156 lines
2.9 KiB
Go
156 lines
2.9 KiB
Go
// Package heart implements a general purpose pacemaker.
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package heart
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import (
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"sync"
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"sync/atomic"
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"time"
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"github.com/pkg/errors"
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)
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// Debug is the default logger that Pacemaker uses.
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var Debug = func(v ...interface{}) {}
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var ErrDead = errors.New("no heartbeat replied")
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// AtomicTime is a thread-safe UnixNano timestamp guarded by atomic.
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type AtomicTime struct {
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unixnano int64
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}
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func (t *AtomicTime) Get() int64 {
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return atomic.LoadInt64(&t.unixnano)
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}
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func (t *AtomicTime) Set(time time.Time) {
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atomic.StoreInt64(&t.unixnano, time.UnixNano())
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}
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func (t *AtomicTime) Time() time.Time {
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return time.Unix(0, t.Get())
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}
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type Pacemaker struct {
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// Heartrate is the received duration between heartbeats.
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Heartrate time.Duration
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// Time in nanoseconds, guarded by atomic read/writes.
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SentBeat AtomicTime
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EchoBeat AtomicTime
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// Any callback that returns an error will stop the pacer.
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Pace func() error
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stop chan struct{}
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death chan error
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}
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func NewPacemaker(heartrate time.Duration, pacer func() error) *Pacemaker {
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return &Pacemaker{
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Heartrate: heartrate,
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Pace: pacer,
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}
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}
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func (p *Pacemaker) Echo() {
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// Swap our received heartbeats
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// p.LastBeat[0], p.LastBeat[1] = time.Now(), p.LastBeat[0]
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p.EchoBeat.Set(time.Now())
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}
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// Dead, if true, will have Pace return an ErrDead.
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func (p *Pacemaker) Dead() bool {
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/* Deprecated
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if p.LastBeat[0].IsZero() || p.LastBeat[1].IsZero() {
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return false
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}
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return p.LastBeat[0].Sub(p.LastBeat[1]) > p.Heartrate*2
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*/
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var (
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echo = p.EchoBeat.Get()
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sent = p.SentBeat.Get()
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)
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if echo == 0 || sent == 0 {
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return false
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}
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return sent-echo > int64(p.Heartrate)*2
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}
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func (p *Pacemaker) Stop() {
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if p.stop != nil {
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p.stop <- struct{}{}
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Debug("(*Pacemaker).stop was sent a stop signal.")
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} else {
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Debug("(*Pacemaker).stop is nil, skipping.")
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}
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}
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func (p *Pacemaker) start() error {
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// Reset states to its old position.
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p.EchoBeat.Set(time.Time{})
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p.SentBeat.Set(time.Time{})
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// Create a new ticker.
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tick := time.NewTicker(p.Heartrate)
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defer tick.Stop()
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// Echo at least once
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p.Echo()
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for {
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Debug("Pacemaker loop restarted.")
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if err := p.Pace(); err != nil {
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return err
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}
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Debug("Paced.")
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// Paced, save:
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p.SentBeat.Set(time.Now())
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if p.Dead() {
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return ErrDead
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}
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select {
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case <-p.stop:
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Debug("Received stop signal.")
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return nil
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case <-tick.C:
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Debug("Ticked. Restarting.")
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}
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}
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}
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// StartAsync starts the pacemaker asynchronously. The WaitGroup is optional.
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func (p *Pacemaker) StartAsync(wg *sync.WaitGroup) (death chan error) {
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p.death = make(chan error)
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p.stop = make(chan struct{})
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if wg != nil {
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wg.Add(1)
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}
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go func() {
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p.death <- p.start()
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// Debug.
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Debug("Pacemaker returned.")
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// Mark the stop channel as nil, so later Close() calls won't block forever.
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p.stop = nil
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// Mark the pacemaker loop as done.
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if wg != nil {
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wg.Done()
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}
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}()
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return p.death
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}
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