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Add an option to Cluster Autoscaler that allows triggering new loops
more frequently: based on new unschedulable pods and every time a previous iteration was productive.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,44 @@ | ||
| /* | ||
| Copyright 2024 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 loop | ||
|
|
||
| import ( | ||
| "time" | ||
|
|
||
| "k8s.io/autoscaler/cluster-autoscaler/metrics" | ||
| "k8s.io/autoscaler/cluster-autoscaler/utils/errors" | ||
| ) | ||
|
|
||
| type autoscaler interface { | ||
| // RunOnce represents an iteration in the control-loop of CA. | ||
| RunOnce(currentTime time.Time) errors.AutoscalerError | ||
| } | ||
|
|
||
| // RunAutoscalerOnce triggers a single autoscaling iteration. | ||
| func RunAutoscalerOnce(autoscaler autoscaler, healthCheck *metrics.HealthCheck, loopStart time.Time) { | ||
| metrics.UpdateLastTime(metrics.Main, loopStart) | ||
| healthCheck.UpdateLastActivity(loopStart) | ||
|
|
||
| err := autoscaler.RunOnce(loopStart) | ||
| if err != nil && err.Type() != errors.TransientError { | ||
| metrics.RegisterError(err) | ||
| } else { | ||
| healthCheck.UpdateLastSuccessfulRun(time.Now()) | ||
| } | ||
|
|
||
| metrics.UpdateDurationFromStart(metrics.Main, loopStart) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,144 @@ | ||
| /* | ||
| Copyright 2024 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 loop | ||
|
|
||
| import ( | ||
| "context" | ||
| "time" | ||
|
|
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| apiv1 "k8s.io/api/core/v1" | ||
| "k8s.io/apimachinery/pkg/fields" | ||
| "k8s.io/autoscaler/cluster-autoscaler/metrics" | ||
| kube_client "k8s.io/client-go/kubernetes" | ||
| "k8s.io/client-go/tools/cache" | ||
| "k8s.io/klog/v2" | ||
| podv1 "k8s.io/kubernetes/pkg/api/v1/pod" | ||
| ) | ||
|
|
||
| const maxPodChangeAge = 10 * time.Second | ||
|
|
||
| var ( | ||
| podsResource = "pods" | ||
| unschedulablePodSelector = fields.ParseSelectorOrDie("spec.nodeName==" + "" + ",status.phase!=" + | ||
| string(apiv1.PodSucceeded) + ",status.phase!=" + string(apiv1.PodFailed)) | ||
| ) | ||
|
|
||
| // scalingTimesGetter exposes recent autoscaler activity | ||
| type scalingTimesGetter interface { | ||
| LastScaleUpTime() time.Time | ||
| LastScaleDownDeleteTime() time.Time | ||
| } | ||
|
|
||
| // LoopTrigger object implements criteria used to start new autoscaling iteration | ||
| type LoopTrigger struct { | ||
| podObserver *UnschedulablePodObserver | ||
| scanInterval time.Duration | ||
| scalingTimesGetter scalingTimesGetter | ||
| } | ||
|
|
||
| // NewLoopTrigger creates a LoopTrigger object | ||
| func NewLoopTrigger(podObserver *UnschedulablePodObserver, scalingTimesGetter scalingTimesGetter, scanInterval time.Duration) *LoopTrigger { | ||
| return &LoopTrigger{ | ||
| podObserver: podObserver, | ||
| scanInterval: scanInterval, | ||
| scalingTimesGetter: scalingTimesGetter, | ||
| } | ||
| } | ||
|
|
||
| // Wait waits for the next autoscaling iteration | ||
| func (t *LoopTrigger) Wait(lastRun time.Time) { | ||
| sleepStart := time.Now() | ||
| defer metrics.UpdateDurationFromStart(metrics.LoopWait, sleepStart) | ||
|
|
||
| // To improve scale-up throughput, Cluster Autoscaler starts new iteration | ||
| // immediately if the previous one was productive. | ||
| if !t.scalingTimesGetter.LastScaleUpTime().Before(lastRun) || | ||
| !t.scalingTimesGetter.LastScaleDownDeleteTime().Before(lastRun) { | ||
| select { | ||
| case <-t.podObserver.unschedulablePodChan: | ||
| klog.Info("Autoscaler loop triggered by unschedulable pod appearing") | ||
| default: | ||
| klog.Infof("Autoscaler loop triggered immediately after a productive iteration") | ||
| } | ||
| return | ||
| } | ||
|
|
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| // Unschedulable pod triggers autoscaling immediately. | ||
| select { | ||
| case <-time.After(t.scanInterval): | ||
| klog.Infof("Autoscaler loop triggered by a %v timer", t.scanInterval) | ||
| case <-t.podObserver.unschedulablePodChan: | ||
| klog.Info("Autoscaler loop triggered by unschedulable pod appearing") | ||
| } | ||
| } | ||
|
|
||
| // UnschedulablePodObserver triggers a new loop if there are new unschedulable pods | ||
| type UnschedulablePodObserver struct { | ||
| unschedulablePodChan <-chan any | ||
| } | ||
|
|
||
| // StartPodObserver creates an informer and starts a goroutine watching for newly added | ||
| // or updated pods. Each time a new unschedulable pod appears or a change causes a pod to become | ||
| // unschedulable, a message is sent to the UnschedulablePodObserver's channel. | ||
| func StartPodObserver(ctx context.Context, kubeClient kube_client.Interface) *UnschedulablePodObserver { | ||
| podChan := make(chan any, 1) | ||
| listWatch := cache.NewListWatchFromClient(kubeClient.CoreV1().RESTClient(), podsResource, apiv1.NamespaceAll, unschedulablePodSelector) | ||
| informer := cache.NewSharedInformer(listWatch, &apiv1.Pod{}, time.Hour) | ||
| addEventHandlerFunc := func(obj any) { | ||
| if isRecentUnschedulablePod(obj) { | ||
| klog.V(5).Infof(" filterPodChanUntilClose emits signal") | ||
| select { | ||
| case podChan <- struct{}{}: | ||
| default: | ||
| } | ||
| } | ||
| } | ||
| updateEventHandlerFunc := func(old any, newOjb any) { addEventHandlerFunc(newOjb) } | ||
| _, _ = informer.AddEventHandler(cache.ResourceEventHandlerFuncs{ | ||
| AddFunc: addEventHandlerFunc, | ||
| UpdateFunc: updateEventHandlerFunc, | ||
| }) | ||
| go informer.Run(ctx.Done()) | ||
| return &UnschedulablePodObserver{ | ||
| unschedulablePodChan: podChan, | ||
| } | ||
| } | ||
|
|
||
| // isRecentUnschedulablePod checks if the object is an unschedulable pod observed recently. | ||
| func isRecentUnschedulablePod(obj any) bool { | ||
| pod, ok := obj.(*apiv1.Pod) | ||
| if !ok { | ||
| return false | ||
| } | ||
| if pod.Status.Phase == apiv1.PodSucceeded || pod.Status.Phase == apiv1.PodFailed { | ||
| return false | ||
| } | ||
| if pod.Spec.NodeName != "" { | ||
| return false | ||
| } | ||
| _, scheduledCondition := podv1.GetPodCondition(&pod.Status, apiv1.PodScheduled) | ||
| if scheduledCondition == nil { | ||
| return false | ||
| } | ||
| if scheduledCondition.Status != apiv1.ConditionFalse || scheduledCondition.Reason != "Unschedulable" { | ||
| return false | ||
| } | ||
| if scheduledCondition.LastTransitionTime.Time.Add(maxPodChangeAge).Before(time.Now()) { | ||
| return false | ||
| } | ||
| return true | ||
| } |
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