Kubernetes conifgMap

ConifgMap

 kubernetes通过ConfigMap来实现对容器中应用的配置管理，所有的配置内容都存储在etcd中。

创建ConfigMap

 创建ConfigMap的方式有两种，一种是通过yaml文件来创建，另一种是通过kubectl直接在命令行下创建。

1. 使用目录创建

ls configmap
game.properties
ui.properties
//文件信息
cat configmap/game.properties
enemies=aliens
livese=3
emenies.cheat=true
secret.code.allowed=true

cat configmap/ui.properties
color.good=purple
color.bad=yellow
allow.textmode=true

//根据目录创建，包含目录中的所有配置文件
kubectl create configmap game-config --from-file=./configmap
//查看
[root@k8s-master xhyan]# kubectl get configmap
NAME          DATA   AGE
game-config   2      21s

//查看具体信息
[root@k8s-master xhyan]# kubectl get configmap game-config -o yaml
apiVersion: v1
data:
  game.properties: |
    enemies=aliens
    livese=3
    emenies.cheat=true
    secret.code.allowed=true
  ui.properties: |
    color.good=purple
    color.bad=yellow
    allow.textmode=true
kind: ConfigMap
metadata:
  creationTimestamp: "2020-08-31T05:19:46Z"
  name: game-config
  namespace: default
  resourceVersion: "370183"
  selfLink: /api/v1/namespaces/default/configmaps/game-config
  uid: c011a3dd-9bab-4255-bd95-3e24a1aa4b7c

2. 使用文件创建（与目录方法一样，指定的是文件名）

[root@k8s-master xhyan]# kubectl create cm game-config2 --from-file=configmap/game.properties
configmap/game-config2 created
[root@k8s-master xhyan]# kubectl get cm
NAME           DATA   AGE
game-config    2      7m53s
game-config2   1      8s

kubectl get方式查看方式查看

[root@k8s-master xhyan]# kubectl get cm game-config2 -o yaml
apiVersion: v1
data:
  game.properties: |
    enemies=aliens
    livese=3
    emenies.cheat=true
    secret.code.allowed=true
kind: ConfigMap
metadata:
  creationTimestamp: "2020-08-31T05:27:31Z"
  name: game-config2
  namespace: default
  resourceVersion: "370919"
  selfLink: /api/v1/namespaces/default/configmaps/game-config2
  uid: 1a088ce6-94ed-4c95-89d7-b2a975239c5c

kubectl describe方式查看

[root@k8s-master configmap]# kubectl describe cm game-config
Name:         game-config
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
ui.properties:
----
color.good=purple
color.bad=yellow
allow.textmode=true

game.properties:
----
enemies=aliens
livese=3
emenies.cheat=true
secret.code.allowed=true

Events:  <none>

3. kubectl直接在命令行下创建。

  使用--from-literal参数传递配置信息，该参数可以使用多次

kubectl create configmap test-config3 --from-literal=db.host=10.5.10.116 --from-literal=db.port='3306'
configmap/test-config3 created
[root@k8s-master xhyan]# kubectl get cm test-config3 -o yaml
apiVersion: v1
data:
  db.host: 10.5.10.116
  db.port: "3306"
kind: ConfigMap
metadata:
  creationTimestamp: "2020-08-31T05:31:27Z"
  name: test-config3
  namespace: default
  resourceVersion: "371292"
  selfLink: /api/v1/namespaces/default/configmaps/test-config3
  uid: 4ec05371-b09c-4779-a5a1-3b1abafae1c5

4. yaml格式文件创建
   yaml资源清单使用kubectl apply 方法创建

cat test-cfg.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: test-cfg
  namespace: default
data:
  cache_host: memcached-gcxt
  cache_port: "11211"
  cache_prefix: gcxt
  my.cnf: |
    [mysqld]
    log-bin = mysql-bin
  app.properties: |
    property.1 = value-1
 property.2 = value-2
 property.3 = value-3
 //yaml资源清单方式创建
 [root@k8s-master configmap]# kubectl apply -f test-cfg.yaml
configmap/test-cfg created

[root@k8s-master configmap]# kubectl get cm test-cfg -o yaml
apiVersion: v1
data:
  test-cfg.yaml: |
    apiVersion: v1
    kind: ConfigMap
    metadata:
      name: test-cfg
      namespace: default
    data:
      cache_host: memcached-gcxt
      cache_port: "11211"
      cache_prefix: gcxt
      my.cnf: |
        [mysqld]
        log-bin = mysql-bin
      app.properties: |
        property.1 = value-1
        property.2 = value-2
        property.3 = value-3
kind: ConfigMap
metadata:
  creationTimestamp: "2020-08-31T05:38:13Z"
  name: test-cfg
  namespace: default
  resourceVersion: "371938"
  selfLink: /api/v1/namespaces/default/configmaps/test-cfg
  uid: 940f21f6-1e33-4051-a3d1-ecd69ce6d933

使用ConfigMap

 使用ConfigMap有三种方式，一种是通过环境变量的方式，直接传递pod，另一种是使用volume的方式挂载入到pod内

1. 通过环境变量的方式，直接传递pod

ConfigMap文件：

cat special-config.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: special-config
  namespace: default
data:
  special.how: very
  special.type: charm

pod示例：

apiVersion: v1
kind: Pod
metadata:
  name: dapi-test-pod
spec:
  containers:
    - name: test-container
      image: gcr.io/google_containers/busybox
      command: [ "/bin/sh", "-c", "env" ]
      env:
        - name: SPECIAL_LEVEL_KEY   //将special-config下的special.how映射为SPECIAL_LEVEL_KEY  
          valueFrom:
            configMapKeyRef:
              name: special-config
              key: special.how
        - name: SPECIAL_TYPE_KEY
          valueFrom:
            configMapKeyRef:
              name: special-config
              key: special.type
  restartPolicy: Never

2. 使用volume将ConfigMap作为文件或目录直接挂载，其中每一个key-value键值对都会生成一个文件，key为文件名，value为内容

第一个pod示例，简单的将上面创建的ConfigMap直接挂载至pod的/etc/config目录下：

apiVersion: v1
kind: Pod
metadata:
  name: dapi-test-pod
spec:
  containers:
    - name: test-container
      image: gcr.io/google_containers/busybox
      command: [ "/bin/sh", "-c", "cat /etc/config/special.how" ]
      volumeMounts:
      - name: config-volume
        mountPath: /etc/config
  volumes:
    - name: config-volume
      configMap:
        name: special-config
  restartPolicy: Never

第二个pod示例，只将ConfigMap的special.how这个key挂载到/etc/config目录下的一个相对路径path/to/special-key，如果存在同名文件，直接覆盖。其他的key不挂载：

apiVersion: v1
kind: Pod
metadata:
  name: dapi-test-pod
spec:
  containers:
    - name: test-container
      image: gcr.io/google_containers/busybox
      command: [ "/bin/sh","-c","cat /etc/config/path/to/special-key" ]
      volumeMounts:
      - name: config-volume
        mountPath: /etc/config
  volumes:
    - name: config-volume
      configMap:
        name: special-config
        items:
        - key: special.how
          path: path/to/special-key
  restartPolicy: Never

最后需要说明两点：

1. ConfigMap必须在Pod之前创建
2. ConfigMap必须和pod在同一个namespace内才能使用，也就是说，ConfigMap不能跨命名空间调用。