k3s/pkg/controller/podautoscaler/horizontal.go

/*
Copyright 2015 The Kubernetes Authors All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package podautoscaler

import (
	"fmt"
	"math"
	"time"

	"github.com/golang/glog"
	"k8s.io/kubernetes/pkg/api"
	"k8s.io/kubernetes/pkg/apis/experimental"
	client "k8s.io/kubernetes/pkg/client/unversioned"
	"k8s.io/kubernetes/pkg/controller/podautoscaler/metrics"
	"k8s.io/kubernetes/pkg/fields"
	"k8s.io/kubernetes/pkg/labels"
	"k8s.io/kubernetes/pkg/util"
)

const (
	heapsterNamespace = "kube-system"
	heapsterService   = "monitoring-heapster"

	// Usage shoud exceed the tolerance before we start downscale or upscale the pods.
	// TODO: make it a flag or HPA spec element.
	tolerance = 0.1
)

type HorizontalController struct {
	client        client.Interface
	metricsClient metrics.MetricsClient
}

var downscaleForbiddenWindow, _ = time.ParseDuration("20m")
var upscaleForbiddenWindow, _ = time.ParseDuration("3m")

func NewHorizontalController(client client.Interface, metricsClient metrics.MetricsClient) *HorizontalController {
	return &HorizontalController{
		client:        client,
		metricsClient: metricsClient,
	}
}

func (a *HorizontalController) Run(syncPeriod time.Duration) {
	go util.Until(func() {
		if err := a.reconcileAutoscalers(); err != nil {
			glog.Errorf("Couldn't reconcile horizontal pod autoscalers: %v", err)
		}
	}, syncPeriod, util.NeverStop)
}

func (a *HorizontalController) reconcileAutoscalers() error {
	ns := api.NamespaceAll
	list, err := a.client.Experimental().HorizontalPodAutoscalers(ns).List(labels.Everything(), fields.Everything())
	if err != nil {
		return fmt.Errorf("error listing nodes: %v", err)
	}
	for _, hpa := range list.Items {
		reference := fmt.Sprintf("%s/%s/%s", hpa.Spec.ScaleRef.Kind, hpa.Spec.ScaleRef.Namespace, hpa.Spec.ScaleRef.Name)

		scale, err := a.client.Experimental().Scales(hpa.Spec.ScaleRef.Namespace).Get(hpa.Spec.ScaleRef.Kind, hpa.Spec.ScaleRef.Name)
		if err != nil {
			glog.Warningf("Failed to query scale subresource for %s: %v", reference, err)
			continue
		}
		currentReplicas := scale.Status.Replicas
		currentConsumption, err := a.metricsClient.ResourceConsumption(hpa.Spec.ScaleRef.Namespace).Get(hpa.Spec.Target.Resource,
			scale.Status.Selector)

		// TODO: what to do on partial errors (like metrics obtained for 75% of pods).
		if err != nil {
			glog.Warningf("Error while getting metrics for %s: %v", reference, err)
			continue
		}

		usageRatio := float64(currentConsumption.Quantity.MilliValue()) / float64(hpa.Spec.Target.Quantity.MilliValue())
		desiredReplicas := int(math.Ceil(usageRatio * float64(currentReplicas)))

		if desiredReplicas < hpa.Spec.MinCount {
			desiredReplicas = hpa.Spec.MinCount
		}

		// TODO: remove when pod ideling is done.
		if desiredReplicas == 0 {
			desiredReplicas = 1
		}

		if desiredReplicas > hpa.Spec.MaxCount {
			desiredReplicas = hpa.Spec.MaxCount
		}
		now := time.Now()
		rescale := false

		if desiredReplicas != currentReplicas {
			// Going down only if the usageRatio dropped significantly below the target
			// and there was no rescaling in the last downscaleForbiddenWindow.
			if desiredReplicas < currentReplicas && usageRatio < (1-tolerance) &&
				(hpa.Status == nil || hpa.Status.LastScaleTimestamp == nil ||
					hpa.Status.LastScaleTimestamp.Add(downscaleForbiddenWindow).Before(now)) {
				rescale = true
			}

			// Going up only if the usage ratio increased significantly above the target
			// and there was no rescaling in the last upscaleForbiddenWindow.
			if desiredReplicas > currentReplicas && usageRatio > (1+tolerance) &&
				(hpa.Status == nil || hpa.Status.LastScaleTimestamp == nil ||
					hpa.Status.LastScaleTimestamp.Add(upscaleForbiddenWindow).Before(now)) {
				rescale = true
			}
		}

		if rescale {
			scale.Spec.Replicas = desiredReplicas
			_, err = a.client.Experimental().Scales(hpa.Namespace).Update(hpa.Spec.ScaleRef.Kind, scale)
			if err != nil {
				glog.Warningf("Failed to rescale %s: %v", reference, err)
				continue
			}
		} else {
			desiredReplicas = currentReplicas
		}

		status := experimental.HorizontalPodAutoscalerStatus{
			CurrentReplicas:    currentReplicas,
			DesiredReplicas:    desiredReplicas,
			CurrentConsumption: currentConsumption,
		}
		hpa.Status = &status
		if rescale {
			now := util.NewTime(now)
			hpa.Status.LastScaleTimestamp = &now
		}

		_, err = a.client.Experimental().HorizontalPodAutoscalers(hpa.Namespace).Update(&hpa)
		if err != nil {
			glog.Warningf("Failed to update HorizontalPodAutoscaler %s: %v", hpa.Name, err)
			continue
		}
	}
	return nil
}