kubernetes系列之ConfigMap使用方式

作用理解

---

核心用途就是容器和配置的分离解耦。

如启用一个mysql容器，mysql容器重要的文件有两部分,一部分为存储数据文件,一部分为配置文件my.cnf，存储数据可以用持久存储实现和容器的分离解耦，配置文件也能够实现和容器的分离解耦,也就是说mysql容器能够直接读取并使用预先配置好的配置文件(而不是使用容器中默认自带的配置文件).这就是configMap的功能。

ConfigMap 用于保存配置数据的键值对，可以用来保存单个属性，也可以用来保存配置文件。ConfigMap 跟 secret 很类似，但它可以更方便地处理不包含敏感信息的字符串。

创建ConfigMap有两种方式

---

通过yaml文件创建
通过kubectl create创建

示例
命令行创建

# 方式一：
[root@master-01 configmap]# kubectl  create cm mysql-config --from-file=mysqld.cnf 
configmap/mysql-config created
[root@master-01 configmap]# kubectl  describe cm mysql-config
Name:         mysql-config
Namespace:    default
Labels:       <none>
Annotations:  <none>
Data
====
mysqld.cnf:
----
[client]
port = 3306
socket = /var/run/mysqld/mysqld.sock
[mysql]
no-auto-rehash
[mysqld]
user = mysql
port = 3306
socket = /var/run/mysqld/mysqld.sock
datadir = /var/lib/mysql
[mysqld_safe]
log-error= /var/log/mysql/mysql_oldboy.err
pid-file = /var/run/mysqld/mysqld.pid
Events:  <none>
# 方式二：
[root@master-01 configmap]# kubectl create configmap env-config --from-literal=log_level=INFO
# 以key：value的形式创建

yaml文件创建

[root@master-01 configmap]# cat my-config.yaml 
apiVersion: v1
kind: ConfigMap
metadata:
  name: mysql-config2
data:
  mysqld.cnf: |
    [client]
    port = 3306
    socket = /var/run/mysqld/mysqld.sock
    [mysql]
    no-auto-rehash
    [mysqld]
    user = mysql
    port = 3306
    socket = /var/run/mysqld/mysqld.sock
    datadir = /var/lib/mysql
    [mysqld_safe]
    log-error= /var/log/mysql/mysql_oldboy.err
    pid-file = /var/run/mysqld/mysqld.pid
[root@master-01 configmap]# kubectl  apply -f my-config.yaml 
configmap/mysql-config2 created
[root@master-01 configmap]# kubectl  describe cm mysql-config2
Name:         mysql-config2
Namespace:    default
Labels:       <none>
Annotations:  kubectl.kubernetes.io/last-applied-configuration:
                {"apiVersion":"v1","data":{"mysqld.cnf":"[client]
port = 3306
socket = /var/run/mysqld/mysqld.sock
[mysql]
no-auto-rehash

[mysqld]...
Data
====
mysqld.cnf:
----
[client]
port = 3306
socket = /var/run/mysqld/mysqld.sock
[mysql]
no-auto-rehash
[mysqld]
user = mysql
port = 3306
socket = /var/run/mysqld/mysqld.sock
datadir = /var/lib/mysql
[mysqld_safe]
log-error= /var/log/mysql/mysql_oldboy.err
pid-file = /var/run/mysqld/mysqld.pid
Events:  <none>

ConfigMap 使用

---

ConfigMap 可以通过三种方式在 Pod 中使用

1.环境变量方式

2.volume挂载方式(一般都是用这个,支持热更新）

3.设置容器命令行参数

用环境变量

[root@master-01 configmap]# kubectl create configmap env-config --from-literal=log_level=INFO
configmap/env-config created
[root@master-01 configmap]# kubectl create configmap special-config --from-literal=special.how=very --from-literal=special.type=charm
configmap/special-config created

编排

[root@master-01 configmap]# cat bu.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: test-pod
spec:
  containers:
    - name: test-container
      image: busybox
      command: ["/bin/sh", "-c", "env"]
      env:
        - name: SPECIAL_LEVEL_KEY
          valueFrom:
            configMapKeyRef:
              name: special-config
              key: special.how
        - name: SPECIAL_TYPE_KEY
          valueFrom:
            configMapKeyRef:
              name: special-config
              key: special.type
      envFrom:
        - configMapRef:
            name: env-config
  restartPolicy: Never
[root@master-01 configmap]# kubectl  apply -f bu.yaml 
pod/test-pod created

查看日志可以发现,环境变量注入到了容器中了

[root@master-01 configmap]# kubectl  logs  test-pod 
...
SPECIAL_TYPE_KEY=charm
SPECIAL_LEVEL_KEY=very
log_level=INFO

用作命令行参数

将 ConfigMap 用作命令行参数时，需要先把 ConfigMap 的数据保存在环境变量中，然后通过 $(VAR_NAME) 的方式引用环境变量.

编排

apiVersion: v1
kind: Pod
metadata:
  name: dapi-test-pod
spec:
  containers:
    - name: test-container
      image: busybox
      command: ["/bin/sh", "-c", "echo $(SPECIAL_LEVEL_KEY) $(SPECIAL_TYPE_KEY)" ]
...

查看日志可以看到环境变量被输出

[root@master-01 configmap]# kubectl  logs dapi-test-pod
very charm

volume挂载方式（支持动态更新）

configmap 挂载文件时，会先覆盖掉挂载目录，然后再将 congfigmap 中的内容作为文件挂载进行。如果想不对原来的文件夹下的文件造成覆盖，只是将 configmap 中的每个 key，按照文件的方式挂载到目录下，可以使用 subpath 参数。

实战例子

编排

[root@master-01 configmap]# cat mysql-d.yaml 
apiVersion: v1
kind: ConfigMap
metadata:
  name: myconfig
data:
  v1: Abc1234!@#
---
apiVersion: v1
kind: Service
metadata:
  name: mysql-t
spec:
  ports:
  - port: 3306
  selector:
    app: mysql-t
---
apiVersion: apps/v1beta1
kind: Deployment
metadata:
  name: mysql-t
spec:
  selector:
    matchLabels:
      app: mysql-t
  template:
    metadata:
      labels:
        app: mysql-t
    spec:
      containers:
      - image: mysql:5.7
        name: mysql-t
        ports:
        - containerPort: 3306
        env:
        - name: MYSQL_ROOT_PASSWORD
          valueFrom:
            configMapKeyRef:
              name: my-config
              key: v2
        volumeMounts:
        - name: mysql-t1
          mountPath: /etc/mysql/mysql.conf.d
      volumes:
      - name: mysql-t1
        configMap:
          name: mysql-config2
[root@master-01 configmap]# kubectl  apply -f mysql-d.yaml 
configmap/myconfig created
service/mysql-t created
deployment.apps/mysql-t created

volumeMounts/mountPath:    容器里挂载的目录，这个目录其实很重要,你要使用个容器的应用,需熟悉这个应用的配置文件存放目录并且挂载到正确目录.挂载目录错了容器应用无法读取到配置文件。

volumes：  定义使用的卷

name: mysql-t1  注意volumes和volumeMounts的name是相对应的.

进入mysql容器中测试，可以看到读取的就是congfigmap,密码已经生效.

[root@master-01 configmap]# kubectl  exec -ti mysql-t-7bb6cbbf77-xqfc2 bash
root@mysql-t-7bb6cbbf77-xqfc2:/# mysql -uroot -pAbc1234!@#
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or g.
Your MySQL connection id is 2
Server version: 5.7.25 MySQL Community Server (GPL)
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
mysql> 

查看pod详情

[root@master-01 configmap]# kubectl  describe pod  mysql-t-7bb6cbbf77-xqfc2 
Name:               mysql-t-7bb6cbbf77-xqfc2
Namespace:          default
Priority:           0
PriorityClassName:  <none>
Node:               192.168.209.131/192.168.209.131
Start Time:         Tue, 02 Apr 2019 10:29:05 +0800
Labels:             app=mysql-t
                    pod-template-hash=7bb6cbbf77
Annotations:        <none>
Status:             Running
IP:                 172.17.12.3
Controlled By:      ReplicaSet/mysql-t-7bb6cbbf77
Containers:
  mysql-t:
    Container ID:   docker://58d61cddb16b6cd14593d7e4d1bc12c6157e7d9c28ffa25c3d3e8a571867bb71
    Image:          mysql:5.7
    Image ID:       docker-pullable://mysql@sha256:dba5fed182e64064b688ccd22b2f9cad4ee88608c82f8cff21e17bab8da72b81
    Port:           3306/TCP
    Host Port:      0/TCP
    State:          Running
      Started:      Tue, 02 Apr 2019 10:29:06 +0800
    Ready:          True
    Restart Count:  0
    Environment:
      MYSQL_ROOT_PASSWORD:  <set to the key 'v1' of config map 'myconfig'>  Optional: false
    Mounts:
      /etc/mysql/mysql.conf.d from mysql-t1 (rw)
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-tb5bg (ro)
Conditions:
  Type              Status
  Initialized       True 
  Ready             True 
  ContainersReady   True 
  PodScheduled      True 
Volumes:
  mysql-t1:
    Type:      ConfigMap (a volume populated by a ConfigMap)
    Name:      mysql-config2
    Optional:  false
  default-token-tb5bg:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-tb5bg
    Optional:    false
QoS Class:       BestEffort
Node-Selectors:  <none>
Tolerations:     node.kubernetes.io/not-ready:NoExecute for 300s
                 node.kubernetes.io/unreachable:NoExecute for 300s
Events:
  Type    Reason     Age    From                      Message
  ----    ------     ----   ----                      -------
  Normal  Scheduled  3m32s  default-scheduler         Successfully assigned default/mysql-t-7bb6cbbf77-xqfc2 to 192.168.209.131
  Normal  Pulled     3m31s  kubelet, 192.168.209.131  Container image "mysql:5.7" already present on machine
  Normal  Created    3m31s  kubelet, 192.168.209.131  Created container
  Normal  Started    3m31s  kubelet, 192.168.209.131  Started container

configmap配置段为

   Environment:
      MYSQL_ROOT_PASSWORD:  <set to the key 'v1' of config map 'myconfig'>  Optional: false
    Mounts:
      /etc/mysql/mysql.conf.d from mysql-t1 (rw)

热更新测试

修改my-cnfig2，使用edit命令

在[mysqld]段添加如下配置

server-id=1

查看my-cnfig2信息

[root@master-01 configmap]# kubectl  describe  cm mysql-config2
...
mysqld.cnf:
----
[client]
port = 3306
socket = /var/run/mysqld/mysqld.sock
[mysql]
no-auto-rehash
[mysqld]
user = mysql
port = 3306
socket = /var/run/mysqld/mysqld.sock
datadir = /var/lib/mysql
server-id=1
[mysqld_safe]
log-error= /var/log/mysql/mysql_oldboy.err
pid-file = /var/run/mysqld/mysqld.pid
Events:  <none>

进mysql容器查看

[root@master-01 configmap]# kubectl  edit cm mysql-config2
configmap/mysql-config2 edited
[root@master-01 configmap]# kubectl  exec -ti mysql-t-7bb6cbbf77-xqfc2 bash
root@mysql-t-7bb6cbbf77-xqfc2:/# cat /etc/mysql/mysql.conf.d/mysqld.cnf 
[client]
port = 3306
socket = /var/run/mysqld/mysqld.sock
[mysql]
no-auto-rehash
[mysqld]
user = mysql
port = 3306
socket = /var/run/mysqld/mysqld.sock
datadir = /var/lib/mysql
server-id=1
[mysqld_safe]
log-error= /var/log/mysql/mysql_oldboy.err
pid-file = /var/run/mysqld/mysqld.pid
root@mysql-t-7bb6cbbf77-xqfc2:/# 

可以看到配置已经热更新了。

往期文章一览

1、Kubernetes集群搭建之系统初始化配置篇

2、Kubernetes集群搭建之企业级环境中基于Harbor搭建自己的私有仓库

3、Kubernetes集群搭建之Etcd集群配置篇

4、Kubernetes集群搭建之CNI-Flanneld部署篇

5、Kubernetes集群搭建之Master配置篇

6、Kubernetes系列之Coredns and Dashboard介绍篇

7、Kubernetes系列之监控Metres-server实战篇

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