Kubernetes的deployment使用
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。备注: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
备注: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）
# 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
# 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
# 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
# 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
# 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）
# kubectl get rs
NAME DESIRED CURRENT READY AGE
nginx-deployment-6c54bd5869 3 3 3 56m
注意ReplicaSet的名称格式为-，后面的hash值是由Deployment自动创建的
查看Pods
# kubectl get pods --show-labels
NAME READY STATUS RESTARTS AGE LABELSnginx-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
# 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: 0RollingUpdateStrategy:25% max unavailable, 25% max surge
Pod Template:
Labels:app=nginx
Containers:
nginx:
Image: nginx:1.9.1
Port: 80/TCP
Environment:
Mounts:
Volumes:
Conditions: Type StatusReason
---- ------------
Available True MinimumReplicas
Available Progressing True NewReplicaSetAvailable
OldReplicaSets:
NewReplicaSet: nginx-deployment-5964dfd755 (3/3 replicas created)
Events: Type Reason Age From Message
---- ------ -------- -------
NormalScalingReplicaSet2m deployment-controllerScaled up replica set nginx-deployment-5964dfd755 to 1
NormalScalingReplicaSet2m deployment-controllerScaled down replica set nginx-deployment-6c54bd5869 to 2
NormalScalingReplicaSet2m deployment-controllerScaled up replica set nginx-deployment-5964dfd755 to 2
NormalScalingReplicaSet2m deployment-controllerScaled down replica set nginx-deployment-6c54bd5869 to 1
NormalScalingReplicaSet2m deployment-controllerScaled up replica set nginx-deployment-5964dfd755 to 3
NormalScalingReplicaSet2m deployment-controllerScaled 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.image
3. 修改yaml文件，通过apply重新部署
# 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
# 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
# kubectl set image deployment/nginx-deployment nginx=nginx:1.91
deployment "nginx-deployment" image updated
追踪状态
# 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
# 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
# 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
# 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
# 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:
Mounts:
Volumes:
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
# kubectl rollout undo deployment/nginx-deployment
deployment "nginx-deployment" rolled back
指定版本，通过--to-revision指定
# kubectl rollout undo deployment/nginx-deployment --to-revision=2
deployment "nginx-deployment" rolled back
查看
kubectl describe deployment/nginx-deployment
...............
可看到有DeploymentRollbackReason的事件
扩展Deployment
可通过如下的命令进行扩展
# kubectl scale deployment nginx-deployment --replicas=5
deployment "nginx-deployment" scaled
查看Pods
# 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
# kubectl rollout pause deployment/nginx-deployment
deployment "nginx-deployment" paused
修改
# kubectl set image deploy/nginx-deployment nginx=nginx:1.7.9
deployment "nginx-deployment" image updated
查看Pods
# 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
# kubectl rollout resume deploy/nginx-deployment
deployment "nginx-deployment" resumed
这时再查看Pods
# kubectl get podsNAME READY STATUS RESTARTS AGEnginx-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
# 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: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：
: => :=> :
部署service服务：
# kubectl create -f nginx-service.yaml s
ervice "nginx-service" created
可看到启动了一个svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
svc/kubernetes ClusterIP 10.96.0.1 443/TCP 1d
svc/nginx-service NodePort 10.101.86.235 80:30080/TCP 4m
浏览器测试
本文出自https://my.oschina.net/u/2306127/blog/1647246
几个重要参数说明
maxSurge与maxUnavailable
maxSurge: 1 表示滚动升级时会先启动1个pod
maxUnavailable: 1 表示滚动升级时允许的最大Unavailable的pod个数
由于replicas为3,则整个升级,pod个数在2-4个之间
terminationGracePeriodSeconds
k8s将会给应用发送SIGTERM信号，可以用来正确、优雅地关闭应用,默认为30秒。
如果需要更优雅地关闭，则可以使用k8s提供的pre-stop lifecycle hook 的配置声明，将会在发送SIGTERM之前执行。
livenessProbe与readinessProbe
livenessProbe是kubernetes认为该pod是存活的，不存在则需要kill掉，然后再新启动一个，以达到replicas指定的个数。
readinessProbe是kubernetes认为该pod是启动成功的，这里根据每个应用的特性，自己去判断，可以执行command，也可以进行httpGet。比如对于使用java web服务的应用来说，并不是简单地说tomcat启动成功就可以对外提供服务的，还需要等待spring容器初始化，数据库连接连接上等等。对于spring boot应用，默认的actuator带有/health接口，可以用来进行启动成功的判断。
其中readinessProbe.initialDelaySeconds可以设置为系统完全启动起来所需的最少时间，livenessProbe.initialDelaySeconds可以设置为系统完全启动起来所需的最大时间+若干秒。
参考使用kubernetes的deployment进行RollingUpdate
https://www.jianshu.com/p/6bc8e0ae65d1
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