Kubernetes Liveness Readiness 区别 | 张志明的个人博客

在kubernetes中有两种负责健康检查的Probe, 分别是Liveness probe 和Readiness Probe

我们最常见到的应该是Liveness probe

例如：

apiVersion: v1
kind: Pod
metadata:
  labels:
    test: liveness
  name: liveness-exec
spec:
  containers:
  - name: liveness
    image: k8s.gcr.io/busybox
    args:
    - /bin/sh
    - -c
    - touch /tmp/healthy; sleep 30; rm -rf /tmp/healthy; sleep 600
    livenessProbe:
      exec:
        command:
        - cat
        - /tmp/healthy
      initialDelaySeconds: 5
      periodSeconds: 5

apiVersion: v1

kind: Pod

metadata:

labels:

test: liveness

spec:

containers:

- name: liveness

image: k8s.gcr.io/busybox

args:

- /bin/sh

- -c

- touch /tmp/healthy; sleep 30; rm -rf /tmp/healthy; sleep 600

livenessProbe:

exec:

command:

- cat

- /tmp/healthy

initialDelaySeconds: 5

periodSeconds: 5

其中periodSeconds 是控制多久执行一次livenessProbe,这个例子中是说每隔5秒就要去执行一次检查

initialDelaySeconds是控制说刚启动Pod的时候你要等5秒，给Pod一点启动时间再去检查

如果我们的LivenessProbe检查通过，也就是 cat /tmp/healthy（在容器中）能够正常执行，那么Kubernetes就认为Pod是健康的，否则，就认为是不健康的，kubernetes会重启这个Pod，尝试修复问题

除了支持命令行外，livenessProbe还支持TCP和HTTP检查

例如：

apiVersion: v1
kind: Pod
metadata:
  labels:
    test: liveness
  name: liveness-http
spec:
  containers:
  - name: liveness
    image: k8s.gcr.io/liveness
    args:
    - /server
    livenessProbe:
      httpGet:
        path: /healthz
        port: 8080
        httpHeaders:
        - name: X-Custom-Header
          value: Awesome
      initialDelaySeconds: 3
      periodSeconds: 3

apiVersion: v1

kind: Pod

metadata:

labels:

test: liveness

spec:

containers:

- name: liveness

image: k8s.gcr.io/liveness

args:

- /server

livenessProbe:

httpGet:

path: /healthz

port: 8080

httpHeaders:

- name: X-Custom-Header

value: Awesome

initialDelaySeconds: 3

periodSeconds: 3

apiVersion: v1
kind: Pod
metadata:
  name: goproxy
  labels:
    app: goproxy
spec:
  containers:
  - name: goproxy
    image: k8s.gcr.io/goproxy:0.1
    ports:
    - containerPort: 8080
    readinessProbe:
      tcpSocket:
        port: 8080
      initialDelaySeconds: 5
      periodSeconds: 10
    livenessProbe:
      tcpSocket:
        port: 8080
      initialDelaySeconds: 15
      periodSeconds: 20

apiVersion: v1

kind: Pod

metadata:

labels:

app: goproxy

spec:

containers:

- name: goproxy

image: k8s.gcr.io/goproxy:0.1

ports:

- containerPort: 8080

readinessProbe:

tcpSocket:

port: 8080

initialDelaySeconds: 5

periodSeconds: 10

livenessProbe:

tcpSocket:

port: 8080

initialDelaySeconds: 15

periodSeconds: 20

readinessProbe

readinessProbe 和livenessProbe类似，都是做检查的

readinessProbe:
  exec:
    command:
    - cat
    - /tmp/healthy
  initialDelaySeconds: 5
  periodSeconds: 5

readinessProbe:

exec:

command:

- cat

- /tmp/healthy

initialDelaySeconds: 5

periodSeconds: 5

区别在于，readinessProbe 不会去重启Pod，它的主要目的是判断我们的Pod是否已经具备接受service分发的流量的资格了，如果readinessProbe检查失败，说明Pod还没准备好，kubernetes会把我们的Pod从service后端拿掉，这样的话流量就不会进入到我们这个没有ready的Pod中