Official Go implementation of the Ethereum protocol
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go-ethereum/les/vflux/client/serverpool.go

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// Copyright 2020 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 client
import (
"errors"
"math/rand"
"reflect"
"sync"
"sync/atomic"
"time"
"github.com/ethereum/go-ethereum/common/mclock"
"github.com/ethereum/go-ethereum/ethdb"
"github.com/ethereum/go-ethereum/les/utils"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/metrics"
"github.com/ethereum/go-ethereum/p2p/enode"
"github.com/ethereum/go-ethereum/p2p/enr"
"github.com/ethereum/go-ethereum/p2p/nodestate"
"github.com/ethereum/go-ethereum/rlp"
)
const (
minTimeout = time.Millisecond * 500 // minimum request timeout suggested by the server pool
timeoutRefresh = time.Second * 5 // recalculate timeout if older than this
dialCost = 10000 // cost of a TCP dial (used for known node selection weight calculation)
dialWaitStep = 1.5 // exponential multiplier of redial wait time when no value was provided by the server
queryCost = 500 // cost of a UDP pre-negotiation query
queryWaitStep = 1.02 // exponential multiplier of redial wait time when no value was provided by the server
waitThreshold = time.Hour * 2000 // drop node if waiting time is over the threshold
nodeWeightMul = 1000000 // multiplier constant for node weight calculation
nodeWeightThreshold = 100 // minimum weight for keeping a node in the the known (valuable) set
minRedialWait = 10 // minimum redial wait time in seconds
preNegLimit = 5 // maximum number of simultaneous pre-negotiation queries
warnQueryFails = 20 // number of consecutive UDP query failures before we print a warning
maxQueryFails = 100 // number of consecutive UDP query failures when then chance of skipping a query reaches 50%
)
// ServerPool provides a node iterator for dial candidates. The output is a mix of newly discovered
// nodes, a weighted random selection of known (previously valuable) nodes and trusted/paid nodes.
type ServerPool struct {
clock mclock.Clock
unixTime func() int64
db ethdb.KeyValueStore
ns *nodestate.NodeStateMachine
vt *ValueTracker
mixer *enode.FairMix
mixSources []enode.Iterator
dialIterator enode.Iterator
validSchemes enr.IdentityScheme
trustedURLs []string
fillSet *FillSet
started, queryFails uint32
timeoutLock sync.RWMutex
timeout time.Duration
timeWeights ResponseTimeWeights
timeoutRefreshed mclock.AbsTime
suggestedTimeoutGauge, totalValueGauge metrics.Gauge
sessionValueMeter metrics.Meter
}
// nodeHistory keeps track of dial costs which determine node weight together with the
// service value calculated by ValueTracker.
type nodeHistory struct {
dialCost utils.ExpiredValue
redialWaitStart, redialWaitEnd int64 // unix time (seconds)
}
type nodeHistoryEnc struct {
DialCost utils.ExpiredValue
RedialWaitStart, RedialWaitEnd uint64
}
// queryFunc sends a pre-negotiation query and blocks until a response arrives or timeout occurs.
// It returns 1 if the remote node has confirmed that connection is possible, 0 if not
// possible and -1 if no response arrived (timeout).
type QueryFunc func(*enode.Node) int
var (
clientSetup = &nodestate.Setup{Version: 2}
sfHasValue = clientSetup.NewPersistentFlag("hasValue")
sfQuery = clientSetup.NewFlag("query")
sfCanDial = clientSetup.NewFlag("canDial")
sfDialing = clientSetup.NewFlag("dialed")
sfWaitDialTimeout = clientSetup.NewFlag("dialTimeout")
sfConnected = clientSetup.NewFlag("connected")
sfRedialWait = clientSetup.NewFlag("redialWait")
sfAlwaysConnect = clientSetup.NewFlag("alwaysConnect")
sfDialProcess = nodestate.MergeFlags(sfQuery, sfCanDial, sfDialing, sfConnected, sfRedialWait)
sfiNodeHistory = clientSetup.NewPersistentField("nodeHistory", reflect.TypeOf(nodeHistory{}),
func(field interface{}) ([]byte, error) {
if n, ok := field.(nodeHistory); ok {
ne := nodeHistoryEnc{
DialCost: n.dialCost,
RedialWaitStart: uint64(n.redialWaitStart),
RedialWaitEnd: uint64(n.redialWaitEnd),
}
enc, err := rlp.EncodeToBytes(&ne)
return enc, err
}
return nil, errors.New("invalid field type")
},
func(enc []byte) (interface{}, error) {
var ne nodeHistoryEnc
err := rlp.DecodeBytes(enc, &ne)
n := nodeHistory{
dialCost: ne.DialCost,
redialWaitStart: int64(ne.RedialWaitStart),
redialWaitEnd: int64(ne.RedialWaitEnd),
}
return n, err
},
)
sfiNodeWeight = clientSetup.NewField("nodeWeight", reflect.TypeOf(uint64(0)))
sfiConnectedStats = clientSetup.NewField("connectedStats", reflect.TypeOf(ResponseTimeStats{}))
sfiLocalAddress = clientSetup.NewPersistentField("localAddress", reflect.TypeOf(&enr.Record{}),
func(field interface{}) ([]byte, error) {
if enr, ok := field.(*enr.Record); ok {
enc, err := rlp.EncodeToBytes(enr)
return enc, err
}
return nil, errors.New("invalid field type")
},
func(enc []byte) (interface{}, error) {
var enr enr.Record
if err := rlp.DecodeBytes(enc, &enr); err != nil {
return nil, err
}
return &enr, nil
},
)
)
// NewServerPool creates a new server pool
func NewServerPool(db ethdb.KeyValueStore, dbKey []byte, mixTimeout time.Duration, query QueryFunc, clock mclock.Clock, trustedURLs []string, requestList []RequestInfo) (*ServerPool, enode.Iterator) {
s := &ServerPool{
db: db,
clock: clock,
unixTime: func() int64 { return time.Now().Unix() },
validSchemes: enode.ValidSchemes,
trustedURLs: trustedURLs,
vt: NewValueTracker(db, &mclock.System{}, requestList, time.Minute, 1/float64(time.Hour), 1/float64(time.Hour*100), 1/float64(time.Hour*1000)),
ns: nodestate.NewNodeStateMachine(db, []byte(string(dbKey)+"ns:"), clock, clientSetup),
}
s.recalTimeout()
s.mixer = enode.NewFairMix(mixTimeout)
knownSelector := NewWrsIterator(s.ns, sfHasValue, sfDialProcess, sfiNodeWeight)
alwaysConnect := NewQueueIterator(s.ns, sfAlwaysConnect, sfDialProcess, true, nil)
s.mixSources = append(s.mixSources, knownSelector)
s.mixSources = append(s.mixSources, alwaysConnect)
s.dialIterator = s.mixer
if query != nil {
s.dialIterator = s.addPreNegFilter(s.dialIterator, query)
}
s.ns.SubscribeState(nodestate.MergeFlags(sfWaitDialTimeout, sfConnected), func(n *enode.Node, oldState, newState nodestate.Flags) {
if oldState.Equals(sfWaitDialTimeout) && newState.IsEmpty() {
// dial timeout, no connection
s.setRedialWait(n, dialCost, dialWaitStep)
s.ns.SetStateSub(n, nodestate.Flags{}, sfDialing, 0)
}
})
return s, &serverPoolIterator{
dialIterator: s.dialIterator,
nextFn: func(node *enode.Node) {
s.ns.Operation(func() {
s.ns.SetStateSub(node, sfDialing, sfCanDial, 0)
s.ns.SetStateSub(node, sfWaitDialTimeout, nodestate.Flags{}, time.Second*10)
})
},
nodeFn: s.DialNode,
}
}
type serverPoolIterator struct {
dialIterator enode.Iterator
nextFn func(*enode.Node)
nodeFn func(*enode.Node) *enode.Node
}
// Next implements enode.Iterator
func (s *serverPoolIterator) Next() bool {
if s.dialIterator.Next() {
s.nextFn(s.dialIterator.Node())
return true
}
return false
}
// Node implements enode.Iterator
func (s *serverPoolIterator) Node() *enode.Node {
return s.nodeFn(s.dialIterator.Node())
}
// Close implements enode.Iterator
func (s *serverPoolIterator) Close() {
s.dialIterator.Close()
}
// AddMetrics adds metrics to the server pool. Should be called before Start().
func (s *ServerPool) AddMetrics(
suggestedTimeoutGauge, totalValueGauge, serverSelectableGauge, serverConnectedGauge metrics.Gauge,
sessionValueMeter, serverDialedMeter metrics.Meter) {
s.suggestedTimeoutGauge = suggestedTimeoutGauge
s.totalValueGauge = totalValueGauge
s.sessionValueMeter = sessionValueMeter
if serverSelectableGauge != nil {
s.ns.AddLogMetrics(sfHasValue, sfDialProcess, "selectable", nil, nil, serverSelectableGauge)
}
if serverDialedMeter != nil {
s.ns.AddLogMetrics(sfDialing, nodestate.Flags{}, "dialed", serverDialedMeter, nil, nil)
}
if serverConnectedGauge != nil {
s.ns.AddLogMetrics(sfConnected, nodestate.Flags{}, "connected", nil, nil, serverConnectedGauge)
}
}
// AddSource adds a node discovery source to the server pool (should be called before start)
func (s *ServerPool) AddSource(source enode.Iterator) {
if source != nil {
s.mixSources = append(s.mixSources, source)
}
}
// addPreNegFilter installs a node filter mechanism that performs a pre-negotiation query.
// Nodes that are filtered out and does not appear on the output iterator are put back
// into redialWait state.
func (s *ServerPool) addPreNegFilter(input enode.Iterator, query QueryFunc) enode.Iterator {
s.fillSet = NewFillSet(s.ns, input, sfQuery)
s.ns.SubscribeState(sfDialProcess, func(n *enode.Node, oldState, newState nodestate.Flags) {
if !newState.Equals(sfQuery) {
if newState.HasAll(sfQuery) {
// remove query flag if the node is already somewhere in the dial process
s.ns.SetStateSub(n, nodestate.Flags{}, sfQuery, 0)
}
return
}
fails := atomic.LoadUint32(&s.queryFails)
failMax := fails
if failMax > maxQueryFails {
failMax = maxQueryFails
}
if rand.Intn(maxQueryFails*2) < int(failMax) {
// skip pre-negotiation with increasing chance, max 50%
// this ensures that the client can operate even if UDP is not working at all
s.ns.SetStateSub(n, sfCanDial, nodestate.Flags{}, time.Second*10)
// set canDial before resetting queried so that FillSet will not read more
// candidates unnecessarily
s.ns.SetStateSub(n, nodestate.Flags{}, sfQuery, 0)
return
}
go func() {
q := query(n)
if q == -1 {
atomic.AddUint32(&s.queryFails, 1)
fails++
if fails%warnQueryFails == 0 {
// warn if a large number of consecutive queries have failed
log.Warn("UDP connection queries failed", "count", fails)
}
} else {
atomic.StoreUint32(&s.queryFails, 0)
}
s.ns.Operation(func() {
// we are no longer running in the operation that the callback belongs to, start a new one because of setRedialWait
if q == 1 {
s.ns.SetStateSub(n, sfCanDial, nodestate.Flags{}, time.Second*10)
} else {
s.setRedialWait(n, queryCost, queryWaitStep)
}
s.ns.SetStateSub(n, nodestate.Flags{}, sfQuery, 0)
})
}()
})
return NewQueueIterator(s.ns, sfCanDial, nodestate.Flags{}, false, func(waiting bool) {
if waiting {
s.fillSet.SetTarget(preNegLimit)
} else {
s.fillSet.SetTarget(0)
}
})
}
// start starts the server pool. Note that NodeStateMachine should be started first.
func (s *ServerPool) Start() {
s.ns.Start()
for _, iter := range s.mixSources {
// add sources to mixer at startup because the mixer instantly tries to read them
// which should only happen after NodeStateMachine has been started
s.mixer.AddSource(iter)
}
for _, url := range s.trustedURLs {
if node, err := enode.Parse(s.validSchemes, url); err == nil {
s.ns.SetState(node, sfAlwaysConnect, nodestate.Flags{}, 0)
} else {
log.Error("Invalid trusted server URL", "url", url, "error", err)
}
}
unixTime := s.unixTime()
s.ns.Operation(func() {
s.ns.ForEach(sfHasValue, nodestate.Flags{}, func(node *enode.Node, state nodestate.Flags) {
s.calculateWeight(node)
if n, ok := s.ns.GetField(node, sfiNodeHistory).(nodeHistory); ok && n.redialWaitEnd > unixTime {
wait := n.redialWaitEnd - unixTime
lastWait := n.redialWaitEnd - n.redialWaitStart
if wait > lastWait {
// if the time until expiration is larger than the last suggested
// waiting time then the system clock was probably adjusted
wait = lastWait
}
s.ns.SetStateSub(node, sfRedialWait, nodestate.Flags{}, time.Duration(wait)*time.Second)
}
})
})
atomic.StoreUint32(&s.started, 1)
}
// stop stops the server pool
func (s *ServerPool) Stop() {
if s.fillSet != nil {
s.fillSet.Close()
}
s.ns.Operation(func() {
s.ns.ForEach(sfConnected, nodestate.Flags{}, func(n *enode.Node, state nodestate.Flags) {
// recalculate weight of connected nodes in order to update hasValue flag if necessary
s.calculateWeight(n)
})
})
s.ns.Stop()
s.vt.Stop()
}
// RegisterNode implements serverPeerSubscriber
func (s *ServerPool) RegisterNode(node *enode.Node) (*NodeValueTracker, error) {
if atomic.LoadUint32(&s.started) == 0 {
return nil, errors.New("server pool not started yet")
}
nvt := s.vt.Register(node.ID())
s.ns.Operation(func() {
s.ns.SetStateSub(node, sfConnected, sfDialing.Or(sfWaitDialTimeout), 0)
s.ns.SetFieldSub(node, sfiConnectedStats, nvt.RtStats())
if node.IP().IsLoopback() {
s.ns.SetFieldSub(node, sfiLocalAddress, node.Record())
}
})
return nvt, nil
}
// UnregisterNode implements serverPeerSubscriber
func (s *ServerPool) UnregisterNode(node *enode.Node) {
s.ns.Operation(func() {
s.setRedialWait(node, dialCost, dialWaitStep)
s.ns.SetStateSub(node, nodestate.Flags{}, sfConnected, 0)
s.ns.SetFieldSub(node, sfiConnectedStats, nil)
})
s.vt.Unregister(node.ID())
}
// recalTimeout calculates the current recommended timeout. This value is used by
// the client as a "soft timeout" value. It also affects the service value calculation
// of individual nodes.
func (s *ServerPool) recalTimeout() {
// Use cached result if possible, avoid recalculating too frequently.
s.timeoutLock.RLock()
refreshed := s.timeoutRefreshed
s.timeoutLock.RUnlock()
now := s.clock.Now()
if refreshed != 0 && time.Duration(now-refreshed) < timeoutRefresh {
return
}
// Cached result is stale, recalculate a new one.
rts := s.vt.RtStats()
// Add a fake statistic here. It is an easy way to initialize with some
// conservative values when the database is new. As soon as we have a
// considerable amount of real stats this small value won't matter.
rts.Add(time.Second*2, 10, s.vt.StatsExpFactor())
// Use either 10% failure rate timeout or twice the median response time
// as the recommended timeout.
timeout := minTimeout
if t := rts.Timeout(0.1); t > timeout {
timeout = t
}
if t := rts.Timeout(0.5) * 2; t > timeout {
timeout = t
}
s.timeoutLock.Lock()
if s.timeout != timeout {
s.timeout = timeout
s.timeWeights = TimeoutWeights(s.timeout)
if s.suggestedTimeoutGauge != nil {
s.suggestedTimeoutGauge.Update(int64(s.timeout / time.Millisecond))
}
if s.totalValueGauge != nil {
s.totalValueGauge.Update(int64(rts.Value(s.timeWeights, s.vt.StatsExpFactor())))
}
}
s.timeoutRefreshed = now
s.timeoutLock.Unlock()
}
// GetTimeout returns the recommended request timeout.
func (s *ServerPool) GetTimeout() time.Duration {
s.recalTimeout()
s.timeoutLock.RLock()
defer s.timeoutLock.RUnlock()
return s.timeout
}
// getTimeoutAndWeight returns the recommended request timeout as well as the
// response time weight which is necessary to calculate service value.
func (s *ServerPool) getTimeoutAndWeight() (time.Duration, ResponseTimeWeights) {
s.recalTimeout()
s.timeoutLock.RLock()
defer s.timeoutLock.RUnlock()
return s.timeout, s.timeWeights
}
// addDialCost adds the given amount of dial cost to the node history and returns the current
// amount of total dial cost
func (s *ServerPool) addDialCost(n *nodeHistory, amount int64) uint64 {
logOffset := s.vt.StatsExpirer().LogOffset(s.clock.Now())
if amount > 0 {
n.dialCost.Add(amount, logOffset)
}
totalDialCost := n.dialCost.Value(logOffset)
if totalDialCost < dialCost {
totalDialCost = dialCost
}
return totalDialCost
}
// serviceValue returns the service value accumulated in this session and in total
func (s *ServerPool) serviceValue(node *enode.Node) (sessionValue, totalValue float64) {
nvt := s.vt.GetNode(node.ID())
if nvt == nil {
return 0, 0
}
currentStats := nvt.RtStats()
_, timeWeights := s.getTimeoutAndWeight()
expFactor := s.vt.StatsExpFactor()
totalValue = currentStats.Value(timeWeights, expFactor)
if connStats, ok := s.ns.GetField(node, sfiConnectedStats).(ResponseTimeStats); ok {
diff := currentStats
diff.SubStats(&connStats)
sessionValue = diff.Value(timeWeights, expFactor)
if s.sessionValueMeter != nil {
s.sessionValueMeter.Mark(int64(sessionValue))
}
}
return
}
// updateWeight calculates the node weight and updates the nodeWeight field and the
// hasValue flag. It also saves the node state if necessary.
// Note: this function should run inside a NodeStateMachine operation
func (s *ServerPool) updateWeight(node *enode.Node, totalValue float64, totalDialCost uint64) {
weight := uint64(totalValue * nodeWeightMul / float64(totalDialCost))
if weight >= nodeWeightThreshold {
s.ns.SetStateSub(node, sfHasValue, nodestate.Flags{}, 0)
s.ns.SetFieldSub(node, sfiNodeWeight, weight)
} else {
s.ns.SetStateSub(node, nodestate.Flags{}, sfHasValue, 0)
s.ns.SetFieldSub(node, sfiNodeWeight, nil)
s.ns.SetFieldSub(node, sfiNodeHistory, nil)
s.ns.SetFieldSub(node, sfiLocalAddress, nil)
}
s.ns.Persist(node) // saved if node history or hasValue changed
}
// setRedialWait calculates and sets the redialWait timeout based on the service value
// and dial cost accumulated during the last session/attempt and in total.
// The waiting time is raised exponentially if no service value has been received in order
// to prevent dialing an unresponsive node frequently for a very long time just because it
// was useful in the past. It can still be occasionally dialed though and once it provides
// a significant amount of service value again its waiting time is quickly reduced or reset
// to the minimum.
// Note: node weight is also recalculated and updated by this function.
// Note 2: this function should run inside a NodeStateMachine operation
func (s *ServerPool) setRedialWait(node *enode.Node, addDialCost int64, waitStep float64) {
n, _ := s.ns.GetField(node, sfiNodeHistory).(nodeHistory)
sessionValue, totalValue := s.serviceValue(node)
totalDialCost := s.addDialCost(&n, addDialCost)
// if the current dial session has yielded at least the average value/dial cost ratio
// then the waiting time should be reset to the minimum. If the session value
// is below average but still positive then timeout is limited to the ratio of
// average / current service value multiplied by the minimum timeout. If the attempt
// was unsuccessful then timeout is raised exponentially without limitation.
// Note: dialCost is used in the formula below even if dial was not attempted at all
// because the pre-negotiation query did not return a positive result. In this case
// the ratio has no meaning anyway and waitFactor is always raised, though in smaller
// steps because queries are cheaper and therefore we can allow more failed attempts.
unixTime := s.unixTime()
plannedTimeout := float64(n.redialWaitEnd - n.redialWaitStart) // last planned redialWait timeout
var actualWait float64 // actual waiting time elapsed
if unixTime > n.redialWaitEnd {
// the planned timeout has elapsed
actualWait = plannedTimeout
} else {
// if the node was redialed earlier then we do not raise the planned timeout
// exponentially because that could lead to the timeout rising very high in
// a short amount of time
// Note that in case of an early redial actualWait also includes the dial
// timeout or connection time of the last attempt but it still serves its
// purpose of preventing the timeout rising quicker than linearly as a function
// of total time elapsed without a successful connection.
actualWait = float64(unixTime - n.redialWaitStart)
}
// raise timeout exponentially if the last planned timeout has elapsed
// (use at least the last planned timeout otherwise)
nextTimeout := actualWait * waitStep
if plannedTimeout > nextTimeout {
nextTimeout = plannedTimeout
}
// we reduce the waiting time if the server has provided service value during the
// connection (but never under the minimum)
a := totalValue * dialCost * float64(minRedialWait)
b := float64(totalDialCost) * sessionValue
if a < b*nextTimeout {
nextTimeout = a / b
}
if nextTimeout < minRedialWait {
nextTimeout = minRedialWait
}
wait := time.Duration(float64(time.Second) * nextTimeout)
if wait < waitThreshold {
n.redialWaitStart = unixTime
n.redialWaitEnd = unixTime + int64(nextTimeout)
s.ns.SetFieldSub(node, sfiNodeHistory, n)
s.ns.SetStateSub(node, sfRedialWait, nodestate.Flags{}, wait)
s.updateWeight(node, totalValue, totalDialCost)
} else {
// discard known node statistics if waiting time is very long because the node
// hasn't been responsive for a very long time
s.ns.SetFieldSub(node, sfiNodeHistory, nil)
s.ns.SetFieldSub(node, sfiNodeWeight, nil)
s.ns.SetStateSub(node, nodestate.Flags{}, sfHasValue, 0)
}
}
// calculateWeight calculates and sets the node weight without altering the node history.
// This function should be called during startup and shutdown only, otherwise setRedialWait
// will keep the weights updated as the underlying statistics are adjusted.
// Note: this function should run inside a NodeStateMachine operation
func (s *ServerPool) calculateWeight(node *enode.Node) {
n, _ := s.ns.GetField(node, sfiNodeHistory).(nodeHistory)
_, totalValue := s.serviceValue(node)
totalDialCost := s.addDialCost(&n, 0)
s.updateWeight(node, totalValue, totalDialCost)
}
// API returns the vflux client API
func (s *ServerPool) API() *PrivateClientAPI {
return NewPrivateClientAPI(s.vt)
}
type dummyIdentity enode.ID
func (id dummyIdentity) Verify(r *enr.Record, sig []byte) error { return nil }
func (id dummyIdentity) NodeAddr(r *enr.Record) []byte { return id[:] }
// DialNode replaces the given enode with a locally generated one containing the ENR
// stored in the sfiLocalAddress field if present. This workaround ensures that nodes
// on the local network can be dialed at the local address if a connection has been
// successfully established previously.
// Note that NodeStateMachine always remembers the enode with the latest version of
// the remote signed ENR. ENR filtering should be performed on that version while
// dialNode should be used for dialing the node over TCP or UDP.
func (s *ServerPool) DialNode(n *enode.Node) *enode.Node {
if enr, ok := s.ns.GetField(n, sfiLocalAddress).(*enr.Record); ok {
n, _ := enode.New(dummyIdentity(n.ID()), enr)
return n
}
return n
}
// Persist immediately stores the state of a node in the node database
func (s *ServerPool) Persist(n *enode.Node) {
s.ns.Persist(n)
}