Deployment

一、简介

Deployment实际上是一个两层控制器，遵循一种滚动更新的方式来实现升级现有的容器。Deployment在内部使用了ReplicaSet来实现目的，无论冲Deployment的作用与目的、YAML定义、还是从它的具体命令操作来看,它都是对RC的一个升级。

Deployment的典型应用场景有以下几个：

• 创建一个Deployment对象来生成对应的Replica Set 并完成Pod副本的创建

• 检查Deployment的状态来看部署动作是否完成（Pod副本数量是否达到预期的值）

• 更新Deployment以创建新的Pod（比如镜像升级）

• 如果当前Deployment不稳定，则回滚到一个早先的Deployment版本

• 暂停Deployment以便于一次性修改多个PodTemplateSpec的配置项，之后再恢复Deployment，进行更新发布

• 扩展Deployment以应对高负载

• 查看Deployment的状态，以此作为发布是否成功的指标

• 清理不再需要的旧版本ReplicaSets

 

二、创建Deployment

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx-web
        image: nginx:1.14.2
        imagePullPolicy: IfNotPresent
        ports:
        - containerPort: 80

在该例中：

• 将创建一个名为nginx-deployment的Deployment，由 .metadata.name 字段指明

• Deployment将创建2个Pod副本，由 .spec.replicas 字段指明

• .spec.selector 字段定义Deployment如何查找要管理的Pods。

• template.spec 字段指示Pods运行一个容器， nginx

• 创建一个容器并使用 name 字段将其命名为 nginx-web

 

2.1 运行Deployment

# kubectl apply -f nginx-deployment.yaml

查看Deployment信息

# kubectl get deployments
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment   2/2     2            2           10m
​
# kubectl get rs
NAME                          DESIRED   CURRENT   READY   AGE
nginx-deployment-559954d9f9   2         2         2       11m
# kubectl describe deployment/nginx-deployment
Name:                   nginx-deployment
Namespace:              default
CreationTimestamp:      Tue, 09 Jun 2020 13:51:00 +0800
Labels:                 app=nginx
Annotations:            deployment.kubernetes.io/revision: 3
Selector:               app=nginx
Replicas:               2 desired | 2 updated | 2 total | 2 available | 0 unavailable
StrategyType:           RollingUpdate
MinReadySeconds:        0
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Pod Template:
  Labels:  app=nginx
  Containers:
   nginx-web:
    Image:        nginx:1.19.0
    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:   nginx-deployment-798656bd4b (2/2 replicas created)
Events:
  Type    Reason             Age   From                   Message
  ----    ------             ----  ----                   -------
  Normal  ScalingReplicaSet  27m   deployment-controller  Scaled up replica set nginx-deployment-674964b5cc to 1
  Normal  ScalingReplicaSet  26m   deployment-controller  Scaled down replica set nginx-deployment-674964b5cc to 0
  Normal  ScalingReplicaSet  26m   deployment-controller  Scaled up replica set nginx-deployment-798656bd4b to 1
  Normal  ScalingReplicaSet  23m   deployment-controller  Scaled down replica set nginx-deployment-559954d9f9 to 1
  Normal  ScalingReplicaSet  23m   deployment-controller  Scaled up replica set nginx-deployment-798656bd4b to 2
  Normal  ScalingReplicaSet  19m   deployment-controller  Scaled down replica set nginx-deployment-559954d9f9 to 0
You have new mail in /var/spool/mail/root

2.2 Pod镜像更新

1. 命令行更新

# kubectl set image deployment/nginx-deployment nginx=nginx:1.19.0 --record=true

2. kubectl edit

# kubectl edit deployment/nginx-deployment

3. 修改deployment YAML文件

 

2.3 回滚

1.返回上一个版本

# kubectl rollout undo deployment/nginx-deployment

2.返回指定版本

使用--record=true参数时，就能在CHANGE-CAUSE中看到每个版本使用的命令

# 先查看更新记录
#kubectl rollout history deployment/nginx-deployment
deployment.apps/nginx-deployment 
REVISION  CHANGE-CAUSE
1         <none>
2         <none>
3         <none>

如果要查看每个更新的详细信息

# kubectl rollout history deployment/nginx-deployment --revision=3
deployment.apps/nginx-deployment with revision #3
Pod Template:
  Labels:    app=nginx
    pod-template-hash=798656bd4b
  Containers:
   nginx-web:
    Image:    nginx:1.19.0
    Port:    80/TCP
    Host Port:    0/TCP
    Environment:    <none>
    Mounts:    <none>
  Volumes:    <none>​

　回滚到指定版本

#kubectl rollout undo deployment/nginx-deployment --to-revision=1

2.4 暂停和恢复Deployment部署操作

对于一次复杂的Deployment配置修改，为了避免频繁的触发Deployment的更新操作，可以先暂停Deployment的更新操作，然后进行配置修改，在恢复Deployment，一次性触发完整的更新操作。

以之前创建的nginx为例

# kubectl get deployments
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment   2/2     2            2           100m

1. 通过kubectl rollout pause 命令暂停Deployment的更新操作

   # kubectl rollout pause deployment/nginx-deployment
   deployment.apps/nginx-deployment paused

2. 然后修改Deployment的镜像信息

   # kubectl set image deployment/nginx-deployment nginx-web=nginx:1.18.0 --record=true
   deployment.apps/nginx-deployment image updated
   # kubectl rollout history deployment/nginx-deployment
   deployment.apps/nginx-deployment 
   REVISION  CHANGE-CAUSE
   1         <none>
   2         <none>
   3         kubectl set image deployment/nginx-deployment nginx=nginx:1.18.0 --record=true

   查看具体pod中nginx的版本信息，其实nginx并没有更新为1.18.0

3. 再次更新容器资源限制

   # kubectl set resources deployment/nginx-deployment -c nginx-web --limits=cpu=200m,memory=256Mi
   deployment.apps/nginx-deployment resource requirements updated

4. 最后恢复Deployment的部署操作

   # kubectl rollout resume deployment/nginx-deployment
   deployment.apps/nginx-deployment resumed
   ​
   # kubectl get pods
   NAME                                READY   STATUS              RESTARTS   AGE
   mysql-lh5dv                         1/1     Running             5          3d22h
   myweb-nxn6s                         1/1     Running             5          3d21h
   nginx-deployment-74564bc45-6nmtq    0/1     ContainerCreating   0          7s
   nginx-deployment-798656bd4b-4z52s   1/1     Running             0          63m
   nginx-deployment-798656bd4b-lhpns   1/1     Running             0          66m
   volume-pod                          2/2     Running             2          22h

   其实能看到nginx在做更新操作了