1.Kubernetes的controller pattern

需要認(rèn)識到Kubernetes操作Pod的邏輯，都是由控制器來完成的。

查看之前寫過的nginx-deployment的YAML文件 [root@kubernetes01 ~]# cat nginx-deployment.yaml apiVersion: apps/v1 kind: Deployment metadata:name: nginx-deploymentlabels: app: nginx spec:replicas: 2selector: matchLabels:app: nginxtemplate:metadata:labels:app: nginxspec:containers:- name: nginximage: nginx:1.8.1ports:- containerPort: 80Kubernetes中的kube-controller-manager組件執(zhí)行了上面的Deployment定義的編排動作。 Deployment定義的template字段，這種字段在Kubernetes中叫做PodTemplate（Pod模版）。 而這個YAML文件描述的就是Deployment這樣一個控制器，template以上的部分是對控制器的定義，template以下的部分屬于對被控制的對象的定義。

2.Kubernetes Pod 的自動伸縮

Pod水平擴(kuò)展和水平收縮的能力依賴于Kubernetes中一個非常重要的API對象，ReplicaSet也就是副本集。

2.1.Pod的水平擴(kuò)展和伸縮

查看例子的YAML文件 [root@kubernetes01 ~]# cat nginx-replicaset.yaml apiVersion: apps/v1 kind: ReplicaSet metadata:name: nginx-replicasetlabels: app: nginx spec:replicas: 3selector:matchLabels:app: nginxtemplate:metadata:labels:app: nginxspec:containers:- name: nginximage: nginx:1.8.0 上面這個例子中，ReplicaSet對象是由一個Pod模版和副本數(shù)目的多少定義組成的。再看這個YAML文件 [root@kubernetes01 ~]# cat nginx-deployment.yaml apiVersion: apps/v1 kind: Deployment metadata:name: nginx-deploymentlabels: app: nginx spec:replicas: 3selector: matchLabels:app: nginxtemplate:metadata:labels:app: nginxspec:containers:- name: nginximage: nginx:1.8.1ports:- containerPort: 80 Deployment控制器實(shí)際操作的是ReplicaSet對象，而不是Pod對象。 這個定義replicas=3的Deployment與他的ReplicaSet以及Pod的關(guān)系可以理解成是一種分層控制層層控制的關(guān)系，replicas的值決定是擴(kuò)展還是收縮，當(dāng)你去擴(kuò)展或是收縮的時候還伴隨著滾動更新。

2.2.Pod的滾動更新

1.首先修改鏡像版本 kubectl edit deployment/nginx-deployment spec:containers:- image: nginx:1.9.1imagePullPolicy: IfNotPresentname: nginxports:- containerPort: 80protocol: TCPresources: {}terminationMessagePath: /dev/termination-logterminationMessagePolicy: FilednsPolicy: ClusterFirstrestartPolicy: AlwaysschedulerName: default-schedulersecurityContext: {}terminationGracePeriodSeconds: 30 這塊兒直接把image中nginx的版本改成了1.9.1然后保存退出，文件有了新的變動會觸發(fā)更新。2.查看滾動更新的效果 [root@kubernetes01 ~]# kubectl describe deployment nginx-deployment | tail -n 10 Events:Type Reason Age From Message---- ------ ---- ---- -------Normal ScalingReplicaSet 30m deployment-controller Scaled up replica set nginx-deployment-7f987f7889 to 3Normal ScalingReplicaSet 8m55s deployment-controller Scaled up replica set nginx-deployment-6987cdb55b to 1Normal ScalingReplicaSet 8m54s deployment-controller Scaled down replica set nginx-deployment-7f987f7889 to 2Normal ScalingReplicaSet 8m54s deployment-controller Scaled up replica set nginx-deployment-6987cdb55b to 2Normal ScalingReplicaSet 8m33s deployment-controller Scaled down replica set nginx-deployment-7f987f7889 to 1Normal ScalingReplicaSet 8m33s deployment-controller Scaled up replica set nginx-deployment-6987cdb55b to 3Normal ScalingReplicaSet 8m12s deployment-controller Scaled down replica set nginx-deployment-7f987f7889 to 0 首先通過Events輸出的內(nèi)容我們可以看到這個deployment滾動更新的Message。[root@kubernetes01 ~]# kubectl get rs NAME DESIRED CURRENT READY AGE nginx-deployment-5c689d88bb 0 0 0 14d nginx-deployment-5cd6d46846 0 0 0 14d nginx-deployment-67d57d6df9 0 0 0 9d nginx-deployment-6987cdb55b 3 3 3 10m nginx-deployment-7f987f7889 0 0 0 9d nginx-replicaset 0 0 0 37m 然后查看這個Deployment控制的ReplicaSet的最終狀態(tài)，這里等待了一會兒所以已經(jīng)是最終的狀態(tài)了，配合前邊Events的信息，nginx-deployment-6987cdb55b up to 1，舊的nginx-deployment-7f987f7889 down to 2，通過交替的逐一的升級和降級“滾動更新”，最終 nginx-deployment-6987cdb55b 的DESIRED，CURRENT，READY都變成了期望值3！狀態(tài)字段的含義： DESIRED：用戶期望的Pod副本個數(shù) CURRENT：當(dāng)前處于Running狀態(tài)的Pod的個數(shù) UP-TO-DATE：當(dāng)前處于最新版本的Pod的個數(shù) READY：處于健康檢查正確狀態(tài)的Pod的個數(shù)，Running狀態(tài)的新版本我們還可以通過 kubectl rollout status deployment/nginx-deployment這條命令實(shí)時的查看Deployment對象的狀態(tài)變化。應(yīng)用的版本和ReplicaSet是一一對應(yīng)的，這也是Kubernetes實(shí)現(xiàn)對多個應(yīng)用版本描述的設(shè)計(jì)思想。

3.Kubernetes Deployment對應(yīng)用的版本控制

1.首先通過命令直接這個Deployment的鏡像修改成錯誤的 [root@kubernetes01 ~]# kubectl set image deployment/nginx-deployment nginx=nginx:1.99 deployment.extensions/nginx-deployment image updated2.查看Deployment的狀態(tài) [root@kubernetes01 ~]# kubectl get rs NAME DESIRED CURRENT READY AGE nginx-deployment-5476c5bdd 1 1 0 12s nginx-deployment-5c689d88bb 0 0 0 15d nginx-deployment-5cd6d46846 0 0 0 14d nginx-deployment-67d57d6df9 0 0 0 10d nginx-deployment-6987cdb55b 3 3 3 46m nginx-deployment-7f987f7889 0 0 0 10d nginx-replicaset 0 0 0 73m nginx-staticwebsite-648bc64544 2 2 2 9d nginx-staticwebsite-8479f8997f 0 0 0 9d tomcat-deployment-001-84d957dc97 2 2 2 6d1h tomcat-test-6cc4d85cf6 2 2 2 6d18h 可以看到nginx-deployment-5476c5bdd這個有問題的Deployment的狀態(tài)。3.回退到上個版本 [root@kubernetes01 ~]# kubectl rollout undo deployment/nginx-deployment deployment.extensions/nginx-deployment4.回退之后查看Deployment的狀態(tài) [root@kubernetes01 ~]# kubectl get rs NAME DESIRED CURRENT READY AGE nginx-deployment-5476c5bdd 0 0 0 90s nginx-deployment-5c689d88bb 0 0 0 15d nginx-deployment-5cd6d46846 0 0 0 14d nginx-deployment-67d57d6df9 0 0 0 10d nginx-deployment-6987cdb55b 3 3 3 47m nginx-deployment-7f987f7889 0 0 0 10d nginx-replicaset 0 0 0 74m nginx-staticwebsite-648bc64544 2 2 2 9d nginx-staticwebsite-8479f8997f 0 0 0 9d tomcat-deployment-001-84d957dc97 2 2 2 6d1h tomcat-test-6cc4d85cf6 2 2 2 6d18h5.查看這個Deployment的歷史版本記錄 [root@kubernetes01 ~]# kubectl rollout history deployment/nginx-deployment deployment.extensions/nginx-deployment REVISION CHANGE-CAUSE 1 <none> 2 <none> 3 <none> 4 <none> 6 <none> 7 <none>6.查看第一個版本的信息 [root@kubernetes01 ~]# kubectl rollout history deployment/nginx-deployment --revision=1 deployment.extensions/nginx-deployment with revision #1 Pod Template:Labels: app=nginxpod-template-hash=5c689d88bbContainers:nginx:Image: nginx:1.7.9Port: 80/TCPHost Port: 0/TCPEnvironment: <none>Mounts: <none>Volumes: <none>7.切換到第一個版本 [root@kubernetes01 ~]# kubectl rollout undo deployment/nginx-deployment --to-revision=1 deployment.extensions/nginx-deployment8.查看Deployment的狀態(tài) [root@kubernetes01 ~]# kubectl get rs NAME DESIRED CURRENT READY AGE nginx-deployment-5476c5bdd 0 0 0 19m nginx-deployment-5c689d88bb 3 3 3 15d nginx-deployment-5cd6d46846 0 0 0 14d nginx-deployment-67d57d6df9 0 0 0 10d nginx-deployment-6987cdb55b 0 0 0 65m nginx-deployment-7f987f7889 0 0 0 10d nginx-replicaset 0 0 0 92m nginx-staticwebsite-648bc64544 2 2 2 9d nginx-staticwebsite-8479f8997f 0 0 0 9d tomcat-deployment-001-84d957dc97 2 2 2 6d1h tomcat-test-6cc4d85cf6 2 2 2 6d18h 這塊兒可以看到副本集nginx-deployment-5c689d88bb已經(jīng)變成了我們期望的狀態(tài)。

4.總結(jié)

PS:文中服務(wù)器使用的是國內(nèi)某??的機(jī)器
歡迎大家留言討論哦，歡迎大家和我一起學(xué)習(xí)Kubernetes～～～

轉(zhuǎn)載于:https://www.cnblogs.com/jason007/p/10718358.html

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