K8S实践Ⅱ（Pod基本用法）

一、Static Pod

静态Pod是由kubectl进行管理的仅存于特定Node上的Pod。其不能通过API Server进行管理，无法与ReplicationController、Deployment或者DaemonSet进行关联，并且kubelet也无法对他们进行健康检查。静态Pod总是由kubectl进行创建，并且总是在kubelet所在的Node上运行。
创建静态 Pod 有两种方式：配置文件和 HTTP 两种方式

由kubeadm安装的集群，对应的kubelet已经配置了静态Pod文件的路径

# cat /var/lib/kubelet/config.yaml |grep staticPodPath
staticPodPath: /etc/kubernetes/manifests

1.配置一个静态Pod的yaml文件放入该路径

# cat static-web.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: static-web
  labels:
    name: static-web
spec:
  containers:
  - name: static-web
    image: nginx
    ports:
    - name: web
      containerPort: 80

2.查看docker进程

# docker ps 
CONTAINER ID        IMAGE                   COMMAND                  CREATED             STATUS              PORTS               NAMES
b682d21563dd        nginx                   "nginx -g 'daemon of…"   6 minutes ago       Up 6 minutes                            k8s_static-web_static-web-k8s-2_default_a850d62a685464dd2c0bdb31222085c9_0

3.查看Pod创建情况

# kubectl get pod
NAME               READY   STATUS    RESTARTS   AGE
static-web-k8s-2   1/1     Running   0          7m14s

4.尝试删除该静态Pod

[root@K8S-1 chapter1]# kubectl delete pod static-web-k8s-2
pod "static-web-k8s-2" deleted
[root@K8S-1 chapter1]# kubectl get pod
NAME               READY   STATUS    RESTARTS   AGE
static-web-k8s-2   0/1     Pending   0          1s
[root@K8S-1 chapter1]# kubectl get pod
NAME               READY   STATUS    RESTARTS   AGE
static-web-k8s-2   0/1     Pending   0          4s
[root@K8S-1 chapter1]# kubectl get pod
NAME               READY   STATUS    RESTARTS   AGE
static-web-k8s-2   1/1     Running   0          6s

5.删除/etc/kubernetes/manifests下的yaml文件

# kubectl get pod
No resources found.

二、Pod容器共享Volume

同一个Pod里面的多个容器能够共享Pod级别的存储卷Volume，Volume可以被定义为各种类型，多个容器各自进行挂载操作，进行数据共享。

配置yaml文件

apiVersion: v1
kind: Pod
metadata:
  name: volume-pod
spec:
  containers:
  - name: tomcat
    image: tomcat
    ports:
    - containerPort: 8080
    volumeMounts:
    - name: app-logs
      mountPath: /usr/local/tomcat/logs
  - name: busybox
    image: busybox
    command: ["sh", "-c", "tail -f /logs/catalina*.log"]
    volumeMounts:
    - name: app-logs
      mountPath: /logs
  volumes:
  - name: app-logs
    emptyDir: {}

创建pod

# kubectl apply -f pod-volume-logs.yaml 
pod/volume-pod created

# kubectl get pod
NAME         READY   STATUS    RESTARTS   AGE
volume-pod   2/2     Running   0          4m42s

pod中有两个容器，一个是tomcat用于写入日志文件，另一个busybox用于读日志文件

# kubectl logs volume-pod -c busybox
31-May-2019 16:54:39.573 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web application directory [/usr/local/tomcat/webapps/docs] has finished in [26] ms
31-May-2019 16:54:39.573 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory [/usr/local/tomcat/webapps/examples]
31-May-2019 16:54:39.954 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web application directory [/usr/local/tomcat/webapps/examples] has finished in [380] ms
31-May-2019 16:54:39.954 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory [/usr/local/tomcat/webapps/host-manager]
31-May-2019 16:54:39.992 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web application directory [/usr/local/tomcat/webapps/host-manager] has finished in [38] ms
31-May-2019 16:54:39.992 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory [/usr/local/tomcat/webapps/manager]
31-May-2019 16:54:40.025 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web application directory [/usr/local/tomcat/webapps/manager] has finished in [32] ms
31-May-2019 16:54:40.031 INFO [main] org.apache.coyote.AbstractProtocol.start Starting ProtocolHandler ["http-nio-8080"]
31-May-2019 16:54:40.045 INFO [main] org.apache.coyote.AbstractProtocol.start Starting ProtocolHandler ["ajp-nio-8009"]
31-May-2019 16:54:40.093 INFO [main] org.apache.catalina.startup.Catalina.start Server startup in 992 ms

# kubectl exec -it volume-pod -c tomcat -- ls /usr/local/tomcat/logs
catalina.2019-05-31.log      localhost_access_log.2019-05-31.txt
host-manager.2019-05-31.log  manager.2019-05-31.log
localhost.2019-05-31.log
# kubectl exec -it volume-pod -c tomcat -- tail /usr/local/tomcat/logs/catalina.2019-05-31.log
31-May-2019 16:54:39.573 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web application directory [/usr/local/tomcat/webapps/docs] has finished in [26] ms
31-May-2019 16:54:39.573 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory [/usr/local/tomcat/webapps/examples]
31-May-2019 16:54:39.954 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web application directory [/usr/local/tomcat/webapps/examples] has finished in [380] ms
31-May-2019 16:54:39.954 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory [/usr/local/tomcat/webapps/host-manager]
31-May-2019 16:54:39.992 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web application directory [/usr/local/tomcat/webapps/host-manager] has finished in [38] ms
31-May-2019 16:54:39.992 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory [/usr/local/tomcat/webapps/manager]
31-May-2019 16:54:40.025 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web application directory [/usr/local/tomcat/webapps/manager] has finished in [32] ms
31-May-2019 16:54:40.031 INFO [main] org.apache.coyote.AbstractProtocol.start Starting ProtocolHandler ["http-nio-8080"]
31-May-2019 16:54:40.045 INFO [main] org.apache.coyote.AbstractProtocol.start Starting ProtocolHandler ["ajp-nio-8009"]
31-May-2019 16:54:40.093 INFO [main] org.apache.catalina.startup.Catalina.start Server startup in 992 ms

三、Pod的应用配置管理ConfigMap

ConfigMap提供了将配置数据注入容器的机制，同时保持容器不受kubernetes的影响。ConfigMap有以下几种使用方式：
1.生成容器内的环境变量
2.设置容器内的命令行参数
3.以Volume的形式挂载为容器内部的文件或目录
ConfigMap可以通过yaml配置文件或直接使用kubectl create configmap命令行方式来创建

1.从目录创建

当--from-file指向一个目录，该目录中的文件名将直接用于填充ConfigMap中的key，key的值是这个文件的内容

# ls
my.cnf  web.xml

# cat my.cnf 
general_log=on
slow_query_log=on
long_query_time = 4
log_bin=on
log-bin=/usr/local/mysql/data/bin.log

# cat web.xml 
<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
                      http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
  version="3.0">
    <distributable/>
......
......
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
</web-app>

# kubectl create configmap test1 --from-file configfiles
configmap/test1 created

# kubectl describe configmap test1
Name:         test1
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
my.cnf:
----
general_log=on
slow_query_log=on
long_query_time = 4
log_bin=on
log-bin=/usr/local/mysql/data/bin.log

web.xml:
----
<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
                      http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
  version="3.0">
    <distributable/>
......
......
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
</web-app>

Events:  <none>

2.从文件创建

通过--from-file从文件创建，可以指定key的名称，也可以在一个命令行中创建包含多个key的ConfigMap

# kubectl create configmap test2 --from-file=my.cnf --from-file=web.xml
configmap/test2 created

# kubectl get configmap test2 -o yaml
apiVersion: v1
data:
  my.cnf: |
    general_log=on
    slow_query_log=on
    long_query_time = 4
    log_bin=on
    log-bin=/usr/local/mysql/data/bin.log
  web.xml: |
    <?xml version="1.0" encoding="ISO-8859-1"?>
    <web-app xmlns="http://java.sun.com/xml/ns/javaee"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
                          http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
      version="3.0">
        <distributable/>
    ......
    ......
        <welcome-file-list>
            <welcome-file>index.html</welcome-file>
            <welcome-file>index.htm</welcome-file>
            <welcome-file>index.jsp</welcome-file>
        </welcome-file-list>
    </web-app>
kind: ConfigMap
metadata:
  creationTimestamp: "2019-06-01T10:49:09Z"
  name: test2
  namespace: default
  resourceVersion: "329312"
  selfLink: /api/v1/namespaces/default/configmaps/test2
  uid: e260c9aa-845a-11e9-a2f2-00505694834d

也可不以文件文件名为key，通过key=value为每个文件重新设置key

# kubectl create configmap test3 --from-file=the.cnf=my.cnf 
configmap/test3 created

# kubectl get configmap test3 -o yaml
apiVersion: v1
data:
  the.cnf: |
    general_log=on
    slow_query_log=on
    long_query_time = 4
    log_bin=on
    log-bin=/usr/local/mysql/data/bin.log
kind: ConfigMap
metadata:
  creationTimestamp: "2019-06-01T10:53:41Z"
  name: test3
  namespace: default
  resourceVersion: "329706"
  selfLink: /api/v1/namespaces/default/configmaps/test3
  uid: 849a9eab-845b-11e9-a2f2-00505694834d

3.使用--from-literal直接在命令行中指定key，value

# kubectl create configmap test4 --from-literal=type=null --from-literal=dir=/var/log
configmap/test4 created

# kubectl describe configmap test4
Name:         test4
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
dir:
----
/var/log
type:
----
null
Events:  <none>

4.通过环境变量方式使用ConfigMap

# cat cm-app.yaml 
apiVersion: v1
kind: ConfigMap
metadata:
  name: cm-app
data:
  apploglevel: info
  appdatadir: /var/data
# cat cm-env.yaml 
apiVersion: v1
kind: ConfigMap
metadata:
  name: cm-env
data:
  APPTYPE: char
# kubectl create -f cm-app.yaml -f cm-env.yaml 
configmap/cm-app created
configmap/cm-env created

# cat cm-test.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: cm-test
spec:
  containers:
    - name: test-container
      image: busybox
      command: [ "/bin/sh", "-c", "env | grep APP" ]
      env:
        - name: APPLOGLEVEL
          valueFrom:
            configMapKeyRef:
              name: cm-app
              key: apploglevel
        - name: APPDATADIR
          valueFrom:
            configMapKeyRef:
              name: cm-app
              key: appdatadir
      envFrom:
        - configMapRef:
            name: cm-env
  restartPolicy: Never

# kubectl create -f cm-test.yaml 
pod/cm-test created
# kubectl logs cm-test
APPDATADIR=/var/data
APPTYPE=char
APPLOGLEVEL=info

上面使用了两种定义环境变量的方式：env和envFrom，使用envFrom会在Pod环境中将ConfigMap中所有定义的key=value自动生成为环境变量

5.通过volumeMount使用ConfigMap

# cat cm-app.yaml 
apiVersion: v1
kind: ConfigMap
metadata:
  name: cm-app
data:
  apploglevel: info
  appdatadir: /var/data

# cat cm-volume.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: cm-volume
spec:
  containers:
    - name: cm-volume
      image: busybox
      command: [ "/bin/sh","-c","cat /etc/config/path/key.app" ]
      volumeMounts:
      - name: volume-test             #引用volume的名称
        mountPath: /etc/config       #挂载到容器内的目录
  volumes:
    - name: volume-test               #定义volume的名称
      configMap:
        name: cm-app                    #使用的ConfigMap
        items:
        - key: apploglevel
          path: path/key.app           #value将写入key.app文件中
  restartPolicy: Never

创建完ConfigMap和Pod后，该Pod会输出：

# kubectl logs cm-volume
info

如果在引用ConfigMap时不指定items，则使用volumeMounts方式在容器内的目录下为每个items都生成一个以key开头的文件。

使用ConfigMap的限制条件：

ConfigMap必须在Pod之前创建

ConfigMap受Namespace限制，只有处于相同Namespace中的Pod才能引用

静态Pod无法引用ConfigMap

四、获取容器内Pod信息 Downward API

      env:
        - name: MY_NODE_NAME
          valueFrom:
            fieldRef:
              fieldPath: spec.nodeName
        - name: MY_POD_NAME
          valueFrom:
            fieldRef:
              fieldPath: metadata.name
        - name: MY_POD_NAMESPACE
          valueFrom:
            fieldRef:
              fieldPath: metadata.namespace
        - name: MY_POD_IP
          valueFrom:
            fieldRef:
              fieldPath: status.podIP
        - name: MY_POD_SERVICE_ACCOUNT
          valueFrom:
            fieldRef:
              fieldPath: spec.serviceAccountName

五、Pod状态和健康检查

1.Pod的状态

挂起（Pending）：API Server已经创建该Pod，但在Pod内还有一个或多个容器的镜像没有创建，包括正在下载的过程

运行中（Running）：Pod内所有容器均已创建，且至少有一个容器处于运行、启动、重启状态

成功（Succeeded）：Pod 中的所有容器都被成功执行后退出，并且不会再重启

失败（Failed）：Pod 中的所有容器都已终止了，但至少有一个容器退出为失败状态，也就是说，容器以非0状态退出或者被系统终止。

未知（Unknown）：因为某些原因无法取得 Pod 的状态，通常是因为与 Pod 所在主机通信失败

2.Pod的重启策略

Pod的重启策略RestartPolicy可能的值为 Always、OnFailure 和 Never，默认为 Always

Always：当容器失效时，由kubelet自动重启

OnFailure：当容器终止运行且退出码不为0时，由kubelet自动重启

Never：不论容器运行状态如何都不会重启

3.Pod健康检查

LivenessProbe：存活性探测
ReadnessProbe：就绪性探测
其存活性探测的方法可配置以下三种实现方式：

ExecAction：在容器内执行指定命令。如果命令退出时返回码为 0 则表明容器健康

TCPSocketAction：对指定端口上的容器的 IP 地址进行 TCP 检查。如果能够建立连接，则表明容器健康。

HTTPGetAction：对指定的端口和路径上的容器的 IP 地址执行 HTTP Get 请求。如果响应的状态码大于等于200 且小于 400则表明容器健康

设置exec探针

# cat pod-exec.yaml 
apiVersion: v1
kind: Pod
metadata:
  labels:
    test: liveness
  name: liveness-exec
spec:
  containers:
  - name: liveness
    image: busybox
    args:
    - /bin/sh
    - -c
    - echo ok > /tmp/health; sleep 10; rm -rf /tmp/health; sleep 600
    livenessProbe:
      exec:
        command:
        - cat
        - /tmp/health
      initialDelaySeconds: 15
      timeoutSeconds: 1

查看Pod事件

# kubectl describe pod liveness-exec

  Type     Reason     Age                  From               Message
  ----     ------     ----                 ----               -------
  Normal   Scheduled  4m10s                default-scheduler  Successfully assigned default/liveness-exec to k8s-2
  Normal   Pulled     77s (x3 over 3m59s)  kubelet, k8s-2     Successfully pulled image "busybox"
  Normal   Created    76s (x3 over 3m59s)  kubelet, k8s-2     Created container liveness
  Normal   Started    76s (x3 over 3m59s)  kubelet, k8s-2     Started container liveness
  Warning  Unhealthy  35s (x9 over 3m35s)  kubelet, k8s-2     Liveness probe failed: cat: can't open '/tmp/health': No such file or directory
  Normal   Killing    35s (x3 over 3m15s)  kubelet, k8s-2     Container liveness failed liveness probe, will be restarted
  Normal   Pulling    5s (x4 over 4m10s)   kubelet, k8s-2     Pulling image "busybox"

# kubectl get pod
NAME            READY   STATUS    RESTARTS   AGE
liveness-exec   1/1     Running   3          4m50s
#此时restart值为3

设置tcp探针

apiVersion: v1
kind: Pod
metadata:
  name: pod-with-healthcheck
spec:
  containers:
  - name: nginx
    image: nginx
    ports:
    - containerPort: 80
    livenessProbe:
      tcpSocket:
        port: 80
      initialDelaySeconds: 30
      timeoutSeconds: 1

设置http探针

apiVersion: v1
kind: Pod
metadata:
  name: pod-with-healthcheck
spec:
  containers:
  - name: nginx
    image: nginx
    ports:
    - containerPort: 80
    livenessProbe:
      httpGet:
        path: /_status/healthz
        port: 80
      initialDelaySeconds: 30
      timeoutSeconds: 1

  Type     Reason     Age                  From               Message
  ----     ------     ----                 ----               -------
  Normal   Scheduled  2m37s                default-scheduler  Successfully assigned default/liveness-http to k8s-2
  Warning  Unhealthy  14s (x6 over 104s)   kubelet, k8s-2     Liveness probe failed: HTTP probe failed with statuscode: 404
  Normal   Killing    14s (x2 over 84s)    kubelet, k8s-2     Container nginx failed liveness probe, will be restarted
  Normal   Pulling    13s (x3 over 2m36s)  kubelet, k8s-2     Pulling image "nginx"
  Normal   Pulled     5s (x3 over 2m19s)   kubelet, k8s-2     Successfully pulled image "nginx"
  Normal   Created    5s (x3 over 2m18s)   kubelet, k8s-2     Created container nginx
  Normal   Started    5s (x3 over 2m18s)   kubelet, k8s-2     Started container nginx

# kubectl get pod
NAME            READY   STATUS    RESTARTS   AGE
liveness-http   1/1     Running   2          3m31s

对于每种探测方式，需要设置initialDelaySeconds和timeoutSeconds参数，分别表示首次检查等待时间以及超时时间。

K8S实践Ⅱ（Pod基本用法）

一、Static Pod

二、Pod容器共享Volume

三、Pod的应用配置管理ConfigMap

四、获取容器内Pod信息 Downward API

五、Pod状态和健康检查

Window 安装 Python 失败 0x80070643，发生严重错误

《最新出炉》系列入门篇-Python+Playwright自动化测试-41-录制视频

K8S實踐Ⅰ（集羣安裝配置）

K8S實踐Ⅱ（Pod基本用法）

K8S實踐Ⅺ （Rook）

K8S實踐Ⅹ（Helm）

K8S實踐Ⅸ（集羣監控）

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