Kubernetes Controller 之 Deployment 介绍

一、Deployment

我们接着前面的文章说，如果不清楚的请查看之前的博文： http://blog.51cto.com/wzlinux/2322616

前面我们已经了解到，Kubernetes 通过各种 Controller 来管理 Pod 的生命周期。为了满足不同业务场景，Kubernetes 开发了 Deployment、ReplicaSet、DaemonSet、StatefuleSet、Job 等多种 Controller。我们首先学习最常用的 Deployment。

1、运行 Deployment

先从例子开始，运行一个 Deployment：

kubectl run nginx-deployment --image=nginx:1.7.9 --replicas=2

上面的命令将部署包含两个副本的 Deployment nginx-deployment ，容器的 image 为 nginx:1.7.9 。

2、查看 Deployment（deploy）

查看刚刚创建的 deployment，其可以简写为deploy。

[root@master ~]# kubectl get deploy
NAME               DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment   2         2         2            2           4m56s

使用命令 kubectl describe deploy 查看内部内容。

kubectl describe deploy nginx-deployment

Name:                   nginx-deployment
Namespace:              default
CreationTimestamp:      Thu, 29 Nov 2018 17:47:16 +0800
Labels:                 run=nginx-deployment
Annotations:            deployment.kubernetes.io/revision: 1
Selector:               run=nginx-deployment
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:  run=nginx-deployment
  Containers:
   nginx-deployment:
    Image:        nginx:1.7.9
    Port:         <none>
    Host Port:    <none>
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Conditions:
  Type           Status  Reason
  ----           ------  ------
  Available      True    MinimumReplicasAvailable
  Progressing    True    NewReplicaSetAvailable
OldReplicaSets:  <none>
NewReplicaSet:   nginx-deployment-5fd98dbf5f (2/2 replicas created)
Events:
  Type    Reason             Age    From                   Message
  ----    ------             ----   ----                   -------
  Normal  ScalingReplicaSet  6m11s  deployment-controller  Scaled up replica set nginx-deployment-5fd98dbf5f to 2

展示的内容大部分都是描述信息，我们看最后一行，这里告诉我们创建了一个 ReplicaSet nginx-deployment-5fd98dbf5f ，Events 是 Deployment 的日志，记录了 ReplicaSet 的启动过程。

通过上面的分析，也验证了 Deployment 通过 ReplicaSet 来管理 Pod 的事实。

3、查看 ReplicaSet（rs）

查看我们有哪些 rs。

[root@master ~]# kubectl get rs
NAME                          DESIRED   CURRENT   READY   AGE
nginx-deployment-5fd98dbf5f   2         2         2       12m

使用命令 kubectl describe rs 查看其详细信息。

kubectl describe rs nginx-deployment-5fd98dbf5f

Name:           nginx-deployment-5fd98dbf5f
Namespace:      default
Selector:       pod-template-hash=5fd98dbf5f,run=nginx-deployment
Labels:         pod-template-hash=5fd98dbf5f
                run=nginx-deployment
Annotations:    deployment.kubernetes.io/desired-replicas: 2
                deployment.kubernetes.io/max-replicas: 3
                deployment.kubernetes.io/revision: 1
Controlled By:  Deployment/nginx-deployment
Replicas:       2 current / 2 desired
Pods Status:    2 Running / 0 Waiting / 0 Succeeded / 0 Failed
Pod Template:
  Labels:  pod-template-hash=5fd98dbf5f
           run=nginx-deployment
  Containers:
   nginx-deployment:
    Image:        nginx:1.7.9
    Port:         <none>
    Host Port:    <none>
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>
Events:
  Type    Reason            Age   From                   Message
  ----    ------            ----  ----                   -------
  Normal  SuccessfulCreate  13m   replicaset-controller  Created pod: nginx-deployment-5fd98dbf5f-8g7nm
  Normal  SuccessfulCreate  13m   replicaset-controller  Created pod: nginx-deployment-5fd98dbf5f-58c4z

我们可以看到 Controlled By: Deployment/nginx-deployment ，说明此 ReplicaSet 由 Deployment nginx-deployment 。

在 Events 记录了两个副本 Pod 的创建，那我们查看一下 Pod。

4、查看 Pod

查看目前的 Pod。

[root@master ~]# kubectl get pods
NAME                                READY   STATUS    RESTARTS   AGE
nginx-deployment-5fd98dbf5f-58c4z   1/1     Running   0          19m
nginx-deployment-5fd98dbf5f-8g7nm   1/1     Running   0          19m

随便选择一个 Pod，查看其详细信息。

kubectl describe pod nginx-deployment-5fd98dbf5f-58c4z

Name:               nginx-deployment-5fd98dbf5f-58c4z
Namespace:          default
Priority:           0
PriorityClassName:  <none>
Node:               node02.wzlinux.com/172.18.8.202
Start Time:         Thu, 29 Nov 2018 17:47:16 +0800
Labels:             pod-template-hash=5fd98dbf5f
                    run=nginx-deployment
Annotations:        <none>
Status:             Running
IP:                 10.244.2.3
Controlled By:      ReplicaSet/nginx-deployment-5fd98dbf5f
Containers:
  nginx-deployment:
    Container ID:   docker://69fa73ed16d634627b69b8968915d9a5704f159206ac0d3b2f1179fa99acd56f
    Image:          nginx:1.7.9
    Image ID:       docker-pullable://nginx@sha256:e3456c851a152494c3e4ff5fcc26f240206abac0c9d794affb40e0714846c451
    Port:           <none>
    Host Port:      <none>
    State:          Running
      Started:      Thu, 29 Nov 2018 17:47:28 +0800
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-sm664 (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  default-token-sm664:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-sm664
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
  Type    Reason     Age   From                         Message
  ----    ------     ----  ----                         -------
  Normal  Scheduled  20m   default-scheduler            Successfully assigned default/nginx-deployment-5fd98dbf5f-58c4z to node02.wzlinux.com
  Normal  Pulling    20m   kubelet, node02.wzlinux.com  pulling image "nginx:1.7.9"
  Normal  Pulled     20m   kubelet, node02.wzlinux.com  Successfully pulled image "nginx:1.7.9"
  Normal  Created    20m   kubelet, node02.wzlinux.com  Created container
  Normal  Started    20m   kubelet, node02.wzlinux.com  Started container

我们可以看到 Controlled By: ReplicaSet/nginx-deployment-5fd98dbf5f ，说明此 Pod 是由 ReplicaSet nginx-deployment-5fd98dbf5f 创建的。

Events 记录了 Pod 的启动过程。

5、总结

1. 用户通过 kubectl 创建 Deployment。
2. Deployment 创建 ReplicaSet。
3. ReplicaSet 创建 Pod。

从上图也可以看出，对象的命名方式是：子对象的名字 = 父对象名字 + 随机字符串或数字。