k8s 使用篇 - deployment_前端_weixin

Deployment管理Pods和ReplicaSets，提供声明式更新。和老的ReplicationController（命令式管理）对应，发展趋势是取代老的，所以后面也不会起文章单独讨论ReplicationController了。

但由Deployment-controller管理的Pods和ReplicaSets最好自始至终都由Deployment-controller管理，最好不要手动去管理，以免发生冲突。

创建Deployment

如下一个Deployment的配置（nginx-deployment.yaml），创建一个ReplicaSet包含3个nginx Pods

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:1.7.9
 ports:
 - containerPort: 80

apiVersion这里为apps/v1，如果是1.9之前的版本为extensions/v1beta1
replicas:3 起3个replicated Pods
selector指明哪个pod被管理，这里我们指定了label（app:nginx）
template: spec 指明了运行一个容器nginx（以nginx:1.7.9为镜像）
开放80端口给container，以使container之间能发送和接收流量

注意这里定义name 或 label 时不要和其他的重复，k8s不会检查这个，需要人工自己确认

要创建此部署，执行下面的命令（在这之前我们提前下好nginx相关的镜像，docker pull nginx:1.7.9）

[root@master yaml]# kubectl create -f nginx-deployment.yaml --record
deployment "nginx-deployment" created

--record会记录操作历史，以便于后面回滚操作

查看deployments

[root@master yaml]# kubectl get deployments
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
nginx-deployment 3 0 0 0 1s

NAME：在集群中的部署名称
DESIRED：显示配置里定义的副本数量，这是应该达到的副本数量
CURRENT：当前正在运行的副本数量
UP-TO-DATE：更新到当前所需状态的副本数量
AVAILABLE：可供使用的副本数量
AEG：显示app存活的时间

通过下面语句可查追踪部署情况

[root@master ~]# kubectl rollout status deployment/nginx-deployment
deployment "nginx-deployment" successfully rolled out
# 这是部署完成的状态 # 未完成的会显示当前部署哪一步了
[root@master ~]# kubectl rollout status deployment/nginx-deployment
Waiting for rollout to finish: 2 out of 3 new replicas have been updated...
deployment "nginx-deployment" successfully rolled out

过一会我们再查看，就全

[root@master ~]# kubectl get deployments
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
nginx-deployment 3 3 3 3 51s

这里注意如果定义了.spec.minReadySeconds，那么必须经过定义的时间才会达到AVAILABLE 状态

通过下面的命令查看Deployment创建的ReplicaSet（rs）

[root@master ~]# kubectl get rs
NAME DESIRED CURRENT READY AGE
nginx-deployment-6c54bd5869 3 3 3 56m

注意ReplicaSet的名称格式为[DEPLOYMENT-NAME]-[POD-TEMPLATE-HASH-VALUE]，后面的hash值是由Deployment自动创建的

查看Pods

[root@master ~]# kubectl get pods --show-labels
NAME READY STATUS RESTARTS AGE LABELS
nginx-deployment-6c54bd5869-9brqp 1/1 Running 0 58m app=nginx,pod-template-hash=2710681425
nginx-deployment-6c54bd5869-dkmgh 1/1 Running 0 58m app=nginx,pod-template-hash=2710681425
nginx-deployment-6c54bd5869-vzsht 1/1 Running 0 58m app=nginx,pod-template-hash=2710681425

创建的ReplicaSet 会确保时刻有3个nginx Pods的副本在运行

更新Deployment

假设我们想把nginx从1.7.9更新到1.9.1，有以下3种方式

1. 直接set命令设置变更的部分

$ kubectl set image deployment/nginx-deployment nginx=nginx:1.9.1
deployment "nginx-deployment" image updated

以上命令会自动回滚更改Pods，即停止一定量的老的，新建新的，直到来的终止完，新的启动完

通过describe即可查看所有的细节

[root@master yaml]# kubectl describe deployment/nginx-deployment
Name: nginx-deployment
Namespace: default
CreationTimestamp: Thu, 15 Mar 2018 02:51:06 -0400
Labels: app=nginx
Annotations: deployment.kubernetes.io/revision=2
 kubernetes.io/change-cause=kubectl set image deployment/nginx-deployment nginx=nginx:1.9.1
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:1.9.1
 Port: 80/TCP
 Environment: <none>
 Mounts: <none>
 Volumes: <none>
Conditions:
 Type Status Reason
 ---- ------ ------
 Available True MinimumReplicasAvailable
 Progressing True NewReplicaSetAvailable
OldReplicaSets: <none>
NewReplicaSet: nginx-deployment-5964dfd755 (3/3 replicas created)
Events:
 Type Reason Age From Message
 ---- ------ ---- ---- -------
 Normal ScalingReplicaSet 2m deployment-controller Scaled up replica set nginx-deployment-5964dfd755 to 1
 Normal ScalingReplicaSet 2m deployment-controller Scaled down replica set nginx-deployment-6c54bd5869 to 2
 Normal ScalingReplicaSet 2m deployment-controller Scaled up replica set nginx-deployment-5964dfd755 to 2
 Normal ScalingReplicaSet 2m deployment-controller Scaled down replica set nginx-deployment-6c54bd5869 to 1
 Normal ScalingReplicaSet 2m deployment-controller Scaled up replica set nginx-deployment-5964dfd755 to 3
 Normal ScalingReplicaSet 2m deployment-controller Scaled down replica set nginx-deployment-6c54bd5869 to 0

可见image已经变了
另外Events可查看滚动更新的过程
另外上面的说的停止和新建的比例在这里体现RollingUpdateStrategy: 25% max unavailable, 25% max surge，25% max unavailable确保在更新时只有部分会关闭（这里是pod数的25%会关闭）。25% max surge确保创建新的pod也在一定比例上（这里默认也是25%）

2. 通过直接修改线上的配置也可直接修改

kubectl edit deployment/nginx-deployment

会打开一个编辑器，修改指定的部分即可，这里是.spec.template.spec.containers[0].image

3. 修改yaml文件，通过apply重新部署

[root@master yaml]# kubectl apply -f nginx-deployment.yaml 
Warning: kubectl apply should be used on resource created by either kubectl create --save-config or kubectl apply
deployment "nginx-deployment" configured

但这里有个警告: 也就是apply方式更新的资源应该是由kubectl create 加--save-config参数创建的或由apply创建的（apply当资源不存在时会创建）

这时我们查看rs，会显示新起了一个rs并将副本扩到3个，旧的rs都缩减为0

[root@master yaml]# kubectl get rs
NAME DESIRED CURRENT READY AGE
nginx-deployment-5964dfd755 3 3 3 21m
nginx-deployment-6c54bd5869 0 0 0 1h

回滚Deployment

有时需要回滚的操作，比如更新错误，手误等一系列问题

比如上面的操作更新到1.9.1时，写错了，写成1.91了

[root@master yaml]# kubectl set image deployment/nginx-deployment nginx=nginx:1.91
deployment "nginx-deployment" image updated

追踪状态

[root@master yaml]# kubectl rollout status deployments nginx-deployment
Waiting for rollout to finish: 1 out of 3 new replicas have been updated...

可见卡住不动了， Ctrl+C终止，查看rs如下

[root@master yaml]# kubectl get rs
NAME DESIRED CURRENT READY AGE
nginx-deployment-5964dfd755 3 3 3 40m
nginx-deployment-5d5cfdbd5f 1 1 0 1m
nginx-deployment-6c54bd5869 0 0 0 2h

新的rs只启动了Pod但没有处于READY状态

查看Pods

[root@master yaml]# kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-deployment-5964dfd755-8z8b7 1/1 Running 0 27m
nginx-deployment-5964dfd755-bnznj 1/1 Running 0 27m
nginx-deployment-5964dfd755-pt54q 1/1 Running 0 27m
nginx-deployment-5d5cfdbd5f-srdcc 0/1 ImagePullBackOff 0 2m

可发现ImagePullBackOff，实际就是镜像不存在

要修复这个，我们就需要rollback到前一个ok的版本

查看操作历史

[root@master yaml]# kubectl rollout history deployment/nginx-deployment
deployments "nginx-deployment"
REVISION CHANGE-CAUSE
1 kubectl create -f docs/user-guide/nginx-deployment.yaml --record
2 kubectl set image deployment/nginx-deployment nginx=nginx:1.9.1
3 kubectl set image deployment/nginx-deployment nginx=nginx:1.91

要查看每个版本的详细情况，指定--revision

[root@master yaml]# kubectl rollout history deployment/nginx-deployment --revision=2
deployments "nginx-deployment" with revision #2
Pod Template:
 Labels: app=nginx
 pod-template-hash=2710681425
 Annotations: kubernetes.io/change-cause=kubectl edit deployment/nginx-deployment
 Containers:
 nginx:
 Image: nginx:1.9.1
 Port: 80/TCP
 Environment: <none>
 Mounts: <none>
 Volumes: <none>

接下来进行回滚的操作

不指定版本，默认回滚到上一个版本

[root@master yaml]# kubectl rollout undo deployment/nginx-deployment
deployment "nginx-deployment" rolled back

指定版本，通过--to-revision指定

[root@master yaml]# kubectl rollout undo deployment/nginx-deployment --to-revision=2
deployment "nginx-deployment" rolled back

查看

kubectl describe deployment/nginx-deployment

....略

Events:
 FirstSeen LastSeen Count From SubobjectPath Type Reason Message
 --------- -------- ----- ---- ------------- -------- ------ -------
 30m 30m 1 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set nginx-deployment-2035384211 to 3
 29m 29m 1 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set nginx-deployment-1564180365 to 1
 29m 29m 1 {deployment-controller } Normal ScalingReplicaSet Scaled down replica set nginx-deployment-2035384211 to 2
 29m 29m 1 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set nginx-deployment-1564180365 to 2
 29m 29m 1 {deployment-controller } Normal ScalingReplicaSet Scaled down replica set nginx-deployment-2035384211 to 0
 29m 29m 1 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set nginx-deployment-3066724191 to 2
 29m 29m 1 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set nginx-deployment-3066724191 to 1
 29m 29m 1 {deployment-controller } Normal ScalingReplicaSet Scaled down replica set nginx-deployment-1564180365 to 2
 2m 2m 1 {deployment-controller } Normal ScalingReplicaSet Scaled down replica set nginx-deployment-3066724191 to 0
 2m 2m 1 {deployment-controller } Normal DeploymentRollback Rolled back deployment "nginx-deployment" to revision 2
 29m 2m 2 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set nginx-deployment-1564180365 to 3

可看到有DeploymentRollback Reason的事件

扩展Deployment

可通过如下的命令进行扩展

[root@master yaml]# kubectl scale deployment nginx-deployment --replicas=5
deployment "nginx-deployment" scaled

查看Pods

[root@master yaml]# kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-deployment-5964dfd755-8z8b7 1/1 Running 0 41m
nginx-deployment-5964dfd755-bhm2s 1/1 Running 0 1m
nginx-deployment-5964dfd755-bnznj 1/1 Running 0 41m
nginx-deployment-5964dfd755-cftfj 1/1 Running 0 6s
nginx-deployment-5964dfd755-pt54q 1/1 Running 0 41m

可见已扩展到5个

使用autoscale还可设置自动水平扩展（hpa），可根据机器负载之类的信息自动扩展或缩减，这个后面细讲

$ kubectl autoscale deployment nginx-deployment --min=10 --max=15 --cpu-percent=80
deployment "nginx-deployment" autoscaled

暂停和恢复Deployment

有时需要修改多个部分，而不是上面的只修改image，这样的话每次改完都自动部署，显然不好，通过pause即可暂停Deployment，更改完了，通过resume即可恢复部署

暂停

[root@master yaml]# kubectl rollout pause deployment/nginx-deployment
deployment "nginx-deployment" paused

修改

[root@master yaml]# kubectl set image deploy/nginx-deployment nginx=nginx:1.7.9
deployment "nginx-deployment" image updated

查看Pods

[root@master yaml]# kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-deployment-5964dfd755-8z8b7 1/1 Running 0 57m
nginx-deployment-5964dfd755-bhm2s 1/1 Running 0 17m
nginx-deployment-5964dfd755-bnznj 1/1 Running 0 57m
nginx-deployment-5964dfd755-cftfj 1/1 Running 0 16m
nginx-deployment-5964dfd755-pt54q 1/1 Running 0 57m

注意后面的AGE还是之前的Pod，这里就不会自动更新了

恢复

[root@master yaml]# kubectl rollout resume deploy/nginx-deployment
deployment "nginx-deployment" resumed

这时再查看Pods

[root@master yaml]# kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-deployment-6c54bd5869-htjxz 1/1 Running 0 25s
nginx-deployment-6c54bd5869-lj288 1/1 Running 0 30s
nginx-deployment-6c54bd5869-nt8lt 1/1 Running 0 30s
nginx-deployment-6c54bd5869-svqz6 1/1 Running 0 29s
nginx-deployment-6c54bd5869-zq8tl 1/1 Running 0 25s

可见已经更新部署了

内部Deployment部分大概就讲完了，下面把nginx服务暴露到外面

删除Deployment

[root@master yaml]# kubectl delete -f nginx-deployment.yaml 
deployment "nginx-deployment" deleted

部署service

服务的暴露需要Service，它是Pod的抽象代理（具体机制见这里）。见nginx-service.yaml

apiVersion: v1
kind: Service
metadata:
 name: nginx-service
spec:
 type: NodePort
 sessionAffinity: ClientIP
 selector:
 app: nginx
 ports:
 - port: 80
 nodePort: 30080

kind：Service代表是一个服务
type：NodePort k8s将会在每个Node上打开一个端口并且每个Node的端口都是一样的，通过<NodeIP>:NodePort的方式Kubernetes集群外部的程序可以访问Service。
selector：哪个服务需要暴露
port：service暴露的端口
TargetPort：pod的端口
nodePort：对外暴露的端口，不设置会默认分配，范围：30000－32767
转发逻辑是：
<NodeIP>:<nodeport> => <ServiceVIP>:<port>=> <PodIP>:<targetport>

部署service服务：

[root@master yaml]# kubectl create -f nginx-service.yaml 
service "nginx-service" created

可看到启动了一个svc

NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
svc/kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 1d
svc/nginx-service NodePort 10.101.86.235 <none> 80:30080/TCP 4m

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