statefulset有状态应用部署

考虑无状态的pod因素，让每个pod独立，保持pod启动顺序和唯一性。拥有唯一的网络标识符，持久存储。启动顺序有序，例如MysqL主从节点

应用场景

为了解决有服务状态的集群部署、集群之间的数据同步问题（MysqL主从等）

稳定的持久化存储：Pod重新调度后访问相同的持久化数据，基于PVC来实现。

稳定的网络标志：Pod重新调度后PodName和HostName不变，基于Headless Service来实现。

有序扩展：在扩展的时候要依据定义的顺序依次依次进行，基于init containers 实现。在下一个Pod运行之前所有Pod必须是Running和Ready状态）。

有序删除，从后到前逐个删除pod。

组成部分

从上面的应用场景可以发现，StatefulSet由以下几个部分组成：

Headless Service，用于定义网络标志（DNS domain）的。

volumeClaimTemplates，用于创建PVC，指定pvc名称大小，pvc必须由存储类提供存储。为每个Pod生成不同的pvc，并绑定pv，从而实现各pod有专用存储。

StatefulSet，定义具体应用，与deployments类似。

deployment和statefulset区别：有身份（具有唯一标识符）

（1）根据主机名+按照一定规则生成域名

（2）每个pod拥有唯一的主机名

（3）唯一域名：格式：

（4）Pod主机名称.service名称.名称空间.svc.cluster.local

部署有状态服务：

声明svc取消ip地址的暴露，将clusterip置位None

root@deploy:/statefulset# kubectl create ns test
namespace/test created

root@deploy:/statefulset# vim statefulset.yaml
apiVersion: apps/v1
kind: StatefulSet
Metadata:
  name: web-statefulset
  namespace: test
spec:
  serviceName: test-statefulset
  replicas: 2
  selector:
    matchLabels:
      app: web
  template:
    Metadata:
      labels:
        app: web
    spec:
      containers:
      - image: Nginx
        name: Nginx
        ports:
          - containerPort: 80
      - name: tomcat
        image: tomcat
        ports:
          - containerPort: 8080
---
apiVersion: v1
kind: Service
Metadata:
  labels:
    app: web
  name: test-statefulset
  namespace: test
spec:
  clusterIP: None
  ports:
    - port: 80
      name: Nginx
      protocol: TCP
      targetPort: 80
    - port: 8080
      protocol: TCP
      targetPort: 8080
      name: tomcat
  selector:
    app: web
    

root@deploy:/statefulset# kubectl apply -f statefulset.yaml

查看statefulset pod

root@deploy:/statefulset# kubectl get pods
NAME                READY   STATUS    RESTARTS   AGE
web-statefulset-0   2/2     Running   0          70s
web-statefulset-1   2/2     Running   0          38s

进入到pod测试网络和主机名称

#查看svc
root@deploy:/statefulset# kubectl get svc
NAME               TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)           AGE
test-statefulset   ClusterIP   None         <none>        80/TCP,8080/TCP   8m33s


root@deploy:/statefulset# kubectl exec -it web-statefulset-0 -- bash
Defaulted container "Nginx" out of: Nginx, tomcat
root@web-statefulset-0:/# cat /etc/hosts
# Kubernetes-managed hosts file.
127.0.0.1	localhost
::1	localhost ip6-localhost ip6-loopback
fe00::0	ip6-localnet
fe00::0	ip6-mcastprefix
fe00::1	ip6-allnodes
fe00::2	ip6-allrouters
10.200.166.175	web-statefulset-0.test-statefulset.test.svc.cluster.local	web-statefulset-0

使用其他namespace下的pod访问test 名称空间下的statefulset应用

root@master1:~# kubectl get pods -n default
NAME                                     READY   STATUS    RESTARTS       AGE
aliyun-web-deployment-668cb5f7b5-5rnqs   1/1     Running   1 (127m ago)   3d21h
aliyun-web-deployment-668cb5f7b5-sgs2g   1/1     Running   1 (127m ago)   3d21h
web-deployment-647db54fb5-fkggx          1/1     Running   1 (127m ago)   4d1h
web-deployment-647db54fb5-lz64s          1/1     Running   1 (127m ago)   4d1h

root@master1:~# kubectl exec -it -n default web-deployment-647db54fb5-lz64s -- curl test-statefulset.test
<!DOCTYPE html>
<html>
<head>
<title>Welcome to Nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to Nginx!</h1>
<p>If you see this page, the Nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://Nginx.org/">Nginx.org</a>.<br/>
Commercial support is available at
<a href="http://Nginx.com/">Nginx.com</a>.</p>

<p><em>Thank you for using Nginx.</em></p>
</body>
</html>
root@master1:~#

pod访问测试

root@web-statefulset-0:/usr/local/tomcat# curl web-statefulset-0.test-statefulset.test.svc.cluster.local
<!DOCTYPE html>
<html>
<head>
<title>Welcome to Nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to Nginx!</h1>
<p>If you see this page, the Nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://Nginx.org/">Nginx.org</a>.<br/>
Commercial support is available at
<a href="http://Nginx.com/">Nginx.com</a>.</p>

<p><em>Thank you for using Nginx.</em></p>
</body>
</html>

基于StatefulSet有状态部署与DaemonSet部署prometheus node-exporter

statefulset有状态应用部署

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