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Refactor Federation Destination Queues (#2807)

Browse source 
This is a refactor of the federation destination queues.
It fixes a few things, namely:
- actually retry outgoing events with backoff behaviour
- obtain enough events from the database to fill messages as much as
possible
- minimize the amount of running goroutines
  - use pure timers for backoff
  - don't restart queue unless necessary
  - close the background task when backing off
- increase max edus in a transaction to match the spec
- cleanup timers more aggresively to reduce memory usage
- add jitter to backoff timers to reduce resource spikes
- add a bunch of tests (with real and fake databases) to ensure
everything is working
This commit is contained in:
devonh 2022-10-19 10:03:16 +00:00 committed by GitHub
parent 3aa92efaa3
commit 241d5c47df
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
8 changed files with 1410 additions and 202 deletions
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9
federationapi/federationapi.go
View file

@ -116,17 +116,14 @@ func NewInternalAPI(
_ = federationDB.RemoveAllServersFromBlacklist()
}
stats := &statistics.Statistics{
DB: federationDB,
FailuresUntilBlacklist: cfg.FederationMaxRetries,
}
stats := statistics.NewStatistics(federationDB, cfg.FederationMaxRetries+1)
js, _ := base.NATS.Prepare(base.ProcessContext, &cfg.Matrix.JetStream)
queues := queue.NewOutgoingQueues(
federationDB, base.ProcessContext,
cfg.Matrix.DisableFederation,
cfg.Matrix.ServerName, federation, rsAPI, stats,
cfg.Matrix.ServerName, federation, rsAPI, &stats,
&queue.SigningInfo{
KeyID: cfg.Matrix.KeyID,
PrivateKey: cfg.Matrix.PrivateKey,
@ -183,5 +180,5 @@ func NewInternalAPI(
}
time.AfterFunc(time.Minute, cleanExpiredEDUs)
return internal.NewFederationInternalAPI(federationDB, cfg, rsAPI, federation, stats, caches, queues, keyRing)
return internal.NewFederationInternalAPI(federationDB, cfg, rsAPI, federation, &stats, caches, queues, keyRing)
}

374
federationapi/queue/destinationqueue.go
View file

@ -35,7 +35,7 @@ import (
const (
maxPDUsPerTransaction = 50
maxEDUsPerTransaction = 50
maxEDUsPerTransaction = 100
maxPDUsInMemory = 128
maxEDUsInMemory = 128
queueIdleTimeout = time.Second * 30
@ -64,7 +64,6 @@ type destinationQueue struct {
pendingPDUs []*queuedPDU // PDUs waiting to be sent
pendingEDUs []*queuedEDU // EDUs waiting to be sent
pendingMutex sync.RWMutex // protects pendingPDUs and pendingEDUs
interruptBackoff chan bool // interrupts backoff
}
// Send event adds the event to the pending queue for the destination.
@ -75,6 +74,7 @@ func (oq *destinationQueue) sendEvent(event *gomatrixserverlib.HeaderedEvent, re
logrus.Errorf("attempt to send nil PDU with destination %q", oq.destination)
return
}
// Create a database entry that associates the given PDU NID with
// this destination queue. We'll then be able to retrieve the PDU
// later.
@ -102,12 +102,12 @@ func (oq *destinationQueue) sendEvent(event *gomatrixserverlib.HeaderedEvent, re
oq.overflowed.Store(true)
}
oq.pendingMutex.Unlock()
// Wake up the queue if it's asleep.
oq.wakeQueueIfNeeded()
select {
case oq.notify <- struct{}{}:
default:
if !oq.backingOff.Load() {
oq.wakeQueueAndNotify()
}
} else {
oq.overflowed.Store(true)
}
}
@ -147,12 +147,37 @@ func (oq *destinationQueue) sendEDU(event *gomatrixserverlib.EDU, receipt *share
oq.overflowed.Store(true)
}
oq.pendingMutex.Unlock()
// Wake up the queue if it's asleep.
oq.wakeQueueIfNeeded()
select {
case oq.notify <- struct{}{}:
default:
if !oq.backingOff.Load() {
oq.wakeQueueAndNotify()
}
} else {
oq.overflowed.Store(true)
}
}
// handleBackoffNotifier is registered as the backoff notification
// callback with Statistics. It will wakeup and notify the queue
// if the queue is currently backing off.
func (oq *destinationQueue) handleBackoffNotifier() {
// Only wake up the queue if it is backing off.
// Otherwise there is no pending work for the queue to handle
// so waking the queue would be a waste of resources.
if oq.backingOff.Load() {
oq.wakeQueueAndNotify()
}
}
// wakeQueueAndNotify ensures the destination queue is running and notifies it
// that there is pending work.
func (oq *destinationQueue) wakeQueueAndNotify() {
// Wake up the queue if it's asleep.
oq.wakeQueueIfNeeded()
// Notify the queue that there are events ready to send.
select {
case oq.notify <- struct{}{}:
default:
}
}
@ -161,10 +186,11 @@ func (oq *destinationQueue) sendEDU(event *gomatrixserverlib.EDU, receipt *share
// then we will interrupt the backoff, causing any federation
// requests to retry.
func (oq *destinationQueue) wakeQueueIfNeeded() {
// If we are backing off then interrupt the backoff.
// Clear the backingOff flag and update the backoff metrics if it was set.
if oq.backingOff.CompareAndSwap(true, false) {
oq.interruptBackoff <- true
destinationQueueBackingOff.Dec()
}
// If we aren't running then wake up the queue.
if !oq.running.Load() {
// Start the queue.
@ -196,38 +222,54 @@ func (oq *destinationQueue) getPendingFromDatabase() {
gotEDUs[edu.receipt.String()] = struct{}{}
}
overflowed := false
if pduCapacity := maxPDUsInMemory - len(oq.pendingPDUs); pduCapacity > 0 {
// We have room in memory for some PDUs - let's request no more than that.
if pdus, err := oq.db.GetPendingPDUs(ctx, oq.destination, pduCapacity); err == nil {
if pdus, err := oq.db.GetPendingPDUs(ctx, oq.destination, maxPDUsInMemory); err == nil {
if len(pdus) == maxPDUsInMemory {
overflowed = true
}
for receipt, pdu := range pdus {
if _, ok := gotPDUs[receipt.String()]; ok {
continue
}
oq.pendingPDUs = append(oq.pendingPDUs, &queuedPDU{receipt, pdu})
retrieved = true
if len(oq.pendingPDUs) == maxPDUsInMemory {
break
}
}
} else {
logrus.WithError(err).Errorf("Failed to get pending PDUs for %q", oq.destination)
}
}
if eduCapacity := maxEDUsInMemory - len(oq.pendingEDUs); eduCapacity > 0 {
// We have room in memory for some EDUs - let's request no more than that.
if edus, err := oq.db.GetPendingEDUs(ctx, oq.destination, eduCapacity); err == nil {
if edus, err := oq.db.GetPendingEDUs(ctx, oq.destination, maxEDUsInMemory); err == nil {
if len(edus) == maxEDUsInMemory {
overflowed = true
}
for receipt, edu := range edus {
if _, ok := gotEDUs[receipt.String()]; ok {
continue
}
oq.pendingEDUs = append(oq.pendingEDUs, &queuedEDU{receipt, edu})
retrieved = true
if len(oq.pendingEDUs) == maxEDUsInMemory {
break
}
}
} else {
logrus.WithError(err).Errorf("Failed to get pending EDUs for %q", oq.destination)
}
}
// If we've retrieved all of the events from the database with room to spare
// in memory then we'll no longer consider this queue to be overflowed.
if len(oq.pendingPDUs) < maxPDUsInMemory && len(oq.pendingEDUs) < maxEDUsInMemory {
if !overflowed {
oq.overflowed.Store(false)
} else {
}
// If we've retrieved some events then notify the destination queue goroutine.
if retrieved {
@ -238,6 +280,24 @@ func (oq *destinationQueue) getPendingFromDatabase() {
}
}
// checkNotificationsOnClose checks for any remaining notifications
// and starts a new backgroundSend goroutine if any exist.
func (oq *destinationQueue) checkNotificationsOnClose() {
// NOTE : If we are stopping the queue due to blacklist then it
// doesn't matter if we have been notified of new work since
// this queue instance will be deleted anyway.
if !oq.statistics.Blacklisted() {
select {
case <-oq.notify:
// We received a new notification in between the
// idle timeout firing and stopping the goroutine.
// Immediately restart the queue.
oq.wakeQueueAndNotify()
default:
}
}
}
// backgroundSend is the worker goroutine for sending events.
func (oq *destinationQueue) backgroundSend() {
// Check if a worker is already running, and if it isn't, then
@ -245,10 +305,17 @@ func (oq *destinationQueue) backgroundSend() {
if !oq.running.CompareAndSwap(false, true) {
return
}
// Register queue cleanup functions.
// NOTE : The ordering here is very intentional.
defer oq.checkNotificationsOnClose()
defer oq.running.Store(false)
destinationQueueRunning.Inc()
defer destinationQueueRunning.Dec()
defer oq.queues.clearQueue(oq)
defer oq.running.Store(false)
idleTimeout := time.NewTimer(queueIdleTimeout)
defer idleTimeout.Stop()
// Mark the queue as overflowed, so we will consult the database
// to see if there's anything new to send.
@ -261,59 +328,33 @@ func (oq *destinationQueue) backgroundSend() {
oq.getPendingFromDatabase()
}
// Reset the queue idle timeout.
if !idleTimeout.Stop() {
select {
case <-idleTimeout.C:
default:
}
}
idleTimeout.Reset(queueIdleTimeout)
// If we have nothing to do then wait either for incoming events, or
// until we hit an idle timeout.
select {
case <-oq.notify:
// There's work to do, either because getPendingFromDatabase
// told us there is, or because a new event has come in via
// sendEvent/sendEDU.
case <-time.After(queueIdleTimeout):
// told us there is, a new event has come in via sendEvent/sendEDU,
// or we are backing off and it is time to retry.
case <-idleTimeout.C:
// The worker is idle so stop the goroutine. It'll get
// restarted automatically the next time we have an event to
// send.
return
case <-oq.process.Context().Done():
// The parent process is shutting down, so stop.
oq.statistics.ClearBackoff()
return
}
// If we are backing off this server then wait for the
// backoff duration to complete first, or until explicitly
// told to retry.
until, blacklisted := oq.statistics.BackoffInfo()
if blacklisted {
// It's been suggested that we should give up because the backoff
// has exceeded a maximum allowable value. Clean up the in-memory
// buffers at this point. The PDU clean-up is already on a defer.
logrus.Warnf("Blacklisting %q due to exceeding backoff threshold", oq.destination)
oq.pendingMutex.Lock()
for i := range oq.pendingPDUs {
oq.pendingPDUs[i] = nil
}
for i := range oq.pendingEDUs {
oq.pendingEDUs[i] = nil
}
oq.pendingPDUs = nil
oq.pendingEDUs = nil
oq.pendingMutex.Unlock()
return
}
if until != nil && until.After(time.Now()) {
// We haven't backed off yet, so wait for the suggested amount of
// time.
duration := time.Until(*until)
logrus.Debugf("Backing off %q for %s", oq.destination, duration)
oq.backingOff.Store(true)
destinationQueueBackingOff.Inc()
select {
case <-time.After(duration):
case <-oq.interruptBackoff:
}
destinationQueueBackingOff.Dec()
oq.backingOff.Store(false)
}
// Work out which PDUs/EDUs to include in the next transaction.
oq.pendingMutex.RLock()
pduCount := len(oq.pendingPDUs)
@ -328,99 +369,52 @@ func (oq *destinationQueue) backgroundSend() {
toSendEDUs := oq.pendingEDUs[:eduCount]
oq.pendingMutex.RUnlock()
// If we didn't get anything from the database and there are no
// pending EDUs then there's nothing to do - stop here.
if pduCount == 0 && eduCount == 0 {
continue
}
// If we have pending PDUs or EDUs then construct a transaction.
// Try sending the next transaction and see what happens.
transaction, pc, ec, terr := oq.nextTransaction(toSendPDUs, toSendEDUs)
terr := oq.nextTransaction(toSendPDUs, toSendEDUs)
if terr != nil {
// We failed to send the transaction. Mark it as a failure.
oq.statistics.Failure()
} else if transaction {
// If we successfully sent the transaction then clear out
// the pending events and EDUs, and wipe our transaction ID.
oq.statistics.Success()
oq.pendingMutex.Lock()
for i := range oq.pendingPDUs[:pc] {
oq.pendingPDUs[i] = nil
_, blacklisted := oq.statistics.Failure()
if !blacklisted {
// Register the backoff state and exit the goroutine.
// It'll get restarted automatically when the backoff
// completes.
oq.backingOff.Store(true)
destinationQueueBackingOff.Inc()
return
} else {
// Immediately trigger the blacklist logic.
oq.blacklistDestination()
return
}
for i := range oq.pendingEDUs[:ec] {
oq.pendingEDUs[i] = nil
}
oq.pendingPDUs = oq.pendingPDUs[pc:]
oq.pendingEDUs = oq.pendingEDUs[ec:]
oq.pendingMutex.Unlock()
} else {
oq.handleTransactionSuccess(pduCount, eduCount)
}
}
}
// nextTransaction creates a new transaction from the pending event
// queue and sends it. Returns true if a transaction was sent or
// false otherwise.
// queue and sends it.
// Returns an error if the transaction wasn't sent.
func (oq *destinationQueue) nextTransaction(
pdus []*queuedPDU,
edus []*queuedEDU,
) (bool, int, int, error) {
// If there's no projected transaction ID then generate one. If
// the transaction succeeds then we'll set it back to "" so that
// we generate a new one next time. If it fails, we'll preserve
// it so that we retry with the same transaction ID.
oq.transactionIDMutex.Lock()
if oq.transactionID == "" {
now := gomatrixserverlib.AsTimestamp(time.Now())
oq.transactionID = gomatrixserverlib.TransactionID(fmt.Sprintf("%d-%d", now, oq.statistics.SuccessCount()))
}
oq.transactionIDMutex.Unlock()
) error {
// Create the transaction.
t := gomatrixserverlib.Transaction{
PDUs: []json.RawMessage{},
EDUs: []gomatrixserverlib.EDU{},
}
t.Origin = oq.origin
t.Destination = oq.destination
t.OriginServerTS = gomatrixserverlib.AsTimestamp(time.Now())
t.TransactionID = oq.transactionID
// If we didn't get anything from the database and there are no
// pending EDUs then there's nothing to do - stop here.
if len(pdus) == 0 && len(edus) == 0 {
return false, 0, 0, nil
}
var pduReceipts []*shared.Receipt
var eduReceipts []*shared.Receipt
// Go through PDUs that we retrieved from the database, if any,
// and add them into the transaction.
for _, pdu := range pdus {
if pdu == nil || pdu.pdu == nil {
continue
}
// Append the JSON of the event, since this is a json.RawMessage type in the
// gomatrixserverlib.Transaction struct
t.PDUs = append(t.PDUs, pdu.pdu.JSON())
pduReceipts = append(pduReceipts, pdu.receipt)
}
// Do the same for pending EDUS in the queue.
for _, edu := range edus {
if edu == nil || edu.edu == nil {
continue
}
t.EDUs = append(t.EDUs, *edu.edu)
eduReceipts = append(eduReceipts, edu.receipt)
}
t, pduReceipts, eduReceipts := oq.createTransaction(pdus, edus)
logrus.WithField("server_name", oq.destination).Debugf("Sending transaction %q containing %d PDUs, %d EDUs", t.TransactionID, len(t.PDUs), len(t.EDUs))
// Try to send the transaction to the destination server.
// TODO: we should check for 500-ish fails vs 400-ish here,
// since we shouldn't queue things indefinitely in response
// to a 400-ish error
ctx, cancel := context.WithTimeout(oq.process.Context(), time.Minute*5)
defer cancel()
_, err := oq.client.SendTransaction(ctx, t)
switch err.(type) {
switch errResponse := err.(type) {
case nil:
// Clean up the transaction in the database.
if pduReceipts != nil {
@ -439,16 +433,128 @@ func (oq *destinationQueue) nextTransaction(
oq.transactionIDMutex.Lock()
oq.transactionID = ""
oq.transactionIDMutex.Unlock()
return true, len(t.PDUs), len(t.EDUs), nil
return nil
case gomatrix.HTTPError:
// Report that we failed to send the transaction and we
// will retry again, subject to backoff.
return false, 0, 0, err
// TODO: we should check for 500-ish fails vs 400-ish here,
// since we shouldn't queue things indefinitely in response
// to a 400-ish error
code := errResponse.Code
logrus.Debug("Transaction failed with HTTP", code)
return err
default:
logrus.WithFields(logrus.Fields{
"destination": oq.destination,
logrus.ErrorKey: err,
}).Debugf("Failed to send transaction %q", t.TransactionID)
return false, 0, 0, err
return err
}
}
// createTransaction generates a gomatrixserverlib.Transaction from the provided pdus and edus.
// It also returns the associated event receipts so they can be cleaned from the database in
// the case of a successful transaction.
func (oq *destinationQueue) createTransaction(
pdus []*queuedPDU,
edus []*queuedEDU,
) (gomatrixserverlib.Transaction, []*shared.Receipt, []*shared.Receipt) {
// If there's no projected transaction ID then generate one. If
// the transaction succeeds then we'll set it back to "" so that
// we generate a new one next time. If it fails, we'll preserve
// it so that we retry with the same transaction ID.
oq.transactionIDMutex.Lock()
if oq.transactionID == "" {
now := gomatrixserverlib.AsTimestamp(time.Now())
oq.transactionID = gomatrixserverlib.TransactionID(fmt.Sprintf("%d-%d", now, oq.statistics.SuccessCount()))
}
oq.transactionIDMutex.Unlock()
t := gomatrixserverlib.Transaction{
PDUs: []json.RawMessage{},
EDUs: []gomatrixserverlib.EDU{},
}
t.Origin = oq.origin
t.Destination = oq.destination
t.OriginServerTS = gomatrixserverlib.AsTimestamp(time.Now())
t.TransactionID = oq.transactionID
var pduReceipts []*shared.Receipt
var eduReceipts []*shared.Receipt
// Go through PDUs that we retrieved from the database, if any,
// and add them into the transaction.
for _, pdu := range pdus {
// These should never be nil.
if pdu == nil || pdu.pdu == nil {
continue
}
// Append the JSON of the event, since this is a json.RawMessage type in the
// gomatrixserverlib.Transaction struct
t.PDUs = append(t.PDUs, pdu.pdu.JSON())
pduReceipts = append(pduReceipts, pdu.receipt)
}
// Do the same for pending EDUS in the queue.
for _, edu := range edus {
// These should never be nil.
if edu == nil || edu.edu == nil {
continue
}
t.EDUs = append(t.EDUs, *edu.edu)
eduReceipts = append(eduReceipts, edu.receipt)
}
return t, pduReceipts, eduReceipts
}
// blacklistDestination removes all pending PDUs and EDUs that have been cached
// and deletes this queue.
func (oq *destinationQueue) blacklistDestination() {
// It's been suggested that we should give up because the backoff
// has exceeded a maximum allowable value. Clean up the in-memory
// buffers at this point. The PDU clean-up is already on a defer.
logrus.Warnf("Blacklisting %q due to exceeding backoff threshold", oq.destination)
oq.pendingMutex.Lock()
for i := range oq.pendingPDUs {
oq.pendingPDUs[i] = nil
}
for i := range oq.pendingEDUs {
oq.pendingEDUs[i] = nil
}
oq.pendingPDUs = nil
oq.pendingEDUs = nil
oq.pendingMutex.Unlock()
// Delete this queue as no more messages will be sent to this
// destination until it is no longer blacklisted.
oq.statistics.AssignBackoffNotifier(nil)
oq.queues.clearQueue(oq)
}
// handleTransactionSuccess updates the cached event queues as well as the success and
// backoff information for this server.
func (oq *destinationQueue) handleTransactionSuccess(pduCount int, eduCount int) {
// If we successfully sent the transaction then clear out
// the pending events and EDUs, and wipe our transaction ID.
oq.statistics.Success()
oq.pendingMutex.Lock()
for i := range oq.pendingPDUs[:pduCount] {
oq.pendingPDUs[i] = nil
}
for i := range oq.pendingEDUs[:eduCount] {
oq.pendingEDUs[i] = nil
}
oq.pendingPDUs = oq.pendingPDUs[pduCount:]
oq.pendingEDUs = oq.pendingEDUs[eduCount:]
oq.pendingMutex.Unlock()
if len(oq.pendingPDUs) > 0 || len(oq.pendingEDUs) > 0 {
select {
case oq.notify <- struct{}{}:
default:
}
}
}

26
federationapi/queue/queue.go
View file

@ -162,23 +162,25 @@ func (oqs *OutgoingQueues) getQueue(destination gomatrixserverlib.ServerName) *d
if !ok || oq == nil {
destinationQueueTotal.Inc()
oq = &destinationQueue{
queues: oqs,
db: oqs.db,
process: oqs.process,
rsAPI: oqs.rsAPI,
origin: oqs.origin,
destination: destination,
client: oqs.client,
statistics: oqs.statistics.ForServer(destination),
notify: make(chan struct{}, 1),
interruptBackoff: make(chan bool),
signing: oqs.signing,
queues: oqs,
db: oqs.db,
process: oqs.process,
rsAPI: oqs.rsAPI,
origin: oqs.origin,
destination: destination,
client: oqs.client,
statistics: oqs.statistics.ForServer(destination),
notify: make(chan struct{}, 1),
signing: oqs.signing,
}
oq.statistics.AssignBackoffNotifier(oq.handleBackoffNotifier)
oqs.queues[destination] = oq
}
return oq
}
// clearQueue removes the queue for the provided destination from the
// set of destination queues.
func (oqs *OutgoingQueues) clearQueue(oq *destinationQueue) {
oqs.queuesMutex.Lock()
defer oqs.queuesMutex.Unlock()
@ -332,7 +334,9 @@ func (oqs *OutgoingQueues) RetryServer(srv gomatrixserverlib.ServerName) {
if oqs.disabled {
return
}
oqs.statistics.ForServer(srv).RemoveBlacklist()
if queue := oqs.getQueue(srv); queue != nil {
queue.statistics.ClearBackoff()
queue.wakeQueueIfNeeded()
}
}

1047
federationapi/queue/queue_test.go Normal file
View file

File diff suppressed because it is too large Load diff

131
federationapi/statistics/statistics.go
View file

@ -2,6 +2,7 @@ package statistics
import (
"math"
"math/rand"
"sync"
"time"
@ -20,12 +21,23 @@ type Statistics struct {
servers map[gomatrixserverlib.ServerName]*ServerStatistics
mutex sync.RWMutex
backoffTimers map[gomatrixserverlib.ServerName]*time.Timer
backoffMutex sync.RWMutex
// How many times should we tolerate consecutive failures before we
// just blacklist the host altogether? The backoff is exponential,
// so the max time here to attempt is 2**failures seconds.
FailuresUntilBlacklist uint32
}
func NewStatistics(db storage.Database, failuresUntilBlacklist uint32) Statistics {
return Statistics{
DB: db,
FailuresUntilBlacklist: failuresUntilBlacklist,
backoffTimers: make(map[gomatrixserverlib.ServerName]*time.Timer),
}
}
// ForServer returns server statistics for the given server name. If it
// does not exist, it will create empty statistics and return those.
func (s *Statistics) ForServer(serverName gomatrixserverlib.ServerName) *ServerStatistics {
@ -45,7 +57,6 @@ func (s *Statistics) ForServer(serverName gomatrixserverlib.ServerName) *ServerS
server = &ServerStatistics{
statistics: s,
serverName: serverName,
interrupt: make(chan struct{}),
}
s.servers[serverName] = server
s.mutex.Unlock()
@ -64,29 +75,43 @@ func (s *Statistics) ForServer(serverName gomatrixserverlib.ServerName) *ServerS
// many times we failed etc. It also manages the backoff time and black-
// listing a remote host if it remains uncooperative.
type ServerStatistics struct {
statistics *Statistics //
serverName gomatrixserverlib.ServerName //
blacklisted atomic.Bool // is the node blacklisted
backoffStarted atomic.Bool // is the backoff started
backoffUntil atomic.Value // time.Time until this backoff interval ends
backoffCount atomic.Uint32 // number of times BackoffDuration has been called
interrupt chan struct{} // interrupts the backoff goroutine
successCounter atomic.Uint32 // how many times have we succeeded?
statistics *Statistics //
serverName gomatrixserverlib.ServerName //
blacklisted atomic.Bool // is the node blacklisted
backoffStarted atomic.Bool // is the backoff started
backoffUntil atomic.Value // time.Time until this backoff interval ends
backoffCount atomic.Uint32 // number of times BackoffDuration has been called
successCounter atomic.Uint32 // how many times have we succeeded?
backoffNotifier func() // notifies destination queue when backoff completes
notifierMutex sync.Mutex
}
const maxJitterMultiplier = 1.4
const minJitterMultiplier = 0.8
// duration returns how long the next backoff interval should be.
func (s *ServerStatistics) duration(count uint32) time.Duration {
return time.Second * time.Duration(math.Exp2(float64(count)))
// Add some jitter to minimise the chance of having multiple backoffs
// ending at the same time.
jitter := rand.Float64()*(maxJitterMultiplier-minJitterMultiplier) + minJitterMultiplier
duration := time.Millisecond * time.Duration(math.Exp2(float64(count))*jitter*1000)
return duration
}
// cancel will interrupt the currently active backoff.
func (s *ServerStatistics) cancel() {
s.blacklisted.Store(false)
s.backoffUntil.Store(time.Time{})
select {
case s.interrupt <- struct{}{}:
default:
}
s.ClearBackoff()
}
// AssignBackoffNotifier configures the channel to send to when
// a backoff completes.
func (s *ServerStatistics) AssignBackoffNotifier(notifier func()) {
s.notifierMutex.Lock()
defer s.notifierMutex.Unlock()
s.backoffNotifier = notifier
}
// Success updates the server statistics with a new successful
@ -95,8 +120,8 @@ func (s *ServerStatistics) cancel() {
// we will unblacklist it.
func (s *ServerStatistics) Success() {
s.cancel()
s.successCounter.Inc()
s.backoffCount.Store(0)
s.successCounter.Inc()
if s.statistics.DB != nil {
if err := s.statistics.DB.RemoveServerFromBlacklist(s.serverName); err != nil {
logrus.WithError(err).Errorf("Failed to remove %q from blacklist", s.serverName)
@ -105,13 +130,17 @@ func (s *ServerStatistics) Success() {
}
// Failure marks a failure and starts backing off if needed.
// The next call to BackoffIfRequired will do the right thing
// after this. It will return the time that the current failure
// It will return the time that the current failure
// will result in backoff waiting until, and a bool signalling
// whether we have blacklisted and therefore to give up.
func (s *ServerStatistics) Failure() (time.Time, bool) {
// Return immediately if we have blacklisted this node.
if s.blacklisted.Load() {
return time.Time{}, true
}
// If we aren't already backing off, this call will start
// a new backoff period. Increase the failure counter and
// a new backoff period, increase the failure counter and
// start a goroutine which will wait out the backoff and
// unset the backoffStarted flag when done.
if s.backoffStarted.CompareAndSwap(false, true) {
@ -122,40 +151,48 @@ func (s *ServerStatistics) Failure() (time.Time, bool) {
logrus.WithError(err).Errorf("Failed to add %q to blacklist", s.serverName)
}
}
s.ClearBackoff()
return time.Time{}, true
}
go func() {
until, ok := s.backoffUntil.Load().(time.Time)
if ok && !until.IsZero() {
select {
case <-time.After(time.Until(until)):
case <-s.interrupt:
}
s.backoffStarted.Store(false)
}
}()
// We're starting a new back off so work out what the next interval
// will be.
count := s.backoffCount.Load()
until := time.Now().Add(s.duration(count))
s.backoffUntil.Store(until)
s.statistics.backoffMutex.Lock()
defer s.statistics.backoffMutex.Unlock()
s.statistics.backoffTimers[s.serverName] = time.AfterFunc(time.Until(until), s.backoffFinished)
}
// Check if we have blacklisted this node.
if s.blacklisted.Load() {
return time.Now(), true
}
return s.backoffUntil.Load().(time.Time), false
}
// If we're already backing off and we haven't yet surpassed
// the deadline then return that. Repeated calls to Failure
// within a single backoff interval will have no side effects.
if until, ok := s.backoffUntil.Load().(time.Time); ok && !time.Now().After(until) {
return until, false
// ClearBackoff stops the backoff timer for this destination if it is running
// and removes the timer from the backoffTimers map.
func (s *ServerStatistics) ClearBackoff() {
// If the timer is still running then stop it so it's memory is cleaned up sooner.
s.statistics.backoffMutex.Lock()
defer s.statistics.backoffMutex.Unlock()
if timer, ok := s.statistics.backoffTimers[s.serverName]; ok {
timer.Stop()
}
delete(s.statistics.backoffTimers, s.serverName)
// We're either backing off and have passed the deadline, or
// we aren't backing off, so work out what the next interval
// will be.
count := s.backoffCount.Load()
until := time.Now().Add(s.duration(count))
s.backoffUntil.Store(until)
return until, false
s.backoffStarted.Store(false)
}
// backoffFinished will clear the previous backoff and notify the destination queue.
func (s *ServerStatistics) backoffFinished() {
s.ClearBackoff()
// Notify the destinationQueue if one is currently running.
s.notifierMutex.Lock()
defer s.notifierMutex.Unlock()
if s.backoffNotifier != nil {
s.backoffNotifier()
}
}
// BackoffInfo returns information about the current or previous backoff.
@ -174,6 +211,12 @@ func (s *ServerStatistics) Blacklisted() bool {
return s.blacklisted.Load()
}
// RemoveBlacklist removes the blacklisted status from the server.
func (s *ServerStatistics) RemoveBlacklist() {
s.cancel()
s.backoffCount.Store(0)
}
// SuccessCount returns the number of successful requests. This is
// usually useful in constructing transaction IDs.
func (s *ServerStatistics) SuccessCount() uint32 {

19
federationapi/statistics/statistics_test.go
View file

@ -7,9 +7,7 @@ import (
)
func TestBackoff(t *testing.T) {
stats := Statistics{
FailuresUntilBlacklist: 7,
}
stats := NewStatistics(nil, 7)
server := ServerStatistics{
statistics: &stats,
serverName: "test.com",
@ -36,7 +34,7 @@ func TestBackoff(t *testing.T) {
// Get the duration.
_, blacklist := server.BackoffInfo()
duration := time.Until(until).Round(time.Second)
duration := time.Until(until)
// Unset the backoff, or otherwise our next call will think that
// there's a backoff in progress and return the same result.
@ -57,8 +55,17 @@ func TestBackoff(t *testing.T) {
// Check if the duration is what we expect.
t.Logf("Backoff %d is for %s", i, duration)
if wanted := time.Second * time.Duration(math.Exp2(float64(i))); !blacklist && duration != wanted {
t.Fatalf("Backoff %d should have been %s but was %s", i, wanted, duration)
roundingAllowance := 0.01
minDuration := time.Millisecond * time.Duration(math.Exp2(float64(i))*minJitterMultiplier*1000-roundingAllowance)
maxDuration := time.Millisecond * time.Duration(math.Exp2(float64(i))*maxJitterMultiplier*1000+roundingAllowance)
var inJitterRange bool
if duration >= minDuration && duration <= maxDuration {
inJitterRange = true
} else {
inJitterRange = false
}
if !blacklist && !inJitterRange {
t.Fatalf("Backoff %d should have been between %s and %s but was %s", i, minDuration, maxDuration, duration)
}
}
}

4
federationapi/storage/shared/storage.go
View file

@ -52,6 +52,10 @@ type Receipt struct {
nid int64
}
func NewReceipt(nid int64) Receipt {
return Receipt{nid: nid}
}
func (r *Receipt) String() string {
return fmt.Sprintf("%d", r.nid)
}

2
go.mod
View file

@ -50,6 +50,7 @@ require (
golang.org/x/term v0.0.0-20220919170432-7a66f970e087
gopkg.in/h2non/bimg.v1 v1.1.9
gopkg.in/yaml.v2 v2.4.0
gotest.tools/v3 v3.4.0
nhooyr.io/websocket v1.8.7
)
@ -127,7 +128,6 @@ require (
gopkg.in/macaroon.v2 v2.1.0 // indirect
gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7 // indirect
gopkg.in/yaml.v3 v3.0.1 // indirect
gotest.tools/v3 v3.4.0 // indirect
)
go 1.18