容器编排之战（十七）连载

ConfigMap祥解

ConfigMap与 Secret 类似，用来存储配置文件的kubernetes资源对象，所有的配置内容都存储在etcd中。

与 Secret 的区别：

ConfigMap 保存的是不需要加密的、应用所需的配置信息。
​
ConfigMap 的用法几乎与 Secret 完全相同：可以使用 kubectl create configmap 从文件或者目录创建 ConfigMap，也可以直接编写 ConfigMap 对象的 YAML 文件。

创建ConfigMap

创建ConfigMap的方式有4种：
​
命令行方式
方式1：通过直接在命令行中指定configmap参数创建，即--from-literal
方式2：通过指定文件创建，即将一个配置文件创建为一个ConfigMap，--from-file=<文件>
方式3：通过指定目录创建，即将一个目录下的所有配置文件创建为一个ConfigMap，--from-file=<目录>
方式4：事先写好标准的configmap的yaml文件，然后kubectl create -f 创建

1.1 通过命令行参数--from-literal创建

创建命令：

[root@kub-k8s-master prome]# kubectl create configmap test-configmap --from-literal=user=admin --from-literal=pass=1122334
configmap/test-configmap created 

结果如下面的data内容所示：

[root@kub-k8s-master prome]# kubectl get configmap test-configmap -o yaml
apiVersion: v1
data:
  pass: "1122334"
  user: admin
kind: ConfigMap
metadata:
  creationTimestamp: "2019-10-21T07:48:15Z"
  name: test-configmap
  namespace: default
  resourceVersion: "187590"
  selfLink: /api/v1/namespaces/default/configmaps/test-configmap
  uid: 62a8a0d0-fab9-4159-86f4-a06aa213f4b1

1.2 通过指定文件创建

编辑配置文件app.properties内容如下：

[root@kub-k8s-master prome]# vim app.properties
property.1 = value-1
property.2 = value-2
property.3 = value-3
property.4 = value-4
[mysqld]
!include /home/wing/mysql/etc/mysqld.cnf
port = 3306
socket = /home/wing/mysql/tmp/mysql.sock
pid-file = /wing/mysql/mysql/var/mysql.pid
basedir = /home/mysql/mysql
datadir = /wing/mysql/mysql/var

创建（可以有多个--from-file）：

[root@kub-k8s-master prome]# kubectl create configmap test-config2 --from-file=app.properties 
configmap/test-config2 created

结果如下面data内容所示：

[root@kub-k8s-master prome]# kubectl get configmap test-config2 -o yaml
apiVersion: v1
data:
  app.properties: |
    property.1 = value-1
    property.2 = value-2
    property.3 = value-3
    property.4 = value-4
​
    [mysqld]
    !include /home/wing/mysql/etc/mysqld.cnf
    port = 3306
    socket = /home/wing/mysql/tmp/mysql.sock
    pid-file = /wing/mysql/mysql/var/mysql.pid
    basedir = /home/mysql/mysql
    datadir = /wing/mysql/mysql/var
kind: ConfigMap
metadata:
  creationTimestamp: "2019-10-21T08:01:43Z"
  name: test-config2
  namespace: default
  resourceVersion: "188765"
  selfLink: /api/v1/namespaces/default/configmaps/test-config2
  uid: 790fca12-3900-4bf3-a017-5af1070792e5

通过指定文件创建时，configmap会创建一个key/value对，key是文件名，value是文件内容。

1.3 指定目录创建

configs 目录下的config-1和config-2内容如下所示：

[root@kub-k8s-master prome]# mkdir config
[root@kub-k8s-master prome]# cd config/
[root@kub-k8s-master config]# vim config1
aaa
bbb
c=d
[root@kub-k8s-master config]# vim config2
eee
fff
h=k

创建：

[root@kub-k8s-master config]# cd ..
[root@kub-k8s-master prome]# kubectl create configmap test-config3 --from-file=./config
configmap/test-config3 created

结果下面data内容所示：

[root@kub-k8s-master prome]# kubectl get configmap test-config3 -o yaml
apiVersion: v1
data:
  config1: |
    aaa
    bbb
    c=d
  config2: |
    eee
    fff
    h=k
kind: ConfigMap
metadata:
  creationTimestamp: "2019-10-21T08:20:42Z"
  name: test-config3
  namespace: default
  resourceVersion: "190420"
  selfLink: /api/v1/namespaces/default/configmaps/test-config3
  uid: 6e00fded-80a8-4297-aeb3-4c48795e6eb9

指定目录创建时，configmap内容中的各个文件会创建一个key/value对，key是文件名，value是文件内容。

1.4 通过事先写好configmap的标准yaml文件创建

yaml文件内容如下： 注意其中一个key的value有多行内容时的写法

[root@kub-k8s-master prome]# vim configmap.yaml
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: test-config4
  namespace: default
data:
  cache_host: memcached-gcxt
  cache_port: "11211"
  cache_prefix: gcxt
  my.cnf: |
   [mysqld]
   log-bin = mysql-bin
   haha = hehe

创建：

[root@kub-k8s-master prome]# kubectl apply -f configmap.yaml 
configmap/test-config4 created 

结果如下面data内容所示：

[root@kub-k8s-master prome]# kubectl get configmap test-config4 -o yaml
apiVersion: v1
data:
  cache_host: memcached-gcxt
  cache_port: "11211"
  cache_prefix: gcxt
  my.cnf: |
    [mysqld]
    log-bin = mysql-bin
    haha = hehe
kind: ConfigMap
metadata:
  annotations:
    kubectl.kubernetes.io/last-applied-configuration: |
      {"apiVersion":"v1","data":{"cache_host":"memcached-gcxt","cache_port":"11211","cache_prefix":"gcxt","my.cnf":"[mysqld]\nlog-bin = mysql-bin\nhaha = hehe\n"},"kind":"ConfigMap","metadata":{"annotations":{},"name":"test-config4","namespace":"default"}}
  creationTimestamp: "2019-10-21T08:30:24Z"
  name: test-config4
  namespace: default
  resourceVersion: "191270"
  selfLink: /api/v1/namespaces/default/configmaps/test-config4
  uid: 2a8cd6e7-db2c-4781-b005-e0b76d26394b

查看configmap的详细信息：

# kubectl describe configmap

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，另一种是通过在pod的命令行下运行的方式，第三种是使用volume的方式挂载入到pod内

示例ConfigMap文件：

[root@kub-k8s-master prome]# vim config-map.yml
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: config-map
  namespace: default
data:
  special.how: very
  special.type: charm  
​
创建  
[root@kub-k8s-master prome]# kubectl apply -f config-map.yml 
configmap/config-map created

2.1 通过环境变量使用

(1) 使用valueFrom、configMapKeyRef、name、key指定要用的key:

[root@kub-k8s-master prome]# vim testpod.yml
---
apiVersion: v1
kind: Pod
metadata:
  name: dapi-test-pod
spec:
  containers:
    - name: test-container
      image: daocloud.io/library/nginx
      env:   #专门在容器里面设置变量的关键字
        - name: SPECIAL_LEVEL_KEY   #这里的-name,是容器里设置的新变量的名字
          valueFrom:
            configMapKeyRef:
              name: config-map   #这里是来源于哪个configMap
              key: special.how      #configMap里的key
        - name: SPECIAL_TYPE_KEY
          valueFrom:
            configMapKeyRef:
              name: config-map
              key: special.type
  restartPolicy: Never
​
创建pod
[root@kub-k8s-master prome]# kubectl apply -f testpod.yml 
pod/dapi-test-pod created

测试：

[root@kub-k8s-master prome]# kubectl exec -it dapi-test-pod /bin/bash
root@dapi-test-pod:/# echo $SPECIAL_TYPE_KEY
charm

(2) 通过envFrom、configMapRef、name使得configmap中的所有key/value对儿 都自动变成环境变量：

[root@kub-k8s-master prome]# kubectl delete -f testpod.yml 
pod "dapi-test-pod" deleted
[root@kub-k8s-master prome]# cp testpod.yml testpod.yml.bak
[root@kub-k8s-master prome]# vim testpod.yml
---
apiVersion: v1
kind: Pod
metadata:
  name: dapi-test-pod
spec:
  containers:
    - name: test-container
      image: daocloud.io/library/nginx
      envFrom:
      - configMapRef:
          name: config-map
  restartPolicy: Never

这样容器里的变量名称直接使用configMap里的key名：

[root@kub-k8s-master prome]# kubectl apply -f testpod.yml
pod/dapi-test-pod created.
[root@kub-k8s-master prome]# kubectl exec -it dapi-test-pod /bin/bash
root@dapi-test-pod:/# env
HOSTNAME=dapi-test-pod
NJS_VERSION=0.3.3
NGINX_VERSION=1.17.1
KUBERNETES_PORT_443_TCP_PROTO=tcp
KUBERNETES_PORT_443_TCP_ADDR=10.96.0.1
PKG_RELEASE=1~stretch
KUBERNETES_PORT=tcp://10.96.0.1:443
PWD=/
special.how=very
HOME=/root
KUBERNETES_SERVICE_PORT_HTTPS=443
KUBERNETES_PORT_443_TCP_PORT=443
KUBERNETES_PORT_443_TCP=tcp://10.96.0.1:443
TERM=xterm
SHLVL=1
KUBERNETES_SERVICE_PORT=443
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
special.type=charm
KUBERNETES_SERVICE_HOST=10.96.0.1
_=/usr/bin/env

2.2 作为volume挂载使用

(1) 把1.4中test-config4所有key/value挂载进来：

[root@kub-k8s-master prome]# kubectl delete -f testpod.yml
pod "dapi-test-pod" deleted
[root@kub-k8s-master prome]# vim volupod.yml
---
apiVersion: v1
kind: Pod
metadata:
  name: nginx-configmap
spec:
  containers:
  - name: nginx-configmap
    image: daocloud.io/library/nginx
    volumeMounts:
    - name: config-volume4
      mountPath: "/tmp/config4"
  volumes:
  - name: config-volume4
    configMap:
      name: test-config4
          
创建pod
[root@kub-k8s-master prome]# kubectl apply -f volupod.yml 
pod/nginx-configmap created

进入容器中/tmp/config4查看：

[root@kub-k8s-master prome]#  kubectl  exec -it nginx-configmap /bin/bash
root@nginx-configmap:/# ls /tmp/config4/
cache_host  cache_port  cache_prefix  my.cnf
root@nginx-configmap:/# cat /tmp/config4/cache_host 
memcached-gcxt
root@nginx-configmap:/#

可以看到，在config4文件夹下以每一个key为文件名value为值创建了多个文件。