mirror of
https://github.com/ceph/ceph-csi.git
synced 2024-11-15 02:40:23 +00:00
265 lines
11 KiB
Go
265 lines
11 KiB
Go
/*
|
|
Copyright 2017 The Kubernetes Authors.
|
|
|
|
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 preemption
|
|
|
|
import (
|
|
"fmt"
|
|
"math"
|
|
|
|
"k8s.io/api/core/v1"
|
|
"k8s.io/client-go/tools/record"
|
|
"k8s.io/klog"
|
|
"k8s.io/kubernetes/pkg/api/v1/resource"
|
|
v1qos "k8s.io/kubernetes/pkg/apis/core/v1/helper/qos"
|
|
"k8s.io/kubernetes/pkg/kubelet/events"
|
|
"k8s.io/kubernetes/pkg/kubelet/eviction"
|
|
"k8s.io/kubernetes/pkg/kubelet/lifecycle"
|
|
kubetypes "k8s.io/kubernetes/pkg/kubelet/types"
|
|
"k8s.io/kubernetes/pkg/kubelet/util/format"
|
|
"k8s.io/kubernetes/pkg/scheduler/algorithm"
|
|
"k8s.io/kubernetes/pkg/scheduler/algorithm/predicates"
|
|
)
|
|
|
|
const message = "Preempted in order to admit critical pod"
|
|
|
|
// CriticalPodAdmissionFailureHandler is an AdmissionFailureHandler that handles admission failure for Critical Pods.
|
|
// If the ONLY admission failures are due to insufficient resources, then CriticalPodAdmissionHandler evicts pods
|
|
// so that the critical pod can be admitted. For evictions, the CriticalPodAdmissionHandler evicts a set of pods that
|
|
// frees up the required resource requests. The set of pods is designed to minimize impact, and is prioritized according to the ordering:
|
|
// minimal impact for guaranteed pods > minimal impact for burstable pods > minimal impact for besteffort pods.
|
|
// minimal impact is defined as follows: fewest pods evicted > fewest total requests of pods.
|
|
// finding the fewest total requests of pods is considered besteffort.
|
|
type CriticalPodAdmissionHandler struct {
|
|
getPodsFunc eviction.ActivePodsFunc
|
|
killPodFunc eviction.KillPodFunc
|
|
recorder record.EventRecorder
|
|
}
|
|
|
|
var _ lifecycle.AdmissionFailureHandler = &CriticalPodAdmissionHandler{}
|
|
|
|
func NewCriticalPodAdmissionHandler(getPodsFunc eviction.ActivePodsFunc, killPodFunc eviction.KillPodFunc, recorder record.EventRecorder) *CriticalPodAdmissionHandler {
|
|
return &CriticalPodAdmissionHandler{
|
|
getPodsFunc: getPodsFunc,
|
|
killPodFunc: killPodFunc,
|
|
recorder: recorder,
|
|
}
|
|
}
|
|
|
|
// HandleAdmissionFailure gracefully handles admission rejection, and, in some cases,
|
|
// to allow admission of the pod despite its previous failure.
|
|
func (c *CriticalPodAdmissionHandler) HandleAdmissionFailure(admitPod *v1.Pod, failureReasons []algorithm.PredicateFailureReason) (bool, []algorithm.PredicateFailureReason, error) {
|
|
if !kubetypes.IsCriticalPod(admitPod) {
|
|
return false, failureReasons, nil
|
|
}
|
|
// InsufficientResourceError is not a reason to reject a critical pod.
|
|
// Instead of rejecting, we free up resources to admit it, if no other reasons for rejection exist.
|
|
nonResourceReasons := []algorithm.PredicateFailureReason{}
|
|
resourceReasons := []*admissionRequirement{}
|
|
for _, reason := range failureReasons {
|
|
if r, ok := reason.(*predicates.InsufficientResourceError); ok {
|
|
resourceReasons = append(resourceReasons, &admissionRequirement{
|
|
resourceName: r.ResourceName,
|
|
quantity: r.GetInsufficientAmount(),
|
|
})
|
|
} else {
|
|
nonResourceReasons = append(nonResourceReasons, reason)
|
|
}
|
|
}
|
|
if len(nonResourceReasons) > 0 {
|
|
// Return only reasons that are not resource related, since critical pods cannot fail admission for resource reasons.
|
|
return false, nonResourceReasons, nil
|
|
}
|
|
err := c.evictPodsToFreeRequests(admitPod, admissionRequirementList(resourceReasons))
|
|
// if no error is returned, preemption succeeded and the pod is safe to admit.
|
|
return err == nil, nil, err
|
|
}
|
|
|
|
// evictPodsToFreeRequests takes a list of insufficient resources, and attempts to free them by evicting pods
|
|
// based on requests. For example, if the only insufficient resource is 200Mb of memory, this function could
|
|
// evict a pod with request=250Mb.
|
|
func (c *CriticalPodAdmissionHandler) evictPodsToFreeRequests(admitPod *v1.Pod, insufficientResources admissionRequirementList) error {
|
|
podsToPreempt, err := getPodsToPreempt(admitPod, c.getPodsFunc(), insufficientResources)
|
|
if err != nil {
|
|
return fmt.Errorf("preemption: error finding a set of pods to preempt: %v", err)
|
|
}
|
|
klog.Infof("preemption: attempting to evict pods %v, in order to free up resources: %s", podsToPreempt, insufficientResources.toString())
|
|
for _, pod := range podsToPreempt {
|
|
status := v1.PodStatus{
|
|
Phase: v1.PodFailed,
|
|
Message: message,
|
|
Reason: events.PreemptContainer,
|
|
}
|
|
// record that we are evicting the pod
|
|
c.recorder.Eventf(pod, v1.EventTypeWarning, events.PreemptContainer, message)
|
|
// this is a blocking call and should only return when the pod and its containers are killed.
|
|
err := c.killPodFunc(pod, status, nil)
|
|
if err != nil {
|
|
return fmt.Errorf("preemption: pod %s failed to evict %v", format.Pod(pod), err)
|
|
}
|
|
klog.Infof("preemption: pod %s evicted successfully", format.Pod(pod))
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// getPodsToPreempt returns a list of pods that could be preempted to free requests >= requirements
|
|
func getPodsToPreempt(pod *v1.Pod, pods []*v1.Pod, requirements admissionRequirementList) ([]*v1.Pod, error) {
|
|
bestEffortPods, burstablePods, guaranteedPods := sortPodsByQOS(pod, pods)
|
|
|
|
// make sure that pods exist to reclaim the requirements
|
|
unableToMeetRequirements := requirements.subtract(append(append(bestEffortPods, burstablePods...), guaranteedPods...)...)
|
|
if len(unableToMeetRequirements) > 0 {
|
|
return nil, fmt.Errorf("no set of running pods found to reclaim resources: %v", unableToMeetRequirements.toString())
|
|
}
|
|
// find the guaranteed pods we would need to evict if we already evicted ALL burstable and besteffort pods.
|
|
guarateedToEvict, err := getPodsToPreemptByDistance(guaranteedPods, requirements.subtract(append(bestEffortPods, burstablePods...)...))
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
// Find the burstable pods we would need to evict if we already evicted ALL besteffort pods, and the required guaranteed pods.
|
|
burstableToEvict, err := getPodsToPreemptByDistance(burstablePods, requirements.subtract(append(bestEffortPods, guarateedToEvict...)...))
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
// Find the besteffort pods we would need to evict if we already evicted the required guaranteed and burstable pods.
|
|
bestEffortToEvict, err := getPodsToPreemptByDistance(bestEffortPods, requirements.subtract(append(burstableToEvict, guarateedToEvict...)...))
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
return append(append(bestEffortToEvict, burstableToEvict...), guarateedToEvict...), nil
|
|
}
|
|
|
|
// getPodsToPreemptByDistance finds the pods that have pod requests >= admission requirements.
|
|
// Chooses pods that minimize "distance" to the requirements.
|
|
// If more than one pod exists that fulfills the remaining requirements,
|
|
// it chooses the pod that has the "smaller resource request"
|
|
// This method, by repeatedly choosing the pod that fulfills as much of the requirements as possible,
|
|
// attempts to minimize the number of pods returned.
|
|
func getPodsToPreemptByDistance(pods []*v1.Pod, requirements admissionRequirementList) ([]*v1.Pod, error) {
|
|
podsToEvict := []*v1.Pod{}
|
|
// evict pods by shortest distance from remaining requirements, updating requirements every round.
|
|
for len(requirements) > 0 {
|
|
if len(pods) == 0 {
|
|
return nil, fmt.Errorf("no set of running pods found to reclaim resources: %v", requirements.toString())
|
|
}
|
|
// all distances must be less than len(requirements), because the max distance for a single requirement is 1
|
|
bestDistance := float64(len(requirements) + 1)
|
|
bestPodIndex := 0
|
|
// Find the pod with the smallest distance from requirements
|
|
// Or, in the case of two equidistant pods, find the pod with "smaller" resource requests.
|
|
for i, pod := range pods {
|
|
dist := requirements.distance(pod)
|
|
if dist < bestDistance || (bestDistance == dist && smallerResourceRequest(pod, pods[bestPodIndex])) {
|
|
bestDistance = dist
|
|
bestPodIndex = i
|
|
}
|
|
}
|
|
// subtract the pod from requirements, and transfer the pod from input-pods to pods-to-evicted
|
|
requirements = requirements.subtract(pods[bestPodIndex])
|
|
podsToEvict = append(podsToEvict, pods[bestPodIndex])
|
|
pods[bestPodIndex] = pods[len(pods)-1]
|
|
pods = pods[:len(pods)-1]
|
|
}
|
|
return podsToEvict, nil
|
|
}
|
|
|
|
type admissionRequirement struct {
|
|
resourceName v1.ResourceName
|
|
quantity int64
|
|
}
|
|
|
|
type admissionRequirementList []*admissionRequirement
|
|
|
|
// distance returns distance of the pods requests from the admissionRequirements.
|
|
// The distance is measured by the fraction of the requirement satisfied by the pod,
|
|
// so that each requirement is weighted equally, regardless of absolute magnitude.
|
|
func (a admissionRequirementList) distance(pod *v1.Pod) float64 {
|
|
dist := float64(0)
|
|
for _, req := range a {
|
|
remainingRequest := float64(req.quantity - resource.GetResourceRequest(pod, req.resourceName))
|
|
if remainingRequest < 0 {
|
|
remainingRequest = 0
|
|
}
|
|
dist += math.Pow(remainingRequest/float64(req.quantity), 2)
|
|
}
|
|
return dist
|
|
}
|
|
|
|
// subtract returns a new admissionRequirementList containing remaining requirements if the provided pod
|
|
// were to be preempted
|
|
func (a admissionRequirementList) subtract(pods ...*v1.Pod) admissionRequirementList {
|
|
newList := []*admissionRequirement{}
|
|
for _, req := range a {
|
|
newQuantity := req.quantity
|
|
for _, pod := range pods {
|
|
newQuantity -= resource.GetResourceRequest(pod, req.resourceName)
|
|
}
|
|
if newQuantity > 0 {
|
|
newList = append(newList, &admissionRequirement{
|
|
resourceName: req.resourceName,
|
|
quantity: newQuantity,
|
|
})
|
|
}
|
|
}
|
|
return newList
|
|
}
|
|
|
|
func (a admissionRequirementList) toString() string {
|
|
s := "["
|
|
for _, req := range a {
|
|
s += fmt.Sprintf("(res: %v, q: %d), ", req.resourceName, req.quantity)
|
|
}
|
|
return s + "]"
|
|
}
|
|
|
|
// sortPodsByQOS returns lists containing besteffort, burstable, and guaranteed pods that
|
|
// can be preempted by preemptor pod.
|
|
func sortPodsByQOS(preemptor *v1.Pod, pods []*v1.Pod) (bestEffort, burstable, guaranteed []*v1.Pod) {
|
|
for _, pod := range pods {
|
|
if kubetypes.Preemptable(preemptor, pod) {
|
|
switch v1qos.GetPodQOS(pod) {
|
|
case v1.PodQOSBestEffort:
|
|
bestEffort = append(bestEffort, pod)
|
|
case v1.PodQOSBurstable:
|
|
burstable = append(burstable, pod)
|
|
case v1.PodQOSGuaranteed:
|
|
guaranteed = append(guaranteed, pod)
|
|
default:
|
|
}
|
|
}
|
|
}
|
|
|
|
return
|
|
}
|
|
|
|
// smallerResourceRequest returns true if pod1 has a smaller request than pod2
|
|
func smallerResourceRequest(pod1 *v1.Pod, pod2 *v1.Pod) bool {
|
|
priorityList := []v1.ResourceName{
|
|
v1.ResourceMemory,
|
|
v1.ResourceCPU,
|
|
}
|
|
for _, res := range priorityList {
|
|
req1 := resource.GetResourceRequest(pod1, res)
|
|
req2 := resource.GetResourceRequest(pod2, res)
|
|
if req1 < req2 {
|
|
return true
|
|
} else if req1 > req2 {
|
|
return false
|
|
}
|
|
}
|
|
return true
|
|
}
|