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syncTime.go
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syncTime.go
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package ntp
import (
"context"
"crypto/rand"
"fmt"
"math"
"math/big"
"sort"
"sync"
"time"
"github.com/beevik/ntp"
"github.com/multiversx/mx-chain-core-go/core"
"github.com/multiversx/mx-chain-core-go/core/closing"
"github.com/multiversx/mx-chain-go/config"
"github.com/multiversx/mx-chain-logger-go"
)
var _ SyncTimer = (*syncTime)(nil)
var _ closing.Closer = (*syncTime)(nil)
var log = logger.GetOrCreate("ntp")
// numRequestsFromHost represents the number of requests to be done from each host
const numRequestsFromHost = 10
// cuttingOutPercent [0, 1) represents the percent of received clock offsets to be removed from the edges (min and max)
const cuttingOutPercent = 0.3
// minResponsesPercent (0, 1] represents the minimum percent of responses, from all requests done, needed to set a new
// clock offset
const minResponsesPercent = 0.25
// maxOffsetPercent [0, 1) represents the maximum percent, from the initial sync period given, which could be added or
// subtracted from it
const maxOffsetPercent = 0.2
// minTimeout represents the minimum time in milliseconds to wait for a response from a host after a NTP request
const minTimeout = 100
const outOfBoundsDuration = time.Second
// NTPOptions defines configuration options for a NTP query
type NTPOptions struct {
Hosts []string
Version int
LocalAddress string
Timeout time.Duration
Port int
}
// NewNTPGoogleConfig creates an NTPConfig object that configures NTP to use a predefined list of hosts. This is useful
// for tests, for example, to avoid loading a configuration file just to have a NTPConfig
func NewNTPGoogleConfig() config.NTPConfig {
return config.NTPConfig{
Hosts: []string{"time.google.com", "time.cloudflare.com", "time.apple.com", "time.windows.com"},
Port: 123,
Version: 0,
TimeoutMilliseconds: 100,
SyncPeriodSeconds: 3600,
}
}
// NewNTPOptions creates a new NTPOptions object
func NewNTPOptions(ntpConfig config.NTPConfig) NTPOptions {
ntpConfig.TimeoutMilliseconds = core.MaxInt(minTimeout, ntpConfig.TimeoutMilliseconds)
timeout := time.Duration(ntpConfig.TimeoutMilliseconds) * time.Millisecond
return NTPOptions{
Hosts: ntpConfig.Hosts,
Port: ntpConfig.Port,
Version: ntpConfig.Version,
LocalAddress: "",
Timeout: timeout,
}
}
// queryNTP wraps beevikntp.QueryWithOptions, in order to use NTPOptions, which contains both Host and Port, unlike
// beevikntp.QueryOptions
func queryNTP(options NTPOptions, hostIndex int) (*ntp.Response, error) {
if hostIndex >= len(options.Hosts) {
return nil, ErrIndexOutOfBounds
}
queryOptions := ntp.QueryOptions{
Timeout: options.Timeout,
Version: options.Version,
LocalAddress: options.LocalAddress,
Port: options.Port,
}
return ntp.QueryWithOptions(options.Hosts[hostIndex], queryOptions)
}
// syncTime defines an object for time synchronization
type syncTime struct {
mut sync.RWMutex
clockOffset time.Duration
syncPeriod time.Duration
ntpOptions NTPOptions
query func(options NTPOptions, hostIndex int) (*ntp.Response, error)
cancelFunc func()
}
// NewSyncTime creates a syncTime object. The customQueryFunc argument allows the caller to set a different NTP-querying
// callback, if desired. If set to nil, then the default queryNTP is used
func NewSyncTime(
ntpConfig config.NTPConfig,
customQueryFunc func(options NTPOptions, hostIndex int) (*ntp.Response, error),
) *syncTime {
queryFunc := customQueryFunc
if queryFunc == nil {
queryFunc = queryNTP
}
s := syncTime{
clockOffset: 0,
syncPeriod: time.Duration(ntpConfig.SyncPeriodSeconds) * time.Second,
query: queryFunc,
ntpOptions: NewNTPOptions(ntpConfig),
}
return &s
}
// StartSyncingTime method does the time synchronization at every syncPeriod time elapsed. This method should be started on go
// routine
func (s *syncTime) StartSyncingTime() {
var ctx context.Context
ctx, s.cancelFunc = context.WithCancel(context.Background())
go s.startSync(ctx)
}
func (s *syncTime) startSync(ctx context.Context) {
for {
s.sync()
select {
case <-ctx.Done():
log.Debug("syncTime's go routine is stopping...")
return
case <-time.After(s.getSleepTime()):
}
}
}
func (s *syncTime) getSleepTime() time.Duration {
maxOffset := int64(float64(s.syncPeriod) * maxOffsetPercent)
maxRandValueToGenerate := maxOffset * 2
randBigInt, err := rand.Int(rand.Reader, big.NewInt(maxRandValueToGenerate+1))
if err != nil {
return s.syncPeriod
}
offset := randBigInt.Int64() - maxOffset
return s.syncPeriod + time.Duration(offset)
}
// sync method does the time synchronization and sets the harmonic mean offset difference between local time
// and servers time which have been used in synchronization
func (s *syncTime) sync() {
clockOffsets := make([]time.Duration, 0)
for hostIndex := 0; hostIndex < len(s.ntpOptions.Hosts); hostIndex++ {
for requests := 0; requests < numRequestsFromHost; requests++ {
response, err := s.query(s.ntpOptions, hostIndex)
if err != nil {
log.Debug("sync.query",
"host", s.ntpOptions.Hosts[hostIndex],
"port", s.ntpOptions.Port,
"error", err.Error())
continue
}
log.Trace("sync.query",
"host", s.ntpOptions.Hosts[hostIndex],
"reference time", response.ReferenceTime.Format("Mon Jan 2 15:04:05 MST 2006"),
"time", response.Time.Format("Mon Jan 2 15:04:05 MST 2006"),
"precision", response.Precision,
"clock offset", response.ClockOffset,
)
clockOffsets = append(clockOffsets, response.ClockOffset)
}
}
numTotalRequests := len(s.ntpOptions.Hosts) * numRequestsFromHost
minClockOffsetsToAllowUpdate := math.Ceil(float64(numTotalRequests) * minResponsesPercent / (1 - cuttingOutPercent))
if len(clockOffsets) < int(minClockOffsetsToAllowUpdate) {
log.Debug("sync.setClockOffset NOT done",
"clock offsets", len(clockOffsets),
"min clock offsets to allow update", int(minClockOffsetsToAllowUpdate))
return
}
clockOffsetsWithoutEdges := s.getClockOffsetsWithoutEdges(clockOffsets)
clockOffsetHarmonicMean := s.getHarmonicMean(clockOffsetsWithoutEdges)
isOutOfBounds := core.AbsDuration(clockOffsetHarmonicMean)-outOfBoundsDuration > 0
if isOutOfBounds {
log.Error("syncTime.sync: clock offset is out of expected bounds",
"clock offset harmonic mean", clockOffsetHarmonicMean)
return
}
s.setClockOffset(clockOffsetHarmonicMean)
log.Debug("sync.setClockOffset done",
"num clock offsets", len(clockOffsets),
"num clock offsets without edges", len(clockOffsetsWithoutEdges),
"clock offset harmonic mean", clockOffsetHarmonicMean)
}
func (s *syncTime) getClockOffsetsWithoutEdges(clockOffsets []time.Duration) []time.Duration {
sort.Slice(clockOffsets, func(i, j int) bool {
return clockOffsets[i] < clockOffsets[j]
})
cuttingOutPercentPerEdge := cuttingOutPercent / 2
startIndex := math.Floor(float64(len(clockOffsets)) * cuttingOutPercentPerEdge)
endIndex := math.Ceil(float64(len(clockOffsets)) * (1 - cuttingOutPercentPerEdge))
return clockOffsets[int(startIndex):int(endIndex)]
}
func (s *syncTime) getHarmonicMean(clockOffsets []time.Duration) time.Duration {
inverseClockOffsetSum := float64(0)
for index, clockOffset := range clockOffsets {
if clockOffset == 0 {
return time.Duration(0)
}
inverseClockOffsetSum += 1 / float64(clockOffset)
log.Trace("getHarmonicMean",
"index", index,
"clock offset", clockOffset,
"inverse clock offset sum", inverseClockOffsetSum)
}
if inverseClockOffsetSum == 0 {
return time.Duration(0)
}
harmonicMean := float64(len(clockOffsets)) / inverseClockOffsetSum
//TODO: figure out why do we need to add 0.5 here
return time.Duration(harmonicMean + 0.5)
}
// ClockOffset method gets the current time offset
func (s *syncTime) ClockOffset() time.Duration {
s.mut.RLock()
clockOffset := s.clockOffset
s.mut.RUnlock()
return clockOffset
}
func (s *syncTime) setClockOffset(clockOffset time.Duration) {
s.mut.Lock()
s.clockOffset = clockOffset
s.mut.Unlock()
}
// FormattedCurrentTime method gets the formatted current time on which is added the current offset
func (s *syncTime) FormattedCurrentTime() string {
return s.formatTime(s.CurrentTime())
}
// formatTime method gets the formatted time for a given time
func (s *syncTime) formatTime(time time.Time) string {
str := fmt.Sprintf("%.4d-%.2d-%.2d %.2d:%.2d:%.2d.%.9d ",
time.Year(), time.Month(), time.Day(), time.Hour(), time.Minute(), time.Second(), time.Nanosecond())
return str
}
// CurrentTime method gets the current time on which is added the current offset
func (s *syncTime) CurrentTime() time.Time {
s.mut.RLock()
currentTime := time.Now().Add(s.clockOffset)
s.mut.RUnlock()
return currentTime
}
// Close will close the endless running go routine
func (s *syncTime) Close() error {
if s.cancelFunc != nil {
s.cancelFunc()
}
return nil
}
// IsInterfaceNil returns true if there is no value under the interface
func (s *syncTime) IsInterfaceNil() bool {
return s == nil
}