feat(scheduler): use an worker pool for scheduler (#1146)

Signed-off-by: Petu Eusebiu <peusebiu@cisco.com>

pkg/extensions/sync/sync.go

@@ -384,6 +384,7 @@ func syncRegistry(ctx context.Context, regCfg RegistryConfig,
 
 					return err
 				}
+
 				// push from cache to repo
 				err = pushSyncedLocalImage(localRepo, tag, localCachePath, imageStore, log)
 				if err != nil {

pkg/extensions/sync/sync_test.go

@@ -1047,7 +1047,7 @@ func TestMandatoryAnnotations(t *testing.T) {
 		defer dcm.StopServer()
 
 		// give it time to set up sync
-		time.Sleep(5 * time.Second)
+		time.Sleep(10 * time.Second)
 
 		resp, err := destClient.R().Get(destBaseURL + "/v2/" + testImage + "/manifests/0.0.1")
 		So(err, ShouldBeNil)

pkg/scheduler/scheduler.go

@@ -85,26 +85,55 @@ func NewScheduler(logC log.Logger) *Scheduler {
 	}
 }
 
-const rateLimit = 5 * time.Second
+const (
+	rateLimit  = 5 * time.Second
+	numWorkers = 3
+)
+
+func (scheduler *Scheduler) poolWorker(numWorkers int, tasks chan Task) {
+	for i := 0; i < numWorkers; i++ {
+		go func(workerID int) {
+			for task := range tasks {
+				scheduler.log.Debug().Int("worker", workerID).Msg("scheduler: starting task")
+
+				if err := task.DoWork(); err != nil {
+					scheduler.log.Error().Int("worker", workerID).Err(err).Msg("scheduler: error while executing task")
+				}
+
+				scheduler.log.Debug().Int("worker", workerID).Msg("scheduler: finished task")
+			}
+		}(i + 1)
+	}
+}
 
 func (scheduler *Scheduler) RunScheduler(ctx context.Context) {
 	throttle := time.NewTicker(rateLimit).C
+	tasksWorker := make(chan Task, numWorkers)
+
+	// start worker pool
+	go scheduler.poolWorker(numWorkers, tasksWorker)
 
 	go func() {
 		for {
 			select {
 			case <-ctx.Done():
+				close(tasksWorker)
 				close(scheduler.stopCh)
 
 				return
 			default:
+				i := 0
+				for i < numWorkers {
 					task := scheduler.getTask()
 					if task != nil {
-					if err := task.DoWork(); err != nil {
-						scheduler.log.Error().Err(err).Msg("error while executing task")
-					}
+						// push tasks into worker pool
+						scheduler.log.Debug().Msg("scheduler: pushing task into worker pool")
+						tasksWorker <- task
+					}
+					i++
 				}
 			}
+
 			<-throttle
 		}
 	}()
@@ -122,7 +151,7 @@ func (scheduler *Scheduler) pushReadyGenerators() {
 				scheduler.waitingGenerators = append(scheduler.waitingGenerators[:i], scheduler.waitingGenerators[i+1:]...)
 				modified = true
 
-				scheduler.log.Debug().Msg("waiting generator is ready, pushing to ready generators")
+				scheduler.log.Debug().Msg("scheduler: waiting generator is ready, pushing to ready generators")
 
 				break
 			}
@@ -221,7 +250,7 @@ func (scheduler *Scheduler) SubmitTask(task Task, priority Priority) {
 	case <-scheduler.stopCh:
 		return
 	case tasksQ <- task:
-		scheduler.log.Info().Msg("Adding a new task to the scheduler")
+		scheduler.log.Info().Msg("scheduler: adding a new task")
 	}
 }
 
@@ -267,7 +296,7 @@ func (gen *generator) generate(sch *Scheduler) {
 	if gen.remainingTask == nil {
 		nextTask, err := gen.taskGenerator.GenerateTask()
 		if err != nil {
-			sch.log.Error().Err(err).Msg("error while executing generator")
+			sch.log.Error().Err(err).Msg("scheduler: error while executing generator")
 
 			return
 		}

pkg/scheduler/scheduler_test.go

@@ -119,19 +119,24 @@ func TestScheduler(t *testing.T) {
 		genL := &generator{log: logger, priority: "low priority"}
 		sch.SubmitGenerator(genL, time.Duration(0), scheduler.LowPriority)
 
+		genM := &generator{log: logger, priority: "medium priority"}
+		sch.SubmitGenerator(genM, time.Duration(0), scheduler.MediumPriority)
+
 		genH := &generator{log: logger, priority: "high priority"}
 		sch.SubmitGenerator(genH, time.Duration(0), scheduler.HighPriority)
 
 		ctx, cancel := context.WithCancel(context.Background())
 		sch.RunScheduler(ctx)
 
-		time.Sleep(500 * time.Millisecond)
+		time.Sleep(4 * time.Second)
 		cancel()
 
 		data, err := os.ReadFile(logFile.Name())
 		So(err, ShouldBeNil)
+
 		So(string(data), ShouldContainSubstring, "executing high priority task; index: 1")
-		So(string(data), ShouldNotContainSubstring, "executing low priority task; index: 1")
+		So(string(data), ShouldContainSubstring, "executing high priority task; index: 2")
+		So(string(data), ShouldNotContainSubstring, "executing medium priority task; index: 1")
 		So(string(data), ShouldNotContainSubstring, "error while executing task")
 	})
 
@@ -155,7 +160,7 @@ func TestScheduler(t *testing.T) {
 
 		data, err := os.ReadFile(logFile.Name())
 		So(err, ShouldBeNil)
-		So(string(data), ShouldContainSubstring, "Adding a new task to the scheduler")
+		So(string(data), ShouldContainSubstring, "scheduler: adding a new task")
 		So(string(data), ShouldContainSubstring, "error while executing task")
 	})
 
@@ -197,7 +202,7 @@ func TestScheduler(t *testing.T) {
 
 		data, err := os.ReadFile(logFile.Name())
 		So(err, ShouldBeNil)
-		So(string(data), ShouldNotContainSubstring, "Adding a new task to the scheduler")
+		So(string(data), ShouldNotContainSubstring, "scheduler: adding a new task")
 	})
 
 	Convey("Test adding a new task when context is done", t, func() {
@@ -220,6 +225,6 @@ func TestScheduler(t *testing.T) {
 
 		data, err := os.ReadFile(logFile.Name())
 		So(err, ShouldBeNil)
-		So(string(data), ShouldNotContainSubstring, "Adding a new task to the scheduler")
+		So(string(data), ShouldNotContainSubstring, "scheduler: adding a new task")
 	})
 }