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clock.go
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clock.go
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package timesync
import (
"sync"
"time"
"github.com/jonboulle/clockwork"
"github.com/prometheus/client_golang/prometheus"
"go.uber.org/zap"
"golang.org/x/sync/errgroup"
"github.com/spacemeshos/go-spacemesh/common/types"
"github.com/spacemeshos/go-spacemesh/metrics"
)
var tickDistance = metrics.NewHistogramWithBuckets(
"tick_distance",
"clock",
"distance between layer ticks",
[]string{},
prometheus.ExponentialBuckets(1, 2, 10),
).WithLabelValues()
// NodeClock is the struct holding a real clock.
type NodeClock struct {
LayerConverter // layer conversions provider
clock clockwork.Clock // provides the time
genesis time.Time
tickInterval time.Duration
mu sync.Mutex // protects the following fields
lastTicked types.LayerID // track last ticked layer
minLayer types.LayerID // track earliest layer that has a channel waiting for tick
layerChannels map[types.LayerID]chan struct{}
stop chan struct{}
once sync.Once
log *zap.Logger
eg errgroup.Group
}
// NewClock return TimeClock struct that notifies tickInterval has passed.
func NewClock(opts ...OptionFunc) (*NodeClock, error) {
cfg := &option{
clock: clockwork.NewRealClock(),
}
for _, opt := range opts {
opt(cfg)
}
if err := cfg.validate(); err != nil {
return nil, err
}
gtime := cfg.genesisTime.Local()
cfg.log.Info("converting genesis time to local time",
zap.Time("genesis", cfg.genesisTime),
zap.Time("local", gtime),
)
t := &NodeClock{
LayerConverter: LayerConverter{duration: cfg.layerDuration, genesis: gtime},
clock: cfg.clock,
tickInterval: cfg.tickInterval,
layerChannels: make(map[types.LayerID]chan struct{}),
genesis: gtime,
stop: make(chan struct{}),
log: cfg.log,
}
t.eg.Go(t.startClock)
return t, nil
}
func (t *NodeClock) startClock() error {
t.log.Info("starting global clock",
zap.Time("now", t.clock.Now()),
zap.Time("genesis", t.genesis),
zap.Duration("layer_duration", t.duration),
zap.Duration("tick_interval", t.tickInterval),
)
ticker := t.clock.NewTicker(t.tickInterval)
for {
currLayer := t.TimeToLayer(t.clock.Now())
t.log.Debug("global clock going to sleep before next tick",
zap.Stringer("curr_layer", currLayer),
)
select {
case <-ticker.Chan():
case <-t.stop:
t.log.Info("stopping global clock")
ticker.Stop()
return nil
}
t.tick()
}
}
// GenesisTime returns at which time this clock has started (used to calculate current tick).
func (t *NodeClock) GenesisTime() time.Time {
return t.genesis
}
// Close closes the clock ticker.
func (t *NodeClock) Close() {
t.once.Do(func() {
t.log.Info("stopping clock")
close(t.stop)
if err := t.eg.Wait(); err != nil {
t.log.Error("failed to stop clock", zap.Error(err))
}
t.log.Info("clock stopped")
})
}
// tick processes the current tick. It iterates over all layers that have passed since the last tick and notifies
// listeners that are awaiting these layers.
func (t *NodeClock) tick() {
t.mu.Lock()
defer t.mu.Unlock()
if t.clock.Now().Before(t.genesis) {
return
}
layer := t.TimeToLayer(t.clock.Now())
switch {
case layer.Before(t.lastTicked):
t.log.Info("clock ticked back in time",
zap.Stringer("layer", layer),
zap.Stringer("last_ticked_layer", t.lastTicked),
)
d := t.lastTicked.Difference(layer)
tickDistance.Observe(float64(-d))
// don't warn right after fresh startup
case layer.Difference(t.lastTicked) > 1 && t.lastTicked > 0:
t.log.Warn("clock skipped layers",
zap.Stringer("layer", layer),
zap.Stringer("last_ticked_layer", t.lastTicked),
)
d := layer.Difference(t.lastTicked)
tickDistance.Observe(float64(d))
case layer == t.lastTicked:
tickDistance.Observe(0)
}
// close await channel for prev layers
for l := t.minLayer; !l.After(layer); l = l.Add(1) {
if layerChan, found := t.layerChannels[l]; found {
close(layerChan)
delete(t.layerChannels, l)
}
}
t.lastTicked = layer
t.minLayer = layer.Add(1)
}
// CurrentLayer gets the current layer.
func (t *NodeClock) CurrentLayer() types.LayerID {
return t.TimeToLayer(t.clock.Now())
}
// AwaitLayer returns a channel that will be signaled when layer id layerID was ticked by the clock,
// or if this layer has passed while sleeping. it does so by closing the returned channel.
func (t *NodeClock) AwaitLayer(layerID types.LayerID) <-chan struct{} {
t.mu.Lock()
defer t.mu.Unlock()
layerTime := t.LayerToTime(layerID)
now := t.clock.Now()
if now.After(layerTime) || now.Equal(layerTime) { // passed the time of layerID
ch := make(chan struct{})
close(ch)
return ch
}
ch := t.layerChannels[layerID]
if ch == nil {
ch = make(chan struct{})
t.layerChannels[layerID] = ch
}
if t.minLayer.After(layerID) {
t.minLayer = layerID
}
return ch
}