【讀書筆記】12 牛刀小試：我的第一個容器化應用

《深入剖析Kubernetes - 12? 牛刀小試：我的第一個容器化應用》

主要包括2個步驟：制作鏡像 和 編寫yaml配置文件(或json)

以 nginx 的deployment 為例

apiVersion:?apps/v1?
kind:?Deployment?
metadata:?
??name:?nginx-deployment?
spec:?
??selector:?
????matchLabels:?
??????app:?nginx?
??replicas:?2?
?template:?
???metadata:?labels:?
?????app:?nginx?
???spec:?
?????containers:?
?????-?name:?nginx?
???????image:?nginx:1.7.9?
???????ports:?
???????-?containerPort:?80

其中kind 字段聲明類型，例如deployment、daemonset 等，metadata 是具體描述，例如name、namespace、labels、annotations等

spec.template 描述了pod 的細節，即容器配置的模板

創建deployment

$?kubectl?create?-f?nginx-deployment.yaml

查看deployment運行情況

$?kubectl?get?pods?-l?app=nginx?
NAME?READY?STATUS?RESTARTS?AGE?n
ginx-deployment-67594d6bf6-9gdvr?1/1?Running?0?10m?
nginx-deployment-67594d6bf6-v6j7w?1/1?Running?0?10m

查看API 對象細節

kubectl?describe?pod?nginx-deployment-67594d6bf6-9gdvr
Name:???????????????nginx-deployment-67594d6bf6-9gdvr
Namespace:??????????default
Priority:???????????0
PriorityClassName:??<none>
Node:???????????????node-1/10.168.0.3
Start?Time:?????????Thu,?16?Aug?2018?08:48:42?+0000
Labels:?????????????app=nginx
????????????????????pod-template-hash=2315082692
Annotations:????????<none>
Status:?????????????Running
IP:?????????????????10.32.0.23
Controlled?By:??????ReplicaSet/nginx-deployment-67594d6bf6
...
Events:

??Type?????Reason??????????????????Age????????????????From???????????????Message

??----?????------??????????????????----???????????????----???????????????-------
??
??Normal???Scheduled???????????????1m?????????????????default-scheduler??Successfully?assigned?default/nginx-deployment-67594d6bf6-9gdvr?to?node-1
??Normal???Pulling?????????????????25s????????????????kubelet,?node-1????pulling?image?"nginx:1.7.9"
??Normal???Pulled??????????????????17s????????????????kubelet,?node-1????Successfully?pulled?image?"nginx:1.7.9"
??Normal???Created?????????????????17s????????????????kubelet,?node-1????Created?container
??Normal???Started?????????????????17s????????????????kubelet,?node-1????Started?container

其中Events 字段可用于后期問題定位，常見的有

(1)找不到合適的node節點調度pod，包括

node節點label匹配不上；

node節點資源不夠分配；

node節點設置了污點；

node節點網絡異常；

(2) 鏡像拉取失敗

升級容器鏡像版本

...????
????spec:
??????containers:
??????-?name:?nginx
????????image:?nginx:1.8?#?這里被從?1.7.9?修改為?1.8
????????ports:
??????-?containerPort:?80

執行

$?kubectl?replace?-f?nginx-deployment.yaml

更常見的方式是，通過apply 執行相關操作，無論是創建還是修改都可以通過該命令完成

$?kubectl?apply?-f?nginx-deployment.yaml?
#?修改?nginx-deployment.yaml?的內容?
$?kubectl?apply?-f?nginx-deployment.yaml

下面是一個volume掛載的例子

通常分為emptyDir 和 hostPath 兩種，兩者的區別在于前者不需要指定宿主機目錄(源目錄)，k8s 會在宿主機上創建一個臨時目錄并掛載進去；而后者，則需要顯式聲明掛載的源目錄，例如將宿主機的/usr/local/nginx/html 目錄掛載到容器同樣的位置

emptyDir的例子

volumes:
??????-?name:?nginx-vol
????????emptyDir:?{}
hostPath的例子
...???
????volumes:
??????-?name:?nginx-vol
????????hostPath:?
??????????path:?/var/data

進入容器

$?kubectl?exec?-it?nginx-deployment-5c678cfb6d-lg9lw?--?/bin/bash?
#?ls?/usr/share/nginx/html

刪除容器

$?kubectl?delete?-f?nginx-deployment.yaml