Kubernetes外挂配置管理—ConfigMap介绍

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　　其他容器编排调度工具会大谈特谈“轻应用”、“十二要素应用”，这样就势必会对企业级复杂应用做很大的改动。Kubernetes是为了解决“如何合理使用容器支撑企业级复杂应用”这个问题而诞生的，所以它的设计理念是要支持绝大多数应用的原生形态。例如，很多应用程序的配置需要通过配置文件，命令行参数和环境变量的组合配置来完成（“十二要素应用”等均要求去配置）。这些配置应该从image内容中解耦，以此来保持容器化应用程序的可移植性。ConfigMap API资源提供了将配置数据注入容器的方式，同时保证该机制对容器来说是透明的。ConfigMap可以被用来保存单个属性，也可以用来保存整个配置文件或者JSON二进制大对象。

　　ConfigMap API资源存储键/值对配置数据，这些数据可以在pods里使用。ConfigMap跟Secrets类似，但是ConfigMap可以更方便的处理不包含敏感信息的字符串。示例如下：

kind: ConfigMap
apiVersion: v1
metadata:
  creationTimestamp: 2016-02-18T19:14:38Z
  name: example-config
  namespace: default
data:
  example.property.1: hello
  example.property.2: world
  example.property.file: |-
    property.1=value-1
    property.2=value-2
    property.3=value-3

　　通过示例代码可以看到：ConfigMap可以包含细粒度的配置项，如：example.property.1；也可以包含粗粒度的配置文件，如：example.property.file。

1、创建ConfigMap

1.1 从文件夹创建

[root@k8s-master propertirs]# cat /home/yaml/propertirs/game.properties 
enemies=aliens
lives=3
enemies.cheat=true
enemies.cheat.level=noGoodRotten
secret.code.passphrase=UUDDLRLRBABAS
secret.code.allowed=true
secret.code.lives=30
[root@k8s-master propertirs]# cat /home/yaml/propertirs/ui.properties 
color.good=purple
color.bad=yellow
allow.textmode=true
how.nice.to.look=fairlyNice
[root@k8s-master propertirs]# kubectl create configmap game-config --from-file=/home/yaml/propertirs/
configmap "game-config" created
[root@k8s-master propertirs]# kubectl describe configmaps game-config  
#该方法只能得到ConfigMap的Key和size
Name:        game-config
Namespace:    default
Labels:        <none>
Annotations:    <none>

Data
====
ui.properties:        83 bytes
game.properties:    158 bytes
#若想得到详细信息，可通过以下命令：
[root@k8s-master propertirs]# kubectl get configmaps game-config -o yaml
apiVersion: v1
data:
  game.properties: |
    enemies=aliens
    lives=3
    enemies.cheat=true
    enemies.cheat.level=noGoodRotten
    secret.code.passphrase=UUDDLRLRBABAS
    secret.code.allowed=true
    secret.code.lives=30
  ui.properties: |
    color.good=purple
    color.bad=yellow
    allow.textmode=true
    how.nice.to.look=fairlyNice
kind: ConfigMap
metadata:
  creationTimestamp: 2017-03-21T03:22:34Z
  name: game-config
  namespace: default
  resourceVersion: "3002770"
  selfLink: /api/v1/namespaces/default/configmaps/game-config
  uid: a04f90f0-0de5-11e7-b3d5-fa163ebba51b

1.2 从文件创建

[root@k8s-master propertirs]# kubectl create configmap game-config-2 --from-file=/home/yaml/propertirs/game.properties --from-file=/home/yaml/propertirs/ui.properties
configmap "game-config-2" created
[root@k8s-master propertirs]# kubectl get configmaps game-config-2 -o yaml
apiVersion: v1
data:
  game.properties: |
    enemies=aliens
    lives=3
    enemies.cheat=true
    enemies.cheat.level=noGoodRotten
    secret.code.passphrase=UUDDLRLRBABAS
    secret.code.allowed=true
    secret.code.lives=30
  ui.properties: |
    color.good=purple
    color.bad=yellow
    allow.textmode=true
    how.nice.to.look=fairlyNice
kind: ConfigMap
metadata:
  creationTimestamp: 2017-03-21T03:30:15Z
  name: game-config-2
  namespace: default
  resourceVersion: "3003415"
  selfLink: /api/v1/namespaces/default/configmaps/game-config-2
  uid: b2e4dfab-0de6-11e7-b3d5-fa163ebba51b

1.3  指定data中的key

[root@k8s-master propertirs]# kubectl create configmap game-config-3 --from-file=game-special-key=/home/yaml/propertirs/game.properties
configmap "game-config-3" created
[root@k8s-master propertirs]# kubectl get configmaps game-config-3 -o yaml
apiVersion: v1
data:
  game-special-key: |
    enemies=aliens
    lives=3
    enemies.cheat=true
    enemies.cheat.level=noGoodRotten
    secret.code.passphrase=UUDDLRLRBABAS
    secret.code.allowed=true
    secret.code.lives=30
kind: ConfigMap
metadata:
  creationTimestamp: 2017-03-21T03:33:23Z
  name: game-config-3
  namespace: default
  resourceVersion: "3003678"
  selfLink: /api/v1/namespaces/default/configmaps/game-config-3
  uid: 2345dad3-0de7-11e7-b3d5-fa163ebba51b

1.4  指定具体的值

[root@k8s-master propertirs]# kubectl create configmap game-config-4 --from-literal=special.user=zhenyu --from-literal=special.passwd=yaodidiao
configmap "game-config-4" created
[root@k8s-master propertirs]# kubectl get configmaps game-config-4 -o yaml
apiVersion: v1
data:
  special.passwd: yaodidiao
  special.user: zhenyu
kind: ConfigMap
metadata:
  creationTimestamp: 2017-03-21T03:36:12Z
  name: game-config-4
  namespace: default
  resourceVersion: "3003915"
  selfLink: /api/v1/namespaces/default/configmaps/game-config-4
  uid: 8802f6d2-0de7-11e7-b3d5-fa163ebba51b

2、使用ConfigMap

2.1 环境变量或参数

　　创建一个Pod，并将一个已经创建好的ConfigMap作为环境变量，注入到Pod中。

[root@k8s-master propertirs]# kubectl get configmaps game-config-4 -o yaml
apiVersion: v1
data:
  special.passwd: yaodidiao
  special.user: zhenyu
kind: ConfigMap
metadata:
  creationTimestamp: 2017-03-21T03:36:12Z
  name: game-config-4
  namespace: default
  resourceVersion: "3003915"
  selfLink: /api/v1/namespaces/default/configmaps/game-config-4
  uid: 8802f6d2-0de7-11e7-b3d5-fa163ebba51b
[root@k8s-master propertirs]# cat testEnv.yaml 
apiVersion: v1
kind: Pod
metadata:
  labels:
    name: testenv
    role: master
  name: testenv
spec:
  containers:
    - name: testenv
      image: busybox
      imagePullPolicy: IfNotPresent
      env:
        - name: SPECIAL_USER
          valueFrom:
            configMapKeyRef:
              name: game-config-4
              key: special.user
      command:
      - sleep
      - "360000"
[root@k8s-master propertirs]# kubectl create -f testEnv.yaml 
pod "testenv" created
[root@k8s-master propertirs]# kubectl exec -ti testenv sh
/ # echo $SPECIAL_USER
zhenyu
/ #

2.2 挂载文件数据卷

[root@k8s-master propertirs]# kubectl get configmaps game-config -o yaml
apiVersion: v1
data:
  game.properties: |
    enemies=aliens
    lives=3
    enemies.cheat=true
    enemies.cheat.level=noGoodRotten
    secret.code.passphrase=UUDDLRLRBABAS
    secret.code.allowed=true
    secret.code.lives=30
  ui.properties: |
    color.good=purple
    color.bad=yellow
    allow.textmode=true
    how.nice.to.look=fairlyNice
kind: ConfigMap
metadata:
  creationTimestamp: 2017-03-21T03:22:34Z
  name: game-config
  namespace: default
  resourceVersion: "3002770"
  selfLink: /api/v1/namespaces/default/configmaps/game-config
  uid: a04f90f0-0de5-11e7-b3d5-fa163ebba51b
[root@k8s-master propertirs]# cat testVolume.yaml 
apiVersion: v1
kind: Pod
metadata:
  labels:
    name: testvolume
    role: master
  name: testvolume
spec:
  containers:
    - name: testvolume
      image: busybox
      imagePullPolicy: IfNotPresent
      volumeMounts:
      - name: config-volume
        mountPath: /etc/config
      command:
      - sleep
      - "360000"
  volumes:
    - name: config-volume
      configMap:
        name: game-config
[root@k8s-master propertirs]# kubectl create -f testVolume.yaml 
pod "testvolume" created
[root@k8s-master propertirs]# kubectl exec -ti testvolume sh
/ # cd /etc/config/
/etc/config # ls
game.properties  ui.properties
/etc/config # cat game.properties 
enemies=aliens
lives=3
enemies.cheat=true
enemies.cheat.level=noGoodRotten
secret.code.passphrase=UUDDLRLRBABAS
secret.code.allowed=true
secret.code.lives=30
/etc/config # cat ui.properties 
color.good=purple
color.bad=yellow
allow.textmode=true
how.nice.to.look=fairlyNice
/etc/config #

2.3 挂载信息数据卷

[root@k8s-master propertirs]# cat testVolume.yaml 
apiVersion: v1
kind: Pod
metadata:
  labels:
    name: testvolume
    role: master
  name: testvolume
spec:
  containers:
    - name: testvolume
      image: busybox
      imagePullPolicy: IfNotPresent
      volumeMounts:
      - name: config-volume
        mountPath: /etc/config
      command:
      - sleep
      - "360000"
  volumes:
    - name: config-volume
      configMap:
        name: game-config-4
[root@k8s-master propertirs]# kubectl get  configmaps game-config-4 -o yaml
apiVersion: v1
data:
  special.passwd: yaodidiao
  special.user: zhenyuyaodidiao
kind: ConfigMap
metadata:
  creationTimestamp: 2017-03-21T06:29:29Z
  name: game-config-4
  namespace: default
  resourceVersion: "3018779"
  selfLink: /api/v1/namespaces/default/configmaps/game-config-4
  uid: bd086dca-0dff-11e7-b3d5-fa163ebba51b
[root@k8s-master propertirs]# kubectl create -f testVolume.yaml 
pod "testvolume" created
[root@k8s-master propertirs]# kubectl exec -ti testvolume sh
/ # cd /etc/config/
/etc/config # ls
special.passwd  special.user
/etc/config # cat special.user 
zhenyuyaodidiao/etc/config # 
/etc/config # exit

2.4 热更新

　　当ConfigMap以数据卷的形式挂载进Pod的时，这时更新ConfigMap（或删掉重建ConfigMap），Pod内挂载的配置信息会热更新。这时可以增加一些监测配置文件变更的脚本，然后reload对应服务。