LimitRange概述

默认情况下，Kubernetes集群上的容器对计算资源维度没有任何限制，可能会导致个别容器资源过大导致影响其他容器正常工作，这时可以使用LimitRange定义容器默认CPU和内存请求值或者最大限制。

LimitRange维度限制：

• 限制容器配置requests.cpu/memory,limits.cpu/memory的最小、最大值
• 限制容器配置requests.cpu/memory,limits.cpu/memory的默认值
• 限制PVC配置requests.storage的最小、最大值

使用前提

LimitRange功能是一个准入控制插件，默认已经启用。检查是否开启LimitRange功能的方法如下：

[root@master ~]# kubectl -n kube-system get pod|grep apiserver
kube-apiserver-master.host.com             1/1     Running   28 (95m ago)   62d
[root@master ~]# kubectl -n kube-system exec kube-apiserver-master.host.com -- kube-apiserver -h|grep enable-admission-plugins
      --admission-control strings              Admission is divided into two phases. In the first phase, only mutating admission plugins run. In the second phase, only validating admission plugins run. The names in the below list may represent a validating plugin, a mutating plugin, or both. The order of plugins in which they are passed to this flag does not matter. Comma-delimited list of: AlwaysAdmit, AlwaysDeny, AlwaysPullImages, CertificateApproval, CertificateSigning, CertificateSubjectRestriction, DefaultIngressClass, DefaultStorageClass, DefaultTolerationSeconds, DenyServiceExternalIPs, EventRateLimit, ExtendedResourceToleration, ImagePolicyWebhook, LimitPodHardAntiAffinityTopology, LimitRanger, MutatingAdmissionWebhook, NamespaceAutoProvision, NamespaceExists, NamespaceLifecycle, NodeRestriction, OwnerReferencesPermissionEnforcement, PersistentVolumeClaimResize, PersistentVolumeLabel, PodNodeSelector, PodSecurity, PodTolerationRestriction, Priority, ResourceQuota, RuntimeClass, SecurityContextDeny, ServiceAccount, StorageObjectInUseProtection, TaintNodesByCondition, ValidatingAdmissionWebhook. (DEPRECATED: Use --enable-admission-plugins or --disable-admission-plugins instead. Will be removed in a future version.)
      --enable-admission-plugins strings       admission plugins that should be enabled in addition to default enabled ones (NamespaceLifecycle, LimitRanger, ServiceAccount, TaintNodesByCondition, PodSecurity, Priority, DefaultTolerationSeconds, DefaultStorageClass, StorageObjectInUseProtection, PersistentVolumeClaimResize, RuntimeClass, CertificateApproval, CertificateSigning, CertificateSubjectRestriction, DefaultIngressClass, MutatingAdmissionWebhook, ValidatingAdmissionWebhook, ResourceQuota). Comma-delimited list of admission plugins: AlwaysAdmit, AlwaysDeny, AlwaysPullImages, CertificateApproval, CertificateSigning, CertificateSubjectRestriction, DefaultIngressClass, DefaultStorageClass, DefaultTolerationSeconds, DenyServiceExternalIPs, EventRateLimit, ExtendedResourceToleration, ImagePolicyWebhook, LimitPodHardAntiAffinityTopology, LimitRanger, MutatingAdmissionWebhook, NamespaceAutoProvision, NamespaceExists, NamespaceLifecycle, NodeRestriction, OwnerReferencesPermissionEnforcement, PersistentVolumeClaimResize, PersistentVolumeLabel, PodNodeSelector, PodSecurity, PodTolerationRestriction, Priority, ResourceQuota, RuntimeClass, SecurityContextDeny, ServiceAccount, StorageObjectInUseProtection, TaintNodesByCondition, ValidatingAdmissionWebhook. The order of plugins in this flag does not matter.

在"--enable-admission-plugins"中寻找"LimitRanger"发现已经开启。

资源清单

计算资源最大、最小限制

apiVersion: v1
kind: LimitRange
metadata:
  name: cpu-memory-max-min
  namespace: test
spec:
  limits:
  - max:
      cpu: 1        
      memory: 1Gi
    min:
      cpu: 100m
      memory: 100Mi
    type: Container

max里面是容器能设置limit的最大值，min里面是容器能设置request的最小值

计算资源默认值

apiVersion: v1
kind: LimitRange
metadata:
  name: cpu-memory-max-min
  namespace: test
spec:
  limits:
  - max:
      cpu: 1
      memory: 1Gi
    min:
      cpu: 100m
      memory: 100Mi
    default:
      cpu: 500m
      memory: 500Mi
    defaultRequest:
      cpu: 100m
      memory: 100Mi
    type: Container

"default"是设置limit的默认值，"defaultRequest"是设置request的默认值

存储资源最大、最小限制

apiVersion: v1
kind: LimitRange
metadata:
  name: storage-max-min
  namespace: test
spec:
  limits:
  - max:
      storage: 10Gi
    min:
      storage: 1Gi
    type: PersistentVolumeClaim

pvc的使用

维度状态

[root@master cks]# kubectl get limits -n test
NAME                 CREATED AT
cpu-memory-max-min   2022-12-17T11:01:11Z
storage-max-min      2022-12-17T10:59:56Z
[root@master cks]# kubectl describe limits -n test
Name:       cpu-memory-max-min
Namespace:  test
Type        Resource  Min    Max  Default Request  Default Limit  Max Limit/Request Ratio
----        --------  ---    ---  ---------------  -------------  -----------------------
Container   memory    100Mi  1Gi  100Mi            500Mi          -
Container   cpu       100m   1    100m             500m           -


Name:                  storage-max-min
Namespace:             test
Type                   Resource  Min  Max   Default Request  Default Limit  Max Limit/Request Ratio
----                   --------  ---  ---   ---------------  -------------  -----------------------
PersistentVolumeClaim  storage   1Gi  10Gi  -                -              -