBalance) DecodeRLP(s *rlp.Stream) error {
var entry struct {
Address string
LogValue uint64
}
if err := s.Decode(&entry); err != nil {
return err
}
e.address = entry.Address
e.logValue = int64(entry.LogValue)
e.queueIndex = -1
return nil
}
// negSetIndex callback updates negBalance item index in negBalanceQueue
func negSetIndex(a interface{}, index int) {
a.(*negBalance).queueIndex = index
}