四、Kubernetes - 08.Deployment - 《Kubernetes》

创建Deployment
查看Deployment
扩展Deployment
滚动升级
rollout升级回滚
删除Deployment

学习了Replication Controller和Replica Set两种资源对象，RC和RS的功能基本上是差不多的，唯一的区别就是RS支持集合的selector。我们也学习到了用RC/RS来控制Pod副本的数量，也实现了滚动升级Pod的功能。现在看上去似乎一切都比较完美的运行着，但是我们上节课最后也提到了现在我们推荐使用Deployment这种控制器了，而不是我们之前的RC或者RS，这是为什么呢？

没有对比就没有伤害对吧，我们来对比下二者之间的功能吧，首先RC是Kubernetes的一个核心概念，当我们把应用部署到集群之后，需要保证应用能够持续稳定的运行，RC就是这个保证的关键，主要功能如下：

确保Pod数量：它会确保Kubernetes中有指定数量的Pod在运行，如果少于指定数量的Pod，RC就会创建新的，反之这会删除多余的，保证Pod的副本数量不变。
确保Pod健康：当Pod不健康，比如运行出错了，总之无法提供正常服务时，RC也会杀死不健康的Pod，重新创建新的。
弹性伸缩：在业务高峰或者低峰的时候，可以用过RC来动态的调整Pod数量来提供资源的利用率，当然我们也提到过如果使用HPA这种资源对象的话可以做到自动伸缩。
滚动升级：滚动升级是一种平滑的升级方式，通过逐步替换的策略，保证整体系统的稳定性。

Deployment同样也是Kubernetes系统的一个核心概念，主要职责和RC一样的都是保证Pod的数量和健康，二者大部分功能都是完全一致的，我们可以看成是一个升级版的RC控制器，那Deployment又具备那些新特性呢？

RC的全部功能：Deployment具备上面描述的RC的全部功能
事件和状态查看：可以查看Deployment的升级详细进度和状态
回滚：当升级Pod的时候如果出现问题，可以使用回滚操作回滚到之前的任一版本
版本记录：每一次对Deployment的操作，都能够保存下来，这也是保证可以回滚到任一版本的基础
暂停和启动：对于每一次升级都能够随时暂停和启动

创建Deployment

[root@master01 ~]# kubectl explain Deployment
KIND:     Deployment
VERSION:  apps/v1
DESCRIPTION:
     Deployment enables declarative updates for Pods and ReplicaSets.
FIELDS:
   apiVersion    <string>
     APIVersion defines the versioned schema of this representation of an
     object. Servers should convert recognized schemas to the latest internal
     value, and may reject unrecognized values. More info:
     https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#resources
   kind    <string>
     Kind is a string value representing the REST resource this object
     represents. Servers may infer this from the endpoint the client submits
     requests to. Cannot be updated. In CamelCase. More info:
     https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#types-kinds
   metadata    <Object>
     Standard object metadata.
   spec    <Object>
     Specification of the desired behavior of the Deployment.
   status    <Object>
     Most recently observed status of the Deployment.

cat > myapp-deploy.yaml << EOF
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-deploy
  namespace: default
  labels:
    app: myapp
    type: deploy
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
      type: deploy
  template:
    metadata:
      name: myapp-pod
      labels:
        app: myapp
        type: deploy
    spec:
      containers:
      - name: myapp
        image: ikubernetes/myapp:v1
        ports:
        - name: http
          containerPort: 80
EOF

kubectl apply -f myapp-deploy.yaml

[root@master01 ~]# kubectl get pods
NAME                            READY   STATUS    RESTARTS   AGE
myapp-deploy-696fdb5868-22lnq   1/1     Running   0          52s
myapp-deploy-696fdb5868-2tjqw   1/1     Running   0          52s
myapp-deploy-696fdb5868-c9c4b   1/1     Running   0          52s

[root@master01 ~]# kubectl get deployment
NAME           READY   UP-TO-DATE   AVAILABLE   AGE
myapp-deploy   3/3     3            3           67s

[root@master01 ~]# kubectl get rs
NAME                      DESIRED   CURRENT   READY   AGE
myapp-deploy-696fdb5868   3         3         3       75s

查看Deployment

[root@master01 ~]# kubectl  describe deployments.apps  myapp-deploy 
Name:                   myapp-deploy
Namespace:              default
CreationTimestamp:      Mon, 13 Jan 2020 15:12:50 +0800
Labels:                 app=myapp
                        type=deploy
Annotations:            deployment.kubernetes.io/revision: 1
                        kubectl.kubernetes.io/last-applied-configuration:
                          {"apiVersion":"apps/v1","kind":"Deployment","metadata":{"annotations":{},"labels":{"app":"myapp","type":"deploy"},"name":"myapp-deploy","n...
Selector:               app=myapp,type=deploy
Replicas:               3 desired | 3 updated | 3 total | 3 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
  Labels:  app=myapp
           type=deploy
  Containers:
   myapp:
    Image:        ikubernetes/myapp:v1
    Port:         80/TCP
    Host Port:    0/TCP
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Available      True    MinimumReplicasAvailable
  Progressing    True    NewReplicaSetAvailable
OldReplicaSets:  <none>
NewReplicaSet:   myapp-deploy-696fdb5868 (3/3 replicas created)
Events:
  Type    Reason             Age    From                   Message
  ----    ------             ----   ----                   -------
  Normal  ScalingReplicaSet  7m53s  deployment-controller  Scaled up replica set myapp-deploy-696fdb5868 to 3

扩展Deployment

[root@master01 ~]# kubectl scale deployment myapp-deploy --replicas=5
deployment.apps/myapp-deploy scaled

[root@master01 ~]# kubectl get pods
NAME                            READY   STATUS    RESTARTS   AGE
myapp-deploy-696fdb5868-22lnq   1/1     Running   0          10m
myapp-deploy-696fdb5868-2tjqw   1/1     Running   0          10m
myapp-deploy-696fdb5868-8f7qq   1/1     Running   0          8s
myapp-deploy-696fdb5868-c9c4b   1/1     Running   0          10m
myapp-deploy-696fdb5868-vlqgk   1/1     Running   0          8s

滚动升级

镜像版本v1-v2

cat > myapp-deploy.yaml << EOF
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-deploy
  namespace: default
  labels:
    app: myapp
    type: deploy
spec:
  replicas: 5
  minReadySeconds: 5
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 1
  selector:
    matchLabels:
      app: myapp
      type: deploy
  template:
    metadata:
      name: myapp-pod
      labels:
        app: myapp
        type: deploy
    spec:
      containers:
      - name: myapp
        image: ikubernetes/myapp:v2
        ports:
        - name: http
          containerPort: 80
EOF

[root@master01 ~]# kubectl get pods
NAME                            READY   STATUS    RESTARTS   AGE
myapp-deploy-8644746745-8f7qz   1/1     Running   0          30s
myapp-deploy-8644746745-cf6ln   1/1     Running   0          22s
myapp-deploy-8644746745-gt8fw   1/1     Running   0          15s
myapp-deploy-8644746745-mhp2q   1/1     Running   0          22s
myapp-deploy-8644746745-wqc8t   1/1     Running   0          30s

[root@master01 ~]# kubectl get deployments.apps 
NAME           READY   UP-TO-DATE   AVAILABLE   AGE
myapp-deploy   5/5     5            5           18m

t@master01 ~]# kubectl get rs
NAME                      DESIRED   CURRENT   READY   AGE
myapp-deploy-696fdb5868   0         0         0       18m
myapp-deploy-8644746745   5         5         5       51s

minReadySeconds:
- Kubernetes在等待设置的时间后才进行升级
- 如果没有设置该值，Kubernetes会假设该容器启动起来后就提供服务了
- 如果没有设置该值，在某些极端情况下可能会造成服务服务正常运行
maxSurge:
- 升级过程中最多可以比原先设置多出的POD数量
- 例如：maxSurage=1，replicas=5,则表示Kubernetes会先启动1一个新的Pod后才删掉一个旧的POD，整个升级过程中最多会有5+1个POD。
maxUnavaible:
- 升级过程中最多有多少个POD处于无法提供服务的状态
- 当maxSurge不为0时，该值也不能为0
- 例如：maxUnavaible=1，则表示Kubernetes整个升级过程中最多会有1个POD处于无法服务的状态。

rollout升级回滚

[root@master01 ~]# kubectl set image deployment myapp-deploy myapp=ikubernetes/myapp:v3
deployment.apps/myapp-deploy image updated

[root@master01 ~]# kubectl rollout status deployment myapp-deploy
deployment "myapp-deploy" successfully rolled out

[root@master01 ~]# kubectl get deployments.apps 
NAME           READY   UP-TO-DATE   AVAILABLE   AGE
myapp-deploy   5/5     5            5           33m
[root@master01 ~]# kubectl get rs
NAME                      DESIRED   CURRENT   READY   AGE
myapp-deploy-66865f759d   5         5         5       2m16s
myapp-deploy-696fdb5868   0         0         0       33m
myapp-deploy-8644746745   0         0         0       16m

查看Deployment的升级历史

[root@master01 ~]# kubectl rollout history deployment myapp-deploy 
deployment.apps/myapp-deploy 
REVISION  CHANGE-CAUSE
1         <none>
2         <none>
3         <none>

接回退到当前版本的上一个版本

kubectl rollout undo deployment myapp-deploy

[root@master01 ~]# kubectl get deployments.apps 
NAME           READY   UP-TO-DATE   AVAILABLE   AGE
myapp-deploy   5/5     5            5           37m

[root@master01 ~]# kubectl get rs
NAME                      DESIRED   CURRENT   READY   AGE
myapp-deploy-66865f759d   0         0         0       6m26s
myapp-deploy-696fdb5868   0         0         0       38m
myapp-deploy-8644746745   5         5         5       20m

[root@master01 ~]# kubectl rollout history deployment myapp-deploy 
deployment.apps/myapp-deploy 
REVISION  CHANGE-CAUSE
1         <none>
3         <none>
4         <none>

回退指定版本

kubectl rollout undo deployment myapp-deploy --to-revision=1

[root@master01 ~]# kubectl get deployments.apps 
NAME           READY   UP-TO-DATE   AVAILABLE   AGE
myapp-deploy   5/5     5            5           46m

[root@master01 ~]# kubectl get rs
NAME                      DESIRED   CURRENT   READY   AGE
myapp-deploy-66865f759d   0         0         0       15m
myapp-deploy-696fdb5868   5         5         5       46m
myapp-deploy-8644746745   0         0         0       28m

ot@master01 ~]# kubectl rollout history deployment myapp-deploy 
deployment.apps/myapp-deploy 
REVISION  CHANGE-CAUSE
3         <none>
4         <none>
5         <none>

在执行Deployment升级的时候最好带上record参数，便于我们查看历史版本信息

[root@master01 ~]# kubectl apply -f myapp-deploy.yaml --record=true
deployment.apps/myapp-deploy configured

[root@master01 ~]# kubectl rollout history deployment myapp-deploy 
deployment.apps/myapp-deploy 
REVISION  CHANGE-CAUSE
3         <none>
5         <none>
6         kubectl apply --filename=myapp-deploy.yaml --record=true

删除Deployment

kubectl delete deployments.apps myapp-deploy