k8s之deployment详解

Deployment介绍

为了更好地解决服务编排的问题，k8s在V1.2版本开始，引入了deployment控制器，值得一提的是，这种控制器并不直接管理pod，

而是通过管理replicaset来间接管理pod，即：deployment管理replicaset，replicaset管理pod。所以deployment比replicaset的功能更强大。

deployment的主要功能有下面几个：

• 支持replicaset的所有功能
• 支持发布的停止、继续
• 支持版本的滚动更新和版本回退

deployment的资源清单文件

apiVersion: apps/v1  #版本号
kind: Deployment  #类型
metadata:    #元数据
  name:    #rs名称
  namespace:   #所属命名空间
  labels:   #标签
    controller: deploy
spec:   #详情描述
  replicas:  #副本数量
  revisionHistoryLimit: #保留历史版本，默认是10
  paused: #暂停部署，默认是false
  progressDeadlineSeconds: #部署超时时间(s)，默认是600
  strategy: #策略
    type: RollingUpdates  #滚动更新策略
    rollingUpdate:  #滚动更新
      maxSurge: #最大额外可以存在的副本数，可以为百分比，也可以为整数
      maxUnavaliable: #最大不可用状态的pod的最大值，可以为百分比，也可以为整数
  selector:  #选择器，通过它指定该控制器管理哪些pod
    matchLabels:   #Labels匹配规则
       app: nginx-pod
    matchExpressions:   #Expression匹配规则
      - {key: app, operator: In, values: [nginx-pod]}
  template:  #模板，当副本数量不足时，会根据下面的模板创建pod副本
    metadata:
        labels:
          app: nginx-pod
    spec:
      containers:
      - name: nginx
        image: nginx:1.17.1
        ports:
        - containerPort: 80

创建deployment

创建pc-deployment.yaml，内容如下：

apiVersion: apps/v1
kind: Deployment
metadata:
  name: pc-deployment
  namespace: dev
spec:
  replicas: 3
  selector:
    matchLabels:
     app: nginx-pod
  template:
    metadata:
      labels:
        app: nginx-pod
    spec:
      containers:
      - name: nginx
        image: nginx:1.17.1

使用配置文件

[root@master ~]# kubectl create -f pc-deployment.yaml
deployment.apps/pc-deployment created
[root@master ~]# kubectl get deploy -n dev -o wide
NAME            READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES         SELECTOR
pc-deployment   3/3     3            3           16s   nginx        nginx:1.17.1   app=nginx-pod

查看deployment控制的rs和pod，发现rs是在deployment之后加了一段字符串，而pod是在rs之后加了一段字符串

[root@master ~]# kubectl get rs -n dev
NAME                       DESIRED   CURRENT   READY   AGE
pc-deployment-5d89bdfbf9   3         3         3       2m13s
[root@master ~]# kubectl get pod -n dev
NAME                             READY   STATUS    RESTARTS   AGE
pc-deployment-5d89bdfbf9-k8j9n   1/1     Running   0          2m42s
pc-deployment-5d89bdfbf9-vw87k   1/1     Running   0          2m42s
pc-deployment-5d89bdfbf9-x7nsm   1/1     Running   0          2m42s

deployment功能

扩缩容

方式一：命令行

格式

kubectl scale deploy deploy名称 --replicas=pod数量 -n 命名空间

通过命令行变更pod数量为5个

[root@master ~]# kubectl scale deploy pc-deployment --replicas=5 -n dev
deployment.apps/pc-deployment scaled
[root@master ~]# kubectl get pod -n dev
NAME                             READY   STATUS    RESTARTS   AGE
pc-deployment-5d89bdfbf9-bhcns   1/1     Running   0          83s
pc-deployment-5d89bdfbf9-cfls7   1/1     Running   0          83s
pc-deployment-5d89bdfbf9-k8j9n   1/1     Running   0          8m54s
pc-deployment-5d89bdfbf9-vw87k   1/1     Running   0          8m54s
pc-deployment-5d89bdfbf9-x7nsm   1/1     Running   0          8m54s

方式二：编辑deploy文件

格式

kubectl edit deploy deploy名字 -n 命名空间

通过编辑deploy文件编辑pod数量为3个

[root@master ~]# kubectl edit deploy pc-deployment -n dev
找到replicas，将其数量改为3
spec:
  progressDeadlineSeconds: 600
  replicas: 3
[root@master ~]# kubectl get pod -n dev
NAME                             READY   STATUS    RESTARTS   AGE
pc-deployment-5d89bdfbf9-k8j9n   1/1     Running   0          15m
pc-deployment-5d89bdfbf9-vw87k   1/1     Running   0          15m
pc-deployment-5d89bdfbf9-x7nsm   1/1     Running   0          15m

镜像更新

deployment支持两种镜像更新策略：重建更新和滚动更新（默认），可以通过strategy选项进行配置

strategy：指定新的pod替换旧的pod的策略，支持两个属性：
  type：指定策略类型，支持两种策略
    Recreate：在创建出新的pod之前会先杀掉所有已存在的pod
    RollingUpdate：滚动更新，就是杀死一部分，就启动一部分，在更新过程中，存在两个版本pod
  rollingUpdate：当type为RollingUpdate时生效，用于为RollingUpdate设置参数，支持两个属性
    maxUnavailable：用来指定在升级过程中不可用pod的最大数量，默认为25%
    maxSurge：用来指定在升级过程中可以超过期望的pod的最大数量，默认为25%

重建更新

编辑pc-deployment.yaml，在spec节点下添加更新策略

spec:
  strategy:  #策略
    type: Recreate  #重建更新策略

[root@master ~]# vim pc-deployment.yaml
[root@master ~]# kubectl apply -f pc-deployment.yaml
Warning: kubectl apply should be used on resource created by either kubectl create --save-config or kubectl apply
deployment.apps/pc-deployment configured

创建deploy进行验证

#首先记录原本的pod名
[root@master ~]# kubectl get pod -n dev
NAME                             READY   STATUS    RESTARTS   AGE
pc-deployment-5d89bdfbf9-bqf86   1/1     Running   0          8s
pc-deployment-5d89bdfbf9-kz6jt   1/1     Running   0          8s
pc-deployment-5d89bdfbf9-z7d9z   1/1     Running   0          8s

#更改pod镜像
[root@master ~]# kubectl set image deploy pc-deployment nginx=nginx:1.17.2 -n dev
deployment.apps/pc-deployment image updated

#再次查看镜像
[root@master ~]# kubectl get pod -n dev
NAME                             READY   STATUS    RESTARTS   AGE
pc-deployment-675d469f8b-b9rwd   1/1     Running   0          27s
pc-deployment-675d469f8b-kc7rr   1/1     Running   0          27s
pc-deployment-675d469f8b-kxgkq   1/1     Running   0          27s

发现pod镜像已经改变了

滚动更新

编辑pc-deployment.yaml，在spec节点下添加滚动更新策略（也可以把strategy去掉，因为默认滚动更新策略）

strategy:
  type: RollingUpdate #滚动更新策略
  rollingUpdate:
    maxUnavailable: 25%
    maxSurge: 25%

[root@master ~]# vim pc-deployment.yaml
[root@master ~]# kubectl apply -f pc-deployment.yaml
Warning: kubectl apply should be used on resource created by either kubectl create --save-config or kubectl apply
deployment.apps/pc-deployment configured

创建deploy进行验证

#记录以前的pod
[root@master ~]# kubectl get pod -n dev
NAME                             READY   STATUS    RESTARTS   AGE
pc-deployment-5d89bdfbf9-526wf   1/1     Running   0          61s
pc-deployment-5d89bdfbf9-b5x5v   1/1     Running   0          64s
pc-deployment-5d89bdfbf9-kc7hb   1/1     Running   0          59s
#更新镜像
[root@master ~]# kubectl set image deploy pc-deployment nginx=nginx:1.17.2 -n dev
deployment.apps/pc-deployment image updated
#查看pod状态
[root@master ~]# kubectl get pod -n dev
NAME                             READY   STATUS              RESTARTS   AGE
pc-deployment-5d89bdfbf9-526wf   0/1     Terminating         0          2m2s
pc-deployment-5d89bdfbf9-b5x5v   1/1     Running             0          2m5s
pc-deployment-5d89bdfbf9-kc7hb   0/1     Terminating         0          2m
pc-deployment-675d469f8b-7vw6x   1/1     Running             0          3s
pc-deployment-675d469f8b-rzq82   0/1     ContainerCreating   0          2s
pc-deployment-675d469f8b-zk4fs   1/1     Running             0          5s
[root@master ~]# kubectl get pod -n dev
NAME                             READY   STATUS    RESTARTS   AGE
pc-deployment-675d469f8b-7vw6x   1/1     Running   0          38s
pc-deployment-675d469f8b-rzq82   1/1     Running   0          37s
pc-deployment-675d469f8b-zk4fs   1/1     Running   0          40s

发现pod是旧的一遍停止新的一边创建，最后全变成了新的

滚动更新的过程

镜像更新中rs的变化

前期准备：

#重建deployment
[root@master ~]# kubectl delete -f pc-deployment.yaml
deployment.apps "pc-deployment" deleted
#添加record参数，表明创建时记录
[root@master ~]# kubectl create -f pc-deployment.yaml --record
deployment.apps/pc-deployment created
[root@master ~]# kubectl get deploy,rs,pod -n dev
NAME                            READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/pc-deployment   3/3     3            3           81s

NAME                                       DESIRED   CURRENT   READY   AGE
replicaset.apps/pc-deployment-5d89bdfbf9   3         3         3       81s

NAME                                 READY   STATUS    RESTARTS   AGE
pod/pc-deployment-5d89bdfbf9-4bg2j   1/1     Running   0          81s
pod/pc-deployment-5d89bdfbf9-gbt95   1/1     Running   0          81s
pod/pc-deployment-5d89bdfbf9-tstlh   1/1     Running   0          81s

新建两个xshell窗口，用于监听rs和pod

在2窗口中监听rs，3窗口中监听pod

#在2窗口中输入
[root@master ~]# kubectl get rs -n dev -w
NAME                       DESIRED   CURRENT   READY   AGE
pc-deployment-5d89bdfbf9   3         3         3       6m18s
#在3窗口中输入
[root@master ~]# kubectl get pod -n dev -w
NAME                             READY   STATUS    RESTARTS   AGE
pc-deployment-5d89bdfbf9-4bg2j   1/1     Running   0          6m56s
pc-deployment-5d89bdfbf9-gbt95   1/1     Running   0          6m56s
pc-deployment-5d89bdfbf9-tstlh   1/1     Running   0          6m56s

在1窗口中改变pod镜像

[root@master ~]# kubectl set image deploy pc-deployment nginx=nginx:1.17.2 -n dev
deployment.apps/pc-deployment image updated

查看3窗口中pod的变化，发现序号5开头的pod在逐渐暂停，序号6开头的pod在逐渐创建

查看2窗口中rs的变化，可以看见序号5开头的rs的pod数在减少，序号6开头的rs的pod数在增加

在1窗口中查看最终rs变化，发现原来的rs依旧存在，只是pod数量变为了0，而后又新产生了一个rs，pod数量为3，其实这就是deployment能够进行版本回退的奥妙所在，后面会详细解释

[root@master ~]# kubectl get rs -n dev
NAME                       DESIRED   CURRENT   READY   AGE
pc-deployment-5d89bdfbf9   0         0         0       11m
pc-deployment-675d469f8b   3         3         3       3m12s

版本回退

deployment支持版本升级过程中的暂停，继续功能以及版本回退等诸多功能，下面具体来看

kubectl rollout：版本升级相关功能，支持下面的选项：

• status：显示当前升级状态
• history：显示升级历史记录
• 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：回滚到上一级版本（可以使用--to-revision回滚到指定版本）

#查看升级状态
[root@master ~]# kubectl rollout status deploy pc-deployment -n dev
deployment "pc-deployment" successfully rolled out

#查看升级历史（注意：如果只显示版本号说明一开始使用yaml创建文件的时候没有加上--record命令）
[root@master ~]# kubectl rollout history deploy pc-deployment -n dev
deployment.apps/pc-deployment
REVISION  CHANGE-CAUSE
1         kubectl create --filename=pc-deployment.yaml --record=true
2         kubectl create --filename=pc-deployment.yaml --record=true

#版本回滚
#这里使用--to-revision=1回滚到1版本，如果省略这个选项，则会回退到上个版本
[root@master ~]# kubectl rollout undo deploy pc-deployment --to-revision=1 -n dev
deployment.apps/pc-deployment rolled back

#查看是否回滚成功，发现5序号开头的rs被启动了
[root@master ~]# kubectl get rs -n dev
NAME                       DESIRED   CURRENT   READY   AGE
pc-deployment-5d89bdfbf9   3         3         3       31m
pc-deployment-675d469f8b   0         0         0       22m

金丝雀发布

deployment支持更新过程中的控制，如"暂停（pause）"或"继续（resume）"更新操作

比如有一批新的pod资源创建完成后立即暂停更新过程，此时，仅存在一部分新版本的应用，主体部分还是旧的版本。然后，再筛选一小部分的用户请求路由到新的pod应用，继续观察能否稳定地按期望的方式运行。确定没问题之后再继续完成余下的pod资源滚动更新，否则立即回滚更新操作。这就是所谓的金丝雀发布。

#更新deployment版本，并配置暂停deployment
[root@master ~]# kubectl set image deploy pc-deployment nginx=nginx:1.17.2 -n dev && kubectl rollout pause deploy pc-deployment -n dev
deployment.apps/pc-deployment image updated
deployment.apps/pc-deployment paused

#查看rs，发现老版本rs没有减少，新版本rs增加一个
[root@master ~]# kubectl get rs -n dev
NAME                       DESIRED   CURRENT   READY   AGE
pc-deployment-5d89bdfbf9   3         3         3       44m
pc-deployment-675d469f8b   1         1         1       35m

#在窗口2中查看deploy状态，发现deploy正在等待更新且已经有1个更新好了
[root@master ~]# kubectl rollout status deploy pc-deployment -n dev
Waiting for deployment "pc-deployment" rollout to finish: 1 out of 3 new replicas have been updated...

#在窗口1中继续deploy的更新
[root@master ~]# kubectl rollout resume deploy pc-deployment -n dev
deployment.apps/pc-deployment resumed

#查看窗口2的状态
Waiting for deployment spec update to be observed...
Waiting for deployment spec update to be observed...
Waiting for deployment "pc-deployment" rollout to finish: 1 out of 3 new replicas have been updated...
Waiting for deployment "pc-deployment" rollout to finish: 1 out of 3 new replicas have been updated...
Waiting for deployment "pc-deployment" rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for deployment "pc-deployment" rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for deployment "pc-deployment" rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for deployment "pc-deployment" rollout to finish: 1 old replicas are pending termination...
Waiting for deployment "pc-deployment" rollout to finish: 1 old replicas are pending termination...
deployment "pc-deployment" successfully rolled out

#在窗口1查看rs更新结果，发现老版本均停止，新版本已经创建好
[root@master ~]# kubectl get rs -n dev
NAME                       DESIRED   CURRENT   READY   AGE
pc-deployment-5d89bdfbf9   0         0         0       49m
pc-deployment-675d469f8b   3         3         3       40m