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Kubernetes部署和升级应用

之前文章中我们都是用POD部署应用，特别是用POD部署应用时如果要更新应用程序，必须先更新镜像（Image）/配置（ConfigMap），删除POD再重新部署应用程序才能整整的更新。Kubernetes提供了更高级的应用部署和升级方法。

使用ReplicationController部署应用

　　 如果用ReplicationController（RC）部署的应用可以通过RC update来更新应用。 具体的kubia-rc.yaml文件如下：

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apiVersion: v1
kind: ReplicationController
metadata:
  name: kubia
spec:
  replicas: 3
  selector:
    app: kubia
  template:
    metadata:
      name: kubia
      labels:
        app: kubia
    spec:
      containers:
        - name: kubia
          image: 172.17.0.1:5000/kubia:v1
          ports:
            - containerPort: 3000

使用kubectl create -f kubia-rc.yaml创建RC，部署成功以后即可看到根据RC的配置会产生3个副本kubectl get rc,po。

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kubectl get po,rc
NAME              READY   STATUS    RESTARTS   AGE
pod/kubia-bqszw   1/1     Running   0          62s
pod/kubia-c4cb9   1/1     Running   0          62s
pod/kubia-wxj55   1/1     Running   0          62s

NAME                          DESIRED   CURRENT   READY   AGE
replicationcontroller/kubia   3         3         3       62s

当前POD到到镜像版本为v1

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kubectl describe po
Name:         kubia-bqszw
Namespace:    default
Priority:     0
Node:         minikube/172.17.0.3
Start Time:   Wed, 14 Oct 2020 20:29:56 +0800
Labels:       app=kubia
Annotations:  <none>
Status:       Running
IP:           172.18.0.3
IPs:
  IP:           172.18.0.3
Controlled By:  ReplicationController/kubia
Containers:
  kubia:
    Container ID:   docker://ec65afaeea2e8726530863981512165bec02ceb8e953a3d6575f6ea4ad7cc3f3
    Image:          172.17.0.1:5000/kubia:v1
    Image ID:       docker-pullable://172.17.0.1:5000/kubia@sha256:0a9705988c08da5cc4fd535f40216a7b0ef89325b594ddb97ffcbd220c6731f1
...

通过kubectl set image rc/kubia kubia=172.17.0.1:5000/kubia:v2更新镜像。此时的应用程序并不会自动更新。当POD 异常或者手工删除以后RC 会自动拉起一个POD ，保证POD的副本数和RC 中配置的一致，此时新的POD 就是使用新的镜像创建应用，也就是说有的POD 使用新的镜像，有的POD 使用老的镜像。可以通过kubectl describe po查询到POD中容器的镜像版本不同。

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kubectl describe po
Name:         kubia-c4cb9
Namespace:    default
Priority:     0
Node:         minikube/172.17.0.3
Start Time:   Wed, 14 Oct 2020 20:29:56 +0800
Labels:       app=kubia
Annotations:  <none>
Status:       Running
IP:           172.18.0.4
IPs:
  IP:           172.18.0.4
Controlled By:  ReplicationController/kubia
Containers:
  kubia:
    Container ID:   docker://2b259af30a0c75987f027ac4516a7ea368774bbac4259a732f8141fdbcae376a
    Image:          172.17.0.1:5000/kubia:v1
    Image ID:       docker-pullable://172.17.0.1:5000/kubia@sha256:0a9705988c08da5cc4fd535f40216a7b0ef89325b594ddb97ffcbd220c6731f1
    Port:           3000/TCP
    Host Port:      0/TCP
    State:          Running
      Started:      Wed, 14 Oct 2020 20:30:04 +0800
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-d2hsm (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  default-token-d2hsm:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-d2hsm
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                 node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
  Type    Reason     Age    From               Message
  ----    ------     ----   ----               -------
  Normal  Scheduled  6m43s  default-scheduler  Successfully assigned default/kubia-c4cb9 to minikube
  Normal  Pulled     6m36s  kubelet            Container image "172.17.0.1:5000/kubia:v1" already present on machine
  Normal  Created    6m36s  kubelet            Created container kubia
  Normal  Started    6m35s  kubelet            Started container kubia


Name:         kubia-s6822                        ‹--自动使用新的镜像创建新的POD
Namespace:    default
Priority:     0
Node:         minikube/172.17.0.3
Start Time:   Wed, 14 Oct 2020 20:35:57 +0800
Labels:       app=kubia
Annotations:  <none>
Status:       Running
IP:           172.18.0.6
IPs:
  IP:           172.18.0.6
Controlled By:  ReplicationController/kubia
Containers:
  kubia:
    Container ID:   docker://91fd664961c798256afbfd9b2e6cd47697a817f27803812da26e28d56212371e
    Image:          172.17.0.1:5000/kubia:v2
    Image ID:       docker-pullable://172.17.0.1:5000/kubia@sha256:0709bbd6e3a34f306a16207b79b045e6a4bf33c22a3e7a88404166caee41e51f
    Port:           3000/TCP
    Host Port:      0/TCP
    State:          Running
      Started:      Wed, 14 Oct 2020 20:36:02 +0800
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-d2hsm (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  default-token-d2hsm:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-d2hsm
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                 node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
  Type    Reason     Age   From               Message
  ----    ------     ----  ----               -------
  Normal  Scheduled  42s   default-scheduler  Successfully assigned default/kubia-s6822 to minikube
  Normal  Pulled     38s   kubelet            Container image "172.17.0.1:5000/kubia:v2" already present on machine
  Normal  Created    37s   kubelet            Created container kubia
  Normal  Started    37s   kubelet            Started container kubia


Name:         kubia-wxj55
Namespace:    default
Priority:     0
Node:         minikube/172.17.0.3
Start Time:   Wed, 14 Oct 2020 20:29:56 +0800
Labels:       app=kubia
Annotations:  <none>
Status:       Running
IP:           172.18.0.2
IPs:
  IP:           172.18.0.2
Controlled By:  ReplicationController/kubia
Containers:
  kubia:
    Container ID:   docker://a5195a7ec8573d429445f7c79218372abc887d360b3564c8659b600c236c0248
    Image:          172.17.0.1:5000/kubia:v1
    Image ID:       docker-pullable://172.17.0.1:5000/kubia@sha256:0a9705988c08da5cc4fd535f40216a7b0ef89325b594ddb97ffcbd220c6731f1
    Port:           3000/TCP
    Host Port:      0/TCP
    State:          Running
      Started:      Wed, 14 Oct 2020 20:30:04 +0800
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-d2hsm (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  default-token-d2hsm:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-d2hsm
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
                 node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
  Type    Reason     Age    From               Message
  ----    ------     ----   ----               -------
  Normal  Scheduled  6m44s  default-scheduler  Successfully assigned default/kubia-wxj55 to minikube
  Normal  Pulled     6m36s  kubelet            Container image "172.17.0.1:5000/kubia:v1" already present on machine
  Normal  Created    6m36s  kubelet            Created container kubia
  Normal  Started    6m35s  kubelet            Started container kubia

使用ReplicationController部署应用，需要手工选择POD 逐一进行升级。实际部署应用过程中我们希望这个过程可以可控、且自动完成，这就需要通过更高级更高级的概念来部署应用。

使用Deployment部署应用

　　 Kubernetes提供更高级的概念来实现应用的部署、滚动升级以及回滚。一个典型的kubernetes的应用会包含：POD、RepliciaSet以及Deployment。他们之间的关系如下：

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apiVersion: apps/v1
kind: Deployment
metadata:
  name: kubia
spec:
  replicas: 3
  selector:
    matchLabels:
      app: kubia
  template:
    metadata:
      labels:
        app: kubia
    spec:
      containers:
      - name: kubia
        image: 172.17.0.1:5000/kubia:v1

还是上面的例子，这次将ReplicationController的yaml文件中kinde替换城Deployment，并另存为kubia-deploymnent.yaml，使用kubectl create -f kubia-deployment.yaml重新部署应用，部署成功以后可以功过kubectl get po,rs,deployment查询部署的应用情况。

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kubectl get po,rs,deployment
NAME                         READY   STATUS    RESTARTS   AGE
pod/kubia-7fc889c9c9-b7b8f   1/1     Running   1          21h
pod/kubia-7fc889c9c9-lp7m8   1/1     Running   1          21h
pod/kubia-7fc889c9c9-qkz9w   1/1     Running   1          21h

NAME                               DESIRED   CURRENT   READY   AGE
replicaset.apps/kubia-7fc889c9c9   3         3         3       21h

NAME                    READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/kubia   3/3     3            3           21h

通过kubectl descibe po查询到POD到详细情况如下：

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kubectl describe po
Name:         kubia-7fc889c9c9-b7b8f
Namespace:    default
Priority:     0
Node:         minikube/172.17.0.3
Start Time:   Tue, 13 Oct 2020 22:44:19 +0800
Labels:       app=kubia
              pod-template-hash=7fc889c9c9
Annotations:  <none>
Status:       Running
IP:           172.18.0.2
IPs:
  IP:           172.18.0.2
Controlled By:  ReplicaSet/kubia-7fc889c9c9
Containers:
  kubia:
    Container ID:   docker://aa524c986c27e53d12961173a5a0adf43a3554e13aeac5fc1c5cca083da09271
    Image:          172.17.0.1:5000/kubia:v1                        ‹-- 镜像版本是v1
    Image ID:       docker-pullable://172.17.0.1:5000/kubia@sha256:0a9705988c08da5cc4fd535f40216a7b0ef89325b594ddb97ffcbd220c6731f1
...

更新应用

  • 配置更新镜像

kubectl set image deployment/kubia kubia=172.17.0.1:5000/kubia:v2

设置完成以后deployment会自动滚动升级，可以通过kubectl rollout deployment/kubia status查询升级状态，此时查询应用部署的详情可以看到PO,RS更新中或者已经更新成功。 kubectl get po,rs,deployment 其中存在2个rs，一个升级前的rs，一个是当前到rs。

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kubectl get po,rs,deployment
NAME                         READY   STATUS              RESTARTS   AGE
pod/kubia-7fc889c9c9-b7b8f   1/1     Running             1          21h
pod/kubia-7fc889c9c9-lp7m8   1/1     Running             1          21h
pod/kubia-7fc889c9c9-qkz9w   1/1     Running             1          21h
pod/kubia-84ddcd9474-bv8fl   0/1     ContainerCreating   0          3s      ‹-- 新建POD

NAME                               DESIRED   CURRENT   READY   AGE
replicaset.apps/kubia-7fc889c9c9   3         3         3       21h          ‹-- 升级前的rs
replicaset.apps/kubia-84ddcd9474   1         1         0       4s           ‹-- 当前的rs

NAME                    READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/kubia   3/3     1            3           21h

查询POD详细信息，可以看到新建到POD已经更新为新到镜像。

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kubectl describe po kubia-84ddcd9474-bv8fl                                  ‹-- 新建POD
Name:         kubia-84ddcd9474-bv8fl
Namespace:    default
Priority:     0
Node:         minikube/172.17.0.3
Start Time:   Wed, 14 Oct 2020 20:19:12 +0800
Labels:       app=kubia
              pod-template-hash=84ddcd9474
Annotations:  <none>
Status:       Running
IP:           172.18.0.6
IPs:
  IP:           172.18.0.6
Controlled By:  ReplicaSet/kubia-84ddcd9474
Containers:
  kubia:
    Container ID:   docker://3de190659e28bebcde082b287c7c4c434ab706c08654f6d1c7db3db455304508
    Image:          172.17.0.1:5000/kubia:v2                                ‹-- 镜像版本是v2
    Image ID:       docker-pullable://172.17.0.1:5000/kubia@sha256:0709bbd6e3a34f306a16207b79b045e6a4bf33c22a3e7a88404166caee41e51f

  • 管理升级

此时如果使用kubectl rollout undo deployment/kubia 即可全部回滚应用，可以通过kubectl rollout pause/resume/restart/history等控制滚动升级过程（如果测试过程中难以观察到升级过程，可以讲deployment中副本数量调高）。

此外，也可以使用StatefulSet部署有状态应用。StatefulSet和Deployment最大的区别是为每个副本POD实例提供店里存储，可以保证POD副本有固定的名字和主机，可以按照预期的顺序启停POD副本。

Kubernetes部署和升级应用

http://mixiang.tech/2020/10/14/2020-10-14-19/

作者

Mixion

发布于

2020-10-14

更新于

2022-12-02

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