kubernetes实战-基于redis和docker的留言簿案例

来源：互联网发布：手机建站系统源码编辑：程序博客网时间：2024/04/25 12:39

一、介绍

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前端通过javascript redis api和redis master交互

kubernetes体系架构

二、配置

0、先决条件

Kubernetes 集群

1、启动redis master

使用replication controller确保只有一个pod在运行（当某个节点down了，rc会在另一个健康的node启动redis master），但可能会有数据丢失。

[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

验证master运行成功，如下展示了pod运行在centos2/192.168.1.112这台机器上

[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状态

[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执行后，如果镜像不存在，会执行docker pull，根据网络情况，下载中的pods 在kubertnetes UI上会显示pending状态

2、启动master service

一个kubernetes service会对一个或多个container进行负载均衡，这是通过我们上面redis-master中定义的labels元数据实现的，值得注意的是，在redis中只有一个master，但是我们依然为它创建一个service，这是因为这样我们就能使用一个elastic IP来路由到具体某一个master。

kubernetes集群中的service是通过container中的环境变量实现服务发现的，service基于pod label实现container的负载均衡。

在第一步中创建的pod包含了一个label“name=redis-master”，service的selector字段决定了service将流量转发给哪个pod，port和targetPort信息定义了service proxy运行在什么端口。

[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

上面的运行成功后，所有pods都能发现redis master运行在6379端口，从salve到master流量走向会有以下两步：

1、一个redis slave会连接到redis master service的port上

2、流量会从service节点上的port到targetPort

如果targetPort未指定，默认和port一致

3、启动replicated slave pod

虽然redis master是一个单独的pod，redis slaves是一个replicated pod，在Kubernetes中，一个Replication Controller负责管理一个replicated pod的多个实例，RC会自动拉起down掉的replica（可以通过杀死docker 进程方式简单测试）

[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

可以看到一个master pod和两个slave pod

4、启动slave service

和master一样，我们希望有一个代理服务连接到redis slave，除了服务发现之外，slave service还为web app client提供了透明代理。

这次service 的selector是name=redis-slave，我们可以方便的使用kubectl get services -l "label=value"命令来定位这些服务

[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、创建frontend pod

这是一个简单的PHP 服务，用来和master service（写请求）或slave service（读请求）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

运行成功后，查看当前pod运行状态

[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

可以看到一个redis master，两个redis slave和三个frontend pods

6、创建guestbook service

和其他service一样，你可以创建一个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

我们可以通过frontend service（10.254.154.111）访问pods，但是这个IP明显是无法在外部访问的，下一节讲解如何在外部网络访问guestbook

7、外部网络访问guestbook

kubernetes 支持两种访问暴露一个服务到外部IP地址NodePorts 和LoadBalancers，https://github.com/GoogleCloudPlatform/kubernetes/blob/master/docs/services.md#external-services

另外可以查看防火墙，找到service对应的端口，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

发现redis-master是在10.254.154.90上，登录到centos2上，执行iptables-save，发现其中有这样一条规则

-A KUBE-PORTALS-HOST -d 10.254.154.90/32 -p tcp -m comment --comment "default/redis-master:" -m tcp --dport 6379 -j DNAT --to-destination 192.168.1.112:49038

说明，centos2本机的49038端口映射到master container内的6379了，当然我们就能执行在本机访问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简单测试

提交数据

curl "localhost:8000/index.php?cmd=set&key=messages&value=jay_sais_hi"

查询数据

curl "localhost:8000/index.php?cmd=get&key=messages"

附本案例用到的6个.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"
      }
   }
}

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