基于Kubernetes和Docke實(shí)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(guò)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(dòng)redis master
使用replication controller確保只有一個(gè)pod在運(yùn)行(當(dāng)某個(gè)節(jié)點(diǎn)down了,rc會(huì)在另一個(gè)健康的node啟動(dòng)redis master),但可能會(huì)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(yàn)證master運(yùn)行成功,如下展示了pod運(yùn)行在centos2/192.168.1.112這臺(tái)機(jī)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(huì)執(zhí)行docker pull,根據(jù)網(wǎng)絡(luò)情況,下載中的pods 在kubertnetes UI上會(huì)顯示pending狀態(tài)
2、啟動(dòng)master service
一個(gè)kubernetes service會(huì)對(duì)一個(gè)或多個(gè)container進(jìn)行負(fù)載均衡,這是通過(guò)我們上面redis-master中定義的labels元數(shù)據(jù)實(shí)現(xiàn)的,值得注意的是,在redis中只有一個(gè)master,但是我們依然為它創(chuàng)建一個(gè)service,這是因?yàn)檫@樣我們就能使用一個(gè)elastic IP來(lái)路由到具體某一個(gè)master。
kubernetes集群中的service是通過(guò)container中的環(huán)境變量實(shí)現(xiàn)服務(wù)發(fā)現(xiàn)的,service基于pod label實(shí)現(xiàn)container的負(fù)載均衡。
在第一步中創(chuàng)建的pod包含了一個(gè)label“name=redis-master”,service的selector字段決定了service將流量轉(zhuǎn)發(fā)給哪個(gè)pod,port和targetPort信息定義了service proxy運(yùn)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(yùn)行成功后,所有pods都能發(fā)現(xiàn)redis master運(yùn)行在6379端口,從salve到master流量走向會(huì)有以下兩步:
1、一個(gè)redis slave會(huì)連接到redis master service的port上
2、流量會(huì)從service節(jié)點(diǎn)上的port到targetPort
如果targetPort未指定,默認(rèn)和port一致
3、啟動(dòng)replicated slave pod
雖然redis master是一個(gè)單獨(dú)的pod,redis slaves是一個(gè)replicated pod,在Kubernetes中,一個(gè)Replication Controller負(fù)責(zé)管理一個(gè)replicated pod的多個(gè)實(shí)例,RC會(huì)自動(dòng)拉起down掉的replica(可以通過(guò)殺死docker 進(jìn)程方式簡(jiǎn)單測(cè)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(gè)master pod和兩個(gè)slave pod
4、啟動(dòng)slave service
和master一樣,我們希望有一個(gè)代理服務(wù)連接到redis slave,除了服務(wù)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(lái)定位這些服務(wù)
[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(gè)簡(jiǎn)單的PHP 服務(wù),用來(lái)和master service(寫(xiě)請(qǐng)求)或slave service(讀請(qǐng)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(yùn)行成功后,查看當(dāng)前pod運(yùn)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(gè)redis master,兩個(gè)redis slave和三個(gè)frontend pods
6、創(chuàng)建guestbook service
和其他service一樣,你可以創(chuàng)建一個(gè)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(guò)frontend service(10.254.154.111)訪問(wèn)pods,但是這個(gè)IP明顯是無(wú)法在外部訪問(wèn)的,下一節(jié)講解如何在外部網(wǎng)絡(luò)訪問(wèn)guestbook
7、外部網(wǎng)絡(luò)訪問(wèn)guestbook
kubernetes 支持兩種訪問(wèn)暴露一個(gè)服務(wù)到外部IP地址NodePorts 和LoadBalancers,另外可以查看防火墻,找到service對(duì)應(yīng)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(shuō)明,centos2本機(jī)的49038端口映射到master container內(nèi)的6379了,當(dāng)然我們就能執(zhí)行在本機(jī)訪問(wèn)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(jiǎn)單測(cè)試
提交數(shù)據(jù)
查詢數(shù)據(jù)
附本案例用到的6個(gè).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?jī)?nèi)容,希望對(duì)大家的學(xué)習(xí)有所幫助,也希望大家多多支持腳本之家。
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