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daemon.go
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daemon.go
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/*
Copyright (c) Facebook, Inc. and its affiliates.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package daemon
import (
"context"
"errors"
"fmt"
"math"
"sync"
"time"
log "github.com/sirupsen/logrus"
"golang.org/x/sync/errgroup"
"github.com/facebook/time/fbclock"
"github.com/facebook/time/leapsectz"
"github.com/facebook/time/phc"
"github.com/facebook/time/ptp/linearizability"
ptp "github.com/facebook/time/ptp/protocol"
)
const (
utcOffsetOriginalS int32 = 10 // UTC-TAI offset was 10s before leap seconds started (1972)
leapDurationS uint64 = 65000 // 18.06 hours
)
var errNotEnoughData = fmt.Errorf("not enough data points")
// DataPoint is what we store in DataPoint ring buffer
type DataPoint struct {
// IngressTimeNS represents ingress time in NanoSeconds
IngressTimeNS int64
// MasterOffsetNS represents master offset in NanoSeconds
MasterOffsetNS float64
// PathDelayNS represents path delay in NanoSeconds
PathDelayNS float64
// FreqAdjustmentPPB represents freq adjustment in parts per billion
FreqAdjustmentPPB float64
// ClockAccuracyNS represents clock accurary in nanoseconds
ClockAccuracyNS float64
}
// SanityCheck checks datapoint for correctness
func (d *DataPoint) SanityCheck() error {
if d.IngressTimeNS == 0 {
return fmt.Errorf("ingress time is 0")
}
if d.MasterOffsetNS == 0 {
return fmt.Errorf("master offset is 0")
}
if d.PathDelayNS == 0 {
return fmt.Errorf("path dealy is 0")
}
if d.FreqAdjustmentPPB == 0 {
return fmt.Errorf("frequency adjustment is 0")
}
if d.ClockAccuracyNS == 0 {
return fmt.Errorf("clock accuracy is 0")
}
if time.Duration(d.ClockAccuracyNS) >= ptp.ClockAccuracyUnknown.Duration() {
return fmt.Errorf("clock accuracy is unknown")
}
return nil
}
// DataFetcher is the data fetcher interface
type DataFetcher interface {
//function to gm data
FetchGMs(cfg *Config) (targest []string, err error)
//function to fetch stats
FetchStats(cfg *Config) (*DataPoint, error)
}
// Daemon is a component of fbclock that
// runs continuously,
// talks to ptp4l,
// does the math
// and populates shared memory for client library to read from.
type Daemon struct {
DataFetcher
cfg *Config
state *daemonState
stats StatsServer
l Logger
// function to get PHC time from configured PHC device
getPHCTime func() (time.Time, error)
// function to get PHC freq from configured PHC device
getPHCFreqPPB func() (float64, error)
}
// minRingSize calculate how many DataPoint we need to have in a ring buffer
// in order to provide aggregate values over 1 minute
func minRingSize(configuredRingSize int, interval time.Duration) int {
size := configuredRingSize
if time.Duration(size)*interval < time.Minute {
size = int(math.Ceil(float64(time.Minute) / float64(interval)))
}
return size
}
type clockSmearing struct {
smearingStartS uint64 // time (TAI) when smearing starts
smearingEndS uint64 // time (TAI) when smearing ends
utcOffsetPreS int32 // DTAI offset prior to Leap Second Event Time
utcOffsetPostS int32 // DTAI offset post Leap Second Event Time
}
func leapSeconds() ([]leapsectz.LeapSecond, error) {
leaps, err := leapsectz.Parse("")
if err != nil {
return []leapsectz.LeapSecond{}, err
}
if len(leaps) < 2 {
return []leapsectz.LeapSecond{}, fmt.Errorf("not enough leap seconds in the file")
}
previousLeap := leaps[len(leaps)-2]
latestLeap := leaps[len(leaps)-1]
return []leapsectz.LeapSecond{previousLeap, latestLeap}, nil
}
func leapSecondSmearing(leaps []leapsectz.LeapSecond) *clockSmearing {
// need a minimum of 2 published leap second events in tzdata
if len(leaps) < 2 {
return &clockSmearing{}
}
latestLeap := leaps[len(leaps)-1]
previousLeap := leaps[len(leaps)-2]
utcOffsetPreS := previousLeap.Nleap + utcOffsetOriginalS
utcOffsetPostS := latestLeap.Nleap + utcOffsetOriginalS
// this is the leap second adjustment time which is either 23:59:60 UTC or 00:00:00 UTC of following day
// if we don't render a timestamp of 23:59:60 UTC
leapSecondEventTimeS := latestLeap.Tleap - uint64(latestLeap.Nleap) + 1
// smearing starts at leap second event time and ends 18.06 hours after
smearingStartS := leapSecondEventTimeS + uint64(utcOffsetPreS)
smearingEndS := leapSecondEventTimeS + leapDurationS + uint64(utcOffsetPreS)
return &clockSmearing{
smearingStartS: smearingStartS,
smearingEndS: smearingEndS,
utcOffsetPreS: utcOffsetPreS,
utcOffsetPostS: utcOffsetPostS,
}
}
// New creates new fbclock-daemon
func New(cfg *Config, stats StatsServer, l Logger) (*Daemon, error) {
// we need at least 1m of samples for aggregate values
effectiveRingSize := minRingSize(cfg.RingSize, cfg.Interval)
s := &Daemon{
stats: stats,
state: newDaemonState(effectiveRingSize),
cfg: cfg,
l: l,
}
if cfg.SPTP {
s.DataFetcher = &HTTPFetcher{}
} else {
s.DataFetcher = &SockFetcher{}
}
phcDevice, err := phc.IfaceToPHCDevice(cfg.Iface)
if err != nil {
return nil, fmt.Errorf("finding PHC device for %q: %w", cfg.Iface, err)
}
// function to get time from phc
s.getPHCTime = func() (time.Time, error) { return phc.TimeFromDevice(phcDevice) }
s.getPHCFreqPPB = func() (float64, error) { return phc.FrequencyPPBFromDevice(phcDevice) }
// calculated values
s.stats.SetCounter("m_ns", 0)
s.stats.SetCounter("w_ns", 0)
s.stats.SetCounter("drift_ppb", 0)
// error counters
s.stats.SetCounter("data_error", 0)
s.stats.SetCounter("phc_error", 0)
s.stats.SetCounter("processing_error", 0)
s.stats.SetCounter("data_sanity_check_error", 0)
// values collected from ptp4l
s.stats.SetCounter("ingress_time_ns", 0)
s.stats.SetCounter("master_offset_ns", 0)
s.stats.SetCounter("path_delay_ns", 0)
s.stats.SetCounter("freq_adj_ppb", 0)
s.stats.SetCounter("clock_accuracy_ns", 0)
// aggregated values
s.stats.SetCounter("master_offset_ns.60.abs_max", 0)
s.stats.SetCounter("path_delay_ns.60.abs_max", 0)
s.stats.SetCounter("freq_adj_ppb.60.abs_max", 0)
return s, nil
}
func (s *Daemon) calcW() (float64, error) {
lastN := s.state.takeDataPoint(s.cfg.RingSize)
params := prepareMathParameters(lastN)
logSample := &LogSample{
MasterOffsetNS: params["offset"][0],
MasterOffsetMeanNS: mean(params["offset"]),
MasterOffsetStddevNS: stddev(params["offset"]),
PathDelayNS: params["delay"][0],
PathDelayMeanNS: mean(params["delay"]),
PathDelayStddevNS: stddev(params["delay"]),
FreqAdjustmentPPB: params["freq"][0],
FreqAdjustmentMeanPPB: mean(params["freq"]),
FreqAdjustmentStddevPPB: stddev(params["freq"]),
ClockAccuracyMean: mean(params["clockaccuracie"]),
}
mRaw, err := s.cfg.Math.mExpr.Evaluate(mapOfInterface(params))
if err != nil {
return 0, err
}
m := mRaw.(float64)
logSample.MeasurementNS = m
s.stats.SetCounter("m_ns", int64(m))
// push m to ring buffer
s.state.pushM(m)
ms := s.state.takeM(s.cfg.RingSize)
if len(ms) != s.cfg.RingSize {
return 0, fmt.Errorf("%w getting W: want %d, got %d", errNotEnoughData, s.cfg.RingSize, len(ms))
}
parameters := map[string]interface{}{
"m": ms,
}
logSample.MeasurementMeanNS = mean(ms)
logSample.MeasurementStddevNS = stddev(ms)
wRaw, err := s.cfg.Math.wExpr.Evaluate(parameters)
if err != nil {
return 0, err
}
w := wRaw.(float64)
logSample.WindowNS = w
if err := s.l.Log(logSample); err != nil {
log.Errorf("failed to log sample: %v", err)
}
s.stats.SetCounter("w_ns", int64(w))
return w, nil
}
func (s *Daemon) calcDriftPPB() (float64, error) {
lastN := s.state.takeDataPoint(s.cfg.RingSize)
if len(lastN) != s.cfg.RingSize {
return 0, fmt.Errorf("%w calculating drift: want %d, got %d", errNotEnoughData, s.cfg.RingSize, len(lastN))
}
params := prepareMathParameters(lastN)
driftRaw, err := s.cfg.Math.driftExpr.Evaluate(mapOfInterface(params))
if err != nil {
return 0, err
}
drift := driftRaw.(float64)
return drift, nil
}
func (s *Daemon) calculateSHMData(data *DataPoint, leaps []leapsectz.LeapSecond) (*fbclock.Data, error) {
if err := data.SanityCheck(); err != nil {
s.stats.UpdateCounterBy("data_sanity_check_error", 1)
return nil, fmt.Errorf("sanity checking data point: %w", err)
}
s.stats.SetCounter("data_sanity_check_error", 0)
// store DataPoint in ring buffer
s.state.pushDataPoint(data)
// calculate W
w, err := s.calcW()
if err != nil {
return nil, fmt.Errorf("calculating W: %w", err)
}
wUint := uint64(w)
if wUint == 0 {
return nil, fmt.Errorf("value of W is 0")
}
// drift is in PPB, parts per billion.
// 1ns = 1/billions of second, so we can just say that
// hValue is measured in ns per second
hValue, err := s.calcDriftPPB()
if err != nil {
return nil, fmt.Errorf("calculating drift: %w", err)
}
s.stats.SetCounter("drift_ppb", int64(hValue))
clockSmearing := leapSecondSmearing(leaps)
return &fbclock.Data{
IngressTimeNS: data.IngressTimeNS,
ErrorBoundNS: wUint,
HoldoverMultiplierNS: hValue,
SmearingStartS: clockSmearing.smearingStartS,
SmearingEndS: clockSmearing.smearingEndS,
UTCOffsetPreS: clockSmearing.utcOffsetPreS,
UTCOffsetPostS: clockSmearing.utcOffsetPostS,
}, nil
}
func (s *Daemon) doWork(shm *fbclock.Shm, data *DataPoint) error {
// push stats
s.stats.SetCounter("master_offset_ns", int64(data.MasterOffsetNS))
s.stats.SetCounter("path_delay_ns", int64(data.PathDelayNS))
s.stats.SetCounter("ingress_time_ns", data.IngressTimeNS)
s.stats.SetCounter("freq_adj_ppb", int64(data.FreqAdjustmentPPB))
s.stats.SetCounter("clock_accuracy_ns", int64(data.ClockAccuracyNS))
// try and calculate how long ago was the ingress time
// use clock_gettime as the fastest and widely available method
if phcTime, err := s.getPHCTime(); err != nil {
log.Warningf("Failed to get PHC time from %s: %v", s.cfg.Iface, err)
} else {
if data.IngressTimeNS > 0 {
s.state.updateIngressTimeNS(data.IngressTimeNS)
}
it := s.state.ingressTimeNS()
if it > 0 {
timeSinceIngress := phcTime.UnixNano() - it
log.Debugf("Time since ingress: %dns", timeSinceIngress)
} else {
log.Warningf("No data for time since ingress")
}
}
// read tzdata for leap seconds
leaps, err := leapSeconds()
if err != nil {
log.Warningf("Failed to get leap seconds: %v", err)
}
// store everything in shared memory
d, err := s.calculateSHMData(data, leaps)
if err != nil {
if errors.Is(err, errNotEnoughData) {
log.Warning(err)
return nil
}
return err
}
if err := fbclock.StoreFBClockData(shm.File.Fd(), *d); err != nil {
return err
}
// aggregated stats over 1 minute
maxDp := s.state.aggregateDataPointsMax(minRingSize(s.cfg.RingSize, s.cfg.Interval))
s.stats.SetCounter("master_offset_ns.60.abs_max", int64(maxDp.MasterOffsetNS))
s.stats.SetCounter("path_delay_ns.60.abs_max", int64(maxDp.PathDelayNS))
s.stats.SetCounter("freq_adj_ppb.60.abs_max", int64(maxDp.FreqAdjustmentPPB))
return nil
}
func targetsDiff(oldTargets []string, targets []string) (added []string, removed []string) {
m := map[string]bool{}
for _, k := range oldTargets {
m[k] = true
}
for _, k := range targets {
if m[k] {
delete(m, k)
} else {
added = append(added, k)
}
}
for k := range m {
removed = append(removed, k)
}
return
}
func (s *Daemon) runLinearizabilityTests(ctx context.Context) {
testers := map[string]linearizability.Tester{}
oldTargets := []string{}
ctx, cancel := context.WithCancel(ctx)
defer cancel()
m := new(sync.Mutex)
ticker := time.NewTicker(s.cfg.LinearizabilityTestInterval)
defer ticker.Stop()
for ; true; <-ticker.C { // first run without delay, then at interval
eg := new(errgroup.Group)
currentResults := map[string]linearizability.TestResult{}
targets, err := s.DataFetcher.FetchGMs(s.cfg)
if err != nil {
log.Errorf("getting linearizability test targets: %v", err)
continue
}
log.Debugf("targets: %v, err: %v", targets, err)
// log when set of targets changes
added, removed := targetsDiff(oldTargets, targets)
if len(added) > 0 || len(removed) > 0 {
log.Infof("new set of linearizability test targets. Added: %v, Removed: %v. Resulting set: %v", added, removed, targets)
// we never remove testers, as stopping background listener goroutine is not easy
oldTargets = targets
}
for _, server := range targets {
server := server
log.Debugf("talking to %s", server)
lt, found := testers[server]
if !found {
if s.cfg.SPTP {
lt, err = linearizability.NewSPTPTester(server, fmt.Sprintf("http://%s/", s.cfg.PTPClientAddress), s.cfg.LinearizabilityTestMaxGMOffset)
} else {
lt, err = linearizability.NewPTP4lTester(server, s.cfg.Iface)
}
if err != nil {
log.Errorf("creating tester: %v", err)
continue
}
testers[server] = lt
}
eg.Go(func() error {
res := lt.RunTest(ctx)
m.Lock()
currentResults[server] = res
m.Unlock()
return nil
})
}
err = eg.Wait()
if err != nil && !errors.Is(err, context.Canceled) {
log.Error(err)
}
// get result, log it and push it into ring buffer
for _, res := range currentResults {
good, err := res.Good()
if err != nil {
log.Errorf(res.Explain())
continue
}
if !good {
log.Warningf(res.Explain())
}
log.Debugf("got linearizability result: %s", res.Explain())
s.state.pushLinearizabilityTestResult(res)
}
// add stats from linearizability checks
stats := linearizability.ProcessMonitoringResults("linearizability.", currentResults)
for k, v := range stats {
s.stats.SetCounter(k, int64(v))
}
}
}
// Run a daemon
func (s *Daemon) Run(ctx context.Context) error {
shm, err := fbclock.OpenFBClockSHM()
if err != nil {
return fmt.Errorf("opening fbclock shm: %w", err)
}
defer shm.Close()
if s.cfg.LinearizabilityTestInterval != 0 {
go s.runLinearizabilityTests(ctx)
}
ticker := time.NewTicker(s.cfg.Interval)
defer ticker.Stop()
for ; true; <-ticker.C { // first run without delay, then at interval
data, err := s.DataFetcher.FetchStats(s.cfg)
if err != nil {
log.Error(err)
s.stats.UpdateCounterBy("data_error", 1)
continue
}
s.stats.SetCounter("data_error", 0)
// get PHC freq adjustment
freqPPB, err := s.getPHCFreqPPB()
if err != nil {
log.Error(err)
s.stats.UpdateCounterBy("phc_error", 1)
continue
}
s.stats.SetCounter("phc_error", 0)
data.FreqAdjustmentPPB = freqPPB
if err := s.doWork(shm, data); err != nil {
log.Error(err)
s.stats.UpdateCounterBy("processing_error", 1)
continue
}
s.stats.SetCounter("processing_error", 0)
}
return nil
}