基于Kubernetes和Docke實現留言簿案例

2024-09-01 13:48:38

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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

Kubernetes,Docke,留言簿

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（當某個節點down了，rc會在另一個健康的node啟動redis master），但可能會有數據丟失。

[root@centos1 example]# kubectl create -f redis-master-controller.json replicationcontrollers/redis-master[root@centos1 example]# kubectl get rcCONTROLLER   CONTAINER(S)  IMAGE(S)  SELECTOR      REPLICASredis-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 podsPOD         IP      CONTAINER(S)  IMAGE(S)  HOST          LABELS       STATUS  CREATED   MESSAGEredis-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

[root@centos2 yum.repos.d]# docker psCONTAINER ID    IMAGE                 COMMAND        CREATED       STATUS       PORTS        NAMES91689ce56668    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執行后，如果鏡像不存在，會執行docker pull，根據網絡情況，下載中的pods 在kubertnetes UI上會顯示pending狀態

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元數據實現的，值得注意的是，在redis中只有一個master，但是我們依然為它創建一個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中的環境變量實現服務發現的，service基于pod label實現container的負載均衡。
在第一步中創建的pod包含了一個label“name=redis-master”，service的selector字段決定了service將流量轉發給哪個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 servicesNAME      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都能發現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 rcCONTROLLER   CONTAINER(S)  IMAGE(S)          SELECTOR      REPLICASredis-master  master     redis            name=redis-master  1redis-slave  slave     kubernetes/redis-slave:v2  name=redis-slave  2[root@centos1 example]# kubectl get podsPOD         IP      CONTAINER(S)  IMAGE(S)          HOST          LABELS       STATUS  CREATED   MESSAGEredis-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，除了服務發現之外，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 servicesNAME      LABELS                  SELECTOR      IP(S)      PORT(S)redis-master  name=redis-master             name=redis-master  10.254.154.90  6379/TCPredis-slave   name=redis-slave             name=redis-slave  10.254.159.145  6379/TCP

5、創建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 rcCONTROLLER   CONTAINER(S)  IMAGE(S)                  SELECTOR      REPLICASfrontend    php-redis   kubernetes/example-guestbook-php-redis:v2  name=frontend    3redis-master  master     redis                    name=redis-master  1redis-slave  slave     kubernetes/redis-slave:v2          name=redis-slave  2

運行成功后，查看當前pod運行狀態

[root@centos1 example]# kubectl get podsPOD         IP      CONTAINER(S)  IMAGE(S)                  HOST          LABELS       STATUS  CREATED   MESSAGEfrontend-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、創建guestbook service
和其他service一樣，你可以創建一個service管理frontend pods

[root@centos1 example]# kubectl create -f frontend-service.json services/frontend[root@centos1 example]# kubectl get servicesNAME      LABELS                  SELECTOR      IP(S)      PORT(S)frontend    name=frontend               name=frontend    10.254.154.111  80/TCPredis-master  name=redis-master             name=redis-master  10.254.154.90  6379/TCPredis-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，下一節講解如何在外部網絡訪問guestbook

7、外部網絡訪問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,servicesPOD         IP      CONTAINER(S)  IMAGE(S)                  HOST          LABELS       STATUS  CREATED     MESSAGEfrontend-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/TCPkubernetes   component=apiserver,provider=kubernetes  <none>       10.254.0.2    443/TCPkubernetes-ro  component=apiserver,provider=kubernetes  <none>       10.254.0.1    80/TCPredis-master  name=redis-master             name=redis-master  10.254.154.90  6379/TCPredis-slave   name=redis-slave             name=redis-slave  10.254.159.145  6379/TCP[root@centos1 example]# kubectl get servicesNAME      LABELS                  SELECTOR      IP(S)      PORT(S)frontend    name=frontend               name=frontend    10.254.154.111  80/TCPkubernetes   component=apiserver,provider=kubernetes  <none>       10.254.0.2    443/TCPkubernetes-ro  component=apiserver,provider=kubernetes  <none>       10.254.0.1    80/TCPredis-master  name=redis-master             name=redis-master  10.254.154.90  6379/TCPredis-slave   name=redis-slave             name=redis-slave  10.254.159.145  6379/TCP

發現redis-master是在10.254.154.90上，登錄到centos2上，執行iptables-save，發現其中有這樣一條規則

復制代碼代碼如下:

	-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

說明，centos2本機的49038端口映射到master container內的6379了，當然我們就能執行在本機訪問redis了

[root@centos2 yum.repos.d]# redis-cli -p 49038127.0.0.1:49038> set a bOK127.0.0.1:49038> get a"b"

8、使用curl簡單測試

提交數據

復制代碼代碼如下:

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

查詢數據

復制代碼代碼如下:

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

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容，希望對大家的學習有所幫助，也希望大家多多支持VEVB武林網。

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