[Kubernetes] Pod - livenessProbe

Liveness Probe

- pod가 계속 실행할 수 있음을 보장
- Pod의 spec에 정의

 

# pod-definitaion

apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
spec:
  containers:
  - name: nginx-container
    image: nginx:1.14

 

# livenessProbe-definitaion

apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
spec:
  containers:
  - name: nginx-container
    image: nginx:1.14
    livenessProbe:
      httpGet:
        path: /
        port: 80

 

Liveness Probe 매커니즘

1. httpGet probe : 지정한 IP주소, port, path에 HTTP GET 요청을 보내, 해당 컨테이너가 응답하는지를 확인한다.

    반환코드가 200이 아닌 값이 나오면 오류, 컨테이너를 다시 시작한다.
     livenessProbe:
       httpGet:
         path: /
         port: 80
2. tcpSocket probe : 지정된 포트에 TCP 연결을 시도, 연결되지 않으면 컨테이너를 다시 시작한다.
     livenessProbe:
       tcpSocket:
         port: 22
3. exec probe : exec 명령을 전달하고 명령의 종료코드가 0이 아니면 컨테이너를 다시 시작한다.
     livenessProbe:
       exec :
         command:
         - ls
         - /data/file

 

Liveness Probe 매개변수

 - periodSecends : health check 반복 실행 시간(초)
 - initialDelaySeconds : Pod 실행 후 delay할 시간(초)
 - timeoutSeconds : health check 후 응답을 기다리는 시간(초)

 

Liveness Probe Pod 실행

# pod-nginx-liveness.yaml

apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod-liveness
spec:
  containers:
  - name: nginx-container
    image: nginx:1.14
    ports:
    - containerPort: 80
      protocol: TCP
    livenessProbe:
      httpGet:
        path: /
        port: 80
      periodSeconds: 10
      successThreshold: 1
      timeoutSeconds: 1
      failureThreshold: 3

 

Liveness Probe Pod describe 확인

# kubectl describe pod nginx-pod-liveness 
Name:             nginx-pod-liveness
Namespace:        default
Priority:         0
Service Account:  default
Node:             node2.example.com/10.100.0.102
Start Time:       Sun, 27 Nov 2022 22:08:38 +0900
Labels:           <none>
Annotations:      <none>
Status:           Running
IP:               10.44.0.1
IPs:
  IP:  10.44.0.1
Containers:
  nginx-container:
    Container ID:   containerd://81690c8a1af8a8830d8e9444fcfef73f64cc8f109c4672c8d34e02e5f495a93a
    Image:          nginx:1.14
    Image ID:       docker.io/library/nginx@sha256:f7988fb6c02e0ce69257d9bd9cf37ae20a60f1df7563c3a2a6abe24160306b8d
    Port:           80/TCP
    Host Port:      0/TCP
    State:          Running
      Started:      Sun, 27 Nov 2022 22:08:41 +0900
    Ready:          True
    Restart Count:  0
    Liveness:       http-get http://:80/ delay=0s timeout=1s period=10s #success=1 #failure=3
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-df8rh (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  kube-api-access-df8rh:
    Type:                    Projected (a volume that contains injected data from multiple sources)
    TokenExpirationSeconds:  3607
    ConfigMapName:           kube-root-ca.crt
    ConfigMapOptional:       <nil>
    DownwardAPI:             true
QoS Class:                   BestEffort
Node-Selectors:              <none>
Tolerations:                 node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                             node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
  Type    Reason     Age   From               Message
  ----    ------     ----  ----               -------
  Normal  Scheduled  29m   default-scheduler  Successfully assigned default/nginx-pod-liveness to node2.example.com
  Normal  Pulled     29m   kubelet            Container image "nginx:1.14" already present on machine
  Normal  Created    29m   kubelet            Created container nginx-container
  Normal  Started    29m   kubelet            Started container nginx-container

 

Liveness:       http-get http://:80/ delay=0s timeout=1s period=10s #success=1 #failure=3 확인 가능

delay : running 몇 초 지난 후에 검사
timeout : 요청 후 아무 응답이 없으면 실패
period : 얼마만에 한번씩 검사
failure : 실패 횟수
success : 성공 횟수

 

 

[참고]

- https://www.youtube.com/watch?v=-NeJS7wQu_Q