基于Kubernetes和Docke實現(xiàn)留言簿案例
一、介紹
本案例基于Kubernetes和Docker,其中包括
1、web前端
2、redis master
3、redis slave
其中web前端通過javascript redis api和redis master交互
kubernetes體系架構(gòu)

二、配置
0、先決條件
Kubernetes 集群
1、啟動redis master
使用replication controller確保只有一個pod在運行(當某個節(jié)點down了,rc會在另一個健康的node啟動redis master),但可能會有數(shù)據(jù)丟失。
[root@centos1 example]# kubectl create -f redis-master-controller.json replicationcontrollers/redis-master [root@centos1 example]# kubectl get rc CONTROLLER CONTAINER(S) IMAGE(S) SELECTOR REPLICAS redis-master master redis name=redis-master 1
驗證master運行成功,如下展示了pod運行在centos2/192.168.1.112這臺機器上
[root@centos1 example]# kubectl get pods
POD IP CONTAINER(S) IMAGE(S) HOST LABELS STATUS CREATED MESSAGE
redis-master-svar7 172.17.0.9 centos2/192.168.1.112 name=redis-master Running 55 seconds
master redis Running 55 seconds
SSH到centos2/192.168.1.112查看docker狀態(tài)
[root@centos2 yum.repos.d]# docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 91689ce56668 redis:latest "/entrypoint.sh redi 3 minutes ago Up 3 minutes k8s_master.52732b08_redis-master-svar7_default_5b6d5485-1894-11e5-b3ad-000c293c8c19_97e79b7b 38c3180813c3 gcr.io/google_containers/pause:0.8.0 "/pause" 3 minutes ago Up 3 minutes k8s_POD.49eee8c2_redis-master-svar7_default_5b6d5485-1894-11e5-b3ad-000c293c8c19_298e038f
注意:kubectl create執(zhí)行后,如果鏡像不存在,會執(zhí)行docker pull,根據(jù)網(wǎng)絡情況,下載中的pods 在kubertnetes UI上會顯示pending狀態(tài)
2、啟動master service
一個kubernetes service會對一個或多個container進行負載均衡,這是通過我們上面redis-master中定義的labels元數(shù)據(jù)實現(xiàn)的,值得注意的是,在redis中只有一個master,但是我們依然為它創(chuàng)建一個service,這是因為這樣我們就能使用一個elastic IP來路由到具體某一個master。
kubernetes集群中的service是通過container中的環(huán)境變量實現(xiàn)服務發(fā)現(xiàn)的,service基于pod label實現(xiàn)container的負載均衡。
在第一步中創(chuàng)建的pod包含了一個label“name=redis-master”,service的selector字段決定了service將流量轉(zhuǎn)發(fā)給哪個pod,port和targetPort信息定義了service proxy運行在什么端口。
[root@centos1 example]# kubectl create -f redis-master-service.json services/redis-master [root@centos1 example]# kubectl get services NAME LABELS SELECTOR IP(S) PORT(S) redis-master name=redis-master name=redis-master 10.254.154.90 6379/TCP
上面的運行成功后,所有pods都能發(fā)現(xiàn)redis master運行在6379端口,從salve到master流量走向會有以下兩步:
1、一個redis slave會連接到redis master service的port上
2、流量會從service節(jié)點上的port到targetPort
如果targetPort未指定,默認和port一致
3、啟動replicated slave pod
雖然redis master是一個單獨的pod,redis slaves是一個replicated pod,在Kubernetes中,一個Replication Controller負責管理一個replicated pod的多個實例,RC會自動拉起down掉的replica(可以通過殺死docker 進程方式簡單測試)
[root@centos1 example]# kubectl create -f redis-slave-controller.json
replicationcontrollers/redis-slave
[root@centos1 example]# kubectl get rc
CONTROLLER CONTAINER(S) IMAGE(S) SELECTOR REPLICAS
redis-master master redis name=redis-master 1
redis-slave slave kubernetes/redis-slave:v2 name=redis-slave 2
[root@centos1 example]# kubectl get pods
POD IP CONTAINER(S) IMAGE(S) HOST LABELS STATUS CREATED MESSAGE
redis-master-svar7 172.17.0.9 centos2/192.168.1.112 name=redis-master Running 41 minutes
master redis Running 41 minutes
redis-slave-31tkb 172.17.0.10 centos2/192.168.1.112 name=redis-slave Running 29 seconds
slave kubernetes/redis-slave:v2 Running 28 seconds
redis-slave-uk8nu 172.17.0.11 centos2/192.168.1.112 name=redis-slave Running 29 seconds
slave kubernetes/redis-slave:v2 Running 28 seconds
可以看到一個master pod和兩個slave pod
4、啟動slave service
和master一樣,我們希望有一個代理服務連接到redis slave,除了服務發(fā)現(xiàn)之外,slave service還為web app client提供了透明代理。
這次service 的selector是name=redis-slave,我們可以方便的使用kubectl get services -l "label=value"命令來定位這些服務
[root@centos1 example]# kubectl create -f redis-slave-service.json services/redis-slave [root@centos1 example]# kubectl get services NAME LABELS SELECTOR IP(S) PORT(S) redis-master name=redis-master name=redis-master 10.254.154.90 6379/TCP redis-slave name=redis-slave name=redis-slave 10.254.159.145 6379/TCP
5、創(chuàng)建frontend pod
這是一個簡單的PHP 服務,用來和master service(寫請求)或slave service(讀請求)交互
[root@centos1 example]# kubectl create -f frontend-controller.json replicationcontrollers/frontend [root@centos1 example]# kubectl get rc CONTROLLER CONTAINER(S) IMAGE(S) SELECTOR REPLICAS frontend php-redis kubernetes/example-guestbook-php-redis:v2 name=frontend 3 redis-master master redis name=redis-master 1 redis-slave slave kubernetes/redis-slave:v2 name=redis-slave 2
運行成功后,查看當前pod運行狀態(tài)
[root@centos1 example]# kubectl get pods
POD IP CONTAINER(S) IMAGE(S) HOST LABELS STATUS CREATED MESSAGE
frontend-fr5z1 172.17.0.13 centos2/192.168.1.112 name=frontend Running 2 minutes
php-redis kubernetes/example-guestbook-php-redis:v2 Running 2 minutes
frontend-gjx3t 172.17.0.14 centos2/192.168.1.112 name=frontend Running 2 minutes
php-redis kubernetes/example-guestbook-php-redis:v2 Running 2 minutes
frontend-v608r 172.17.0.12 centos2/192.168.1.112 name=frontend Running 2 minutes
php-redis kubernetes/example-guestbook-php-redis:v2 Running 2 minutes
redis-master-svar7 172.17.0.9 centos2/192.168.1.112 name=redis-master Running 53 minutes
master redis Running 53 minutes
redis-slave-31tkb 172.17.0.10 centos2/192.168.1.112 name=redis-slave Running 12 minutes
slave kubernetes/redis-slave:v2 Running 12 minutes
redis-slave-uk8nu 172.17.0.11 centos2/192.168.1.112 name=redis-slave Running 12 minutes
slave kubernetes/redis-slave:v2 Running 12 minutes
可以看到一個redis master,兩個redis slave和三個frontend pods
6、創(chuàng)建guestbook service
和其他service一樣,你可以創(chuàng)建一個service管理frontend pods
[root@centos1 example]# kubectl create -f frontend-service.json services/frontend [root@centos1 example]# kubectl get services NAME LABELS SELECTOR IP(S) PORT(S) frontend name=frontend name=frontend 10.254.154.111 80/TCP redis-master name=redis-master name=redis-master 10.254.154.90 6379/TCP redis-slave name=redis-slave name=redis-slave 10.254.159.145 6379/TCP
我們可以通過frontend service(10.254.154.111)訪問pods,但是這個IP明顯是無法在外部訪問的,下一節(jié)講解如何在外部網(wǎng)絡訪問guestbook
7、外部網(wǎng)絡訪問guestbook
kubernetes 支持兩種訪問暴露一個服務到外部IP地址NodePorts 和LoadBalancers,另外可以查看防火墻,找到service對應的端口,如下
[root@centos1 example]# kubectl get pods,services
POD IP CONTAINER(S) IMAGE(S) HOST LABELS STATUS CREATED MESSAGE
frontend-fr5z1 172.17.0.13 centos2/192.168.1.112 name=frontend Running 22 minutes
php-redis kubernetes/example-guestbook-php-redis:v2 Running 22 minutes
frontend-gjx3t 172.17.0.14 centos2/192.168.1.112 name=frontend Running 22 minutes
php-redis kubernetes/example-guestbook-php-redis:v2 Running 22 minutes
frontend-v608r 172.17.0.12 centos2/192.168.1.112 name=frontend Running 22 minutes
php-redis kubernetes/example-guestbook-php-redis:v2 Running 22 minutes
redis-master-svar7 172.17.0.9 centos2/192.168.1.112 name=redis-master Running About an hour
master redis Running About an hour
redis-slave-31tkb 172.17.0.10 centos2/192.168.1.112 name=redis-slave Running 32 minutes
slave kubernetes/redis-slave:v2 Running 32 minutes
redis-slave-uk8nu 172.17.0.11 centos2/192.168.1.112 name=redis-slave Running 32 minutes
slave kubernetes/redis-slave:v2 Running 32 minutes
NAME LABELS SELECTOR IP(S) PORT(S)
frontend name=frontend name=frontend 10.254.154.111 80/TCP
kubernetes component=apiserver,provider=kubernetes <none> 10.254.0.2 443/TCP
kubernetes-ro component=apiserver,provider=kubernetes <none> 10.254.0.1 80/TCP
redis-master name=redis-master name=redis-master 10.254.154.90 6379/TCP
redis-slave name=redis-slave name=redis-slave 10.254.159.145 6379/TCP
[root@centos1 example]# kubectl get services
NAME LABELS SELECTOR IP(S) PORT(S)
frontend name=frontend name=frontend 10.254.154.111 80/TCP
kubernetes component=apiserver,provider=kubernetes <none> 10.254.0.2 443/TCP
kubernetes-ro component=apiserver,provider=kubernetes <none> 10.254.0.1 80/TCP
redis-master name=redis-master name=redis-master 10.254.154.90 6379/TCP
redis-slave name=redis-slave name=redis-slave 10.254.159.145 6379/TCP
發(fā)現(xiàn)redis-master是在10.254.154.90上,登錄到centos2上,執(zhí)行iptables-save,發(fā)現(xiàn)其中有這樣一條規(guī)則
說明,centos2本機的49038端口映射到master container內(nèi)的6379了,當然我們就能執(zhí)行在本機訪問redis了
[root@centos2 yum.repos.d]# redis-cli -p 49038 127.0.0.1:49038> set a b OK 127.0.0.1:49038> get a "b"
8、使用curl簡單測試
提交數(shù)據(jù)
查詢數(shù)據(jù)
附本案例用到的6個.json文件
1、redis-master-controller.json
{
"kind":"ReplicationController",
"apiVersion":"v1beta3",
"metadata":{
"name":"redis-master",
"labels":{
"name":"redis-master"
}
},
"spec":{
"replicas":1,
"selector":{
"name":"redis-master"
},
"template":{
"metadata":{
"labels":{
"name":"redis-master"
}
},
"spec":{
"containers":[
{
"name":"master",
"image":"redis",
"ports":[
{
"containerPort":6379
}
]
}
]
}
}
}
}
2、redis-master-service.json
{
"kind":"Service",
"apiVersion":"v1beta3",
"metadata":{
"name":"redis-master",
"labels":{
"name":"redis-master"
}
},
"spec":{
"ports": [
{
"port":6379,
"targetPort":6379
}
],
"selector":{
"name":"redis-master"
}
}
}
3、redis-slave-controller.json
{
"kind":"ReplicationController",
"apiVersion":"v1beta3",
"metadata":{
"name":"redis-slave",
"labels":{
"name":"redis-slave"
}
},
"spec":{
"replicas":2,
"selector":{
"name":"redis-slave"
},
"template":{
"metadata":{
"labels":{
"name":"redis-slave"
}
},
"spec":{
"containers":[
{
"name":"slave",
"image":"kubernetes/redis-slave:v2",
"ports":[
{
"containerPort":6379
}
]
}
]
}
}
}
}
4、redis-slave-service.json
{
"kind":"Service",
"apiVersion":"v1beta3",
"metadata":{
"name":"redis-slave",
"labels":{
"name":"redis-slave"
}
},
"spec":{
"ports": [
{
"port":6379
}
],
"selector":{
"name":"redis-slave"
}
}
}
5、frontend-controller.json
{
"kind":"ReplicationController",
"apiVersion":"v1beta3",
"metadata":{
"name":"frontend",
"labels":{
"name":"frontend"
}
},
"spec":{
"replicas":3,
"selector":{
"name":"frontend"
},
"template":{
"metadata":{
"labels":{
"name":"frontend"
}
},
"spec":{
"containers":[
{
"name":"php-redis",
"image":"kubernetes/example-guestbook-php-redis:v2",
"ports":[
{
"containerPort":80
}
]
}
]
}
}
}
}
6、frontend-service.json
{
"kind":"Service",
"apiVersion":"v1beta3",
"metadata":{
"name":"frontend",
"labels":{
"name":"frontend"
}
},
"spec":{
"ports": [
{
"port":80
}
],
"selector":{
"name":"frontend"
}
}
}
以上就是本文的全部內(nèi)容,希望對大家的學習有所幫助,也希望大家多多支持腳本之家。
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