10-pod的健康检查

Liveness Probe
LivenessProbe：kubelet使用livenessProbe在容器出现异常的时候进行重启的操作。
ReadinessProbe：Kubelet使用ReadinessProbe来指定Container是否为Ready状态。
结合Service用来限定哪些Ready的Container来接受流量。因为Service会将Container状态为Ready的Pod添加到Endpoint里，进行流量的分发。

Crontainer诊断方法：
Exec：在Container内执行指定的命令。如果命令以状态代码0退出，则认为诊断成功。
TCPSocket：对指定端口上的Container的IP地址执行TCP检查。如果端口打开，则诊断被认为是成功的。
HTTPGet：对指定端口和路径上的Container的IP地址执行HTTP Get请求。如果响应的状态代码大于或等于200且小于400，则认为诊断成功。

cat << EOF > pod-liveness-command.yaml
apiVersion: v1
kind: Pod
metadata:
  labels:
    test: liveness
  name: liveness-exec
spec:
  containers:
  - name: liveness
    image: radial/busyboxplus
    imagePullPolicy: IfNotPresent
    args:
    - /bin/sh
    - -c
    - touch /tmp/healthy; sleep 60; rm -rf /tmp/healthy; sleep 600
    livenessProbe:
      exec:
        command:
        - cat
        - /tmp/healthy
      initialDelaySeconds: 5
      periodSeconds: 5
EOF

[root@master01 damon]# kubectl apply -f pod-liveness-command.yaml

[root@master01 damon]# watch -n1 kubectl get pod //通过查看发现liveness-exec的RESTARTS 在30秒后由于检测到不健康一直在重启
NAME READY STATUS RESTARTS AGE
liveness-exec 1/1 Running 0 3s
nginx-deployment-676cc869-bnnvd 1/1 Running 0 30m
nginx-deployment-676cc869-ft8bw 1/1 Running 0 26m

[root@master01 damon]# kubectl get event // 查看Kubernetes事件

liveness HTTP request
**

cat << EOF > pod-liveness-http.yaml
apiVersion: v1
kind: Pod
metadata:
  labels:
    test: liveness
  name: liveness-http
spec:
  containers:
  - name: liveness
    image: seedoflife/liveness
    imagePullPolicy: IfNotPresent
    args:
    - /server
    livenessProbe:
      httpGet:
        path: /healthz
        port: 8080
        httpHeaders:
        - name: X-Custom-Header
          value: Awesome
      initialDelaySeconds: 3
      periodSeconds: 3
EOF

[root@master01 damon]# kubectl apply -f pod-liveness-http.yaml

[root@master01 damon]# curl -v 192.168.1.62:8080/healthz
About to connect() to 192.168.1.62 port 8080 (#0)
Trying 192.168.1.62…
Connected to 192.168.1.62 (192.168.1.62) port 8080 (#0)
> GET /healthz HTTP/1.1
> User-Agent: curl/7.29.0
> Host: 192.168.1.62:8080
> Accept: /
>
< HTTP/1.1 200 OK // OK显示正常
< Date: Tue, 20 Nov 2018 12:01:26 GMT
< Content-Length: 2
< Content-Type: text/plain; charset=utf-8
<
Connection #0 to host 192.168.1.62 left intact
ok[root@master01 damon]# curl -v 192.168.1.62:8080/healthz
About to connect() to 192.168.1.62 port 8080 (#0)
Trying 192.168.1.62…
Connected to 192.168.1.62 (192.168.1.62) port 8080 (#0)
> GET /healthz HTTP/1.1
> User-Agent: curl/7.29.0
> Host: 192.168.1.62:8080
> Accept: /
>
< HTTP/1.1 500 Internal Server Error // error检测异常
< Date: Tue, 20 Nov 2018 12:01:39 GMT
< Content-Length: 19
< Content-Type: text/plain; charset=utf-8
<
Connection #0 to host 192.168.1.62 left intact

TCP liveness probe

cat << EOF > pod-liveness-tcp.yaml
apiVersion: v1
kind: Pod
metadata:
  name: liveness-tcp
  labels:
    app: liveness-tcp
spec:
  containers:
  - name: liveness-tcp
    image: python:2.7
    imagePullPolicy: IfNotPresent
    command: ["bash", "-c", "echo test > index.html && sleep 30 && python -m SimpleHTTPServer 8080"] 
    ports:
    - containerPort: 8080
    readinessProbe:
      tcpSocket:
        port: 8080
      initialDelaySeconds: 35
      periodSeconds: 10
    livenessProbe:
      tcpSocket:
        port: 8080
      initialDelaySeconds: 15
      periodSeconds: 20
EOF

[root@master01 ~]# kubectl apply -f pod-liveness-tcp.yaml

[root@master01 ~]# kubectl get pod —watch //参看30秒以内podr的R
NAME READY STATUS RESTARTS AGE
goproxy 1/1 Running 1 5h46m
liveness-tcp 0/1 Running 0 4s

readinessProbe


readinessProbe + livenessProbe+Service**
探针具有许多字段，可用于更精确地控制活动性和准备情况检查的行为：
initialDelaySeconds：启动容器后，启动活动或就绪探测器的秒数。默认为0秒。最小值为0。
periodSeconds：执行探测的频率（以秒为单位）。默认为10秒。最小值为1。
timeoutSeconds：探测超时的秒数。默认为1秒。最小值为1。
successThreshold：探测失败后，连续最小成功探测为成功。默认值为1，最小值为1。
failureThreshold：当Pod启动并且探测失败时，Kubernetes会尝试failureThreshold多次，当多次探测失败后执行重启容器的动作。放弃。默认值为3，最小值为1

cat << EOF > service-healthcheck.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: service-health
spec:
  replicas: 2
  selector:
    matchLabels:
      app: service-health
  template:
    metadata:
      labels:
        app: service-health
    spec:
      containers:
      - name: service-health
        image: python:2.7
        imagePullPolicy: IfNotPresent
        command: ["/bin/bash","-c","echo \$(hostname) > index.html && sleep 30 && python -m SimpleHTTPServer 8080"]
        ports:
        - containerPort: 8080
        readinessProbe:
          tcpSocket:
            port: 8080
          initialDelaySeconds: 10
          periodSeconds: 10
EOF

**
kubectl apply -f service-healthcheck.yaml

创建service
kubectl expose deployment service-health

[root@master01 ~]# kubectl get service
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kubernetes ClusterIP 10.96.0.1 443/TCP 6d
service-health ClusterIP 10.109.21.81 8080/TCP 4s

curl 10.109.21.81:8080