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scheduler.go
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scheduler.go
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package dkron
import (
"context"
"errors"
"expvar"
"strings"
"sync"
"github.com/armon/go-metrics"
"github.com/distribworks/dkron/v3/extcron"
"github.com/robfig/cron/v3"
"github.com/sirupsen/logrus"
)
var (
cronInspect = expvar.NewMap("cron_entries")
schedulerStarted = expvar.NewInt("scheduler_started")
// ErrScheduleParse is the error returned when the schedule parsing fails.
ErrScheduleParse = errors.New("can't parse job schedule")
)
type EntryJob struct {
entry *cron.Entry
job *Job
}
// Scheduler represents a dkron scheduler instance, it stores the cron engine
// and the related parameters.
type Scheduler struct {
// mu is to prevent concurrent edits to Cron and Started
mu sync.RWMutex
Cron *cron.Cron
started bool
logger *logrus.Entry
}
// NewScheduler creates a new Scheduler instance
func NewScheduler(logger *logrus.Entry) *Scheduler {
schedulerStarted.Set(0)
return &Scheduler{
Cron: cron.New(cron.WithParser(extcron.NewParser())),
started: false,
logger: logger,
}
}
// Start the cron scheduler, adding its corresponding jobs and
// executing them on time.
func (s *Scheduler) Start(jobs []*Job, agent *Agent) error {
s.mu.Lock()
defer s.mu.Unlock()
if s.started {
return errors.New("scheduler: cron already started, should be stopped first")
}
s.ClearCron()
metrics.IncrCounter([]string{"scheduler", "start"}, 1)
for _, job := range jobs {
job.Agent = agent
if err := s.AddJob(job); err != nil {
return err
}
}
s.Cron.Start()
s.started = true
schedulerStarted.Set(1)
return nil
}
// Stop stops the cron scheduler if it is running; otherwise it does nothing.
// A context is returned so the caller can wait for running jobs to complete.
func (s *Scheduler) Stop() context.Context {
s.mu.Lock()
defer s.mu.Unlock()
ctx := s.Cron.Stop()
if s.started {
s.logger.Debug("scheduler: Stopping scheduler")
s.started = false
// expvars
cronInspect.Do(func(kv expvar.KeyValue) {
kv.Value = nil
})
}
schedulerStarted.Set(0)
return ctx
}
// Restart the scheduler
func (s *Scheduler) Restart(jobs []*Job, agent *Agent) {
// Stop the scheduler, running jobs will continue to finish but we
// can not actively wait for them blocking the execution here.
s.Stop()
if err := s.Start(jobs, agent); err != nil {
s.logger.Fatal(err)
}
}
// ClearCron clears the cron scheduler
func (s *Scheduler) ClearCron() {
for _, e := range s.Cron.Entries() {
if j, ok := e.Job.(*Job); !ok {
s.logger.Errorf("scheduler: Failed to cast job to *Job found type %T and removing it", e.Job)
s.Cron.Remove(e.ID)
} else {
s.RemoveJob(j.Name)
}
}
}
// Started will safely return if the scheduler is started or not
func (s *Scheduler) Started() bool {
s.mu.RLock()
defer s.mu.RUnlock()
return s.started
}
// GetEntryJob returns a EntryJob object from a snapshot in
// the current time, and whether or not the entry was found.
func (s *Scheduler) GetEntryJob(jobName string) (EntryJob, bool) {
for _, e := range s.Cron.Entries() {
if j, ok := e.Job.(*Job); !ok {
s.logger.Errorf("scheduler: Failed to cast job to *Job found type %T", e.Job)
} else {
j.logger = s.logger
if j.Name == jobName {
return EntryJob{
entry: &e,
job: j,
}, true
}
}
}
return EntryJob{}, false
}
// AddJob Adds a job to the cron scheduler
func (s *Scheduler) AddJob(job *Job) error {
// Check if the job is already set and remove it if exists
if _, ok := s.GetEntryJob(job.Name); ok {
s.RemoveJob(job.Name)
}
if job.Disabled || job.ParentJob != "" {
return nil
}
s.logger.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
}
_, err := s.Cron.AddJob(schedule, job)
if err != nil {
return err
}
cronInspect.Set(job.Name, job)
metrics.IncrCounterWithLabels([]string{"scheduler", "job_add"}, 1, []metrics.Label{{Name: "job", Value: job.Name}})
return nil
}
// RemoveJob removes a job from the cron scheduler if it exists.
func (s *Scheduler) RemoveJob(jobName string) {
s.logger.WithFields(logrus.Fields{
"job": jobName,
}).Debug("scheduler: Removing job from cron")
if ej, ok := s.GetEntryJob(jobName); ok {
s.Cron.Remove(ej.entry.ID)
cronInspect.Delete(jobName)
metrics.IncrCounterWithLabels([]string{"scheduler", "job_delete"}, 1, []metrics.Label{{Name: "job", Value: jobName}})
}
}