feat(stacks): support automated sync for stacks [EE-248] (#5340)

api/scheduler/scheduler.go

@@ -0,0 +1,73 @@
+package scheduler
+
+import (
+	"context"
+	"log"
+	"strconv"
+	"time"
+
+	"github.com/pkg/errors"
+	"github.com/robfig/cron/v3"
+)
+
+type Scheduler struct {
+	crontab     *cron.Cron
+	shutdownCtx context.Context
+}
+
+func NewScheduler(ctx context.Context) *Scheduler {
+	crontab := cron.New(cron.WithChain(cron.Recover(cron.DefaultLogger)))
+	crontab.Start()
+
+	s := &Scheduler{
+		crontab: crontab,
+	}
+
+	if ctx != nil {
+		go func() {
+			<-ctx.Done()
+			s.Shutdown()
+		}()
+	}
+
+	return s
+}
+
+// Shutdown stops the scheduler and waits for it to stop if it is running; otherwise does nothing.
+func (s *Scheduler) Shutdown() error {
+	if s.crontab == nil {
+		return nil
+	}
+
+	log.Println("[DEBUG] Stopping scheduler")
+	ctx := s.crontab.Stop()
+	<-ctx.Done()
+
+	for _, j := range s.crontab.Entries() {
+		s.crontab.Remove(j.ID)
+	}
+
+	err := ctx.Err()
+	if err == context.Canceled {
+		return nil
+	}
+	return err
+}
+
+// StopJob stops the job from being run in the future
+func (s *Scheduler) StopJob(jobID string) error {
+	id, err := strconv.Atoi(jobID)
+	if err != nil {
+		return errors.Wrapf(err, "failed convert jobID %q to int", jobID)
+	}
+	s.crontab.Remove(cron.EntryID(id))
+
+	return nil
+}
+
+// StartJobEvery schedules a new periodic job with a given duration.
+// Returns job id that could be used to stop the given job
+func (s *Scheduler) StartJobEvery(duration time.Duration, job func()) string {
+	entryId := s.crontab.Schedule(cron.Every(duration), cron.FuncJob(job))
+	return strconv.Itoa(int(entryId))
+}