deployment(部署)
==================

部署应用的对象，一个 Deployment 控制器为 Pods 和 ReplicaSets 提供声明式的更新能力，也就是应用的滚动更新和回滚。也可以进行设定数。

deployment是一个控制器，用于部署无状态应用。

控制器用于管理pod, 通过标签来管理pod.



下面是 Deployment 示例。负责启动3个 nginx Pods deployment.yaml文件内容为 ::

	apiVersion: apps/v1
	kind: Deployment
	metadata:
	  name: nginx-deployment
	  labels:
		app: nginx
	spec:
	  replicas: 3
	  selector:
		matchLabels:
		  app: nginx
	  template:
		metadata:
		  labels:
			app: nginx
		spec:
		  containers:
		  - name: nginx
			image: nginx:1.14.2
			ports:
			- containerPort: 80


创建deployment ::
   
   kubectl  apply -f deployment.yaml 
   
查看deployments状态, 现在还没有Ready::
 
   [root@zhang1 k8s]# kubectl get deployments
	NAME               READY   UP-TO-DATE   AVAILABLE   AGE
	nginx-deployment   0/3     3            0           27s

过了一段时间，查看deployments状态, 现在已经有两个Ready ::

   [root@zhang1 k8s]# kubectl get deployments
	NAME               READY   UP-TO-DATE   AVAILABLE   AGE
	nginx-deployment   2/3     3            2           5m13s
 

在检查集群中的 Deployment 时，所显示的字段有：

* NAME 列出了集群中 Deployment 的名称。
* READY 显示应用程序的可用的副本数。显示的模式是“就绪个数/期望个数”。
* UP-TO-DATE 
* AVAILABLE 显示应用可供用户使用的副本数。
* AGE 显示应用程序运行的时间。

查看部署状态 ::

	$ kubectl rollout status deployment.v1.apps/nginx-deployment
	deployment "nginx-deployment" successfully rolled out

使用describe获取 Deployment 的更多信息 ::

	[root@zhang1 ]# kubectl describe deployments nginx-deployment
	Name:                   nginx-deployment
	Namespace:              default
	CreationTimestamp:      Mon, 09 Nov 2020 01:15:15 -0500
	Labels:                 app=nginx
	Annotations:            deployment.kubernetes.io/revision: 1
	Selector:               app=nginx
	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=nginx
	  Containers:
	   nginx:
		Image:        nginx:1.14.2
		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:   nginx-deployment-66b6c48dd5 (3/3 replicas created)
	Events:
	  Type    Reason             Age   From                   Message
	  ----    ------             ----  ----                   -------
	  Normal  ScalingReplicaSet  34m   deployment-controller  Scaled up replica set nginx-deployment-66b6c48dd5 to 3


扩缩容 
-------

缩放 Deployment, 可以使用如下指令缩放 Deployment ::

	$ kubectl scale deployment.v1.apps/nginx-deployment --replicas=2
	deployment.apps/nginx-deployment scaled
	
更新(滚动升级)	
----------------

会部署新的版本，待成功后再有序删除旧版本，命令如下
::

   kubectl set image deployment/nginx-deployment nginx=nginx:1.16.1 --record


可以使用 kubectl get pod -o yaml来查看容器版本，看看是否升级ok。




涉及到以下几个命令 ::

   kubectl scale # 扩容
   kubectl rollout status
   kubectl rollout history # 
   kubectl rollout undo # 回到先前版本。





参考资料
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