K8S基础 - 04Pod生命周期
一、Pod生命周期
状态： Pending, Running, Failed, Succeeded, Unknown
官网文档： https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle/#pod-phase
Pending The Pod has been accepted by the Kubernetes cluster, but one or more of the containers has not been set up and made ready to run.
This includes time a Pod spends waiting to be scheduled as well as the time spent downloading container images over the network.
Running The Pod has been bound to a node, and all of the containers have been created.
At least one container is still running, or is in the process of starting or restarting.
Succeeded All containers in the Pod have terminated in success, and will not be restarted.
Failed All containers in the Pod have terminated, and at least one container has terminated in failure.
That is, the container either exited with non-zero status or was terminated by the system.
Unknown For some reason the state of the Pod could not be obtained.
This phase typically occurs due to an error in communicating with the node where the Pod should be running.
Pod生命周期
二、初始化容器
三、 容器探测
livenessProbe (存活检查) # 如果检查失败， 将杀死容器, 根据Pod的restartPolicy来操作
readinessProbe(就绪检查) # 如果检查失败， Kubernetes会把Pod从Service Endpoints中剔除。
Probe三种检查方法：
- httpGet： 发送HTTP请求, 返回200-400范围内状态码为成功
- exec： 执行shell命令返回状态码为0表示成功。
- tcpSocket： 发起TCP Socket建立成功。
3.1 livenessProbe
[root@k8s-master pod-k8s]# cat pod-live.yaml
apiVersion: v1
kind: Pod
metadata:
name: pod-live-exec
namespace: default
spec:
containers:
- name: container-live-exec
image: busybox
imagePullPolicy: IfNotPresent
command: ["/bin/sh", "-c", "touch /tmp/healthy-test; sleep 60; rm -rf /tmp/healthy-test; sleep 3600"]
livenessProbe:
exec:
command: ["test", "-e", "/tmp/healthy-test"]
initialDelaySeconds: 1 # 容器初始化后 多久开始执行 livenessProbe探测
periodSeconds: 3 # 探测执行频率
[root@k8s-master ~]# kubectl create -f pod-live.yaml
pod/pod-live-exec created
[root@k8s-master ~]# kubectl get pods
NAME READY STATUS RESTARTS AGE
pod-live-exec 1/1 Running 0 7s
[root@k8s-master ~]# kubectl describe pod pod-live-exec
State: Running
Started: Sat, 23 Oct 2021 16:37:40 +0800
State: Running
Started: Sat, 23 Oct 2021 16:39:19 +0800
Last State: Terminated
Reason: Error
Exit Code: 137
Started: Sat, 23 Oct 2021 16:37:40 +0800
Finished: Sat, 23 Oct 2021 16:39:18 +0800
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 2m42s default-scheduler Successfully assigned default/pod-live-exec to k8s-node32.bearpx.com
Warning Unhealthy 93s (x3 over 99s) kubelet Liveness probe failed:
Normal Killing 93s kubelet Container container-live-exec failed liveness probe, will be restarted
Normal Pulled 63s (x2 over 2m42s) kubelet Container image "busybox" already present on machine
Normal Created 62s (x2 over 2m42s) kubelet Created container container-live-exec
Normal Started 62s (x2 over 2m41s) kubelet Started container container-live-exec
[root@k8s-master ~]# kubectl get pods
NAME READY STATUS RESTARTS AGE
pod-live-exec 1/1 Running 2 4m2s
3.2 liveness HTTPGET方式
[root@k8s-master pod-k8s]# cat pod-live-httpget.yaml
apiVersion: v1
kind: Pod
metadata:
name: pod-live-httpget
namespace: default
spec:
containers:
- name: container-live-httpget
image: sun2010wg/my-nginx:v2
imagePullPolicy: IfNotPresent
ports:
- name: http
containerPort: 81
livenessProbe:
httpGet:
port: http
initialDelaySeconds: 1
periodSeconds: 3
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 16s default-scheduler Successfully assigned default/pod-live-httpget to k8s-node32.bearpx.com
Normal Killing 9s kubelet Container container-live-httpget failed liveness probe, will be restarted
Normal Pulled 8s (x2 over 17s) kubelet Container image "sun2010wg/my-nginx:v2" already present on machine
Normal Created 8s (x2 over 17s) kubelet Created container container-live-httpget
Normal Started 8s (x2 over 16s) kubelet Started container container-live-httpget
Warning Unhealthy 3s (x5 over 15s) kubelet Liveness probe failed: Get "http://10.244.3.14:81/": dial tcp 10.244.3.14:81: connect: connection refused
[root@k8s-master ~]# kubectl get pods
NAME READY STATUS RESTARTS AGE
pod-live-httpget 1/1 Running 1 2m38s
3.3 readinessProbe
[root@k8s-master pod-k8s]# cat pod-read-httpget.yml
apiVersion: v1
kind: Pod
metadata:
name: pod-live-httpget
namespace: default
spec:
containers:
- name: container-live-httpget
image: sun2010wg/my-nginx:v2
imagePullPolicy: IfNotPresent
ports:
- name: http
containerPort: 80
readinessProbe:
httpGet:
port: http
path: /index.html
initialDelaySeconds: 1
periodSeconds: 3
### 1. Pod正常启动
Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 28s default-scheduler Successfully assigned default/pod-live-readiness to k8s-node33.bearpx.com Normal Pulled 27s kubelet Container image "sun2010wg/my-nginx:v2" already present on machine Normal Created 27s kubelet Created container container-live-httpget Normal Started 27s kubelet Started container container-live-httpget ### 2. 删除容器的index.html [root@k8s-master pod-k8s]# kubectl exec -it pod-live-readiness -- /bin/sh /usr/share/nginx/html # rm -rf index.html ### 3. Pod内的容器READY数量变化 [root@k8s-master ~]# kubectl get pods NAME READY STATUS RESTARTS AGE pod-live-readiness 0/1 Running 0 103s ### 4. Pod检测到Unhealthy Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 3m25s default-scheduler Successfully assigned default/pod-live-readiness to k8s-node33.bearpx.com Normal Pulled 3m25s kubelet Container image "sun2010wg/my-nginx:v2" already present on machine Normal Created 3m25s kubelet Created container container-live-httpget Normal Started 3m25s kubelet Started container container-live-httpget Warning Unhealthy 58s (x22 over 2m1s) kubelet Readiness probe failed: HTTP probe failed with statuscode: 404 ### 5. 新增index.html /usr/share/nginx/html # echo "123" > index.html ### 6. Pod内的容器恢复正常 [root@k8s-master ~]# kubectl get pods NAME READY STATUS RESTARTS AGE pod-live-readiness 1/1 Running 0 3m58s [root@k8s-master ~]# curl 10.244.2.32 123
四、 Post Start
# 执行失败
apiVersion: v1 kind: Pod metadata: name: pod-poststart namespace: default spec: containers: - name: busybox-httpd image: busybox imagePullPolicy: IfNotPresent lifecycle: postStart: exec: command: ["/bin/sh","-c","mkdir -p /data/web/html; echo 'Home Page' >> /data/web/html/home.html"] command: ["/bin/httpd"] args: ["-f","-h /data/web/html"]
在容器启动时， 需要 /data/web/html， 容器启动失败
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 40s default-scheduler Successfully assigned default/pod-poststart to k8s-node32.bearpx.com
Normal Pulled 24s (x3 over 41s) kubelet Container image "busybox" already present on machine
Normal Created 24s (x3 over 40s) kubelet Created container busybox-httpd
Normal Started 24s (x3 over 40s) kubelet Started container busybox-httpd
Warning FailedPostStartHook 24s (x3 over 40s) kubelet Exec lifecycle hook ([/bin/sh -c mkdir -p /data/web/html; echo 'Home Page' >> /data/web/html/home.html])
for Container "busybox-httpd" in Pod "pod-poststart_default(6b5e789f-8213-4a6f-9c38-bb34889005df)" failed - error:
command '/bin/sh -c mkdir -p /data/web/html; echo 'Home Page' >> /data/web/html/home.html' exited with 126: , message: "cannot exec in a stopped state: unknown\r\n"
Normal Killing 24s (x3 over 40s) kubelet FailedPostStartHook
Warning BackOff 9s (x4 over 39s) kubelet Back-off restarting failed container
[root@k8s-master pod-k8s]# cat pod-lifecycle.yaml
apiVersion: v1
kind: Pod
metadata:
name: pod-poststart
namespace: default
spec:
containers:
- name: busybox-httpd
image: busybox
imagePullPolicy: IfNotPresent
lifecycle:
postStart:
exec:
command: ["/bin/sh","-c","echo Home_Page >> /tmp/index.html"]
command: ["/bin/httpd"]
args: ["-f", "-h /tmp"]
[root@k8s-master ~]# kubectl logs pod-poststart
httpd: can't change directory to ' /tmp': No such file or directory
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 4s default-scheduler Successfully assigned default/pod-poststart to k8s-node32.bearpx.com
Normal Pulled 3s (x2 over 3s) kubelet Container image "busybox" already present on machine
Normal Created 3s (x2 over 3s) kubelet Created container busybox-httpd
Normal Started 3s (x2 over 3s) kubelet Started container busybox-httpd
Warning FailedPostStartHook 3s (x2 over 3s) kubelet Exec lifecycle hook ([/bin/sh -c echo Home_Page >> /tmp/index.html]) for Container "busybox-httpd"
in Pod "pod-poststart_default(e22da6dc-b4d4-47ac-879f-659f08dcce5e)" failed - error: command '/bin/sh -c echo Home_Page >> /tmp/index.html' exited with 126: ,
message: "cannot exec in a stopped state: unknown\r\n"
Normal Killing 3s (x2 over 3s) kubelet FailedPostStartHook
Warning BackOff 1s (x2 over 2s) kubelet Back-off restarting failed container
[root@k8s-master pod-k8s]# cat pod-poststart.yaml
apiVersion: v1
kind: Pod
metadata:
name: pod-poststart-ok
namespace: default
spec:
containers:
- name: busybox-httpd
image: busybox
imagePullPolicy: IfNotPresent
lifecycle:
postStart:
exec:
command: ["/bin/sh","-c","echo Home_Page >> /tmp/index.html"]
command: ["/bin/httpd"]
args: ["-f"]
[root@k8s-master pod-k8s]# kubectl exec -it pod-poststart-ok -- /bin/sh / # netstat -tunlp Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 :::80 :::* LISTEN 1/httpd / # cd /tmp/ /tmp # ls index.html /tmp # cat index.html Home_Page
Pod回顾总结
apiVersion, kind, metadata, spec, status(只读)
spec:
containers
initContainers
nodeName
nodeSelector <map[string]string>
restartPolicy <string> One of Always, OnFailure,Never. Default to Always.
tolerations <[]Object>
volumes <[]Object>
containers:
name
image
imagePullPolicy: Always、 Never、 IfNotPresent
ports:
name
containerPort
lifecycle
livenessProbe
readinessProbe
ExecAction: exec
TcpSocketAction: tcpSocket
HTTPGetAction: httpGet
