ConfigMap

一、Pod的配置管理

应用部署的一个最佳实践是将应用所需的配置信息和程序进行分离，这样就可以是应用程序被更好的服用，通过不同的配置也能实现更灵活的功能。ConfigMap允许将配置文件和镜像文件分离，以是容器化的应用程序具有可移植性。

二、ConfigMap概述

ConfigMap供容器使用的典型用法如下：

生成为容器内的环境变量
设置容器启动命令的启动参数（需设置为环境变量）
以volume的形式挂在为容器内部的文件或目录

ConfigMap以一个或多个key:value的形式保存在Kubernetes系统中供应用使用，即可以表示一个变量的值（apploglevel=info），也可以表示一个完整的配置文件的内容（server.xml=<?xml...>...）

三、创建ConfigMap资源对象

3.1 cm-appvars.yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: cm-appvars
data:
  apploglevel: info
  appdatadir: /var/data

创建ConfigMap

kubectl create -f cm-appvars.yaml

查看ConfigMap

kubectl get configmap
NAME         DATA   AGE
cm-appvars   2      12s
kubectl describe configmap/cm-appvars
Name:         cm-appvars
Namespace:    default
Labels:       <none>
Annotations:  
Data
====
appdatadir:
----
/var/data
apploglevel:
----
info
Events:  <none>
kubectl get configmap/cm-appvars -o yaml

apiVersion: v1
data:
  appdatadir: /var/data
  apploglevel: info
kind: ConfigMap
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"v1","data":{"appdatadir":"/var/data","apploglevel":"info"},"kind":"ConfigMap","metadata":{"annotations":{},"name":"cm-appvars","namespace":"default"}}
  creationTimestamp: "2020-06-10T02:45:21Z"
  managedFields:
  - apiVersion: v1
    fieldsType: FieldsV1
    fieldsV1:
      f:data:
        .: {}
        f:appdatadir: {}
        f:apploglevel: {}
      f:metadata:
        f:annotations:
          .: {}
          f:kubectl.kubernetes.io/last-applied-configuration: {}
    manager: kubectl
    operation: Update
    time: "2020-06-10T02:45:21Z"
  name: cm-appvars
  namespace: default
  resourceVersion: "268969"
  selfLink: /api/v1/namespaces/default/configmaps/cm-appvars
  uid: e9f40932-d0de-4419-8e94-cc8941c20e6c

3.2 同一目录多个文件创建ConfigMap

分别设置key为配置文件别名，value则是配置文件文本内容

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

使用上述两个文件创建ConfigMap

# kubectl create configmap cm-appconfigfiles --from-file=/usr/local/k8s/configmap/configmapfiles/

configmap/cm-appconfigfiles created

查看创建的cm-appconfigfiles

# kubectl get configmap
NAME                DATA   AGE
cm-appconfigfiles   2      10s

# kubectl describe configmap cm-appconfigfiles
Name:         cm-appconfigfiles
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
ui.properties:
----
color.good=purple
color.bad=yellow
allow.textmode=true
how.nice.to.look=fairlyNice

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
Events:  <none>

# kubectl get  configmap cm-appconfigfiles -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: "2020-06-10T05:56:50Z"
  managedFields:
  - apiVersion: v1
    fieldsType: FieldsV1
    fieldsV1:
      f:data:
        .: {}
        f:game.properties: {}
        f:ui.properties: {}
    manager: kubectl
    operation: Update
    time: "2020-06-10T05:56:50Z"
  name: cm-appconfigfiles
  namespace: default
  resourceVersion: "283535"
  selfLink: /api/v1/namespaces/default/configmaps/cm-appconfigfiles
  uid: d3dbf64d-b381-47b6-9fc6-fbdc286f80c0

3.3 根据文字值创建ConfigMap

--from-literal

# kubectl create configmap cm-appenv --from-literal=loglevel=info --from-literal=appdatadir=/var/data

查看创建的configmap

# kubectl create configmap cm-appenv --from-literal=loglevel=info --from-literal=appdatadir=/var/data

# kubectl get configmap
NAME                DATA   AGE
cm-appconfigfiles   2      7m42s
cm-appenv           2      6s
cm-appvars          2      3h19m


kubectl describe configmap cm-appenv
Name:         cm-appenv
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
appdatadir:
----
/var/data
loglevel:
----
info
Events:  <none>

四、在Pod中使用ConfigMap

4.1 通过环境变量方式使用ConfigMap

以cm-appvars ConfigMap为例

apiVersion: v1
kind: ConfigMap
metadata:
  name: cm-appvars
data:
  apploglevel: info
  appdatadir: /var/data

在Pod “cm-test-pod”中，将ConfigMap “cm-appvars”中的内容以环境变量的方式设置为容器内部的环境变量

apiVersion: v1
kind: Pod
metadata:
  name: cm-test-pod
spec:
  containers:
  - name: cm-test
    image: busybox
    command: ["/bin/bash","-c","env|grep APP"]
    env:
    - name: APPLOGLEVEL
      valueFrom:
        configMapKeyRef:
          name: cm-appvars
          key: apploglevel
    - name: APPDATADIR
      valueFrom:
        configMapKeyRef:
          name: cm-appvars
          key: appdatadir
  restartPolicy: Never

查看容器环境变量

# kubectl logs cm-test-pod
APPDATADIR=/var/data
APPLOGLEVEL=info

4.2 envFrom

Kubernetes从1.6版本开始，引入一个新的字段envFrom，实现了在Pod环境中将ConfigMap中所有定义的key=value自动生成为环境变量

apiVersion: v1
kind: Pod
metadata:
  name: cm-envfrom-pod
spec:
  containers:
  - name: envfrom-test
    image: busybox
    command: ["sh","-c","env"]
    envFrom:
    - configMapRef:
        name: cm-appvars
  restartPolicy: Never