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Kubernetes API のヘルスチェック

手順

各コンポーネントの起動確認

kubectl get pods -n kube-system

実行例 
$ kubectl get pods -n kube-system
NAME                                 READY   STATUS    RESTARTS   AGE
etcd-k8s-master                      1/1     Running   0          5m56s
kube-apiserver-k8s-master            1/1     Running   0          6m7s
kube-controller-manager-k8s-master   1/1     Running   0          4m2s
kube-scheduler-k8s-master            1/1     Running   0          2m48s

master node上のresource確認

kubectl get nodes
kubectl describe node <pod_name>

実行例 
$ kubectl get nodes
NAME         STATUS   ROLES    AGE     VERSION
k8s-master   Ready    <none>   7m57s   v1.20.1

$ kubectl describe node k8s-master
Name:               k8s-master
Roles:              <none>
Labels:             beta.kubernetes.io/arch=arm64
                    beta.kubernetes.io/os=linux
                    kubernetes.io/arch=arm64
                    kubernetes.io/hostname=k8s-master
                    kubernetes.io/os=linux
Annotations:        node.alpha.kubernetes.io/ttl: 0
                    volumes.kubernetes.io/controller-managed-attach-detach: true
CreationTimestamp:  Sat, 17 Apr 2021 15:13:42 +0000
Taints:             node-role.kubernetes.io/master:NoSchedule
Unschedulable:      false
Lease:
  HolderIdentity:  k8s-master
  AcquireTime:     <unset>
  RenewTime:       Sat, 17 Apr 2021 16:34:29 +0000
Conditions:
  Type             Status  LastHeartbeatTime                 LastTransitionTime                Reason                       Message
  ----             ------  -----------------                 ------------------                ------                       -------
  MemoryPressure   False   Sat, 17 Apr 2021 16:34:09 +0000   Sat, 17 Apr 2021 15:13:41 +0000   KubeletHasSufficientMemory   kubelet has sufficient memory available
  DiskPressure     False   Sat, 17 Apr 2021 16:34:09 +0000   Sat, 17 Apr 2021 15:13:41 +0000   KubeletHasNoDiskPressure     kubelet has no disk pressure
  PIDPressure      False   Sat, 17 Apr 2021 16:34:09 +0000   Sat, 17 Apr 2021 15:13:41 +0000   KubeletHasSufficientPID      kubelet has sufficient PID available
  Ready            True    Sat, 17 Apr 2021 16:34:09 +0000   Sat, 17 Apr 2021 15:13:52 +0000   KubeletReady                 kubelet is posting ready status. AppArmor enabled
Addresses:
  InternalIP:  192.168.10.50
  Hostname:    k8s-master
Capacity:
  cpu:                4
  ephemeral-storage:  30459624Ki
  memory:             1892528Ki
  pods:               110
Allocatable:
  cpu:                3400m
  ephemeral-storage:  28071589432
  memory:             1380528Ki
  pods:               110
System Info:
  Machine ID:                 58f6de70444c4198b56b30122b6c77dc
  System UUID:                58f6de70444c4198b56b30122b6c77dc
  Boot ID:                    79af3428-cf70-4189-a447-0b917a035a42
  Kernel Version:             5.4.0-1032-raspi
  OS Image:                   Ubuntu 20.04.2 LTS
  Operating System:           linux
  Architecture:               arm64
  Container Runtime Version:  cri-o://1.20.2
  Kubelet Version:            v1.20.1
  Kube-Proxy Version:         v1.20.1
PodCIDR:                      10.200.0.0/24
PodCIDRs:                     10.200.0.0/24
Non-terminated Pods:          (4 in total)
  Namespace                   Name                                  CPU Requests  CPU Limits  Memory Requests  Memory Limits  AGE
  ---------                   ----                                  ------------  ----------  ---------------  -------------  ---
  kube-system                 etcd-k8s-master                       500m (14%)    1 (29%)     256Mi (18%)      384Mi (28%)    78m
  kube-system                 kube-apiserver-k8s-master             500m (14%)    1 (29%)     256Mi (18%)      384Mi (28%)    78m
  kube-system                 kube-controller-manager-k8s-master    100m (2%)     300m (8%)   128Mi (9%)       256Mi (18%)    76m
  kube-system                 kube-scheduler-k8s-master             100m (2%)     300m (8%)   128Mi (9%)       256Mi (18%)    75m
Allocated resources:
  (Total limits may be over 100 percent, i.e., overcommitted.)
  Resource           Requests     Limits
  --------           --------     ------
  cpu                1200m (35%)  2600m (76%)
  memory             768Mi (56%)  1280Mi (94%)
  ephemeral-storage  0 (0%)       0 (0%)
Events:              <none>

health checks

kube-apiserverの起動オプションで --anonymous-auth=false を付加しているため https://localhost:6443 へのanonymousアカウントでの確認は行わずに kubectl で確認する

  1. API endpoints for health 

    kubectl get --raw='/readyz?verbose'
    実行例 
    $ kubectl get --raw='/readyz?verbose'
[+]ping ok
[+]log ok
[+]etcd ok
[+]informer-sync ok
[+]poststarthook/start-kube-apiserver-admission-initializer ok
[+]poststarthook/generic-apiserver-start-informers ok
[+]poststarthook/max-in-flight-filter ok
[+]poststarthook/start-apiextensions-informers ok
[+]poststarthook/start-apiextensions-controllers ok
[+]poststarthook/crd-informer-synced ok
[+]poststarthook/bootstrap-controller ok
[+]poststarthook/rbac/bootstrap-roles ok
[+]poststarthook/scheduling/bootstrap-system-priority-classes ok
[+]poststarthook/priority-and-fairness-config-producer ok
[+]poststarthook/start-cluster-authentication-info-controller ok
[+]poststarthook/start-kube-aggregator-informers ok
[+]poststarthook/apiservice-registration-controller ok
[+]poststarthook/apiservice-status-available-controller ok
[+]poststarthook/kube-apiserver-autoregistration ok
[+]autoregister-completion ok
[+]poststarthook/apiservice-openapi-controller ok
[+]shutdown ok
readyz check passed

  2. Individual health checks 

    kubectl get --raw='/livez/etcd'
    実行例 
    $ kubectl get --raw='/livez/etcd'
ok

$ kubectl get --raw='/livez/poststarthook/start-apiextensions-controllers'
ok

参考資料