我們 k8s叢集使用的是1.7.7版本的，該版本中官方已經推薦使用 Deployment代替 ReplicationController(rc)了， Deployment繼承了rc的全部功能外，還可以檢視升級詳細進度和狀態，當升級出現問題的時候，可以使用回滾操作回滾到指定的版本，每一次對Deployment的操作，都會儲存下來，變能方便的進行回滾操作了，另外對於每一次升級都可以隨時暫停和啟動，擁有多種升級方案： Recreate刪除現在的 Pod，重新建立； RollingUpdate滾動升級，逐步替換現有 Pod，對於生產環境的服務升級，顯然這是一種最好的方式。

建立Deployment

可以看出一個Deployment擁有多個Replica Set，而一個Replica Set擁有一個或多個Pod。一個Deployment控制多個rs主要是為了支援回滾機制，每當Deployment操作時，Kubernetes會重新生成一個Replica Set並保留，以後有需要的話就可以回滾至之前的狀態。 下面建立一個Deployment，它建立了一個Replica Set來啟動3個nginx pod，yaml檔案如下：

apiVersion: apps/v1beta1 kind: Deployment metadata: name: nginx-deploy labels: k8s-app: nginx-demo spec: replicas: 3 template: metadata: labels: app: nginx spec: containers: - name: nginx image: nginx:1.7.9 ports: - containerPort: 80

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apiVersion: apps/v1beta1kind: Deploymentmetadata:name: nginx-deploylabels:k8s-app: nginx-demospec:replicas: 3template:metadata:labels:app: nginxspec:containers:- name: nginximage: nginx:1.7.9ports:- containerPort: 80

將上面內容儲存為: nginx-deployment.yaml，執行命令:

$ kubectl create -f nginx-deployment.yaml deployment "nginx-deploy" created

12	$kubectlcreate-fnginx-deployment.yamldeployment"nginx-deploy"created

然後執行一下命令檢視剛剛建立的Deployment:

$ kubectl get deployments NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE nginx-deploy 3 0 0 0 1s

123	$kubectlgetdeploymentsNAMEDESIREDCURRENTUP-TO-DATEAVAILABLEAGEnginx-deploy30001s

隔一會再次執行上面命令：

$ kubectl get deployments NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE nginx-deploy 3 3 3 3 4m

123	$kubectlgetdeploymentsNAMEDESIREDCURRENTUP-TO-DATEAVAILABLEAGEnginx-deploy33334m

我們可以看到Deployment已經建立了3個Replica Set了，執行下面的命令檢視rs和pod:

$ kubectl get rs NAME DESIRED CURRENT READY AGE nginx-deploy-431080787 3 3 3 6m

123	$kubectlgetrsNAMEDESIREDCURRENTREADYAGEnginx-deploy-4310807873336m

$ kubectl get pod --show-labels NAME READY STATUS RESTARTS AGE LABELS nginx-deploy-431080787-53z8q 1/1 Running 0 7m app=nginx,pod-template-hash=431080787 nginx-deploy-431080787-bhhq0 1/1 Running 0 7m app=nginx,pod-template-hash=431080787 nginx-deploy-431080787-sr44p 1/1 Running 0 7m app=nginx,pod-template-hash=431080787

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$kubectlgetpod--show-labelsNAMEREADYSTATUSRESTARTSAGELABELSnginx-deploy-431080787-53z8q1/1Running07mapp=nginx,pod-template-hash=431080787nginx-deploy-431080787-bhhq01/1Running07mapp=nginx,pod-template-hash=431080787nginx-deploy-431080787-sr44p1/1Running07mapp=nginx,pod-template-hash=431080787

上面的Deployment的yaml檔案中的 replicas:3將會保證我們始終有3個POD在執行。

滾動升級Deployment

現在我們將剛剛儲存的yaml檔案中的nginx映象修改為 nginx:1.13.3，然後在spec下面新增滾動升級策略：

minReadySeconds: 5 strategy: # indicate which strategy we want for rolling update type: RollingUpdate rollingUpdate: maxSurge: 1 maxUnavailable: 1

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minReadySeconds: 5strategy:# indicate which strategy we want for rolling updatetype: RollingUpdaterollingUpdate:maxSurge: 1maxUnavailable: 1

• minReadySeconds:
  • Kubernetes在等待設定的時間後才進行升級
  • 如果沒有設定該值，Kubernetes會假設該容器啟動起來後就提供服務了
  • 如果沒有設定該值，在某些極端情況下可能會造成服務服務正常執行
• maxSurge:
  • 升級過程中最多可以比原先設定多出的POD數量
  • 例如：maxSurage=1，replicas=5,則表示Kubernetes會先啟動1一個新的Pod後才刪掉一箇舊的POD，整個升級過程中最多會有5 1個POD。
• maxUnavaible:
  • 升級過程中最多有多少個POD處於無法提供服務的狀態
  • 當 maxSurge不為0時，該值也不能為0
  • 例如：maxUnavaible=1，則表示Kubernetes整個升級過程中最多會有1個POD處於無法服務的狀態。

然後執行命令：

$ kubectl apply -f nginx-deployment.yaml deployment "nginx-deploy" configured

12	$kubectlapply-fnginx-deployment.yamldeployment"nginx-deploy"configured

然後我們可以使用 rollout命令：

• 檢視狀態：

  $ kubectl rollout status deployment/nginx-deploy Waiting for rollout to finish: 1 out of 3 new replicas have been updated.. deployment "nginx-deploy" successfully rolled out

  123	$kubectlrolloutstatusdeployment/nginx-deployWaitingforrollouttofinish:1outof3newreplicashavebeenupdated..deployment"nginx-deploy"successfullyrolledout

• 暫停升級

  $ kubectl rollout pause deployment <deployment>

  1	$kubectlrolloutpausedeployment<deployment>

• 繼續升級

  $ kubectl rollout resume deployment <deployment>

  1	$kubectlrolloutresumedeployment<deployment>

升級結束後，繼續檢視rs的狀態：

$ kubectl get rs NAME DESIRED CURRENT READY AGE nginx-deploy-2078889897 0 0 0 47m nginx-deploy-3297445372 3 3 3 42m nginx-deploy-431080787 0 0 0 1h

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$kubectlgetrsNAMEDESIREDCURRENTREADYAGEnginx-deploy-207888989700047mnginx-deploy-329744537233342mnginx-deploy-4310807870001h

根據AGE我們可以看到離我們最近的當前狀態是：3，和我們的yaml檔案是一致的，證明升級成功了。用 describe命令可以檢視升級的全部資訊：

Name: nginx-deploy Namespace: default CreationTimestamp: Wed, 18 Oct 2017 16:58:52 +0800 Labels: k8s-app=nginx-demo Annotations: deployment.kubernetes.io/revision=3 kubectl.kubernetes.io/last-applied-configuration={"apiVersion":"apps/v1beta1","kind":"Deployment","metadata":{"annotations":{},"labels":{"k8s-app":"nginx-demo"},"name":"nginx-deploy","namespace":"defa... 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:1.13.3 Port: 80/TCP Environment: <none> Mounts: <none> Volumes: <none> Conditions: Type Status Reason ---- ------ ------ Progressing True NewReplicaSetAvailable Available True MinimumReplicasAvailable OldReplicaSets: <none> NewReplicaSet: nginx-deploy-3297445372 (3/3 replicas created) Events: FirstSeen LastSeen Count From SubObjectPath Type Reason Message --------- -------- ----- ---- ------------- -------- ------ ------- 50m 50m 1 deployment-controller Normal ScalingReplicaSet Scaled up replica set nginx-deploy-2078889897 to 1 45m 45m 1 deployment-controller Normal ScalingReplicaSet Scaled down replica set nginx-deploy-2078889897 to 0 45m 45m 1 deployment-controller Normal ScalingReplicaSet Scaled up replica set nginx-deploy-3297445372 to 1 39m 39m 1 deployment-controller Normal ScalingReplicaSet Scaled down replica set nginx-deploy-431080787 to 2 39m 39m 1 deployment-controller Normal ScalingReplicaSet Scaled up replica set nginx-deploy-3297445372 to 2 38m 38m 1 deployment-controller Normal ScalingReplicaSet Scaled down replica set nginx-deploy-431080787 to 1 38m 38m 1 deployment-controller Normal ScalingReplicaSet Scaled up replica set nginx-deploy-3297445372 to 3 38m 38m 1 deployment-controller Normal ScalingReplicaSet Scaled down replica set nginx-deploy-431080787 to 0

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Name:nginx-deployNamespace:defaultCreationTimestamp:Wed,18Oct201716:58:52+0800Labels:k8s-app=nginx-demoAnnotations:deployment.kubernetes.io/revision=3kubectl.kubernetes.io/last-applied-configuration={"apiVersion":"apps/v1beta1","kind":"Deployment","metadata":{"annotations":{},"labels":{"k8s-app":"nginx-demo"},"name":"nginx-deploy","namespace":"defa...Selector:app=nginxReplicas:3desired|3updated|3total|3available|0unavailableStrategyType:RollingUpdateMinReadySeconds:0RollingUpdateStrategy:25%maxunavailable,25%maxsurgePodTemplate:Labels:app=nginxContainers:nginx:Image:nginx:1.13.3Port:80/TCPEnvironment:<none>    Mounts:   <none>  Volumes:    <none>Conditions:  Type    Status  Reason  ----    ------  ------  Progressing   True  NewReplicaSetAvailable  Available   True  MinimumReplicasAvailableOldReplicaSets: <none>NewReplicaSet:nginx-deploy-3297445372(3/3replicascreated)Events:FirstSeenLastSeenCountFromSubObjectPathTypeReasonMessage------------------------------------------------------------50m50m1deployment-controllerNormalScalingReplicaSetScaledupreplicasetnginx-deploy-2078889897to145m45m1deployment-controllerNormalScalingReplicaSetScaleddownreplicasetnginx-deploy-2078889897to045m45m1deployment-controllerNormalScalingReplicaSetScaledupreplicasetnginx-deploy-3297445372to139m39m1deployment-controllerNormalScalingReplicaSetScaleddownreplicasetnginx-deploy-431080787to239m39m1deployment-controllerNormalScalingReplicaSetScaledupreplicasetnginx-deploy-3297445372to238m38m1deployment-controllerNormalScalingReplicaSetScaleddownreplicasetnginx-deploy-431080787to138m38m1deployment-controllerNormalScalingReplicaSetScaledupreplicasetnginx-deploy-3297445372to338m38m1deployment-controllerNormalScalingReplicaSetScaleddownreplicasetnginx-deploy-431080787to0

回滾Deployment

我們已經能夠滾動平滑的升級我們的Deployment了，但是如果升級後的POD出了問題該怎麼辦？我們能夠想到的最好最快的方式當然是回退到上一次能夠提供正常工作的版本，Deployment就為我們提供了回滾機制。

首先，檢視Deployment的升級歷史：

$ kubectl rollout history deployment nginx-deploy deployments "nginx-deploy" REVISION CHANGE-CAUSE 1 <none> 2 <none> 3 kubectl apply --filename=Desktop/nginx-deployment.yaml --record=true

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$kubectlrollouthistorydeploymentnginx-deploydeployments"nginx-deploy"REVISIONCHANGE-CAUSE1<none>2   <none>3kubectlapply--filename=Desktop/nginx-deployment.yaml--record=true

從上面的結果可以看出在執行Deployment升級的時候最好帶上 record引數，便於我們檢視歷史版本資訊。同樣我們可以使用下面的命令檢視單個REVISION的資訊：

$ kubectl rollout history deployment nginx-deploy --revision=3 deployments "nginx-deploy" with revision #3 Pod Template: Labels: app=nginx pod-template-hash=3297445372 Annotations: kubernetes.io/change-cause=kubectl apply --filename=nginx-deployment.yaml --record=true Containers: nginx: Image: nginx:1.13.3 Port: 80/TCP Environment: <none> Mounts: <none> Volumes: <none>

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$kubectlrollouthistorydeploymentnginx-deploy--revision=3deployments"nginx-deploy"withrevision#3PodTemplate:Labels:app=nginxpod-template-hash=3297445372Annotations:kubernetes.io/change-cause=kubectlapply--filename=nginx-deployment.yaml--record=trueContainers:nginx:Image:nginx:1.13.3Port:80/TCPEnvironment:<none>    Mounts: <none>  Volumes:  <none>

假如現在要直接回退到當前版本的前一個版本：

$ kubectl rollout undo deployment nginx-deploy deployment "nginx-deploy" rolled back

12	$kubectlrolloutundodeploymentnginx-deploydeployment"nginx-deploy"rolledback

當然也可以用

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