k8s 学习笔记：2 测试一个容器应用

作者: 董泽润 | 来源:发表于2019-02-28 14:24 被阅读4次

k8s 学习笔记：2 测试一个容器应用
k8s学习笔记（二）k8s的结构和功能
新手搭建 kubernetes 测试环境
Kubernetes
高阶测试开发必备技能: k8s入门
深入剖析k8s中的存储
通过K8S Ingress Controller来实现应用的流量
ChartCenter ——为您的K8s之旅保驾护航
深入剖析容器的发展历程及底层原理
如何基于 k8s 开发高可靠服务？容器云牛人有话说

上一节搭建了 k8s 集群环境，两台机器，一台 master, 一个 worker. 就像一个机器的池子一样，我的应用以 pod 的形式跑在某台机器上，这个应用所需要 cpu, memory 等资源都会由 k8s 来调度

启动两个 nginx 应用

k8s 描述一个 pod 都会用 yaml 配置，而不是裸用 docker run 去跑

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  selector:
    matchLabels:
      app: nginx
  replicas: 2
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.7.9
        ports:
        - containerPort: 80

上面定义一个 nginx-deployment.yaml, 其中 replicas: 2 表示启动两个的意思，其它暂时不管了，也看不懂

kubectl create -f nginx-deployment.yaml

然后执行查看命令

kubectl get pods --all-namespaces
或是
kubectl get pods -l app=nginx

NAME                                READY   STATUS    RESTARTS   AGE
nginx-deployment-76bf4969df-t5cj4   1/1     Running   0          36m
nginx-deployment-76bf4969df-zc8pc   1/1     Running   0          36m

可以看到两个 nginx 的 pod 正在运行

查看 nginx pod

此时己经运行了两个 nginx pod, 查看详细信息

kubectl describe pod nginx-deployment-76bf4969df-t5cj4

Name:               nginx-deployment-76bf4969df-t5cj4
Namespace:          default
Priority:           0
PriorityClassName:  <none>
Node:               jjh-fusion-sre-backup3/10.20.76.23
Start Time:         Wed, 27 Feb 2019 14:41:29 +0800
Labels:             app=nginx
                    pod-template-hash=76bf4969df
Annotations:        <none>
Status:             Running
IP:                 10.44.0.9
Controlled By:      ReplicaSet/nginx-deployment-76bf4969df
Containers:
  nginx:
    Container ID:   docker://5fc7612b01cb8f6148c4306db73565a30989bda932ec13aa82d07507a96ae33e
    Image:          nginx:1.7.9
    Image ID:       docker-pullable://nginx@sha256:e3456c851a152494c3e4ff5fcc26f240206abac0c9d794affb40e0714846c451
    Port:           80/TCP
    Host Port:      0/TCP
    State:          Running
      Started:      Wed, 27 Feb 2019 14:41:54 +0800
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-r78v4 (ro)
Conditions:
  Type              Status
  Initialized       True
  Ready             True
  ContainersReady   True
  PodScheduled      True
Volumes:
  default-token-r78v4:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-r78v4
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
  Type    Reason     Age   From                             Message
  ----    ------     ----  ----                             -------
  Normal  Scheduled  40m   default-scheduler                Successfully assigned default/nginx-deployment-76bf4969df-t5cj4 to jjh-fusion-sre-backup3
  Normal  Pulling    40m   kubelet, jjh-fusion-sre-backup3  pulling image "nginx:1.7.9"
  Normal  Pulled     40m   kubelet, jjh-fusion-sre-backup3  Successfully pulled image "nginx:1.7.9"
  Normal  Created    40m   kubelet, jjh-fusion-sre-backup3  Created container
  Normal  Started    40m   kubelet, jjh-fusion-sre-backup3  Started container

可以看到分配的 ip 是 10.44.0.9，那么直接访问就可以了

curl http://10.44.0.9

下面还有镜像的详细信息，运行在 worker 机器上面等等。一般来说，对一个应用做的所有操作，都会返映在 describe 信息里面

升级 nginx

修改 nginx-deployment.yaml 文件，将 nginx 版本变成 1.8

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  selector:
    matchLabels:
      app: nginx
  replicas: 2
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.8
        ports:
        - containerPort: 80

执行以下命令应用

kubectl apply -f nginx-deployment.yaml

查看当前 pods

# kubectl get pods -l app=nginx
NAME                                READY   STATUS    RESTARTS   AGE
nginx-deployment-5896fbb489-8zjdg   1/1     Running   0          18s
nginx-deployment-5896fbb489-dczqn   1/1     Running   0          37s

查看详细某一个 pod

# kubectl describe pod nginx-deployment-5896fbb489-8zjdg
Name:               nginx-deployment-5896fbb489-8zjdg
Namespace:          default
Priority:           0
PriorityClassName:  <none>
Node:               jjh-fusion-sre-backup3/10.20.76.23
Start Time:         Wed, 27 Feb 2019 15:32:06 +0800
Labels:             app=nginx
                    pod-template-hash=5896fbb489
Annotations:        <none>
Status:             Running
IP:                 10.44.0.9
Controlled By:      ReplicaSet/nginx-deployment-5896fbb489
Containers:
  nginx:
    Container ID:   docker://dfeb8fed612173c94d0c48547d068025fa8e76d4c6e6fa39e24b9ceeae58de0d
    Image:          nginx:1.8
    Image ID:       docker-pullable://nginx@sha256:c97ee70c4048fe79765f7c2ec0931957c2898f47400128f4f3640d0ae5d60d10
    Port:           80/TCP
    Host Port:      0/TCP
    State:          Running
      Started:      Wed, 27 Feb 2019 15:32:08 +0800
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-r78v4 (ro)
Conditions:
  Type              Status
  Initialized       True
  Ready             True
  ContainersReady   True
  PodScheduled      True
Volumes:
  default-token-r78v4:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-r78v4
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
  Type    Reason     Age   From                             Message
  ----    ------     ----  ----                             -------
  Normal  Scheduled  57s   default-scheduler                Successfully assigned default/nginx-deployment-5896fbb489-8zjdg to jjh-fusion-sre-backup3
  Normal  Pulled     55s   kubelet, jjh-fusion-sre-backup3  Container image "nginx:1.8" already present on machine
  Normal  Created    55s   kubelet, jjh-fusion-sre-backup3  Created container
  Normal  Started    55s   kubelet, jjh-fusion-sre-backup3  Started container

可以看到，己经变成了 nginx 1.8 的版本

挂载 volume 卷

现在对这个 nginx pod 增加 volume，挂载点是 /usr/share/nginx/html

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  selector:
    matchLabels:
      app: nginx
  replicas: 2
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.8
        ports:
        - containerPort: 80
        volumeMounts:
        - mountPath: "/usr/share/nginx/html"
          name: nginx-vol
      volumes:
      - name: nginx-vol
        emptyDir: {}

挂载的卷是 nginx-vol，emptyDir 表示在宿主机临时生成一个目录。重新应用这个 yaml

kubectl apply -f nginx-deployment.yaml

然后立马查看 pods 状态，会发现在滚动升机重启

# kubectl get pods
NAME                                READY   STATUS        RESTARTS   AGE
nginx-deployment-5896fbb489-dczqn   0/1     Terminating   0          20h
nginx-deployment-58bbdfd545-4rg8s   1/1     Running       0          10s
nginx-deployment-58bbdfd545-69kp5   1/1     Running       0          12s

通过 describe 查看其中一个 pod 详情

# kubectl describe pod nginx-deployment-58bbdfd545-4rg8s
Name:               nginx-deployment-58bbdfd545-4rg8s
Namespace:          default
Priority:           0
PriorityClassName:  <none>
Node:               jjh-fusion-sre-backup3/10.20.76.23
Start Time:         Thu, 28 Feb 2019 11:50:21 +0800
Labels:             app=nginx
                    pod-template-hash=58bbdfd545
Annotations:        <none>
Status:             Running
IP:                 10.44.0.9
Controlled By:      ReplicaSet/nginx-deployment-58bbdfd545
Containers:
  nginx:
    Container ID:   docker://fc26530dbc54377c7034700777498d6815ca8d578806c03c4175a33388cd3f9b
    Image:          nginx:1.8
    Image ID:       docker-pullable://nginx@sha256:c97ee70c4048fe79765f7c2ec0931957c2898f47400128f4f3640d0ae5d60d10
    Port:           80/TCP
    Host Port:      0/TCP
    State:          Running
      Started:      Thu, 28 Feb 2019 11:55:49 +0800
    Last State:     Terminated
      Reason:       Completed
      Exit Code:    0
      Started:      Thu, 28 Feb 2019 11:50:23 +0800
      Finished:     Thu, 28 Feb 2019 11:55:47 +0800
    Ready:          True
    Restart Count:  1
    Environment:    <none>
    Mounts:
      /usr/share/nginx/html from nginx-vol (rw)
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-r78v4 (ro)

可以看到 Mounts 挂载信息，此时我们访问这个 nginx 会报错

# curl http://10.44.0.9
<html>
<head><title>403 Forbidden</title></head>
<body bgcolor="white">
<center><h1>403 Forbidden</h1></center>
<hr><center>nginx/1.8.1</center>
</body>
</html>

因为我们此时目录虽然挂载了，但是是空的，所以需要进入容器中写一个 html，进到 node 机器上 docer ps 查看 nginx 容器的 ID

docker exec -it e3c3007ad67a /bin/bash

也可以直接用 kubectl 命令来操作，这样就完全屏敝了底层 docker

kubectl exec -it nginx-deployment-58bbdfd545-4rg8s -- /bin/bash

然后随变写一个 hello world

echo "hello world" >> /usr/share/nginx/html/index.html

此时再访问就会看到 hello world

小结

至此，己经成功用 k8s 集群创建了第一个应用，还有很多概念与功能不太熟悉。万事开头难，搞起~~~

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