《kubernetes-1.8.0》20-examples-Deployments
《kubernetes 1.8.0 测试环境安装部署》
时间:2017-12-19
一、基础知识:
Deployment
为 Pod
和 ReplicaSet
提供了一个声明式定义declarative
方法,用来替代以前的ReplicationController
来方便的管理应用。
您只需要在 Deployment 中描述您想要的目标状态是什么,Deployment controller 就会帮您将 Pod 和ReplicaSet 的实际状态改变到您的目标状态。您可以定义一个全新的 Deployment 来创建 ReplicaSet 或者删除已有的 Deployment 并创建一个新的来替换。
应用场景包括:
- 创建Deployment来展示ReplicaSet:ReplicaSet在后台创建pod,Deployment用意检查ReplicaSet的状态以及是否成功部署;
- 声明pod的新状态:通过更新Deployment的 PodTemplateSpec字段,新的ReplicaSet将被创建Deployment manages按照控制的速率将pods从旧的的ReplicaSet迁移至新的ReplicaSet,每个新创建的ReplicaSet将更新Deployment的修订号;
- 如果当前状态不稳定,将会回滚到之前的deployment修订版本
- 扩容以满足更高的负载
- 暂停和继续Deployment
- 如果旧的ReplicaSet不在需要则clean up
这么理解可以看成Deployment是ReplicaSet的一个状态管理工具,以及相比RC支持更多的特性;
二、例子:
创建Deployment:
apiVersion: apps/v1beta2 # for versions 1.9.0 and later use apps/v1
kind: Deployment
metadata:
name: nginx-deployment-demo
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
-
metadata.name
:一个名为nginx-deployment-demo的被创建
-
spec.replicas
:该Deployment将创建3个pod副本
-
spec.selector
:改字段声明了deployment如何找到对应的pod进行管理。本例中简单选择一个在pod template中定义的labelapp:nginx
-
spec.template.spec.containers
:pod模板,定义包含的container name、其所使用的镜像、container暴露的端口等
-
spec.template.spec.metadata.labels
:定义pod的label为app:nginx
应用yaml:
[root@node-131 deployment-demo]# kubectl create -f nginx-deployment-demo.yaml --record
deployment "nginx-deployment-demo" created
- 可以添加
--record
参数,用来记录当前命令创建或者升级的资源。这在未来会很有用,例如,查看在每个 Deployment revision 中执行了哪些命令。
查看:
[root@node-131 deployment-demo]# kubectl get deployments
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
...
nginx-deployment-demo 3 3 3 3 7m
- 我们可以看到Deployment已经创建了3个 replica,所有的 replica 都已经是最新的了(包含最新的pod template)
- 可用的(根据Deployment中的
.spec.minReadySeconds
声明,处于已就绪状态的pod的最少个数)
[root@node-131 deployment-demo]# kubectl get rs
NAME DESIRED CURRENT READY AGE
...
nginx-deployment-demo-6d8f46cfb7 3 3 3 10m
-
ReplicaSet
的命名规范是[DEPLOYMENT-NAME]-[POD-TEMPLATE-HASH-VALUE]
[root@node-131 deployment-demo]# kubectl get pods --show-labels
NAME READY STATUS RESTARTS AGE LABELS
...
nginx-deployment-demo-6d8f46cfb7-4m7lq 1/1 Running 0 11m app=nginx,pod-template-hash=2849027963
nginx-deployment-demo-6d8f46cfb7-rbz5x 1/1 Running 0 11m app=nginx,pod-template-hash=2849027963
nginx-deployment-demo-6d8f46cfb7-xwtfh 1/1 Running 0 11m app=nginx,pod-template-hash=2849027963
...
-
--show-labels
:用来查看自动为每个pod创建的labels
- 需要合理规划
pod template
的label
(在本例中是 app : nginx),不要跟其他的 controller
的 selector
中指定的 pod template label
搞混了(包括 Deployment、Replica Set、Replication Controller
等)。Kubernetes 本身并不会阻止您任意指定 pod template label
,但是如果您真的这么做了,这些 controller
之间会相互打架,并可能导致不正确的行为。
-
pod-template-hash
: 这个label不是指定的且不允许修改,而是在Deployment创建或者接管RS的时候自动为pod添加的,目的是防止Deployment所管理的replicaSet名字重复。
更新一个Deployment:
注意: Deployment
的 rollout 当且仅当 Deployment
的 pod template
(例如.spec.template
)中的label
更新或者镜像更改时被触发。其他更新,例如扩容Deployment不会触发 rollout。
假如现在想要让 nginx pods
使用nginx:1.9.1
的镜像来代替原来的nginx:1.7.9
的镜像。
1、kubectl set命令更新镜像设置:
$ kubectl set image deployment/nginx-deployment-demo nginx=nginx:1.9.1
deployment "nginx-deployment" image updated
2、kubectl edit在线修改Deployment yaml,修改 .spec.template.spec.containers[0].image ,将nginx:1.7.9 改写成 nginx:1.9.1:
kubectl edit deployment/nginx-deployment-demo
deployment "nginx-deployment-demo" edited
查看rollout状态:
[root@node-132 ~]# kubectl rollout status deployment/nginx-deployment-demo
Waiting for rollout to finish: 1 out of 3 new replicas have been updated...
Waiting for rollout to finish: 1 out of 3 new replicas have been updated...
Waiting for rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for rollout to finish: 1 old replicas are pending termination...
Waiting for rollout to finish: 1 old replicas are pending termination...
rollout成功后,查看Deployment:
[root@node-132 ~]# kubectl get deployments
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
...
nginx-deployment-demo 3 3 3 3 59m
[root@node-132 ~]# kubectl get pods
NAME READY STATUS RESTARTS AGE
...
nginx-deployment-demo-58b94fcb9-869qp 1/1 Running 0 1m
nginx-deployment-demo-58b94fcb9-f7qpz 1/1 Running 0 1m
nginx-deployment-demo-58b94fcb9-ztwpv 1/1