/
head_tracker.go
602 lines (533 loc) · 18.3 KB
/
head_tracker.go
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package services
import (
"context"
"fmt"
"math/big"
"reflect"
"sync"
"time"
"github.com/smartcontractkit/chainlink/core/logger"
strpkg "github.com/smartcontractkit/chainlink/core/store"
"github.com/smartcontractkit/chainlink/core/store/models"
"github.com/smartcontractkit/chainlink/core/store/presenters"
"github.com/smartcontractkit/chainlink/core/utils"
ethereum "github.com/ethereum/go-ethereum"
"github.com/pkg/errors"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promauto"
)
var (
promCurrentHead = promauto.NewGauge(prometheus.GaugeOpts{
Name: "head_tracker_current_head",
Help: "The highest seen head number",
})
promNumHeadsReceived = promauto.NewCounter(prometheus.CounterOpts{
Name: "head_tracker_heads_received",
Help: "The total number of heads seen",
})
promHeadsInQueue = promauto.NewGauge(prometheus.GaugeOpts{
Name: "head_tracker_heads_in_queue",
Help: "The number of heads currently waiting to be executed. You can think of this as the 'load' on the head tracker. Should rarely or never be more than 0",
})
promCallbackDuration = promauto.NewGauge(prometheus.GaugeOpts{
Name: "head_tracker_callback_execution_duration",
Help: "How long it took to execute all callbacks (ms)",
})
promCallbackDurationHist = promauto.NewHistogram(prometheus.HistogramOpts{
Name: "head_tracker_callback_execution_duration_hist",
Help: "How long it took to execute all callbacks (ms) histogram",
Buckets: []float64{50, 100, 250, 500, 1000, 2000, 5000, 10000, 15000, 30000, 100000},
})
promNumHeadsDropped = promauto.NewCounter(prometheus.CounterOpts{
Name: "head_tracker_num_heads_dropped",
Help: "The total number of heads dropped",
})
// kovanChainID is the Chain ID for Kovan test network
kovanChainID = big.NewInt(42)
)
// headRingBuffer is a small goroutine that sits between the eth client and the
// head tracker and drops the oldest head if necessary in order to keep to a fixed
// queue size (defined by the buffer size of out channel)
type headRingBuffer struct {
in <-chan *models.Head
out chan models.Head
start sync.Once
}
func newHeadRingBuffer(in <-chan *models.Head, size int) (r *headRingBuffer, out chan models.Head) {
out = make(chan models.Head, size)
return &headRingBuffer{
in: in,
out: out,
start: sync.Once{},
}, out
}
// Start the headRingBuffer goroutine
// It will be stopped implicitly by closing the in channel
func (r *headRingBuffer) Start() {
r.start.Do(func() {
go r.run()
})
}
func (r *headRingBuffer) run() {
for h := range r.in {
if h == nil {
logger.Error("HeadTracker: got nil block header")
continue
}
promNumHeadsReceived.Inc()
hInQueue := len(r.out)
promHeadsInQueue.Set(float64(hInQueue))
if hInQueue > 0 {
logger.Infof("HeadTracker: Head %v is lagging behind, there are %v more heads in the queue. Your node is operating close to its maximum capacity and may start to miss jobs.", h.Number, hInQueue)
}
select {
case r.out <- *h:
default:
// Need to select/default here because it's conceivable (although
// improbable) that between the previous select and now, all heads were drained
// from r.out by another goroutine
//
// NOTE: In this unlikely event, we may drop an extra head unnecessarily.
// The probability of this seems vanishingly small, and only hits
// if the queue was already full anyway, so we can live with this
select {
case dropped := <-r.out:
promNumHeadsDropped.Inc()
logger.Errorf("HeadTracker: dropping head %v with hash 0x%x because queue is full. WARNING: Your node is overloaded and may start missing jobs.", dropped.Number, h.Hash)
r.out <- *h
default:
r.out <- *h
}
}
}
close(r.out)
}
// HeadTracker holds and stores the latest block number experienced by this particular node
// in a thread safe manner. Reconstitutes the last block number from the data
// store on reboot.
type HeadTracker struct {
callbacks []strpkg.HeadTrackable
inHeaders chan *models.Head
outHeaders chan models.Head
headSubscription ethereum.Subscription
highestSeenHead *models.Head
store *strpkg.Store
headMutex sync.RWMutex
connected bool
sleeper utils.Sleeper
done chan struct{}
started bool
listenForNewHeadsWg sync.WaitGroup
subscriptionSucceeded chan struct{}
}
// NewHeadTracker instantiates a new HeadTracker using the orm to persist new block numbers.
// Can be passed in an optional sleeper object that will dictate how often
// it tries to reconnect.
func NewHeadTracker(store *strpkg.Store, callbacks []strpkg.HeadTrackable, sleepers ...utils.Sleeper) *HeadTracker {
var sleeper utils.Sleeper
if len(sleepers) > 0 {
sleeper = sleepers[0]
} else {
sleeper = utils.NewBackoffSleeper()
}
return &HeadTracker{
store: store,
callbacks: callbacks,
sleeper: sleeper,
}
}
// Start retrieves the last persisted block number from the HeadTracker,
// subscribes to new heads, and if successful fires Connect on the
// HeadTrackable argument.
func (ht *HeadTracker) Start() error {
ht.headMutex.Lock()
defer ht.headMutex.Unlock()
if ht.started {
return nil
}
if err := ht.setHighestSeenHeadFromDB(); err != nil {
return err
}
if ht.highestSeenHead != nil {
logger.Debug("Tracking logs from last block ", presenters.FriendlyBigInt(ht.highestSeenHead.ToInt()), " with hash ", ht.highestSeenHead.Hash.Hex())
}
ht.done = make(chan struct{})
ht.subscriptionSucceeded = make(chan struct{})
ht.listenForNewHeadsWg.Add(1)
go ht.listenForNewHeads()
ht.started = true
return nil
}
// Stop unsubscribes all connections and fires Disconnect.
func (ht *HeadTracker) Stop() error {
ht.headMutex.Lock()
if !ht.started {
ht.headMutex.Unlock()
return nil
}
if ht.connected {
ht.connected = false
ht.disconnect()
}
logger.Info(fmt.Sprintf("Head tracker disconnecting from %v", ht.store.Config.EthereumURL()))
close(ht.done)
close(ht.subscriptionSucceeded)
ht.started = false
ht.headMutex.Unlock()
ht.listenForNewHeadsWg.Wait()
return nil
}
// Save updates the latest block number, if indeed the latest, and persists
// this number in case of reboot. Thread safe.
func (ht *HeadTracker) Save(h models.Head) error {
ht.headMutex.Lock()
if h.GreaterThan(ht.highestSeenHead) {
ht.highestSeenHead = &h
}
ht.headMutex.Unlock()
err := ht.store.IdempotentInsertHead(h)
if err != nil {
return err
}
return ht.store.TrimOldHeads(ht.store.Config.EthHeadTrackerHistoryDepth())
}
// HighestSeenHead returns the block header with the highest number that has been seen, or nil
func (ht *HeadTracker) HighestSeenHead() *models.Head {
ht.headMutex.RLock()
defer ht.headMutex.RUnlock()
return ht.highestSeenHead
}
// Connected returns whether or not this HeadTracker is connected.
func (ht *HeadTracker) Connected() bool {
ht.headMutex.RLock()
defer ht.headMutex.RUnlock()
return ht.connected
}
func (ht *HeadTracker) connect(bn *models.Head) {
for _, trackable := range ht.callbacks {
logger.WarnIf(trackable.Connect(bn))
}
}
func (ht *HeadTracker) disconnect() {
for _, trackable := range ht.callbacks {
trackable.Disconnect()
}
}
func (ht *HeadTracker) listenForNewHeads() {
defer ht.listenForNewHeadsWg.Done()
defer func() {
err := ht.unsubscribeFromHead()
logger.ErrorIf(err, "failed when unsubscribe from head")
}()
for {
if !ht.subscribe() {
return
}
if err := ht.receiveHeaders(); err != nil {
logger.Errorw(fmt.Sprintf("Error in new head subscription, unsubscribed: %s", err.Error()), "err", err)
continue
} else {
return
}
}
}
// subscribe periodically attempts to connect to the ethereum node via websocket.
// It returns true on success, and false if cut short by a done request and did not connect.
func (ht *HeadTracker) subscribe() bool {
ht.sleeper.Reset()
for {
err := ht.unsubscribeFromHead()
if err != nil {
logger.ErrorIf(err, "failed when unsubscribe from head")
return false
}
logger.Info("Connecting to ethereum node ", ht.store.Config.EthereumURL(), " in ", ht.sleeper.Duration())
select {
case <-ht.done:
return false
case <-time.After(ht.sleeper.After()):
err := ht.subscribeToHead()
if err != nil {
logger.Warnw(fmt.Sprintf("Failed to connect to ethereum node %v", ht.store.Config.EthereumURL()), "err", err)
} else {
logger.Info("Connected to ethereum node ", ht.store.Config.EthereumURL())
return true
}
}
}
}
// This should be safe to run concurrently across multiple nodes connected to the same database
func (ht *HeadTracker) receiveHeaders() error {
for {
select {
case <-ht.done:
return nil
case blockHeader, open := <-ht.outHeaders:
if !open {
return errors.New("HeadTracker: outHeaders prematurely closed")
}
ctx, cancel := context.WithTimeout(context.Background(), ht.totalNewHeadTimeBudget())
if err := ht.handleNewHead(ctx, blockHeader); err != nil {
cancel()
return err
}
cancel()
case err, open := <-ht.headSubscription.Err():
if open && err != nil {
return err
}
}
}
}
func (ht *HeadTracker) handleNewHead(ctx context.Context, head models.Head) error {
defer func(start time.Time, number int64) {
elapsed := time.Since(start)
ms := float64(elapsed.Milliseconds())
promCallbackDuration.Set(ms)
promCallbackDurationHist.Observe(ms)
if elapsed > ht.callbackExecutionThreshold() {
logger.Warnw(fmt.Sprintf("HeadTracker finished processing head %v in %s which exceeds callback execution threshold of %s", number, elapsed.String(), ht.callbackExecutionThreshold().String()), "blockNumber", number, "time", elapsed, "id", "head_tracker")
} else {
logger.Debugw(fmt.Sprintf("HeadTracker finished processing head %v in %s", number, elapsed.String()), "blockNumber", number, "time", elapsed, "id", "head_tracker")
}
}(time.Now(), int64(head.Number))
prevHead := ht.HighestSeenHead()
logger.Debugw(fmt.Sprintf("Received new head %v", presenters.FriendlyBigInt(head.ToInt())),
"blockHeight", head.ToInt(),
"blockHash", head.Hash,
)
if err := ht.Save(head); err != nil {
return err
}
if prevHead == nil || head.Number > prevHead.Number {
return ht.handleNewHighestHead(head)
}
if head.Number == prevHead.Number {
if head.Hash != prevHead.Hash {
logger.Debugw("HeadTracker: got duplicate head", "blockNum", head.Number, "gotHead", head.Hash.Hex(), "highestSeenHead", ht.highestSeenHead.Hash.Hex())
} else {
logger.Debugw("HeadTracker: head already in the database", "gotHead", head.Hash.Hex())
}
} else {
logger.Debugw("HeadTracker: got out of order head", "blockNum", head.Number, "gotHead", head.Hash.Hex(), "highestSeenHead", ht.highestSeenHead.Number)
}
return nil
}
func (ht *HeadTracker) handleNewHighestHead(head models.Head) error {
promCurrentHead.Set(float64(head.Number))
// NOTE: We must set a hard time limit on this, backfilling heads should
// not block the head tracker
ctx, cancel := context.WithTimeout(context.Background(), ht.backfillTimeBudget())
defer cancel()
headWithChain, err := ht.GetChainWithBackfill(ctx, head, ht.store.Config.EthFinalityDepth())
if err != nil {
return err
}
ht.onNewLongestChain(ctx, headWithChain)
return nil
}
func (ht *HeadTracker) isKovan() bool {
return ht.store.Config.ChainID().Cmp(kovanChainID) == 0
}
// totalNewHeadTimeBudget is the timeout on the shared context for all
// requests triggered by a new head
//
// These values are chosen to be roughly 2 * block time (to give some leeway
// for temporary overload). They are by no means set in stone and may require
// adjustment based on real world feedback.
func (ht *HeadTracker) totalNewHeadTimeBudget() time.Duration {
if ht.isKovan() {
return 8 * time.Second
}
return 26 * time.Second
}
// Maximum time we are allowed to spend backfilling heads. This should be
// somewhat shorter than the average time between heads to ensure we
// don't starve the runqueue.
func (ht *HeadTracker) backfillTimeBudget() time.Duration {
if ht.isKovan() {
return 3 * time.Second
}
return 10 * time.Second
}
// If total callback execution time exceeds this threshold we consider this to
// be a problem and will log a warning.
// Here we set it to the average time between blocks.
func (ht *HeadTracker) callbackExecutionThreshold() time.Duration {
if ht.isKovan() {
return 4 * time.Second
}
return 13 * time.Second
}
// GetChainWithBackfill returns a chain of the given length, backfilling any
// heads that may be missing from the database
func (ht *HeadTracker) GetChainWithBackfill(ctx context.Context, head models.Head, depth uint) (models.Head, error) {
ctx, cancel := context.WithTimeout(ctx, ht.backfillTimeBudget())
defer cancel()
head, err := ht.store.Chain(head.Hash, depth)
if err != nil {
return head, errors.Wrap(err, "GetChainWithBackfill failed fetching chain")
}
if uint(head.ChainLength()) >= depth {
return head, nil
}
baseHeight := head.Number - int64(depth-1)
if baseHeight < 0 {
baseHeight = 0
}
if err := ht.backfill(ctx, head.EarliestInChain(), baseHeight); err != nil {
return head, errors.Wrap(err, "GetChainWithBackfill failed backfilling")
}
return ht.store.Chain(head.Hash, depth)
}
// backfill fetches all missing heads up until the base height
func (ht *HeadTracker) backfill(ctx context.Context, head models.Head, baseHeight int64) error {
if head.Number <= baseHeight {
return nil
}
mark := time.Now()
fetched := 0
defer func() {
logger.Debugw("HeadTracker: finished backfill",
"fetched", fetched,
"blockNumber", head.Number,
"time", time.Since(mark),
"id", "head_tracker",
"n", head.Number-baseHeight,
"fromBlockHeight", baseHeight,
"toBlockHeight", head.Number-1)
}()
for i := head.Number - 1; i >= baseHeight; i-- {
// NOTE: Sequential requests here mean it's a potential performance bottleneck, be aware!
existingHead, err := ht.store.HeadByHash(head.ParentHash)
if err != nil {
return errors.Wrap(err, "HeadByHash failed")
}
if existingHead != nil {
head = *existingHead
continue
}
head, err = ht.fetchAndSaveHead(ctx, i)
fetched++
if err != nil {
if errors.Cause(err) == ethereum.NotFound {
logger.Errorw("HeadTracker: backfill failed to fetch head (not found), chain will be truncated for this head", "headNum", i)
} else if errors.Cause(err) == context.DeadlineExceeded {
logger.Infow("HeadTracker: backfill deadline exceeded, chain will be truncated for this head", "headNum", i)
} else {
logger.Errorw("HeadTracker: backfill encountered unknown error, chain will be truncated for this head", "headNum", i, "err", err)
}
break
}
}
return nil
}
func (ht *HeadTracker) fetchAndSaveHead(ctx context.Context, n int64) (models.Head, error) {
logger.Debugw("HeadTracker: fetching head", "blockHeight", n)
head, err := ht.store.EthClient.HeaderByNumber(ctx, big.NewInt(n))
if err != nil {
return models.Head{}, err
} else if head == nil {
return models.Head{}, errors.New("got nil head")
}
if err := ht.store.IdempotentInsertHead(*head); err != nil {
return models.Head{}, err
}
return *head, nil
}
func (ht *HeadTracker) onNewLongestChain(ctx context.Context, headWithChain models.Head) {
ht.headMutex.Lock()
defer ht.headMutex.Unlock()
logger.Debugw("HeadTracker initiating callbacks",
"headNum", headWithChain.Number,
"chainLength", headWithChain.ChainLength(),
"numCallbacks", len(ht.callbacks),
)
if ht.store.Config.EnableBulletproofTxManager() {
ht.concurrentlyExecuteCallbacks(ctx, headWithChain)
} else {
// NOTE: Legacy tx manager probably has implicit ordering requirements, so it's not safe to parallelise
ht.seriallyExecuteCallbacks(ctx, headWithChain)
}
}
func (ht *HeadTracker) concurrentlyExecuteCallbacks(ctx context.Context, headWithChain models.Head) {
wg := sync.WaitGroup{}
wg.Add(len(ht.callbacks))
for idx, trackable := range ht.callbacks {
go func(i int, t strpkg.HeadTrackable) {
start := time.Now()
t.OnNewLongestChain(ctx, headWithChain)
elapsed := time.Since(start)
logger.Debugw(fmt.Sprintf("HeadTracker: finished callback %v in %s", i, elapsed), "callbackType", reflect.TypeOf(t), "callbackIdx", i, "blockNumber", headWithChain.Number, "time", elapsed, "id", "head_tracker")
wg.Done()
}(idx, trackable)
}
wg.Wait()
}
func (ht *HeadTracker) seriallyExecuteCallbacks(ctx context.Context, headWithChain models.Head) {
for i, t := range ht.callbacks {
start := time.Now()
t.OnNewLongestChain(ctx, headWithChain)
elapsed := time.Since(start)
logger.Debugw(fmt.Sprintf("HeadTracker: finished callback %v in %s", i, elapsed), "callbackType", reflect.TypeOf(t), "callbackIdx", i, "blockNumber", headWithChain.Number, "time", elapsed, "id", "head_tracker")
}
}
func (ht *HeadTracker) subscribeToHead() error {
ht.headMutex.Lock()
defer ht.headMutex.Unlock()
ht.inHeaders = make(chan *models.Head)
var rb *headRingBuffer
rb, ht.outHeaders = newHeadRingBuffer(ht.inHeaders, int(ht.store.Config.EthHeadTrackerMaxBufferSize()))
// It will autostop when we close inHeaders channel
rb.Start()
sub, err := ht.store.EthClient.SubscribeNewHead(context.Background(), ht.inHeaders)
if err != nil {
return errors.Wrap(err, "EthClient#SubscribeNewHead")
}
if err := verifyEthereumChainID(ht); err != nil {
return errors.Wrap(err, "verifyEthereumChainID failed")
}
ht.headSubscription = sub
ht.connected = true
ht.connect(ht.highestSeenHead)
return nil
}
func (ht *HeadTracker) unsubscribeFromHead() error {
ht.headMutex.Lock()
defer ht.headMutex.Unlock()
if !ht.connected {
return nil
}
timedUnsubscribe(ht.headSubscription)
ht.connected = false
ht.disconnect()
close(ht.inHeaders)
// Drain channel and wait for ringbuffer to close it
for range ht.outHeaders {
}
return nil
}
func (ht *HeadTracker) setHighestSeenHeadFromDB() error {
head, err := ht.store.LastHead()
if err != nil {
return err
}
ht.highestSeenHead = head
return nil
}
// chainIDVerify checks whether or not the ChainID from the Chainlink config
// matches the ChainID reported by the ETH node connected to this Chainlink node.
func verifyEthereumChainID(ht *HeadTracker) error {
ethereumChainID, err := ht.store.EthClient.ChainID(context.TODO())
if err != nil {
return err
}
if ethereumChainID.Cmp(ht.store.Config.ChainID()) != 0 {
return fmt.Errorf(
"ethereum ChainID doesn't match chainlink config.ChainID: config ID=%d, eth RPC ID=%d",
ht.store.Config.ChainID(),
ethereumChainID,
)
}
return nil
}