Disable Prometheus metrics by default (#331)

internal/controller/controller.go

@@ -61,6 +61,7 @@ type Controller struct {
 	maxWorkersPerLicense uint
 	experimentalRPCV2    bool
 	pingInterval         time.Duration
+	prometheusMetrics    bool
 
 	sshListenAddr   string
 	sshSigner       ssh.Signer
@@ -122,7 +123,7 @@ func New(opts ...Option) (*Controller, error) {
 
 	// Instantiate the scheduler
 	controller.scheduler, err = scheduler.NewScheduler(store, controller.workerNotifier,
-		controller.workerOfflineTimeout, controller.logger)
+		controller.workerOfflineTimeout, controller.prometheusMetrics, controller.logger)
 	if err != nil {
 		return nil, err
 	}

internal/controller/option.go

@@ -65,6 +65,12 @@ func WithPingInterval(pingInterval time.Duration) Option {
 	}
 }
 
+func WithPrometheusMetrics() Option {
+	return func(controller *Controller) {
+		controller.prometheusMetrics = true
+	}
+}
+
 func WithLogger(logger *zap.Logger) Option {
 	return func(controller *Controller) {
 		controller.logger = logger.Sugar()

internal/controller/scheduler/scheduler.go

@@ -49,6 +49,7 @@ type Scheduler struct {
 	workerOfflineTimeout time.Duration
 	logger               *zap.SugaredLogger
 	schedulingRequested  chan bool
+	prometheusMetrics    bool
 
 	schedulingTimeHistogram metric.Float64Histogram
 }
@@ -57,6 +58,7 @@ func NewScheduler(
 	store storepkg.Store,
 	notifier *notifier.Notifier,
 	workerOfflineTimeout time.Duration,
+	prometheusMetrics bool,
 	logger *zap.SugaredLogger,
 ) (*Scheduler, error) {
 	scheduler := &Scheduler{
@@ -65,6 +67,7 @@ func NewScheduler(
 		workerOfflineTimeout: workerOfflineTimeout,
 		logger:               logger,
 		schedulingRequested:  make(chan bool, 1),
+		prometheusMetrics:    prometheusMetrics,
 	}
 
 	// Metrics
@@ -104,7 +107,9 @@ func (scheduler *Scheduler) Run() {
 
 		if err != nil {
 			scheduler.logger.Errorf("Failed to schedule VMs: %v", err)
-		} else {
+		}
+
+		if scheduler.prometheusMetrics {
 			schedulerLoopIterationStat.Inc()
 		}
 	}
@@ -395,12 +400,14 @@ func (scheduler *Scheduler) healthCheckingLoopIteration() error {
 		}
 
 		// Update metrics
-		workers, err := txn.ListWorkers()
-		if err != nil {
-			return err
-		}
+		if scheduler.prometheusMetrics {
+			workers, err := txn.ListWorkers()
+			if err != nil {
+				return err
+			}
 
-		scheduler.reportStats(workers, vms)
+			scheduler.reportStats(workers, vms)
+		}
 
 		return nil
 	}); err != nil {