Merge pull request #40188 from jayunit100/NewSchedulerFromInterface

Automatic merge from submit-queue (batch tested with PRs 39538, 40188, 40357, 38214, 40195)

Decoupling scheduler creation from creation of scheduler.Config struc…

**What this PR does / why we need it**:

Adds functionality to the scheduler to initialize from an Configurator interface, rather then via a Config struct.

**Which issue this PR fixes** 

Reduces coupling to `scheduler.Config` data structure format so that we can proliferate more interface driven composition of scheduler components.

plugin/cmd/kube-scheduler/app/server.go

@@ -78,24 +78,20 @@ func Run(s *options.SchedulerServer) error {
 	if err != nil {
 		return fmt.Errorf("unable to create kube client: %v", err)
 	}
-	config, err := createConfig(s, kubecli)
+	recorder := createRecorder(kubecli, s)
+	sched, err := createScheduler(s, kubecli, recorder)
 	if err != nil {
-		return fmt.Errorf("failed to create scheduler configuration: %v", err)
+		return fmt.Errorf("error creating scheduler: %v", err)
 	}
-	sched := scheduler.New(config)
-
 	go startHTTP(s)
-
 	run := func(_ <-chan struct{}) {
 		sched.Run()
 		select {}
 	}
-
 	if !s.LeaderElection.LeaderElect {
 		run(nil)
 		panic("unreachable")
 	}
-
 	id, err := os.Hostname()
 	if err != nil {
 		return fmt.Errorf("unable to get hostname: %v", err)
@@ -109,7 +105,7 @@ func Run(s *options.SchedulerServer) error {
 		Client: kubecli,
 		LockConfig: resourcelock.ResourceLockConfig{
 			Identity:      id,
-			EventRecorder: config.Recorder,
+			EventRecorder: recorder,
 		},
 	}
 	leaderelection.RunOrDie(leaderelection.LeaderElectionConfig{
@@ -127,6 +123,13 @@ func Run(s *options.SchedulerServer) error {
 	panic("unreachable")
 }
 
+func createRecorder(kubecli *clientset.Clientset, s *options.SchedulerServer) record.EventRecorder {
+	eventBroadcaster := record.NewBroadcaster()
+	eventBroadcaster.StartLogging(glog.Infof)
+	eventBroadcaster.StartRecordingToSink(&v1core.EventSinkImpl{Interface: kubecli.Core().Events("")})
+	return eventBroadcaster.NewRecorder(v1.EventSource{Component: s.SchedulerName})
+}
+
 func startHTTP(s *options.SchedulerServer) {
 	mux := http.NewServeMux()
 	healthz.InstallHandler(mux)
@@ -171,33 +174,42 @@ func createClient(s *options.SchedulerServer) (*clientset.Clientset, error) {
 	return cli, nil
 }
 
-func createConfig(s *options.SchedulerServer, kubecli *clientset.Clientset) (*scheduler.Config, error) {
-	configFactory := factory.NewConfigFactory(kubecli, s.SchedulerName, s.HardPodAffinitySymmetricWeight, s.FailureDomains)
-	if _, err := os.Stat(s.PolicyConfigFile); err == nil {
-		var (
-			policy     schedulerapi.Policy
-			configData []byte
-		)
-		configData, err := ioutil.ReadFile(s.PolicyConfigFile)
+// schedulerConfigurator is an interface wrapper that provides default Configuration creation based on user
+// provided config file.
+type schedulerConfigurator struct {
+	scheduler.Configurator
+	policyFile        string
+	algorithmProvider string
+}
+
+func (sc schedulerConfigurator) Create() (*scheduler.Config, error) {
+	if _, err := os.Stat(sc.policyFile); err != nil {
+		return sc.Configurator.CreateFromProvider(sc.algorithmProvider)
+	}
+
+	// policy file is valid, try to create a configuration from it.
+	var policy schedulerapi.Policy
+	configData, err := ioutil.ReadFile(sc.policyFile)
 	if err != nil {
 		return nil, fmt.Errorf("unable to read policy config: %v", err)
 	}
 	if err := runtime.DecodeInto(latestschedulerapi.Codec, configData, &policy); err != nil {
 		return nil, fmt.Errorf("invalid configuration: %v", err)
 	}
-		return configFactory.CreateFromConfig(policy)
+	return sc.CreateFromConfig(policy)
 }
 
-	// if the config file isn't provided, use the specified (or default) provider
-	config, err := configFactory.CreateFromProvider(s.AlgorithmProvider)
-	if err != nil {
-		return nil, err
-	}
+// createScheduler encapsulates the entire creation of a runnable scheduler.
+func createScheduler(s *options.SchedulerServer, kubecli *clientset.Clientset, recorder record.EventRecorder) (*scheduler.Scheduler, error) {
+	configurator := factory.NewConfigFactory(kubecli, s.SchedulerName, s.HardPodAffinitySymmetricWeight, s.FailureDomains)
 
-	eventBroadcaster := record.NewBroadcaster()
-	config.Recorder = eventBroadcaster.NewRecorder(v1.EventSource{Component: s.SchedulerName})
-	eventBroadcaster.StartLogging(glog.Infof)
-	eventBroadcaster.StartRecordingToSink(&v1core.EventSinkImpl{Interface: kubecli.Core().Events("")})
+	// Rebuild the configurator with a default Create(...) method.
+	configurator = &schedulerConfigurator{
+		configurator,
+		s.PolicyConfigFile,
+		s.AlgorithmProvider}
 
-	return config, nil
+	return scheduler.NewFromConfigurator(configurator, func(cfg *scheduler.Config) {
+		cfg.Recorder = recorder
+	})
 }

plugin/pkg/scheduler/scheduler.go

@@ -51,6 +51,10 @@ type Scheduler struct {
 	config *Config
 }
 
+func (sched *Scheduler) StopEverything() {
+	close(sched.config.StopEverything)
+}
+
 // These are the functions which need to be provided in order to build a Scheduler configuration.
 // An implementation of this can be seen in factory.go.
 type Configurator interface {
@@ -78,6 +82,7 @@ type Configurator interface {
 	CreateFromKeys(predicateKeys, priorityKeys sets.String, extenders []algorithm.SchedulerExtender) (*Config, error)
 }
 
+// TODO over time we should make this struct a hidden implementation detail of the scheduler.
 type Config struct {
 	// It is expected that changes made via SchedulerCache will be observed
 	// by NodeLister and Algorithm.
@@ -108,6 +113,7 @@ type Config struct {
 }
 
 // New returns a new scheduler.
+// TODO replace this with NewFromConfigurator.
 func New(c *Config) *Scheduler {
 	s := &Scheduler{
 		config: c,
@@ -116,6 +122,25 @@ func New(c *Config) *Scheduler {
 	return s
 }
 
+// NewFromConfigurator returns a new scheduler that is created entirely by the Configurator.  Assumes Create() is implemented.
+// Supports intermediate Config mutation for now if you provide modifier functions which will run after Config is created.
+func NewFromConfigurator(c Configurator, modifiers ...func(c *Config)) (*Scheduler, error) {
+	cfg, err := c.Create()
+	if err != nil {
+		return nil, err
+	}
+	// Mutate it if any functions were provided, changes might be required for certain types of tests (i.e. change the recorder).
+	for _, modifier := range modifiers {
+		modifier(cfg)
+	}
+	// From this point on the config is immutable to the outside.
+	s := &Scheduler{
+		config: cfg,
+	}
+	metrics.Register()
+	return s, nil
+}
+
 // Run begins watching and scheduling. It starts a goroutine and returns immediately.
 func (s *Scheduler) Run() {
 	go wait.Until(s.scheduleOne, 0, s.config.StopEverything)

test/integration/scheduler_perf/util.go

@@ -40,7 +40,7 @@ import (
 // remove resources after finished.
 // Notes on rate limiter:
 //   - client rate limit is set to 5000.
-func mustSetupScheduler() (schedulerConfigFactory scheduler.Configurator, destroyFunc func()) {
+func mustSetupScheduler() (schedulerConfigurator scheduler.Configurator, destroyFunc func()) {
 
 	h := &framework.MasterHolder{Initialized: make(chan struct{})}
 	s := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
@@ -57,20 +57,23 @@ func mustSetupScheduler() (schedulerConfigFactory scheduler.Configurator, destro
 		Burst:         5000,
 	})
 
-	schedulerConfigFactory = factory.NewConfigFactory(clientSet, v1.DefaultSchedulerName, v1.DefaultHardPodAffinitySymmetricWeight, v1.DefaultFailureDomains)
+	schedulerConfigurator = factory.NewConfigFactory(clientSet, v1.DefaultSchedulerName, v1.DefaultHardPodAffinitySymmetricWeight, v1.DefaultFailureDomains)
 
-	schedulerConfig, err := schedulerConfigFactory.Create()
-	if err != nil {
-		panic("Couldn't create scheduler config")
-	}
 	eventBroadcaster := record.NewBroadcaster()
-	schedulerConfig.Recorder = eventBroadcaster.NewRecorder(v1.EventSource{Component: "scheduler"})
 	eventBroadcaster.StartRecordingToSink(&v1core.EventSinkImpl{Interface: clientSet.Core().Events("")})
-	scheduler.New(schedulerConfig).Run()
+
+	sched, err := scheduler.NewFromConfigurator(schedulerConfigurator, func(conf *scheduler.Config) {
+		conf.Recorder = eventBroadcaster.NewRecorder(v1.EventSource{Component: "scheduler"})
+	})
+	if err != nil {
+		glog.Fatalf("Error creating scheduler: %v", err)
+	}
+
+	sched.Run()
 
 	destroyFunc = func() {
 		glog.Infof("destroying")
-		close(schedulerConfig.StopEverything)
+		sched.StopEverything()
 		s.Close()
 		glog.Infof("destroyed")
 	}