要资料 文章 文库 Lib 视频 Code iProcess 课程 认证 咨询 工具 火云堂 讲座吧   成长之路  
会员   
 
追随技术信仰

随时听讲座
每天看新闻
 
 

Kubernetes教程
Kubernetes概述
Kubernetes设计架构
kubernetes设计理念
创建Kubernetes集群
基于Docker本地运行Kubernetes
使用Vagrant
本地运行Kubrenetes v1.0
Google Computer Engine入门
AWS EC2快速入门
在Azure上使用CoreOS和Weave的 Kubernetes
从零开始k8s
CoreOS部署Kubernetes集群
CloudStack部署Kubernetes集群
vSphere部署Kubernetes集群
Ferdora部署Kubernetes集群
CentOS部署Kubernetes集群
Ubuntu物理节点上部署Kubernets集群
Mesos部署Kubernetes集群
Kubernetes用户指南:应用程序管理
名词解释 Pods
名词解释 Labels
名词解释:Namespace
名词解释 Replication Controller
名词解释:Node
名词解释:ReplicaSets
名词解释 Services
名词解释 Volumes
名词解释:PV/PVC/StorageClass
名称解释:Deployment
名词解释:Secret
名词解释:StatefulSet
名词解释:DaemonSet
名词解释:Service Account
名词解释:CronJob
名词解释:Job
名词解释:Security Context和PSP
名词解释:Resource Quotas
名词解释:Network Policy
名词解释:Ingress
名词解释:ThirdPartyResources
名词解释:ConfigMap
名词解释:PodPreset
配置Kubernetes
管理应用:部署持续运行的应用
Horizontal Pod Autoscaling
管理应用:连接应用
管理应用: 在生产环境中使用Pods和容器
Kubernetes UI
Kube-API Server
授权插件
认证插件
API Server端口配置
Admission Controller
Service Accounts集群管理指南
使用Kubernetes在云上原生部署cassandra
 
 

名词解释:StatefulSet
 
27 次浏览
6次  
 捐助

StatefulSet

StatefulSet是为了解决有状态服务的问题(对应Deployments和ReplicaSets是为无状态服务而设计),其应用场景包括

稳定的持久化存储,即Pod重新调度后还是能访问到相同的持久化数据,基于PVC来实现

稳定的网络标志,即Pod重新调度后其PodName和HostName不变,基于Headless Service(即没有Cluster IP的Service)来实现

有序部署,有序扩展,即Pod是有顺序的,在部署或者扩展的时候要依据定义的顺序依次依次进行(即从0到N-1,在下一个Pod运行之前所有之前的Pod必须都是Running和Ready状态),基于init containers来实现

有序收缩,有序删除(即从N-1到0)

从上面的应用场景可以发现,StatefulSet由以下几个部分组成:

用于定义网络标志(DNS domain)的Headless Service

用于创建PersistentVolumes的volumeClaimTemplates

定义具体应用的StatefulSet

StatefulSet中每个Pod的DNS格式为statefulSetName-{0..N-1}.serviceName.namespace.svc.cluster.local,其中

serviceName为Headless Service的名字

0..N-1为Pod所在的序号,从0开始到N-1

statefulSetName为StatefulSet的名字

namespace为服务所在的namespace,Headless Servic和StatefulSet必须在相同的namespace

.cluster.local为Cluster Domain,

简单示例

以一个简单的nginx服务web.yaml为例:

---
apiVersion: v1
kind: Service
metadata:
name: nginx
labels:
app: nginx
spec:
ports:
- port: 80
name: web
clusterIP: None
selector:
app: nginx
---
apiVersion: apps/v1beta1
kind: StatefulSet
metadata:
name: web
spec:
serviceName: "nginx"
replicas: 2
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: gcr.io/google_containers/nginx-slim:0.8
ports:
- containerPort: 80
name: web
volumeMounts:
- name: www
mountPath: /usr/share/nginx/html
volumeClaimTemplates:
- metadata:
name: www
annotations:
volume.alpha.kubernetes.io/storage-class: anything
spec:
accessModes: [ "ReadWriteOnce" ]
resources:
requests:
storage: 1Gi

$ kubectl create -f web.yaml
service "nginx" created
statefulset "web" created

# 查看创建的headless service和statefulset
$ kubectl get service nginx
NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE
nginx None <none> 80/TCP 1m
$ kubectl get statefulset web
NAME DESIRED CURRENT AGE
web 2 2 2m

# 根据volumeClaimTemplates自动创建PVC(在GCE中会自动创建kubernetes.io/gce-pd类型的volume)
$ kubectl get pvc
NAME STATUS VOLUME CAPACITY ACCESSMODES AGE
www-web-0 Bound pvc-d064a004-d8d4-11e6-b521-42010a800002 1Gi RWO 16s
www-web-1 Bound pvc-d06a3946-d8d4-11e6-b521-42010a800002 1Gi RWO 16s

# 查看创建的Pod,他们都是有序的
$ kubectl get pods -l app=nginx
NAME READY STATUS RESTARTS AGE
web-0 1/1 Running 0 5m
web-1 1/1 Running 0 4m

# 使用nslookup查看这些Pod的DNS
$ kubectl run -i --tty --image busybox dns-test --restart=Never --rm /bin/sh
/ # nslookup web-0.nginx
Server: 10.0.0.10
Address 1: 10.0.0.10 kube-dns.kube-system.svc.cluster.local

Name: web-0.nginx
Address 1: 10.244.2.10
/ # nslookup web-1.nginx
Server: 10.0.0.10
Address 1: 10.0.0.10 kube-dns.kube-system.svc.cluster.local

Name: web-1.nginx
Address 1: 10.244.3.12
/ # nslookup web-0.nginx.default.svc.cluster.local
Server: 10.0.0.10
Address 1: 10.0.0.10 kube-dns.kube-system.svc.cluster.local

Name: web-0.nginx.default.svc.cluster.local
Address 1: 10.244.2.10

还可以进行其他的操作

# 扩容
$ kubectl scale statefulset web --replicas=5

# 缩容
$ kubectl patch statefulset web -p '{"spec":{"replicas":3}}'

# 镜像更新(目前还不支持直接更新image,需要patch来间接实现)
$ kubectl patch statefulset web --type='json' -p='[{"op": "replace", "path": "/spec/template/spec/containers/0/image", "value":"gcr.io/google_containers/nginx-slim:0.7"}]'

# 删除StatefulSet和Headless Service
$ kubectl delete statefulset web
$ kubectl delete service nginx

# StatefulSet删除后PVC还会保留着,数据不再使用的话也需要删除
$ kubectl delete pvc www-web-0 www-web-1

zookeeper

另外一个更能说明StatefulSet强大功能的示例为zookeeper.yaml。

---
apiVersion: v1
kind: Service
metadata:
name: zk-headless
labels:
app: zk-headless
spec:
ports:
- port: 2888
name: server
- port: 3888
name: leader-election
clusterIP: None
selector:
app: zk
---
apiVersion: v1
kind: ConfigMap
metadata:
name: zk-config
data:
ensemble: "zk-0;zk-1;zk-2"
jvm.heap: "2G"
tick: "2000"
init: "10"
sync: "5"
client.cnxns: "60"
snap.retain: "3"
purge.interval: "1"
---
apiVersion: policy/v1beta1
kind: PodDisruptionBudget
metadata:
name: zk-budget
spec:
selector:
matchLabels:
app: zk
minAvailable: 2
---
apiVersion: apps/v1beta1
kind: StatefulSet
metadata:
name: zk
spec:
serviceName: zk-headless
replicas: 3
template:
metadata:
labels:
app: zk
annotations:
pod.alpha.kubernetes.io/initialized: "true"
scheduler.alpha.kubernetes.io/affinity: >
{
"podAntiAffinity": {
"requiredDuringScheduling RequiredDuringExecution": [{
"labelSelector": {
"matchExpressions": [{
"key": "app",
"operator": "In",
"values": ["zk-headless"]
}]
},
"topologyKey": "kubernetes.io/hostname"
}]
}
}
spec:
containers:
- name: k8szk
imagePullPolicy: Always
image: gcr.io/ google_samples/k8szk:v1
resources:
requests:
memory: "4Gi"
cpu: "1"
ports:
- containerPort: 2181
name: client
- containerPort: 2888
name: server
- containerPort: 3888
name: leader-election
env:
- name : ZK_ENSEMBLE
valueFrom:
configMapKeyRef:
name: zk-config
key: ensemble
- name : ZK_HEAP_SIZE
valueFrom:
configMapKeyRef:
name: zk-config
key: jvm.heap
- name : ZK_TICK_TIME
valueFrom:
configMapKeyRef:
name: zk-config
key: tick
- name : ZK_INIT_LIMIT
valueFrom:
configMapKeyRef:
name: zk-config
key: init
- name : ZK_SYNC_LIMIT
valueFrom:
configMapKeyRef:
name: zk-config
key: tick
- name : ZK_MAX_CLIENT_CNXNS
valueFrom:
configMapKeyRef:
name: zk-config
key: client.cnxns
- name: ZK_SNAP_RETAIN_COUNT
valueFrom:
configMapKeyRef:
name: zk-config
key: snap.retain
- name: ZK_PURGE_INTERVAL
valueFrom:
configMapKeyRef:
name: zk-config
key: purge.interval
- name: ZK_CLIENT_PORT
value: "2181"
- name: ZK_SERVER_PORT
value: "2888"
- name: ZK_ELECTION_PORT
value: "3888"
command:
- sh
- -c
- zkGenConfig.sh && zkServer.sh start-foreground
readinessProbe:
exec:
command:
- "zkOk.sh"
initialDelaySeconds: 15
timeoutSeconds: 5
livenessProbe:
exec:
command:
- "zkOk.sh"
initialDelaySeconds: 15
timeoutSeconds: 5
volumeMounts:
- name: datadir
mountPath: /var/lib/zookeeper
securityContext:
runAsUser: 1000
fsGroup: 1000
volumeClaimTemplates:
- metadata:
name: datadir
annotations:
volume.alpha.kubernetes.io/ storage-class: anything
spec:
accessModes: [ "ReadWriteOnce" ]
resources:
requests:
storage: 20Gi

kubectl create -f zookeeper.yaml

详细的使用说明见zookeeper stateful application。

StatefulSet注意事项

还在beta状态,需要kubernetes v1.5版本以上才支持

所有Pod的Volume必须使用PersistentVolume或者是管理员事先创建好

为了保证数据安全,删除StatefulSet时不会删除Volume

StatefulSet需要一个Headless Service来定义DNS domain,需要在StatefulSet之前创建好

目前StatefulSet还没有feature complete,比如更新操作还需要手动patch。

更多可以参考Kubernetes文档。


您可以捐助,支持我们的公益事业。

1元 10元 50元





认证码: 验证码,看不清楚?请点击刷新验证码 必填



27 次浏览
6次
 捐助
 

每天2个文档/视频
扫描微信二维码订阅
订阅技术月刊
获得每月300个技术资源
 
 

关于我们 | 联系我们 | 京ICP备10020922号 京公海网安备110108001071号