ReplicaSet如果要实现滚动更新和蓝绿部署需要手工进行实现，所以这种类型的控制器并非是我们生产中所需要的，而更加高级的控制器称之为Deployment。

Deployment的工作过程和使用ReplicaSet手动实现蓝绿部署和滚动部署相似，Deployment会间接的使用1到多个ReplicaSet来管理Pod。

Deployment工作流程

Deployment在更新Pod时会创建一个新的RS，由新的RS以新的pod模板创建出pod，然后逐渐将Pod切换到新版本上去。Deployment每一次更新都会创建出一个新的RS，其更新历史中默认允许保存10个RS。如果Deployment需要回滚时可以向前回滚9个版本。

需要注意的是虽然Deployment会保留历史RS，但是在历史中RS的pod为0，只有最新的RS其下的pod数为用户所定义的值。当回滚时才会将其pod副本的数量定义为用户所指定的值。

Deployment资源定义规范

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apiVersion: apps/v1  # API群组及版本
kind: Deployment  # 资源类型特有标识
metadata:
  name <string>  # 资源名称，在作用域中要唯一
  namespace <string>  # 名称空间；Deployment隶属名称空间级别
spec:
  minReadySeconds <integer>  # Pod就绪后多少秒内任一容器无crash方可视为“就绪”
  replicas <integer> # 期望的Pod副本数，默认为1
  selector <object> # 标签选择器，必须匹配template字段中Pod模板中的标签
  template <object>  # Pod模板对象
  revisionHistoryLimit <integer> # 滚动更新历史记录数量，默认为10
  strategy <Object> # 滚动更新策略
    type <string>  # 滚动更新类型，可用值有Recreate和RollingUpdate；
    rollingUpdate <Object>  # 滚动更新参数，专用于RollingUpdate类型
      maxSurge <string>  # 更新期间可比期望的Pod数量多出的数量或比例；
      maxUnavailable <string>  # 更新期间可比期望的Pod数量缺少的数量或比例，10， 
  progressDeadlineSeconds <integer> # 滚动更新故障超时时长，默认为600秒
  paused <boolean>  # 是否暂停部署过程

Deployment示例

1.编写资源配置清单

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root@k8s-master01:~/yaml/chapter08# vim deployment-demo.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: deployment-demo
spec:
  replicas: 4
  selector:
    matchLabels:
      app: demoapp
      release: stable
  template:
    metadata:
      labels:
        app: demoapp
        release: stable
    spec:
      containers:
      - name: demoapp
        image: ikubernetes/demoapp:${VERSION}
        ports:
        - containerPort: 80
          name: http

2.应用配置清单

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root@k8s-master01:~/yaml/chapter08# VERSION=v1.0 envsubst < deployment-demo.yaml | kubectl apply -f -
deployment.apps/deployment created

# 查看deployment信息
root@k8s-master01:~/yaml/chapter08# kubectl get deployments.apps
NAME              READY   UP-TO-DATE   AVAILABLE   AGE
deployment-demo   4/4     4            4           12s

# 查看pod信息
root@k8s-master01:~/yaml/chapter08# kubectl get pods -l 'app=demoapp,release=stable'
NAME                              READY   STATUS    RESTARTS   AGE
deployment-demo-fb544c5d8-2687q   1/1     Running   0          2m16s
deployment-demo-fb544c5d8-2t6q4   1/1     Running   0          2m16s
deployment-demo-fb544c5d8-pkgzn   1/1     Running   0          2m16s
deployment-demo-fb544c5d8-w52qp   1/1     Running   0          2m16s
# 可以看到第一段为deployment名字，最后一段为随机值，中间的fb544c5d8为replicaset中Pod模板的哈希值，也就是template字段的哈希值

# 查看replicaset信息
root@k8s-master01:~/yaml/chapter08# kubectl get replicasets.apps
NAME                        DESIRED   CURRENT   READY   AGE
deployment-demo-fb544c5d8   4         4         4       4m5s

# 一旦pod模板发生变更，会导致ReplicaSet的哈希值发生变化，然后出发deployment更新的

3.查看deployment的描述信息

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root@k8s-master01:~/yaml/chapter08# kubectl describe deployments.apps deployment-demo
Name:                   deployment-demo
Namespace:              default
CreationTimestamp:      Wed, 21 Jul 2021 13:23:13 +0000
Labels:                 <none>
Annotations:            deployment.kubernetes.io/revision: 1
Selector:               app=demoapp,release=stable
Replicas:               4 desired | 4 updated | 4 total | 4 available | 0 unavailable
StrategyType:           RollingUpdate						# 一旦模板发生变化将触发滚动跟新
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge     # 滚动更新逻辑
Pod Template:
  Labels:  app=demoapp
           release=stable
  Containers:
   demoapp:
    Image:        ikubernetes/demoapp:v1.0
    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:   deployment-demo-fb544c5d8 (4/4 replicas created)
Events:
  Type    Reason             Age   From                   Message
  ----    ------             ----  ----                   -------
  Normal  ScalingReplicaSet  19m   deployment-controller  Scaled up replica set deployment-demo-fb544c5d8 to 4

更新

1.对deployment实行滚动更新

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root@k8s-master01:~/yaml/chapter08# VERSION=v1.1 envsubst < deployment-demo.yaml | kubectl apply -f -
deployment.apps/deployment-demo configured

2.使用rollout查看滚动更新的状态

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root@k8s-master01:~# kubectl rollout status deployment deployment-demo
deployment "deployment-demo" successfully rolled out

3.查看pod是否更新为v1.1版本

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root@k8s-master01:~# kubectl get pods -o wide
NAME                               READY   STATUS      RESTARTS   AGE     IP            NODE         NOMINATED NODE   READINESS GATES
deployment-demo-867c7d9d55-4r5hw   1/1     Running     0          11m     10.244.2.30   k8s-node02   <none>           <none>
deployment-demo-867c7d9d55-b4trp   1/1     Running     0          11m     10.244.3.33   k8s-node03   <none>           <none>
deployment-demo-867c7d9d55-qrh8c   1/1     Running     0          11m     10.244.2.31   k8s-node02   <none>           <none>
deployment-demo-867c7d9d55-qxjnq   1/1     Running     0          11m     10.244.3.34   k8s-node03   <none>           <none>

# 对pod进行访问
root@k8s-master01:~# curl 10.244.3.33
iKubernetes demoapp v1.1 !! ClientIP: 10.244.0.0, ServerName: deployment-demo-867c7d9d55-b4trp, ServerIP: 10.244.3.33!

回滚

1.查看deployment的更新历史信息

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root@k8s-master01:~# kubectl rollout history deployment deployment-demo
deployment.apps/deployment-demo
REVISION  CHANGE-CAUSE
1         <none>
2         <none>   # 此为当前版本信息

2.将其回滚到上一个版本

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root@k8s-master01:~# kubectl rollout undo deployment deployment-demo
deployment.apps/deployment-demo rolled back

3.查看replicaset信息

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root@k8s-master01:~# kubectl get rs
NAME                         DESIRED   CURRENT   READY   AGE
deployment-demo-867c7d9d55   0         0         0       24m
deployment-demo-fb544c5d8    4         4         4       48m
# 原本的deployment-demo-867c7d9d55已经变为0

4.再次查看更新历史

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root@k8s-master01:~# kubectl rollout history deployment deployment-demo
deployment.apps/deployment-demo
REVISION  CHANGE-CAUSE
2         <none>
3         <none>
# 可以看到原本的1没有了新增了3，3表示当前的

金丝雀发布

1.再次对版本进行更新

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# 更新完毕后立即暂停
root@k8s-master01:~/yaml/chapter08# VERSION=v1.2 envsubst < deployment-demo.yaml | kubectl apply -f - && kubectl rollout pause deployment deployment-demo
deployment.apps/deployment-demo configured
deployment.apps/deployment-demo paused

2.查看更新状态

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root@k8s-master01:~/yaml/chapter08# kubectl rollout status deployment deployment-demo
Waiting for deployment "deployment-demo" rollout to finish: 2 out of 4 new replicas have been updated...

# 现在可以看到总数有5个pod，有2个pod已经被更新。
root@k8s-master01:~/yaml/chapter08# kubectl get rs
NAME                         DESIRED   CURRENT   READY   AGE
deployment-demo-77d46c4794   2         2         2       118s
deployment-demo-867c7d9d55   0         0         0       12h
deployment-demo-fb544c5d8    3         3         3       12h

3.当经过一段时间没有问题时，再将其更新继续

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root@k8s-master01:~# kubectl rollout resume deployment deployment-demo

Deployment自定义更新策略示例

Deployment默认跟新策略为一批更新25%，在pod量较大的情况下不适用，所以需要自定义。

1.编写资源配置清单

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root@k8s-master01:~/yaml/chapter08# vim deployment-demo-with-strategy.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: deployment-demo-with-strategy
spec:
  replicas: 4
  selector:
    matchLabels:
      app: demoapp
      release: stable
      strategy: "true"
  template:
    metadata:
      labels:
        app: demoapp
        release: stable
        strategy: "true"
    spec:
      containers:
      - name: demoapp
        image: ikubernetes/demoapp:${VERSION}
        ports:
        - containerPort: 80
          name: http
  strategy:
    type: Rollingupdate
    rollingUpdate:
      maxSurge: 0             # 做多能多出0个pod
      maxUnavailable: 1				# 做多能有1个pod不可调度
 
 # 用来实现先减，再创建pod

2.应用配置清单

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root@k8s-master01:~/yaml/chapter08# VERSION=v1.0 envsubst < deployment-demo-with-strategy.yaml | kubectl apply -f -
deployment.apps/deployment-demo-with-strategy created

3.对版本进行更新，并查看跟新过程。

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root@k8s-master01:~/yaml/chapter08# VERSION=v1.1 envsubst < deployment-demo-with-strategy.yaml | kubectl apply -f - && kubectl rollout status deployment deployment-demo-with-strategy
deployment.apps/deployment-demo-with-strategy configured
Waiting for deployment spec update to be observed...
Waiting for deployment "deployment-demo-with-strategy" rollout to finish: 0 out of 4 new replicas have been updated...
Waiting for deployment "deployment-demo-with-strategy" rollout to finish: 0 out of 4 new replicas have been updated...
Waiting for deployment "deployment-demo-with-strategy" rollout to finish: 1 out of 4 new replicas have been updated...
Waiting for deployment "deployment-demo-with-strategy" rollout to finish: 1 out of 4 new replicas have been updated...
Waiting for deployment "deployment-demo-with-strategy" rollout to finish: 1 out of 4 new replicas have been updated...
Waiting for deployment "deployment-demo-with-strategy" rollout to finish: 2 out of 4 new replicas have been updated...
Waiting for deployment "deployment-demo-with-strategy" rollout to finish: 2 out of 4 new replicas have been updated...
Waiting for deployment "deployment-demo-with-strategy" rollout to finish: 2 out of 4 new replicas have been updated...
Waiting for deployment "deployment-demo-with-strategy" rollout to finish: 3 out of 4 new replicas have been updated...
Waiting for deployment "deployment-demo-with-strategy" rollout to finish: 3 out of 4 new replicas have been updated...
Waiting for deployment "deployment-demo-with-strategy" rollout to finish: 3 out of 4 new replicas have been updated...
Waiting for deployment "deployment-demo-with-strategy" rollout to finish: 3 of 4 updated replicas are available...
deployment "deployment-demo-with-strategy" successfully rolled out