110 lines
4.5 KiB
Go
110 lines
4.5 KiB
Go
/*
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Copyright 2016 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package priorities
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import (
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"fmt"
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"strings"
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v1 "k8s.io/api/core/v1"
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framework "k8s.io/kubernetes/pkg/scheduler/framework/v1alpha1"
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schedulernodeinfo "k8s.io/kubernetes/pkg/scheduler/nodeinfo"
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"k8s.io/kubernetes/pkg/util/parsers"
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)
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// The two thresholds are used as bounds for the image score range. They correspond to a reasonable size range for
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// container images compressed and stored in registries; 90%ile of images on dockerhub drops into this range.
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const (
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mb int64 = 1024 * 1024
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minThreshold int64 = 23 * mb
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maxThreshold int64 = 1000 * mb
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)
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// ImageLocalityPriorityMap is a priority function that favors nodes that already have requested pod container's images.
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// It will detect whether the requested images are present on a node, and then calculate a score ranging from 0 to 10
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// based on the total size of those images.
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// - If none of the images are present, this node will be given the lowest priority.
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// - If some of the images are present on a node, the larger their sizes' sum, the higher the node's priority.
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func ImageLocalityPriorityMap(pod *v1.Pod, meta interface{}, nodeInfo *schedulernodeinfo.NodeInfo) (framework.NodeScore, error) {
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node := nodeInfo.Node()
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if node == nil {
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return framework.NodeScore{}, fmt.Errorf("node not found")
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}
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var score int
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if priorityMeta, ok := meta.(*priorityMetadata); ok {
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score = calculatePriority(sumImageScores(nodeInfo, pod.Spec.Containers, priorityMeta.totalNumNodes))
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} else {
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// if we are not able to parse priority meta data, skip this priority
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score = 0
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}
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return framework.NodeScore{
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Name: node.Name,
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Score: int64(score),
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}, nil
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}
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// calculatePriority returns the priority of a node. Given the sumScores of requested images on the node, the node's
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// priority is obtained by scaling the maximum priority value with a ratio proportional to the sumScores.
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func calculatePriority(sumScores int64) int {
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if sumScores < minThreshold {
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sumScores = minThreshold
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} else if sumScores > maxThreshold {
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sumScores = maxThreshold
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}
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return int(int64(framework.MaxNodeScore) * (sumScores - minThreshold) / (maxThreshold - minThreshold))
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}
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// sumImageScores returns the sum of image scores of all the containers that are already on the node.
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// Each image receives a raw score of its size, scaled by scaledImageScore. The raw scores are later used to calculate
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// the final score. Note that the init containers are not considered for it's rare for users to deploy huge init containers.
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func sumImageScores(nodeInfo *schedulernodeinfo.NodeInfo, containers []v1.Container, totalNumNodes int) int64 {
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var sum int64
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imageStates := nodeInfo.ImageStates()
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for _, container := range containers {
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if state, ok := imageStates[normalizedImageName(container.Image)]; ok {
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sum += scaledImageScore(state, totalNumNodes)
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}
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}
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return sum
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}
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// scaledImageScore returns an adaptively scaled score for the given state of an image.
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// The size of the image is used as the base score, scaled by a factor which considers how much nodes the image has "spread" to.
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// This heuristic aims to mitigate the undesirable "node heating problem", i.e., pods get assigned to the same or
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// a few nodes due to image locality.
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func scaledImageScore(imageState *schedulernodeinfo.ImageStateSummary, totalNumNodes int) int64 {
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spread := float64(imageState.NumNodes) / float64(totalNumNodes)
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return int64(float64(imageState.Size) * spread)
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}
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// normalizedImageName returns the CRI compliant name for a given image.
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// TODO: cover the corner cases of missed matches, e.g,
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// 1. Using Docker as runtime and docker.io/library/test:tag in pod spec, but only test:tag will present in node status
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// 2. Using the implicit registry, i.e., test:tag or library/test:tag in pod spec but only docker.io/library/test:tag
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// in node status; note that if users consistently use one registry format, this should not happen.
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func normalizedImageName(name string) string {
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if strings.LastIndex(name, ":") <= strings.LastIndex(name, "/") {
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name = name + ":" + parsers.DefaultImageTag
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}
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return name
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}
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