K8S（2）RC、RS和Deployment（上）-阿里云开发者社区

一、RC 与 RS

RC全称为ReplicationController（复制控制器），RS全称为ReplicaSet（复制集）

RC和RS是K8S中两种简单部署pod的方式，但是由于在生产环境中，主要使用更高级的Deployment等方式对pod进行部署、运行、管理，所以这里只对RC和RS进行简单介绍

- Replication Controller（RC）

使用RC可以使Pod副本数达到指定数量，确保一个Pod或者一组同类Pod总是可用的

如果存在的Pod大于了设置的数量，那么RC将会终止多余的Pod，相反，如果小于设置的数量，RC则会启动一些Pod以达到设置的数量

和手动创建Pod不同，使用RC维护的Pod在失败、删除、终止时会自动替换，因此就算所需的应用程序只需要一个Pod，也应该使用RC或者其他的方式进行管理

RC类似于进程管理程序，但是RC不是监视单个节点上的各个进程，而是监视多个节点上的多个Pod

定义一个RC的示例：

apiVersion: v1
kind: ReplicationController
metadata:
 name: nginx
spec:
 replicas: 3
 selector:
  app: nginx
 template:
  metadata:
   name: nginx
   labels:
     app: nginx
  spec:
   containers:
   - name: nginx
     image: nginx
     ports:
     - containerPort: 80

- ReplicaSet（RS）

RS是支持基于集合的标签选择器的新一代RC，RS主要作用于Deployment协调创建、删除、更新Pod，和RC的区别是，RS支持标签选择器

在实际应用中，RS可以单独使用，但是一般使用Deployment来自动管理RS，除非自定义的Pod不需要更新或者其他编排等

定义一个RS的示例：

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: frontend
  labels:
    app: test
sepc:
  replicas: 3
  selector:
    matchLabels:
      app: test
    matchExpressions:
    - {key: tier,operator: ln,values: [frontend]}
  template:
    metadata:
      labels: 
      app: test
    sepc:
      containers:
      - name: redis
        images: redis:v1.0
        resources:
          requests:
            cpu: 100m
            memory: 100Mi
        env:
        - name: GET_HOSTS_FROM
          value: dns
        ports:
        - containerPort: 6379

RC和RS的创建删除和Pod并没有太大的区别，并且RC在实际生产环境基本已经不再使用，RS也很少单独使用，一般都会根据需求使用更高级的Deployment、DaemonSet、StatefulSet来管理Pod

二、Deployment

Deployment主要用于部署无状态的服务，是最常用的Pod控制器，一般用于管理公司中无状态的微服务，例如Config-Server注册中心、Zuul网关、SpringBoot微服务框架等，Deployment可以管理多个副本的Pod，实现无缝迁移、自动扩容缩容、自动灾难恢复、一键回滚功能等

注释：有状态服务与无状态服务：

有状态服务

1. 服务本身依赖或者存在局部的状态数据，这些数据需要自身持久化或者可以通过其他节点恢复。
2. 一个请求只能被某个节点（或者同等状态下的节点）处理。
3. 存储状态数据，实例的拓展需要整个系统参与状态的迁移。
4. 在一个封闭的系统中，存在多个数据闭环，需要考虑这些闭环的数据一致性问题。
5. 有状态服务通常存在于分布式架构中。

无状态服务

1. 服务不依赖自身的状态，实例的状态数据可以维护在内存中。
2. 任何一个请求都可以被任意一个实例处理。
3. 不存储状态数据，实例可以水平拓展，通过负载均衡将请求分发到各个节点。
4. 在一个封闭的系统中，只存在一个数据闭环。
5.无状态服务通常存在于单体架构的集群中。

虽然RS可以确保在任何给定时间运行的Pod副本数达到指定数量，但是Deployment是一个更高级的概念，它会管理RS，并且为Pod喝RS提供声明性更新，以及许多其他功能呢，一般实际工作中，会使用Deployment代替RS

如果在Deployment对象中描述了所需要的状态，那么Deployment控制器就会以可控制的速率将实际状态更改为期望状态，也可以在Deployment中创建RS，或者删除现有的Deployment并使用新的Deployment部署所需要的资源

- 创建Deployment

[root@master1 ~]# kubectl create deployment nginx --image=nginx   #创建deployment
deployment.apps/nginx created
[root@master1 ~]# kubectl get pods
NAME                    READY   STATUS              RESTARTS   AGE
nginx-f89759699-fjwr8   0/1     ContainerCreating   0          3s
[root@master1 ~]# kubectl get deployment   #查看deployment的pod
NAME    READY   UP-TO-DATE   AVAILABLE   AGE
nginx   1/1     1            1           39s
[root@master1 ~]# kubectl get deployment nginx -o yaml > nginx.yaml  #导出deployment的yaml文件，用于修改
[root@master1 ~]# ll
total 8
-rw-------. 1 root root 1259 Feb 23 17:13 anaconda-ks.cfg
-rw-r--r--  1 root root 3703 Jun 22 09:59 nginx.yaml

使用kubectl replace命令，参数-f指定yaml或json文件，替换资源（类似于重载配置）

[root@master1 ~]# kubectl replace -f nginx.yaml  
deployment.apps/nginx replaced

使用kubectl edit命令，可以直接编辑、修改资源，edit命令会打开KUBE_EDITOR、GIT_EDITOR或者EDITOR环境变量定义的编辑器，可以同时编辑多个资源，但是编辑过的资源只会一次性提交，默认是YAML格式，加参数-o json可以以JSON格式编辑

[root@master1 ~]# kubectl edit deployment nginx  #进入编辑模式后与vim类似，修改完后会直接生效
Edit cancelled, no changes made.

下面来创建一个Deployment

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-alpine
        ports:
        - containerPort: 80
#注释：
示例解析：
kind：指定类型为Deployment的控制器
第一个metadata是定义Deployment的名称与标签
第一个sepc定义Deployment的资源
replicas：定义pod的副本数
template定义pod的详细信息
template下的spec定义容器的详细信息

创建此Deployment

[root@master1 ~]# kubectl create -f nginx.yaml
deployment.apps/nginx-deployment created
[root@master1 ~]# kubectl get pods
NAME                                READY   STATUS    RESTARTS   AGE
nginx-deployment-6b75f4cbdd-8nmlv   1/1     Running   0          42m
nginx-deployment-6b75f4cbdd-f56z8   1/1     Running   0          39m
nginx-deployment-6b75f4cbdd-llhht   1/1     Running   0          42m
[root@master1 ~]# kubectl get deployment
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment   3/3     3            3           42m
[root@master1 ~]# kubectl get deploy -o wide  #查看deployment的信息
NAME               READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES              SELECTOR
nginx-deployment   3/3     3            3           43m   nginx        nginx:1.14-alpine   app=nginx
#注释：
name：集群中deployment的名称
ready：pod的状态，已经ready的pod个数
up-to-date：显示已经达到期望状态的副本数
available：显示用户可以使用的应用程序副本数
age：显示应用程序运行的时间
containers：容器的名称
images：镜像名称
selector：管理的pod标签

查看pod标签

[root@master1 ~]# kubectl get pod --show-labels
NAME                                READY   STATUS    RESTARTS   AGE   LABELS
nginx-deployment-6b75f4cbdd-8nmlv   1/1     Running   0          50m   app=nginx,pod-template-hash=6b75f4cbdd
nginx-deployment-6b75f4cbdd-f56z8   1/1     Running   0          47m   app=nginx,pod-template-hash=6b75f4cbdd
nginx-deployment-6b75f4cbdd-llhht   1/1     Running   0          50m   app=nginx,pod-template-hash=6b75f4cbdd
#注释
标签中'pod-template-hash=6b75f4cbdd'的这个值，表示RS的hash哈希值

查看RS

[root@master1 ~]# kubectl get rs
NAME                          DESIRED   CURRENT   READY   AGE
nginx-deployment-6b75f4cbdd   3         3         3       52m

看此时Deployment rollout的状态：

[root@master1 ~]# kubectl rollout status deployment/nginx-deployment   #查看资源状态
deployment "nginx-deployment" successfully rolled out
[root@master1 ~]# kubectl get deploy  #查看deployment
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment   3/3     3            3           3h12m
[root@master1 ~]# kubectl get rs   #查看rs
NAME                          DESIRED   CURRENT   READY   AGE
nginx-deployment-6b75f4cbdd   3         3         3       3h12m
[root@master1 ~]# kubectl get pods --show-labels   #查看deployment创建的pod
NAME                                READY   STATUS    RESTARTS   AGE     LABELS
nginx-deployment-6b75f4cbdd-8nmlv   1/1     Running   0          3h12m   app=nginx,pod-template-hash=6b75f4cbdd
nginx-deployment-6b75f4cbdd-f56z8   1/1     Running   0          3h10m   app=nginx,pod-template-hash=6b75f4cbdd
nginx-deployment-6b75f4cbdd-llhht   1/1     Running   0          3h12m   app=nginx,pod-template-hash=6b75f4cbdd

- 更新Deployment

通常对应用程序的升级、版本迭代都会通过Deployment对Pod进行滚动更新
下面来看示例：

[root@master1 ~]# kubectl get deploy  #可以使用缩写进行查看
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment   3/3     3            3           23h
[root@master1 ~]# kubectl get deployment
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
nginx-deployment   3/3     3            3           23h
#修改此deployment的镜像
[root@master1 ~]# kubectl set image deployment nginx-deployment nginx=nginxdemos/hello:plain-text --record
————————————————————————————————
#除了使用set image进行修改，也可以使用kubectl edit deployment nginx直接对yaml文件进行编辑
————————————————————————————————
deployment.apps/nginx-deployment image updated
[root@master1 ~]# kubectl rollout status deployment.v1.apps/nginx-deployment  #查看状态
Waiting for deployment "nginx-deployment" rollout to finish: 1 out of 3 new replicas have been updated...
Waiting for deployment "nginx-deployment" rollout to finish: 1 out of 3 new replicas have been updated...
Waiting for deployment "nginx-deployment" rollout to finish: 1 out of 3 new replicas have been updated...
Waiting for deployment "nginx-deployment" rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for deployment "nginx-deployment" rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for deployment "nginx-deployment" rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for deployment "nginx-deployment" rollout to finish: 1 old replicas are pending termination...
Waiting for deployment "nginx-deployment" rollout to finish: 1 old replicas are pending termination...
deployment "nginx-deployment" successfully rolled out
[root@master1 ~]# kubectl get rs  #查看rs
NAME                          DESIRED   CURRENT   READY   AGE
nginx-deployment-5d6b8b588c   3         3         3       3m58s
nginx-deployment-6b75f4cbdd   0         0         0       23h
[root@master1 ~]# kubectl describe deployments.apps nginx-deployment  #使用describe查看deployment的详细信息
Name:                   nginx-deployment
Namespace:              default
CreationTimestamp:      Thu, 23 Jun 2022 10:31:28 +0800
Labels:                 app=nginx
Annotations:            deployment.kubernetes.io/revision: 2
                        kubernetes.io/change-cause: kubectl set image deployment nginx-deployment nginx=nginxdemos/hello:plain-text --record=true
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:        nginxdemos/hello:plain-text
    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-5d6b8b588c (3/3 replicas created)
Events:
  Type    Reason             Age                  From                   Message
  ----    ------             ----                 ----                   -------
  Normal  ScalingReplicaSet  7m8s                 deployment-controller  Scaled up replica set nginx-deployment-5d6b8b588c to 1
  Normal  ScalingReplicaSet  6m47s (x2 over 23h)  deployment-controller  Scaled down replica set nginx-deployment-6b75f4cbdd to 2
  Normal  ScalingReplicaSet  6m47s                deployment-controller  Scaled up replica set nginx-deployment-5d6b8b588c to 2
  Normal  ScalingReplicaSet  6m46s                deployment-controller  Scaled down replica set nginx-deployment-6b75f4cbdd to 1
  Normal  ScalingReplicaSet  6m46s                deployment-controller  Scaled up replica set nginx-deployment-5d6b8b588c to 3
  Normal  ScalingReplicaSet  6m45s                deployment-controller  Scaled down replica set nginx-deployment-6b75f4cbdd to 0
#注释：
events的过程可以看到：
1、创建了一个新的deployment为'nginx-deployment-5d6b8b588c'，并且增加了一个RS，现在新的deploymentRS数量为1个
2、旧的deployment ' nginx-deployment-6b75f4cbdd'减少1个RS，现在旧的deploymentRS数量为2两个
3、新的deploymentRS数量再次增加，增加1个，现在新的deploymentRS数量为2两个
4、相应的旧的deploymentRS数量减少一个，数量为1个
5、新的deploymentRS再次增加，增加一个，现在为3个
6、旧的deploymentRS再次减少，减少一个，数量为0，同时也完成滚动更新

从上面的kubectl describe命令，可以看到deployment更新后的过程，是滚动更新

- 回滚Deployment

如果Deployment在更新后出现了问题，可以对其进行回滚操作，默认情况下，所有Deployment的rollout（回退）历史都保存在系统中，可以随时进行回滚
下面来看案例：

[root@master1 ~]# kubectl rollout history deployment nginx-deployment  #使用kubectl rollout history可以查看修改记录
deployment.apps/nginx-deployment
REVISION  CHANGE-CAUSE
1         <none>
2         kubectl set image deployment nginx-deployment nginx=nginxdemos/hello:plain-text --record=true
[root@master1 ~]# kubectl set image deployment nginx-deployment nginx=nginx:1.14-alpine --record  #再次修改镜像，加--record可以记录到history中
deployment.apps/nginx-deployment image updated
[root@master1 ~]# kubectl describe deployments.apps nginx-deployment  #查看详细信息
Name:                   nginx-deployment
Namespace:              default
CreationTimestamp:      Thu, 23 Jun 2022 10:31:28 +0800
Labels:                 app=nginx
Annotations:            deployment.kubernetes.io/revision: 3
                        kubernetes.io/change-cause: kubectl set image deployment nginx-deployment nginx=nginx:1.14-alpine --record=true
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-alpine  #可以看到镜像已经更换
    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-6b75f4cbdd (3/3 replicas created)
Events:
  Type    Reason             Age                From                   Message
  ----    ------             ----               ----                   -------
  Normal  ScalingReplicaSet  34s                deployment-controller  Scaled up replica set nginx-deployment-6b75f4cbdd to 1
  Normal  ScalingReplicaSet  28s                deployment-controller  Scaled down replica set nginx-deployment-5d6b8b588c to 2
  Normal  ScalingReplicaSet  28s                deployment-controller  Scaled up replica set nginx-deployment-6b75f4cbdd to 2
  Normal  ScalingReplicaSet  27s (x2 over 28h)  deployment-controller  Scaled up replica set nginx-deployment-6b75f4cbdd to 3
  Normal  ScalingReplicaSet  27s                deployment-controller  Scaled down replica set nginx-deployment-5d6b8b588c to 1
  Normal  ScalingReplicaSet  25s                deployment-controller  Scaled down replica set nginx-deployment-5d6b8b588c to 0
[root@master1 ~]# kubectl rollout history deployment nginx-deployment  #查看历史记录，发现增加了一条
deployment.apps/nginx-deployment
REVISION  CHANGE-CAUSE
2         kubectl set image deployment nginx-deployment nginx=nginxdemos/hello:plain-text --record=true
3         kubectl set image deployment nginx-deployment nginx=nginx:1.14-alpine --record=true
[root@master1 ~]# kubectl rollout history deployment nginx-deployment --revision=2  #查看编号2记录的详细信息，使用--revision可以指定版本查看详细信息
deployment.apps/nginx-deployment with revision #2
Pod Template:
  Labels:       app=nginx
        pod-template-hash=5d6b8b588c
  Annotations:  kubernetes.io/change-cause: kubectl set image deployment nginx-deployment nginx=nginxdemos/hello:plain-text --record=true
  Containers:
   nginx:
    Image:      nginxdemos/hello:plain-text
    Port:       80/TCP
    Host Port:  0/TCP
    Environment:        <none>
    Mounts:     <none>
  Volumes:      <none>
[root@master1 ~]# kubectl rollout undo deployment nginx-deployment  #回滚到上一个版本
deployment.apps/nginx-deployment rolled back
[root@master1 ~]# kubectl describe deployments.apps nginx-deployment  #再次查看详细信息
Name:                   nginx-deployment
Namespace:              default
CreationTimestamp:      Thu, 23 Jun 2022 10:31:28 +0800
Labels:                 app=nginx
Annotations:            deployment.kubernetes.io/revision: 4
                        kubernetes.io/change-cause: kubectl set image deployment nginx-deployment nginx=nginxdemos/hello:plain-text --record=true
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:        nginxdemos/hello:plain-text   #可以发现镜像已经变成了上一个版本的镜像
    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-5d6b8b588c (3/3 replicas created)
Events:
  Type    Reason             Age                From                   Message
  ----    ------             ----               ----                   -------
  Normal  ScalingReplicaSet  6m7s               deployment-controller  Scaled up replica set nginx-deployment-6b75f4cbdd to 1
  Normal  ScalingReplicaSet  6m1s               deployment-controller  Scaled up replica set nginx-deployment-6b75f4cbdd to 2
  Normal  ScalingReplicaSet  6m1s               deployment-controller  Scaled down replica set nginx-deployment-5d6b8b588c to 2
  Normal  ScalingReplicaSet  6m                 deployment-controller  Scaled down replica set nginx-deployment-5d6b8b588c to 1
  Normal  ScalingReplicaSet  6m (x2 over 28h)   deployment-controller  Scaled up replica set nginx-deployment-6b75f4cbdd to 3
  Normal  ScalingReplicaSet  5m58s              deployment-controller  Scaled down replica set nginx-deployment-5d6b8b588c to 0
  Normal  ScalingReplicaSet  4s (x2 over 5h8m)  deployment-controller  Scaled up replica set nginx-deployment-5d6b8b588c to 1
  Normal  ScalingReplicaSet  3s (x2 over 5h8m)  deployment-controller  Scaled up replica set nginx-deployment-5d6b8b588c to 2
  Normal  ScalingReplicaSet  3s (x3 over 28h)   deployment-controller  Scaled down replica set nginx-deployment-6b75f4cbdd to 2
  Normal  ScalingReplicaSet  1s (x3 over 2s)    deployment-controller  (combined from similar events): Scaled down replica set nginx-deployment-6b75f4cbdd to 0

使用–to-revision返回到指定版本：

[root@master1 ~]# kubectl rollout history deployment nginx-deployment
deployment.apps/nginx-deployment
REVISION  CHANGE-CAUSE
3         kubectl set image deployment nginx-deployment nginx=nginx:1.14-alpine --record=true
4         kubectl scale deployment nginx-deployment --replicas=3 --record=true
[root@master1 ~]# kubectl rollout undo deployment nginx-deployment --to-revision=3  #返回3版本
deployment.apps/nginx-deployment rolled back
[root@master1 ~]# kubectl rollout history deployment nginx-deployment
deployment.apps/nginx-deployment
REVISION  CHANGE-CAUSE
4         kubectl scale deployment nginx-deployment --replicas=3 --record=true
5         kubectl set image deployment nginx-deployment nginx=nginx:1.14-alpine --record=true

K8S（2）RC、RS和Deployment（上）

一、RC 与 RS

- Replication Controller（RC）

- ReplicaSet（RS）

二、Deployment

- 创建Deployment

- 更新Deployment

- 回滚Deployment

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插件

K8S（2）RC、RS和Deployment（上）

一、RC 与 RS

- Replication Controller（RC）

- ReplicaSet（RS）

二、Deployment

- 创建Deployment

- 更新Deployment

- 回滚Deployment

热门文章

最新文章

相关课程

相关电子书

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推荐镜像