Kubernetes Deployment 之擴縮容與滾動更新

Deployment 擴縮容

擴縮容非常簡單，我們可以直接調整 replica 副本數目，然后 kubectl apply指定進行動態更新。下面將nginx-deployment動態改為 1 個 Pod 和 3 個 Pod 的操作

apiVersion: apps/v1
kind: Deployment
metadata:name: deployment-nginxnamespace: defaultlabels:app: deployment-nginx
spec:replicas: 2 # 將此處動態改為 1 或者 3selector:matchLabels:app: pod-nginxtemplate:metadata:labels:app: pod-nginxspec:containers:- name: nginximage: docker.io/k8s-test:v1.0imagePullPolicy: IfNotPresentports:- containerPort: 80

root@k8s-master1:~# kubectl apply -f deploy-nginx.yaml
deployment.apps/deployment-nginx configured
root@k8s-master1:~# kubectl get deploy
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
deployment-nginx   1/1     1            1           17h
root@k8s-master1:~# kubectl apply -f deploy-nginx.yaml
deployment.apps/deployment-nginx configured
root@k8s-master1:~# kubectl get deploy
NAME               READY   UP-TO-DATE   AVAILABLE   AGE
deployment-nginx   3/3     3            3           17h# 它也會識別原來的 Pod 有沒有被更新，如果沒有被更新，它仍然會繼續被保留運行
root@k8s-master1:~# kubectl get pods -owide
NAME                                READY   STATUS    RESTARTS      AGE   IP               NODE          NOMINATED NODE   READINESS GATES
deployment-nginx-6977747dd9-knx9r   1/1     Running   0             31s   10.244.194.126   k8s-worker1   <none>           <none>
deployment-nginx-6977747dd9-nqxgd   1/1     Running   0             31s   10.244.194.125   k8s-worker1   <none>           <none>
deployment-nginx-6977747dd9-sz42q   1/1     Running   1 (34m ago)   17h   10.244.126.24    k8s-worker2   <none>           <none>

Deployment 滾動更新策略

Deployment 更新策略分為兩種，分別為Recreate和RollingUpdate。Recreate是將所有 Pod 全部殺死，然后啟動新版本，這是一個極其危險的行為，幾乎不被使用。滾動更新是指，新增一定數量的 Pod 后，再殺死一定的數量的 Pod。Deployment 默認使用滾動更新策略。

實現滾動更新需要設置MaxSurge最大 Pod 新增數量和MaxUnavailable最大 Pod 不可用數據數目。它們可以設置成整數或者百分比，且兩者不能同時為0，不然無法根本更新。以副本數 3 為例，如果我們 MaxSurge設置為 10%，那么我們新增個數為 0.3，這里需要向上取整，即個數為1；同理我們 MaxUnavailable設置為 10%，這里我們允許不可用的個數也為 0.3，這里要向下取整為 0；最終我們的更新策略是要等到 4 個 Pod 完全在運行狀態，滾動更新才回去殺死 1 個老 Pod。

Deployment 滾動更新使用

1. 我們先將 k8s-test:v1.0 鏡像標記為 k8s-test:v1.1

   root@k8s-worker1:~# ctr -n k8s.io image tag docker.io/library/k8s-test:v1.0 docker.io/library/k8s-test:v1.1
   docker.io/library/k8s-test:v1.1
   root@k8s-worker2:~# ctr -n k8s.io image tag docker.io/library/k8s-test:v1.0 docker.io/library/k8s-test:v1.1
   docker.io/library/k8s-test:v1.1
   

2. 修改 yaml鏡像版本號和更新策略

   apiVersion: apps/v1
   kind: Deployment
   metadata:name: deployment-nginxnamespace: defaultlabels:app: deployment-nginx
   spec:strategy:rollingUpdate:maxSurge: 10%maxUnavailable: 10%replicas: 2selector:matchLabels:app: pod-nginxtemplate:metadata:labels:app: pod-nginxspec:containers:- name: nginximage: docker.io/k8s-test:v1.1imagePullPolicy: IfNotPresentports:- containerPort: 80
   

3. 執行如下指令開啟 Pods 監聽

   kubectl get pods -owide -w
   

4. 更新過程如下，舊的 Pod 會先被標記，但不是真的被終止

   root@k8s-master1:~# kubectl get pods -owide -w
   NAME                                READY   STATUS    RESTARTS      AGE   IP               NODE          NOMINATED NODE   READINESS GATES
   deployment-nginx-6977747dd9-knx9r   1/1     Running   0             30m   10.244.194.126   k8s-worker1   <none>           <none>
   deployment-nginx-6977747dd9-nqxgd   1/1     Running   0             30m   10.244.194.125   k8s-worker1   <none>           <none>
   deployment-nginx-6977747dd9-sz42q   1/1     Running   1 (63m ago)   17h   10.244.126.24    k8s-worker2   <none>           <none>
   deployment-nginx-6977747dd9-nqxgd   1/1     Terminating   0             35m   10.244.194.125   k8s-worker1   <none>           <none>
   deployment-nginx-6c94d644bd-ft9s6   0/1     Pending       0             0s    <none>           <none>        <none>           <none>
   deployment-nginx-6c94d644bd-ft9s6   0/1     Pending       0             0s    <none>           k8s-worker2   <none>           <none>
   deployment-nginx-6c94d644bd-ft9s6   0/1     ContainerCreating   0             0s    <none>           k8s-worker2   <none>           <none>
   deployment-nginx-6977747dd9-nqxgd   1/1     Terminating         0             35m   10.244.194.125   k8s-worker1   <none>           <none>
   deployment-nginx-6977747dd9-nqxgd   0/1     Terminating         0             35m   <none>           k8s-worker1   <none>           <none>
   deployment-nginx-6c94d644bd-ft9s6   0/1     ContainerCreating   0             0s    <none>           k8s-worker2   <none>           <none>
   deployment-nginx-6977747dd9-nqxgd   0/1     Terminating         0             35m   10.244.194.125   k8s-worker1   <none>           <none>
   deployment-nginx-6c94d644bd-ft9s6   1/1     Running             0             1s    10.244.126.26    k8s-worker2   <none>           <none>
   deployment-nginx-6977747dd9-nqxgd   0/1     Terminating         0             35m   10.244.194.125   k8s-worker1   <none>           <none>
   deployment-nginx-6977747dd9-nqxgd   0/1     Terminating         0             35m   10.244.194.125   k8s-worker1   <none>           <none>
   deployment-nginx-6977747dd9-sz42q   1/1     Terminating         1 (69m ago)   17h   10.244.126.24    k8s-worker2   <none>           <none>
   deployment-nginx-6c94d644bd-sj4hv   0/1     Pending             0             0s    <none>           <none>        <none>           <none>
   deployment-nginx-6c94d644bd-sj4hv   0/1     Pending             0             0s    <none>           k8s-worker1   <none>           <none>
   deployment-nginx-6c94d644bd-sj4hv   0/1     ContainerCreating   0             0s    <none>           k8s-worker1   <none>           <none>
   deployment-nginx-6977747dd9-sz42q   1/1     Terminating         1 (69m ago)   17h   10.244.126.24    k8s-worker2   <none>           <none>
   deployment-nginx-6977747dd9-sz42q   0/1     Terminating         1 (69m ago)   17h   <none>           k8s-worker2   <none>           <none>
   deployment-nginx-6c94d644bd-sj4hv   0/1     ContainerCreating   0             0s    <none>           k8s-worker1   <none>           <none>
   deployment-nginx-6c94d644bd-sj4hv   1/1     Running             0             1s    10.244.194.127   k8s-worker1   <none>           <none>
   deployment-nginx-6977747dd9-sz42q   0/1     Terminating         1 (69m ago)   17h   10.244.126.24    k8s-worker2   <none>           <none>
   deployment-nginx-6977747dd9-knx9r   1/1     Terminating         0             35m   10.244.194.126   k8s-worker1   <none>           <none>
   deployment-nginx-6977747dd9-sz42q   0/1     Terminating         1 (69m ago)   17h   10.244.126.24    k8s-worker2   <none>           <none>
   deployment-nginx-6977747dd9-sz42q   0/1     Terminating         1 (69m ago)   17h   10.244.126.24    k8s-worker2   <none>           <none>
   deployment-nginx-6977747dd9-knx9r   1/1     Terminating         0             35m   10.244.194.126   k8s-worker1   <none>           <none>
   deployment-nginx-6977747dd9-knx9r   0/1     Terminating         0             35m   <none>           k8s-worker1   <none>           <none>
   deployment-nginx-6977747dd9-knx9r   0/1     Terminating         0             35m   10.244.194.126   k8s-worker1   <none>           <none>
   deployment-nginx-6977747dd9-knx9r   0/1     Terminating         0             35m   10.244.194.126   k8s-worker1   <none>           <none>
   deployment-nginx-6977747dd9-knx9r   0/1     Terminating         0             35m   10.244.194.126   k8s-worker1   <none>           <none>
   

5. 查看更新后的結果

   root@k8s-master1:~# kubectl get pods -owide
   NAME                                READY   STATUS    RESTARTS   AGE     IP               NODE          NOMINATED NODE   READINESS GATES
   deployment-nginx-6c94d644bd-ft9s6   1/1     Running   0          4m55s   10.244.126.26    k8s-worker2   <none>           <none>
   deployment-nginx-6c94d644bd-sj4hv   1/1     Running   0          4m54s   10.244.194.127   k8s-worker1   <none>           <none>
   root@k8s-master1:~# kubectl get deploy
   NAME               READY   UP-TO-DATE   AVAILABLE   AGE
   deployment-nginx   2/2     2            2           17h
   root@k8s-master1:~# kubectl get rs
   NAME                          DESIRED   CURRENT   READY   AGE
   deployment-nginx-6977747dd9   0         0         0       17h
   deployment-nginx-6c94d644bd   2         2         2       6m1s