配置信息注入 configmap、secret
简介

  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。

configmap

创建 configmap

通过命令行创建

kubectl create cm nginx-config --from-literal=nginx_port=80 --from-literal=server_name=myapp.test.org  
kubectl create configmap nginx-www --from-file=./www.conf

# cat www.conf
server {
        server_name myapp.test.org;
        listen 80;
        root /data/web/html;
}

查看 configmap

# kubectl get cm
NAME           DATA   AGE
nginx-config   2      29m
nginx-www      1      37m
实例一
# cat pod-configmap.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: pod-cm-1
  namespace: default
  labels:
    app: myapp
    tier: frontend
spec:
  containers:
  - name: myapp
    image: ikubernetes/myapp:v1
    ports:
    - name: http
      containerPort: 80
    env:
    - name: NGINX_SERVER_PORT
      valueFrom:
        configMapKeyRef:
          name: nginx-config
          key: nginx_port
    - name: NGINX_SERVER_NAME
      valueFrom:
        configMapKeyRef:
          name:  nginx-config
          key: server_name
实例二

挂载方式，通过 kubectl edit cm nginx-config 进行编辑后，pod 里面的变量也会进行更新

# cat pod-configmap2.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: pod-cm-2
  namespace: default
  labels:
    app: myapp
    tier: frontend
spec:
  containers:
  - name: myapp
    image: ikubernetes/myapp:v1
    ports:
    - name: http
      containerPort: 80
    volumeMounts:
    - name: nginxconf
      mountPath: /etc/nginx/config.d/
      readOnly: true
  volumes:
  - name: nginxconf
    configMap:
      name: nginx-config
实例三

通过 kubectl edit cm nginx-www 进行编辑后，pod 里面的配置文件也会进行更新,但是监听端口不会更新，需要重载

# cat pod-configmap3.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: pod-cm-3
  namespace: default
  labels:
    app: myapp
    tier: frontend
spec:
  containers:
  - name: myapp
    image: ikubernetes/myapp:v1
    ports:
    - name: http
      containerPort: 80
    volumeMounts:
    - name: nginxconf
      mountPath: /etc/nginx/conf.d/
      readOnly: true
  volumes:
  - name: nginxconf
    configMap:
      name: nginx-www
创建 secret
# 支持三种方式：docker-registry、generic、tls
# kubectl create secret generic mysql-root-password --from-literal=password=123456
# kubectl get secrets  mysql-root-password 
NAME                  TYPE     DATA   AGE
mysql-root-password   Opaque   1      15s
# kubectl get  secrets  mysql-root-password -o yaml 
apiVersion: v1
data:
  password: MTIzNDU2
kind: Secret
metadata:
  creationTimestamp: "2018-12-18T03:29:02Z"
  name: mysql-root-password
  namespace: default
  resourceVersion: "1518882"
  selfLink: /api/v1/namespaces/default/secrets/mysql-root-password
  uid: 10721e2e-0275-11e9-928f-005056bae900
type: Opaque
# echo MTIzNDU2 | base64 -d  # 这种并不是真正的加密
123456
实例
# cat pod-secret-1.yaml
apiVersion: v1
kind: Pod
metadata:
  name: pod-secret-1
  namespace: default
  labels:
    app: myapp
    tier: frontend
spec:
  containers:
  - name: myapp
    image: ikubernetes/myapp:v1
    ports:
    - name: http
      containerPort: 80
    env:
    - name: MYSQL_ROOT_PASSWORD
      valueFrom:
        secretKeyRef:
          name: mysql-root-password
          key: password

# kubectl exec -it pod-secret-1 -- printenv | grep MYSQL_ROOT_PASSWORD
MYSQL_ROOT_PASSWORD=123456

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。

Ref