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本文次要钻研一下dkron的Scheduler
Scheduler
// Scheduler represents a dkron scheduler instance, it stores the cron engine// and the related parameters.type Scheduler struct { Cron *cron.Cron Started bool EntryJobMap sync.Map}// NewScheduler creates a new Scheduler instancefunc NewScheduler() *Scheduler { schedulerStarted.Set(0) return &Scheduler{ Cron: nil, Started: false, EntryJobMap: sync.Map{}, }}// Start the cron scheduler, adding its corresponding jobs and// executing them on time.func (s *Scheduler) Start(jobs []*Job, agent *Agent) error { s.Cron = cron.New(cron.WithParser(extcron.NewParser())) metrics.IncrCounter([]string{"scheduler", "start"}, 1) for _, job := range jobs { job.Agent = agent s.AddJob(job) } s.Cron.Start() s.Started = true schedulerStarted.Set(1) return nil}// Stop stops the scheduler effectively not running any job.func (s *Scheduler) Stop() { if s.Started { log.Debug("scheduler: Stopping scheduler") s.Cron.Stop() s.Started = false // Keep Cron exists and let the jobs which have been scheduled can continue to finish, // even the node's leadership will be revoked. // Ignore the running jobs and make s.Cron to nil may cause whole process crashed. //s.Cron = nil // expvars cronInspect.Do(func(kv expvar.KeyValue) { kv.Value = nil }) } schedulerStarted.Set(0)}// Restart the schedulerfunc (s *Scheduler) Restart(jobs []*Job, agent *Agent) { s.Stop() s.ClearCron() s.Start(jobs, agent)}// Clear cron separately, this can only be called when agent will be stop.func (s *Scheduler) ClearCron() { s.Cron = nil}Scheduler定义了Cron、Started、EntryJobMap属性；NewScheduler办法创立默认的Scheduler；Start办法遍历jobs，挨个设置job.Agent，而后增加到Scheduler中，之后执行Scheduler.Cron.Start()；Stop办法执行Scheduler.Cron.Stop()；Restart办法执行Stop、ClearCron、Start办法；ClearCron设置Cron为nil
AddJob
// AddJob Adds a job to the cron schedulerfunc (s *Scheduler) AddJob(job *Job) error { // Check if the job is already set and remove it if exists if _, ok := s.EntryJobMap.Load(job.Name); ok { s.RemoveJob(job) } if job.Disabled || job.ParentJob != "" { return nil } log.WithFields(logrus.Fields{ "job": job.Name, }).Debug("scheduler: Adding job to cron") // If Timezone is set on the job, and not explicitly in its schedule, // AND its not a descriptor (that don't support timezones), add the // timezone to the schedule so robfig/cron knows about it. schedule := job.Schedule if job.Timezone != "" && !strings.HasPrefix(schedule, "@") && !strings.HasPrefix(schedule, "TZ=") && !strings.HasPrefix(schedule, "CRON_TZ=") { schedule = "CRON_TZ=" + job.Timezone + " " + schedule } id, err := s.Cron.AddJob(schedule, job) if err != nil { return err } s.EntryJobMap.Store(job.Name, id) cronInspect.Set(job.Name, job) metrics.IncrCounterWithLabels([]string{"scheduler", "job_add"}, 1, []metrics.Label{{Name: "job", Value: job.Name}}) return nil}AddJob办法先移除EntryJobMap中的同名job，而后执行Cron.AddJob(schedule, job)，最初存储到EntryJobMap
RemoveJob
// RemoveJob removes a job from the cron schedulerfunc (s *Scheduler) RemoveJob(job *Job) { log.WithFields(logrus.Fields{ "job": job.Name, }).Debug("scheduler: Removing job from cron") if v, ok := s.EntryJobMap.Load(job.Name); ok { s.Cron.Remove(v.(cron.EntryID)) s.EntryJobMap.Delete(job.Name) cronInspect.Delete(job.Name) metrics.IncrCounterWithLabels([]string{"scheduler", "job_delete"}, 1, []metrics.Label{{Name: "job", Value: job.Name}}) }}RemoveJob办法先从EntryJobMap移除同名job，而后执行cronInspect.Delete(job.Name)
小结
dkron的Scheduler定义了Cron、Started、EntryJobMap属性；NewScheduler办法创立默认的Scheduler；它提供了Start、Stop、Restart、ClearCron、AddJob、RemoveJob办法。
doc
- dkron