Kubernetes(k8s)的Pod控制器Deployment详细讲解

1. 概述

Deployment控制器并不直接管理Pod，而是通过管理ReplicaSet来间接管理Pod。所以Deployment的功能比ReplicaSet强大。支持扩缩容、 发布的停止和继续、镜像版本滚动变更、ReplicaSet版本回退

Deployment的资源清单文件模板

apiVersion: apps/v1                    
kind: Deployment                      
metadata:                             
  name: pod-controller                # deploy名称 
  namespace: dev                      # deploy所属命名空间 
  labels:                             # 给deploy打标签 
    controller: deploy 
spec:                                
  replicas: 3                         # pod副本数量。默认是1
  revisionHistoryLimit: 3             # 保留ReplicaSet历史版本数量，默认为10 
  paused: false                       # 暂停部署，默认是false 
  progressDeadlineSeconds: 600        # 部署超时时间(s)，默认是600 
  strategy:                           # Pod更新策略，默认是RollingUpdate 
    type: RollingUpdate               # 滚动更新策略。另一种是Recreate，其没有子属性配置参数 
    rollingUpdate:                    # 当type为RollingUpdate的时候生效，为其配置参数
      maxSurge: 25%                   # 升级过程中可以超过期望的Pod的最大数量，可以为百分比，也可以为整数。默认是25%
      maxUnavailable: 25%             # 升级过程中最大不可用状态的Pod数量，可以为百分比，也可以为整数。默认是25% 
  selector:                           # 选择器，通过该控制器管理哪些pod 
    matchLabels:                      # Labels匹配规则。和matchExpressions类似
      app: nginx-pod 
    matchExpressions:                 # Expressions匹配规则。和matchLabels类似 
      - {key: app, operator: In, values: ["nginx-pod"]} 
  template:                           # pod副本创建模板。属性和Pod的属性一样
    metadata: 
      labels: 
        app: nginx-pod 
    spec: 
      containers: 
      - name: nginx 
        image: nginx:latest
        ports: 
        - name: nginx-port
          containerPort: 80
          protocol: TCP

2. 创建Deployment

新建pod-controller.yaml，内容如下。并运行deployment

[root@k8s-master ~]# cat pod-controller.yaml 
apiVersion: apps/v1
kind: Deployment
metadata:
  name: pod-controller
  namespace: dev
  labels:
    controller: deploy 
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx-pod
  template:
    metadata:
      labels:
        app: nginx-pod
    spec:
      containers:
        - name: nginx
          image: nginx:latest
          ports:
            - name: nginx-port
              containerPort: 80
              protocol: TCP
[root@k8s-master ~]# 
[root@k8s-master ~]# kubectl apply -f pod-controller.yaml 
deployment.apps/pod-controller created
[root@k8s-master ~]#

2.1 查看Deployment

UP-TO-DATE表示更新时最新版本的Pod数量

[root@k8s-master ~]# kubectl get deploy pod-controller -n dev
NAME             READY   UP-TO-DATE   AVAILABLE   AGE
pod-controller   3/3     3            3           2m13s
[root@k8s-master ~]# 

3. 扩缩容

方式一：使用以下命令，编辑文本内容：spec: replicas: 4

[root@k8s-master ~]# kubectl edit deploy pod-controller -n dev
deployment.apps/pod-controller edited
[root@k8s-master ~]#

方式二：直接使用命令

[root@k8s-master ~]# kubectl scale deploy pod-controller --replicas=2 -n dev
deployment.apps/pod-controller scaled
[root@k8s-master ~]#

4. 镜像版本变更

4.1 概述

新的Pod替代旧的Pod支持两种镜像更新策略：

• 重建更新Recreate：在创建出新的Pod之前会先杀掉所有已经存在的Pod
• 滚动更新RollingUpdate(默认)：先杀死一部分，再启动一部分。再杀死一部分，再启动一部分。如此循环。在更新过程中，存在两个版本的Pod

通过strategy属性进行配置

4.2 重建更新

在spec属性下面新增strategy属性，最终的pod-controller.yaml内容如下。然后使yaml配置文件生效

[root@k8s-master ~]# cat pod-controller.yaml 
apiVersion: apps/v1
kind: Deployment
metadata:
  name: pod-controller
  namespace: dev
  labels:
    controller: deploy 
spec:
  replicas: 3
  strategy:
    type: Recreate
  selector:
    matchLabels:
      app: nginx-pod
  template:
    metadata:
      labels:
        app: nginx-pod
    spec:
      containers:
        - name: nginx
          image: nginx:latest
          ports:
            - name: nginx-port
              containerPort: 80
              protocol: TCP
[root@k8s-master ~]#
[root@k8s-master ~]# kubectl apply -f pod-controller.yaml 
deployment.apps/pod-controller configured
[root@k8s-master ~]# 

更新镜像版本

[root@k8s-master ~]# kubectl set image deploy pod-controller nginx=nginx:1.21.6 -n dev
deployment.apps/pod-controller image updated
[root@k8s-master ~]# 

持续查看Pod版本变更情况

[root@k8s-master ~]# kubectl get pod -n dev -w
NAME                              READY   STATUS              RESTARTS   AGE
pod-controller-5bdd9d95bf-9lljw   0/1     ContainerCreating   0          11s
pod-controller-5bdd9d95bf-9nph6   0/1     ContainerCreating   0          11s
pod-controller-5bdd9d95bf-z7n5c   0/1     ContainerCreating   0          11s
pod-controller-5bdd9d95bf-9nph6   1/1     Running             0          95s
pod-controller-5bdd9d95bf-z7n5c   1/1     Running             0          106s
pod-controller-5bdd9d95bf-9lljw   1/1     Running             0          113s

4.3 滚动更新

在spec属性下面新增strategy属性，最终的pod-controller.yaml内容如下。然后使yaml配置文件生效

[root@k8s-master ~]# cat pod-controller.yaml 
apiVersion: apps/v1
kind: Deployment
metadata:
  name: pod-controller
  namespace: dev
  labels:
    controller: deploy 
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 25%
      maxSurge: 25%
  selector:
    matchLabels:
      app: nginx-pod
  template:
    metadata:
      labels:
        app: nginx-pod
    spec:
      containers:
        - name: nginx
          image: nginx:latest
          ports:
            - name: nginx-port
              containerPort: 80
              protocol: TCP
[root@k8s-master ~]# 
[root@k8s-master ~]# kubectl apply -f pod-controller.yaml 
deployment.apps/pod-controller configured
[root@k8s-master ~]# 

更新镜像版本

[root@k8s-master ~]# kubectl set image deploy pod-controller nginx=nginx:1.21 -n dev
deployment.apps/pod-controller image updated
[root@k8s-master ~]# 

持续查看Pod版本变更情况。可以看到是滚动更新的

[root@k8s-master ~]# kubectl get pod -n dev -w
NAME                              READY   STATUS              RESTARTS   AGE
pod-controller-5b899bbdb4-2w59n   1/1     Running             0          53s
pod-controller-5b899bbdb4-9bfm9   1/1     Running             0          19s
pod-controller-5b899bbdb4-fn5ck   1/1     Running             0          37s
pod-controller-bcc5899bf-mcfnh    0/1     ContainerCreating   0          2s
pod-controller-bcc5899bf-mcfnh    1/1     Running             0          16s
pod-controller-5b899bbdb4-9bfm9   1/1     Terminating         0          33s
pod-controller-bcc5899bf-w6vfb    0/1     Pending             0          0s
pod-controller-bcc5899bf-w6vfb    0/1     ContainerCreating   0          1s
pod-controller-bcc5899bf-w6vfb    1/1     Running             0          17s
pod-controller-5b899bbdb4-fn5ck   1/1     Terminating         0          68s
pod-controller-bcc5899bf-zkfkb    0/1     Pending             0          0s
pod-controller-bcc5899bf-zkfkb    0/1     ContainerCreating   0          0s
pod-controller-bcc5899bf-zkfkb    1/1     Running             0          16s
pod-controller-5b899bbdb4-2w59n   1/1     Terminating         0          100s

查看ReplicaSet情况。可以看到原来的rs依旧存在，只是Pod的数量变为0。这就是Deployment可以进行版本回退的原因

[root@k8s-master ~]# kubectl get rs -n dev
NAME                        DESIRED   CURRENT   READY   AGE
pod-controller-5b899bbdb4   0         0         0       18m
pod-controller-5bdd9d95bf   0         0         0       13m
pod-controller-bcc5899bf    3         3         3       5m54s
[root@k8s-master ~]#

5. 版本回退(镜像版本变更回退)

Deployment支持版本升级过程中的暂停、继续功能，以及版本回退等功能

版本回退的命令语法如下所示：

[root@k8s-master ~]# kubetl rollout 参数 deploy deploy-name

支持的参数如下：

• status：显示当前升级的状态
• history：显示升级历史记录。kubectl apply -f deploy.yaml需要加上--record参数，CHANGE-CAUSE字段才有数据
• pause：暂停版本升级过程
• resume：继续已经暂停的版本升级过程
• restart：重启版本升级过程
• undo：回滚到上一个版本(可以使用–to-revision参数回滚到指定的版本，可通过history进行查看版本号)

5.1 查看当前升级版本的状态

[root@k8s-master ~]# kubectl rollout status deployment pod-controller -n dev
deployment "pod-controller" successfully rolled out
[root@k8s-master ~]# 

5.2 查看升级历史记录：

[root@k8s-master ~]# kubectl rollout history deployment pod-controller -n dev
deployment.apps/pod-controller 
REVISION  CHANGE-CAUSE
1         
2         
3         

[root@k8s-master ~]# 

5.3 版本回退：

回退到最老的一个版本。回退的时候将当前版本的Pod数量降为0，然后将回退版本的Pod数量提升为目标数量

[root@k8s-master ~]# kubectl rollout undo deployment pod-controller --to-revision=1 -n dev
deployment.apps/pod-controller rolled back
[root@k8s-master ~]# 
[root@k8s-master ~]# kubectl get deployment pod-controller -n dev -o wide
NAME             READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES         SELECTOR
pod-controller   3/3     3            3           43m   nginx        nginx:latest   app=nginx-pod
[root@k8s-master ~]# 
[root@k8s-master ~]# kubectl get rs -n dev
NAME                        DESIRED   CURRENT   READY   AGE
pod-controller-5b899bbdb4   3         3         3       43m
pod-controller-5bdd9d95bf   0         0         0       38m
pod-controller-bcc5899bf    0         0         0       31m
[root@k8s-master ~]# 

6 金丝雀发布/灰度发布

Deployment支持更新过程中的控制，如暂停版本变更(pause)或继续版本变更操作(resume)

暂停版本变更操作，可以检查变更后的Pod能否正常提供服务。如不能则可以进行回退。如可以则继续版本变更操作

变更Deployment的版本，并配置暂停Deployment

[root@k8s-master ~]# kubectl get rs -n dev
NAME                        DESIRED   CURRENT   READY   AGE
pod-controller-5b899bbdb4   3         3         3       56m
pod-controller-5bdd9d95bf   0         0         0       51m
pod-controller-bcc5899bf    0         0         0       43m
[root@k8s-master ~]# 
[root@k8s-master ~]# kubectl set image deployment pod-controller nginx=nginx:1.20.2 -n dev && kubectl rollout pause deployment pod-controller -n dev
deployment.apps/pod-controller image updated
deployment.apps/pod-controller paused
[root@k8s-master ~]# 
[root@k8s-master ~]# kubectl get rs -n dev
NAME                        DESIRED   CURRENT   READY   AGE
pod-controller-59d5b49ffd   1         1         1       54s
pod-controller-5b899bbdb4   3         3         3       56m
pod-controller-5bdd9d95bf   0         0         0       51m
pod-controller-bcc5899bf    0         0         0       43m
[root@k8s-master ~]# 
[root@k8s-master ~]# kubectl get pod -n dev
NAME                              READY   STATUS    RESTARTS   AGE
pod-controller-59d5b49ffd-tvqlt   1/1     Running   0          4m11s
pod-controller-5b899bbdb4-bvfjn   1/1     Running   0          18m
pod-controller-5b899bbdb4-vmbhb   1/1     Running   0          18m
pod-controller-5b899bbdb4-xcxxs   1/1     Running   0          19m
[root@k8s-master ~]# 

查看版本变更状态

[root@k8s-master ~]# kubectl rollout status deployment pod-controller -n dev
Waiting for deployment "pod-controller" rollout to finish: 1 out of 3 new replicas have been updated...

确保变更后的Pod没问题之后，继续更新

[root@k8s-master ~]# kubectl rollout resume deployment pod-controller -n dev
deployment.apps/pod-controller resumed
[root@k8s-master ~]#

7. 删除Deployment

Deployment管理的ReplicaSet和Pod也会一起被删除

[root@k8s-master ~]# kubectl delete -f pod-controller.yaml 
deployment.apps "pod-controller" deleted
[root@k8s-master ~]#