使用 Deployment 运行一个无状态应用
本文介绍如何通过 Kubernetes Deployment 对象去运行一个应用.
Objectives
- 创建一个 nginx Deployment.
- 使用 kubectl 列举关于 Deployment 的信息.
- 更新 Deployment。
Before you begin
你必须拥有一个 Kubernetes 的集群,同时你的 Kubernetes 集群必须带有 kubectl 命令行工具。 建议在至少有两个节点的集群上运行本教程,且这些节点不作为控制平面主机。 如果你还没有集群,你可以通过 Minikube 构建一个你自己的集群,或者你可以使用下面任意一个 Kubernetes 工具构建:
Your Kubernetes server must be at or later than version v1.9. To check the version, enter kubectl version
.
创建并了解一个 nginx Deployment
你可以通过创建一个 Kubernetes Deployment 对象来运行一个应用, 且你可以在一个 YAML 文件中描述 Deployment。例如, 下面这个 YAML 文件描述了一个运行 nginx:1.14.2 Docker 镜像的 Deployment:
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx-deployment
spec:
selector:
matchLabels:
app: nginx
replicas: 2 # tells deployment to run 2 pods matching the template
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx:1.14.2
ports:
- containerPort: 80
通过 YAML 文件创建一个 Deployment:
kubectl apply -f https://k8s.io/examples/application/deployment.yaml
显示 Deployment 相关信息:
kubectl describe deployment nginx-deployment
输出类似于这样:
Name: nginx-deployment
Namespace: default
CreationTimestamp: Tue, 30 Aug 2016 18:11:37 -0700
Labels: app=nginx
Annotations: deployment.kubernetes.io/revision=1
Selector: app=nginx
Replicas: 2 desired | 2 updated | 2 total | 2 available | 0 unavailable
StrategyType: RollingUpdate
MinReadySeconds: 0
RollingUpdateStrategy: 1 max unavailable, 1 max surge
Pod Template:
Labels: app=nginx
Containers:
nginx:
Image: nginx:1.7.9
Port: 80/TCP
Environment: <none>
Mounts: <none>
Volumes: <none>
Conditions:
Type Status Reason
---- ------ ------
Available True MinimumReplicasAvailable
Progressing True NewReplicaSetAvailable
OldReplicaSets: <none>
NewReplicaSet: nginx-deployment-1771418926 (2/2 replicas created)
No events.
列出 Deployment 创建的 Pods:
kubectl get pods -l app=nginx
输出类似于这样:
NAME READY STATUS RESTARTS AGE
nginx-deployment-1771418926-7o5ns 1/1 Running 0 16h
nginx-deployment-1771418926-r18az 1/1 Running 0 16h
展示某一个 Pod 信息:
kubectl describe pod <pod-name>
这里的
<pod-name>
是某一 Pod 的名称。
更新 Deployment
你可以通过更新一个新的 YAML 文件来更新 Deployment。下面的 YAML 文件指定该 Deployment 镜像更新为 nginx 1.16.1。
application/deployment-update.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx-deployment
spec:
selector:
matchLabels:
app: nginx
replicas: 2
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx:1.16.1 # Update the version of nginx from 1.14.2 to 1.16.1
ports:
- containerPort: 80
应用新的 YAML:
kubectl apply -f https://k8s.io/examples/application/deployment-update.yaml
查看该 Deployment 以新的名称创建 Pods 同时删除旧的 Pods:
kubectl get pods -l app=nginx
通过增加副本数来扩缩应用
你可以通过应用新的 YAML 文件来增加 Deployment 中 Pods 的数量。 下面的 YAML 文件将 replicas
设置为 4,指定该 Deployment 应有 4 个 Pods:
application/deployment-scale.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx-deployment
spec:
selector:
matchLabels:
app: nginx
replicas: 4 # Update the replicas from 2 to 4
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx:1.14.2
ports:
- containerPort: 80
应用新的 YAML 文件:
kubectl apply -f https://k8s.io/examples/application/deployment-scale.yaml
验证 Deployment 有 4 个 Pods:
kubectl get pods -l app=nginx
输出的结果类似于:
NAME READY STATUS RESTARTS AGE
nginx-deployment-148880595-4zdqq 1/1 Running 0 25s
nginx-deployment-148880595-6zgi1 1/1 Running 0 25s
nginx-deployment-148880595-fxcez 1/1 Running 0 2m
nginx-deployment-148880595-rwovn 1/1 Running 0 2m
删除 Deployment
基于名称删除 Deployment:
kubectl delete deployment nginx-deployment
ReplicationControllers — 旧的方式
创建一个多副本应用首选方法是使用 Deployment,Deployment 内部使用 ReplicaSet。 在 Deployment 和 ReplicaSet 被引入到 Kubernetes 之前,多副本应用通过 ReplicationController 来配置。
What’s next
- 进一步了解 Deployment 对象。
最后修改 May 14, 2021 at 1:41 PM PST: [zh] Resync tasks for 1.21 (4) (1638e3543)