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Add EmptyDir volume and container overlay capacity isolation #45686

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merged 1 commit into from
Jun 6, 2017

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@jingxu97 jingxu97 commented May 11, 2017

This PR adds the support for isolating the emptyDir volume use. If user
sets a size limit for emptyDir volume, kubelet's eviction manager monitors its usage
and evict the pod if the usage exceeds the limit.

This feature is part of local storage capacity isolation and described in the proposal kubernetes/community#306

Release note:

Alpha feature: allows users to set storage limit to isolate EmptyDir volumes. It enforces the limit by evicting pods that exceed their storage limits  

@k8s-ci-robot k8s-ci-robot added the cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. label May 11, 2017
@k8s-github-robot k8s-github-robot added kind/api-change Categorizes issue or PR as related to adding, removing, or otherwise changing an API size/L Denotes a PR that changes 100-499 lines, ignoring generated files. release-note-label-needed labels May 11, 2017
if used != nil && size.Cmp(*zero) > 0 && used.Cmp(size) > 0 {
// the emptyDir usage exceeds the size limit, evict the pod
gracePeriod := int64(0)
m.evictPod(pod, v1.ResourceName("EmptyDir"), gracePeriod, fmt.Sprintf("emptyDir usage exceeds the limit %q", size.String()))
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err = m.evictPod(...) ?

@@ -0,0 +1,213 @@
/*
Copyright 2016 The Kubernetes Authors.
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s/2016/2017

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Files should not have capital letters in their names

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I did not review all the eviction logic, just the API

@@ -668,6 +668,11 @@ type EmptyDirVolumeSource struct {
// More info: http://kubernetes.io/docs/user-guide/volumes#emptydir
// +optional
Medium StorageMedium `json:"medium,omitempty" protobuf:"bytes,1,opt,name=medium,casttype=StorageMedium"`
// Total amount of local storage required for this directory.
// The default is nil which means that the directory can use all available local storage on the node.
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Don't document the default as "nil" (that's a go-ism). Instead document as "If not specified, the default is to not enforce a limit". Though we might want to loosen this and say "If not specified, the default limit is implementation defined". Default tmpfs is (I think) 1/2 physical mem. Default disk is all storage, etc. I don't think we need to define that here, though.

if !utilfeature.DefaultFeatureGate.Enabled(features.LocalStorageCapacityIsolation) {
unsetSizeLimit := resource.Quantity{}
if unsetSizeLimit.Cmp(source.EmptyDir.SizeLimit) != 0 {
allErrs = append(allErrs, field.Forbidden(fldPath.Child("emptyDir").Child("sizeLimit"), "LocalStorageCapacityIsolation are disabled by feature-gate"))
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"is disabled"

@@ -0,0 +1,213 @@
/*
Copyright 2016 The Kubernetes Authors.
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Files should not have capital letters in their names

@k8s-github-robot k8s-github-robot added size/XL Denotes a PR that changes 500-999 lines, ignoring generated files. needs-rebase Indicates a PR cannot be merged because it has merge conflicts with HEAD. and removed size/L Denotes a PR that changes 100-499 lines, ignoring generated files. labels May 18, 2017
@@ -32,6 +32,7 @@ import (
"k8s.io/client-go/util/clock"
"k8s.io/kubernetes/pkg/api/v1"
"k8s.io/kubernetes/pkg/features"
statsapi "k8s.io/kubernetes/pkg/kubelet/api/v1alpha1/stats"
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Shouldn't this be k8s.io/kubernetes/pkg/kubelet/apis/stats/v1alpha1?

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Thanks for catching it. fix it. strange it was working in this way too...

glog.Errorf("eviction manager: pod %s exceeds emptyDir sizeLimit but failed to evict %v", format.Pod(pod), err)
} else {
glog.Infof("eviction manager: pod %s exceeds emptyDir sizeLimit and is evicted successfully", format.Pod(pod))
evict = true
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Why can't we return early since the pod is already evicted?

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The logic here is to evict all pods that violate the size limit for emptyDir volume. So we have to continue with the loop even after some pods are evicted.

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Actually, you are right, return early is fine.

@jingxu97 jingxu97 requested a review from dashpole May 26, 2017 19:05
@jingxu97 jingxu97 added this to the v1.7 milestone May 26, 2017
@jingxu97 jingxu97 force-pushed the May/emptyDir branch 2 times, most recently from adb9650 to 431baee Compare May 26, 2017 23:37
@k8s-github-robot k8s-github-robot added size/XXL Denotes a PR that changes 1000+ lines, ignoring generated files. needs-rebase Indicates a PR cannot be merged because it has merge conflicts with HEAD. and removed needs-rebase Indicates a PR cannot be merged because it has merge conflicts with HEAD. size/XL Denotes a PR that changes 500-999 lines, ignoring generated files. labels May 26, 2017

// evict pods if there is a resource uage violation from local volume temporary storage
// If eviction happenes in localVolumeEviction function, skip the rest of eviction action
if m.localVolumeEviction(activePods) {
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@vishh @derekwaynecarr, any preference as to whether doing local volume evictions is part of the same control loop as the rest of evictions? The main advantage of having them together is to not perform other evictions when pods are already being evicted for exceeding their local volume storage space

return evict
}

func (m *managerImpl) evictPod(pod *v1.Pod, resourceName v1.ResourceName, gracePeriod int64, evictMsg string) error {
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gracePeriod is always passed as 0, so you dont need it as an argument.

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will this change in the future?

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It could, but adding a parameter to a function is easy enough. Better to leave it out for now.

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Changes to the eviction manager need unit testing as well.

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Just a couple small things

size := source.EmptyDir.SizeLimit
used := podVolumeUsed[pod.Spec.Volumes[i].Name]
zero := resource.NewQuantity(int64(0), resource.BinarySI)
glog.Infof("Jing pod %s limit %v, used %v", format.Pod(pod), size, used)
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This is probably left over from testing. Remove

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fixed

used := podVolumeUsed[pod.Spec.Volumes[i].Name]
zero := resource.NewQuantity(int64(0), resource.BinarySI)
glog.Infof("Jing pod %s limit %v, used %v", format.Pod(pod), size, used)
if used != nil && size.Cmp(*zero) > 0 && used.Cmp(size) > 0 {
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instead of Cmp(*zero), I think you can use Sign

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changed

if overlayThreshold, ok := thresholdsMap[containerStat.Name]; ok {
if overlayThreshold.Cmp(*rootfs) < 0 {
gracePeriod := int64(0)
err := m.evictPod(pod, v1.ResourceName("containerOverlay"), gracePeriod, fmt.Sprintf("container's overlay usage exceeds the limit %q", overlayThreshold.String()))
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Since we are passing in a relevant message to evictPod, why not do the logging inside of evictPod using that message. evictPod doesnt need to return an error in this case, and we can avoid having essentially the same log messages duplicated in 3 places.

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fixed, put logging inside of evictPod, and return bool to indicate whether pod is evicted or not

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Does it matter whether the pod is evicted or not? I believe we set the pod's status to failed, so kubelet housekeeping will terminate it even if the eviction manager failed.
Essentially, we should treat any pod that we attempt to evict as evicted.

@k8s-github-robot k8s-github-robot removed the needs-rebase Indicates a PR cannot be merged because it has merge conflicts with HEAD. label May 30, 2017
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addressed the comments. @dashpole PTAL

@k8s-github-robot k8s-github-robot removed the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Jun 1, 2017
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falenn commented Jun 1, 2017 via email

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: falenn, jingxu97, thockin, vishh

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these OWNERS Files:

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jingxu97 commented Jun 1, 2017

@k8s-bot unit test this

@jingxu97 jingxu97 added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Jun 1, 2017
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jingxu97 commented Jun 1, 2017

@k8s-bot pull-kubernetes-e2e-kops-aws test this

@k8s-github-robot k8s-github-robot added the needs-rebase Indicates a PR cannot be merged because it has merge conflicts with HEAD. label Jun 3, 2017
This PR adds two features:
1. add support for isolating the emptyDir volume use. If user
sets a size limit for emptyDir volume, kubelet's eviction manager
monitors its usage
and evict the pod if the usage exceeds the limit.
2. add support for isolating the local storage for container overlay. If
the container's overly usage exceeds the limit defined in container
spec, eviction manager will evict the pod.
@k8s-github-robot k8s-github-robot removed needs-rebase Indicates a PR cannot be merged because it has merge conflicts with HEAD. lgtm "Looks good to me", indicates that a PR is ready to be merged. labels Jun 5, 2017
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jingxu97 commented Jun 5, 2017

@k8s-bot gce etcd3 e2e test this

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jingxu97 commented Jun 5, 2017

@k8s-bot pull-kubernetes-verify test this

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jingxu97 commented Jun 5, 2017

@k8s-bot kops aws e2e test this

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k8s-ci-robot commented Jun 5, 2017

@jingxu97: The following tests failed, say /retest to rerun them all:

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@jingxu97 jingxu97 added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Jun 6, 2017
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jingxu97 commented Jun 6, 2017

@k8s-bot kops aws e2e test this

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jingxu97 commented Jun 6, 2017

rebased, add /lgtm back

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Automatic merge from submit-queue

@k8s-github-robot k8s-github-robot merged commit cb68132 into kubernetes:master Jun 6, 2017
@jingxu97 jingxu97 changed the title Add EmptyDir volume capacity isolation Add EmptyDir volume and container overlay capacity isolation Jun 30, 2017
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  • Why we choose to evict a pod when the usage if exceed the limit?
  • IMO, we use the monitor and check logic to enforce this logic? Kubelet does not depends on any disk quota hard limit that underlying fs supports, i.e., xfs quota.

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