feat(queue): handle errors in ScheduledJobs and Size methods

examples/queue/file_system.go

@@ -42,7 +42,13 @@ func main() {
 	}, jobQueue)
 	scheduler.Start(ctx)
 
-	if jobQueue.Size() == 0 {
+	jobQueueSize, err := jobQueue.Size()
+	if err != nil {
+		logger.Errorf("Failed to fetch job queue size: %s", err)
+		return
+	}
+
+	if jobQueueSize == 0 {
 		logger.Info("Scheduling new jobs")
 		jobDetail1 := quartz.NewJobDetail(&printJob{5}, quartz.NewJobKey("job1"))
 		if err := scheduler.ScheduleJob(jobDetail1, quartz.NewSimpleTrigger(5*time.Second)); err != nil {
@@ -58,7 +64,11 @@ func main() {
 
 	<-ctx.Done()
 
-	scheduledJobs := jobQueue.ScheduledJobs(nil)
+	scheduledJobs, err := jobQueue.ScheduledJobs(nil)
+	if err != nil {
+		logger.Errorf("Failed to fetch scheduled jobs: %s", err)
+		return
+	}
 	jobNames := make([]string, 0, len(scheduledJobs))
 	for _, job := range scheduledJobs {
 		jobNames = append(jobNames, job.JobDetail().JobKey().String())
@@ -289,14 +299,16 @@ func (jq *jobQueue) Remove(jobKey *quartz.JobKey) (quartz.ScheduledJob, error) {
 }
 
 // ScheduledJobs returns the slice of all scheduled jobs in the queue.
-func (jq *jobQueue) ScheduledJobs(matchers []quartz.Matcher[quartz.ScheduledJob]) []quartz.ScheduledJob {
+func (jq *jobQueue) ScheduledJobs(
+	matchers []quartz.Matcher[quartz.ScheduledJob],
+) ([]quartz.ScheduledJob, error) {
 	jq.mtx.Lock()
 	defer jq.mtx.Unlock()
 	logger.Trace("ScheduledJobs")
 	var jobs []quartz.ScheduledJob
 	fileInfo, err := os.ReadDir(dataFolder)
 	if err != nil {
-		return jobs
+		return nil, err
 	}
 	for _, file := range fileInfo {
 		if !file.IsDir() {
@@ -309,7 +321,7 @@ func (jq *jobQueue) ScheduledJobs(matchers []quartz.Matcher[quartz.ScheduledJob]
 			}
 		}
 	}
-	return jobs
+	return jobs, nil
 }
 
 func isMatch(job quartz.ScheduledJob, matchers []quartz.Matcher[quartz.ScheduledJob]) bool {
@@ -323,12 +335,15 @@ func isMatch(job quartz.ScheduledJob, matchers []quartz.Matcher[quartz.Scheduled
 }
 
 // Size returns the size of the job queue.
-func (jq *jobQueue) Size() int {
+func (jq *jobQueue) Size() (int, error) {
 	jq.mtx.Lock()
 	defer jq.mtx.Unlock()
 	logger.Trace("Size")
-	files, _ := os.ReadDir(dataFolder)
-	return len(files)
+	files, err := os.ReadDir(dataFolder)
+	if err != nil {
+		return 0, err
+	}
+	return len(files), nil
 }
 
 // Clear clears the job queue.

quartz/queue.go

@@ -46,9 +46,11 @@ type JobQueue interface {
 	Push(job ScheduledJob) error
 
 	// Pop removes and returns the next to run scheduled job from the queue.
+	// Implementations should return quartz.ErrQueueEmpty if the queue is empty.
 	Pop() (ScheduledJob, error)
 
 	// Head returns the first scheduled job without removing it from the queue.
+	// Implementations should return quartz.ErrQueueEmpty if the queue is empty.
 	Head() (ScheduledJob, error)
 
 	// Get returns the scheduled job with the specified key without removing it
@@ -75,10 +77,10 @@ type JobQueue interface {
 	//			// ... WHERE group_name = m.Pattern
 	//		}
 	//	}
-	ScheduledJobs([]Matcher[ScheduledJob]) []ScheduledJob
+	ScheduledJobs([]Matcher[ScheduledJob]) ([]ScheduledJob, error)
 
 	// Size returns the size of the job queue.
-	Size() int
+	Size() (int, error)
 
 	// Clear clears the job queue.
 	Clear() error
@@ -212,11 +214,11 @@ func (jq *jobQueue) Remove(jobKey *JobKey) (ScheduledJob, error) {
 // ScheduledJobs returns a slice of scheduled jobs in the queue.
 // For a job to be returned, it must satisfy all of the specified matchers.
 // Given an empty matchers it returns all scheduled jobs.
-func (jq *jobQueue) ScheduledJobs(matchers []Matcher[ScheduledJob]) []ScheduledJob {
+func (jq *jobQueue) ScheduledJobs(matchers []Matcher[ScheduledJob]) ([]ScheduledJob, error) {
 	jq.mtx.Lock()
 	defer jq.mtx.Unlock()
 	if len(matchers) == 0 {
-		return jq.scheduledJobs()
+		return jq.scheduledJobs(), nil
 	}
 	matchedJobs := make([]ScheduledJob, 0)
 JobLoop:
@@ -229,7 +231,7 @@ JobLoop:
 		}
 		matchedJobs = append(matchedJobs, job)
 	}
-	return matchedJobs
+	return matchedJobs, nil
 }
 
 // scheduledJobs returns all scheduled jobs.
@@ -242,10 +244,10 @@ func (jq *jobQueue) scheduledJobs() []ScheduledJob {
 }
 
 // Size returns the size of the job queue.
-func (jq *jobQueue) Size() int {
+func (jq *jobQueue) Size() (int, error) {
 	jq.mtx.Lock()
 	defer jq.mtx.Unlock()
-	return len(jq.delegate)
+	return len(jq.delegate), nil
 }
 
 // Clear clears the job queue.

quartz/scheduler.go

@@ -239,7 +239,7 @@ func (sched *StdScheduler) GetJobKeys(matchers ...Matcher[ScheduledJob]) []*JobK
 	sched.mtx.Lock()
 	defer sched.mtx.Unlock()
 
-	scheduledJobs := sched.queue.ScheduledJobs(matchers)
+	scheduledJobs, _ := sched.queue.ScheduledJobs(matchers)
 	keys := make([]*JobKey, 0, len(scheduledJobs))
 	for _, scheduled := range scheduledJobs {
 		keys = append(keys, scheduled.JobDetail().jobKey)
@@ -382,31 +382,33 @@ func (sched *StdScheduler) Stop() {
 
 func (sched *StdScheduler) startExecutionLoop(ctx context.Context) {
 	defer sched.wg.Done()
+	maxTimerDuration := time.Duration(1<<63 - 1)
+	timer := time.NewTimer(maxTimerDuration)
 	for {
-		if sched.queue.Size() == 0 {
-			select {
-			case <-sched.interrupt:
-				logger.Trace("Interrupted in empty queue.")
-			case <-ctx.Done():
-				logger.Info("Exit the empty execution loop.")
-				return
-			}
-		} else {
-			timer := time.NewTimer(sched.calculateNextTick())
-			select {
-			case <-timer.C:
-				logger.Trace("Tick.")
-				sched.executeAndReschedule(ctx)
+		queueSize, err := sched.queue.Size()
+		switch {
+		case err != nil:
+			logger.Errorf("Failed to fetch queue size: %s", err)
+			timer.Reset(sched.opts.RetryInterval)
+		case queueSize == 0:
+			logger.Trace("Queue is empty.")
+			timer.Reset(maxTimerDuration)
+		default:
+			timer.Reset(sched.calculateNextTick())
+		}
+		select {
+		case <-timer.C:
+			logger.Trace("Tick.")
+			sched.executeAndReschedule(ctx)
 
-			case <-sched.interrupt:
-				logger.Trace("Interrupted waiting for next tick.")
-				timer.Stop()
+		case <-sched.interrupt:
+			logger.Trace("Interrupted waiting for next tick.")
+			timer.Stop()
 
-			case <-ctx.Done():
-				logger.Info("Exit the execution loop.")
-				timer.Stop()
-				return
-			}
+		case <-ctx.Done():
+			logger.Info("Exit the execution loop.")
+			timer.Stop()
+			return
 		}
 	}
 }
@@ -439,7 +441,7 @@ func (sched *StdScheduler) calculateNextTick() time.Duration {
 			logger.Debug("Queue is empty")
 			return nextTickDuration
 		}
-		logger.Warnf("Failed to calculate next tick: %s", err)
+		logger.Errorf("Failed to calculate next tick: %s", err)
 		return sched.opts.RetryInterval
 	}
 	nextRunTime := scheduledJob.NextRunTime()