k8s-configmap

一.目的

把应用的代码和配置分开，经过配置configmap管理pod，一种统一的集群配置管理方案。
ConfigMap API资源提供了将配置数据注入容器的方式，同时保持容器是不知道Kubernetes的。ConfigMap能够被用来保存单个属性，也能够用来保存整个配置文件或者JSON二进制等对象。

二.基本原理

ConfigMap是存储通用的配置变量的。ConfigMap有点儿像一个统一的配置文件，使用户能够将分布式系统中用于不一样模块的环境变量统一到一个对象中管理；而它与配置文件的区别在于它是存在集群的“环境”中的，而且支持K8s集群中全部通用的操做调用方式。

而资源的使用者能够经过ConfigMap来存储这个资源的配置，这样须要访问这个资源的应用就能够同经过ConfigMap来引用这个资源。至关经过建立Configmap封装资源配置。

configmap以一个或者多个key:value的形式保存在k8s系统中供应用使用，既能够用于表示一个变量的值（eg.apploglevel:info)，也能够用于表示一个完整配置文件的内容（eg： server.xml=<?xml...>...)
能够经过yaml配置文件或者直接用kubectl create configmap 命令行的方式来建立 ConfigMap。

三.ConfigMap 配置

能够经过创建ConfigMap来支持应用从环境变量和包含配置数据的文件读取信息，以下面例子了展现了configMap如何得到这两种配置的。

图片.png

data 一栏包括了配置数据。就如同大家看到的那样，ConfigMap能够被用来保存单个属性，也能够用来保存一个配置文件。

1.kubectl 命令行方式建立

(1) 从目录中建立
该目录中已经存在一些配置文件，并且目录中全部的文件都将做为configMap中的数据，一个文件为一个data。
key的名字为文件的名字，value为文件的内容。
kubectl create configmap game-config --from-file=/opt/configmap/file/

[root@master file]# ls game.properties ui.properties

[root@master file]# kubectl create configmap game-config --from-file=/opt/configmap/file/ [root@master file]# kubectl describe configmap game-config Name: game-config Namespace: default Labels: <none> Annotations: <none> Data ==== game.properties: 158 bytes ui.properties: 83 bytes

经过kubectl get configmap game-config -o yaml 能够看到value的值。
(2) 从文件中建立

[root@master file]# kubectl create configmap game-config2 --from-file=/opt/configmap/file/game.properties --from-file=/opt/configmap/file/ui.properties [root@master file]# kubectl describe configmap game-config2 Name: game-config2 Namespace: default Labels: <none> Annotations: <none> Data ==== game.properties: 158 bytes ui.properties: 83 bytes

(3) 从文本中建立，直接指定key的名字

[root@master file]# kubectl create  configmap game-config-3 --from-file=game-special-key=/opt/configmap/file/game.properties
[root@master file]# kubectl  describe configmap game-config-3
Name:        game-config-3
Namespace:    default
Labels:        <none>
Annotations:    <none>

Data ==== game-special-key: 158 bytes

(4) 从文字值（literal values）中建立

[root@master yaml]# kubectl create configmap special-config --from-literal=special.how=very --from-literal=special.type=charm [root@master yaml]# kubectl get configmaps special-config -o yaml apiVersion: v1 data: special.how: very special.type: charm kind: ConfigMap metadata:  creationTimestamp: 2017-03-02T15:28:29Z  name: special-config  namespace: default  resourceVersion: "128440"  selfLink: /api/v1/namespaces/default/configmaps/special-config  uid: e30d9c0f-ff5c-11e6-9929-000c29962b4f [root@master yaml]# kubectl describe configmap special-config Name: special-config Namespace: default Labels: <none> Annotations: <none> Data ==== special.how: 4 bytes special.type: 5 bytes

2.yaml文件方式建立

例子1

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

例子2

apiVersion: v1
kind: ConfigMap
metadata:
  name: example-config
data:
  example.property.1: hello example.property.2: world example.property.file: |- property.1=value-1 property.2=value-2 property.3=value-3

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

Data ==== example.property.1: 5 bytes example.property.2: 5 bytes example.property.file: 56 bytes

例子3

apiVersion: v1
kind: ConfigMap
metadata:
  name: cm-serverxml
data:
  key-serverxml: |
    <?xml version='1.0' encoding='utf-8'?> <Server port="8005" shutdown="SHUTDOWN"> <Listener className="org.apache.catalina.startup.VersionLoggerListener" /> <Listener className="org.apache.catalina.core.AprLifecycleListener" SSLEngine="on" /> <Listener className="org.apache.catalina.core.JreMemoryLeakPreventionListener" /> <Listener className="org.apache.catalina.mbeans.GlobalResourcesLifecycleListener" /> <Listener className="org.apache.catalina.core.ThreadLocalLeakPreventionListener" /> <GlobalNamingResources> <Resource name="UserDatabase" auth="Container" type="org.apache.catalina.UserDatabase" description="User database that can be updated and saved" factory="org.apache.catalina.users.MemoryUserDatabaseFactory" pathname="conf/tomcat-users.xml" /> </GlobalNamingResources> <Service name="Catalina"> <Connector port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" /> <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" /> <Engine name="Catalina" defaultHost="localhost"> <Realm className="org.apache.catalina.realm.LockOutRealm"> <Realm className="org.apache.catalina.realm.UserDatabaseRealm" resourceName="UserDatabase"/> </Realm> <Host name="localhost" appBase="webapps" unpackWARs="true" autoDeploy="true"> <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" prefix="localhost_access_log" suffix=".txt" pattern="%h %l %u %t "%r" %s %b" /> </Host> </Engine> </Service> </Server>

四. ConfigMap的使用

ConfigMap供容器使用的典型用法以下：

1.生成为容器内的环境变量。
2.设置容器启动命令的启动参数（需设置为环境变量）
3.以Volume的形式挂载为容器内部的文件或者目录

（1）经过环境变量获取定义好的ConfigMap 中的内容。

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

apiVersion: v1 kind: Pod metadata: name: cm-test-pod spec: containers: - name: cm-test image: test-registry:5000/busybox imagePullPolicy: IfNotPresent command: [ "/bin/sh", "-c", "env | grep APP" ] env: - name: APPLOGLEVEL valueFrom: configMapKeyRef: name: appvars key: apploglevel - name: APPDATADIR valueFrom: configMapKeyRef: name: appvars key: appdatadir restartPolicy: Never

经过kubectl logs cm-test-pod 能够看到pod曾经执行过的结果.

[root@master ~]# kubectl logs cm-test-pod APPDATADIR=/var/data APPLOGLEVEL=info

(2) 经过volume挂载的方式将configmap中的内容挂载为容器内部的文件或目录.

apiVersion: v1 kind: ConfigMap metadata: name: cm-appconfigfiles data: key-serverxml: | <?xml version='1.0' encoding='utf-8'?> <Server port="8005" shutdown="SHUTDOWN"> <Listener className="org.apache.catalina.startup.VersionLoggerListener" /> <Listener className="org.apache.catalina.core.AprLifecycleListener" SSLEngine="on" /> <Listener className="org.apache.catalina.core.JreMemoryLeakPreventionListener" /> <Listener className="org.apache.catalina.mbeans.GlobalResourcesLifecycleListener" /> <Listener className="org.apache.catalina.core.ThreadLocalLeakPreventionListener" /> <GlobalNamingResources> <Resource name="UserDatabase" auth="Container" type="org.apache.catalina.UserDatabase" description="User database that can be updated and saved" factory="org.apache.catalina.users.MemoryUserDatabaseFactory" pathname="conf/tomcat-users.xml" /> </GlobalNamingResources> <Service name="Catalina"> <Connector port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" /> <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" /> <Engine name="Catalina" defaultHost="localhost"> <Realm className="org.apache.catalina.realm.LockOutRealm"> <Realm className="org.apache.catalina.realm.UserDatabaseRealm" resourceName="UserDatabase"/> </Realm> <Host name="localhost" appBase="webapps" unpackWARs="true" autoDeploy="true"> <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" prefix="localhost_access_log" suffix=".txt" pattern="%h %l %u %t "%r" %s %b" /> </Host> </Engine> </Service> </Server> key-loggingproperties: "handlers = 1catalina.org.apache.juli.FileHandler, 2localhost.org.apache.juli.FileHandler, 3manager.org.apache.juli.FileHandler, 4host-manager.org.apache.juli.FileHandler, java.util.logging.ConsoleHandler\r\n\r\n.handlers = 1catalina.org.apache.juli.FileHandler, java.util.logging.ConsoleHandler\r\n\r\n1catalina.org.apache.juli.FileHandler.level = FINE\r\n1catalina.org.apache.juli.FileHandler.directory = ${catalina.base}/logs\r\n1catalina.org.apache.juli.FileHandler.prefix = catalina.\r\n\r\n2localhost.org.apache.juli.FileHandler.level = FINE\r\n2localhost.org.apache.juli.FileHandler.directory = ${catalina.base}/logs\r\n2localhost.org.apache.juli.FileHandler.prefix = localhost.\r\n\r\n3manager.org.apache.juli.FileHandler.level = FINE\r\n3manager.org.apache.juli.FileHandler.directory = ${catalina.base}/logs\r\n3manager.org.apache.juli.FileHandler.prefix = manager.\r\n\r\n4host-manager.org.apache.juli.FileHandler.level = FINE\r\n4host-manager.org.apache.juli.FileHandler.directory = ${catalina.base}/logs\r\n4host-manager.org.apache.juli.FileHandler.prefix = host-manager.\r\n\r\njava.util.logging.ConsoleHandler.level = FINE\r\njava.util.logging.ConsoleHandler.formatter = java.util.logging.SimpleFormatter\r\n\r\n\r\norg.apache.catalina.core.ContainerBase.[Catalina].[localhost].level = INFO\r\norg.apache.catalina.core.ContainerBase.[Catalina].[localhost].handlers = 2localhost.org.apache.juli.FileHandler\r\n\r\norg.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/manager].level = INFO\r\norg.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/manager].handlers = 3manager.org.apache.juli.FileHandler\r\n\r\norg.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/host-manager].level = INFO\r\norg.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/host-manager].handlers = 4host-manager.org.apache.juli.FileHandler\r\n\r\n"

apiVersion: v1 kind: Pod metadata: name: cm-test-app spec: containers: - name: cm-test-app image: test-registry:5000/tomcat ports: - containerPort: 8080 volumeMounts: - name: serverxml mountPath: /configfiles volumes: - name: serverxml configMap: name: cm-appconfigfiles items: - key: key-serverxml path: server.xml - key: key-loggingproperties path: logging.properties

[root@master volume]# kubectl  exec -it cm-test-app /bin/bash root@cm-test-app:/usr/local/tomcat# cd /configfiles/ root@cm-test-app:/configfiles# ls logging.properties server.xml

(3).设置容器启动命令的启动参数

apiVersion: v1 kind: ConfigMap metadata: name: var namespace: default data: special.how: very special.type: charm

apiVersion: v1 kind: Pod metadata: name: var-test spec: containers: - name: test-container image: test-registry:5000/busybox command: [ "/bin/sh", "-c", "echo $(SPECIAL_LEVEL_KEY) $(SPECIAL_TYPE_KEY)" ] env: - name: SPECIAL_LEVEL_KEY valueFrom: configMapKeyRef: name: var key: special.how - name: SPECIAL_TYPE_KEY valueFrom: configMapKeyRef: name: var key: special.type restartPolicy: Never

[root@master var]# kubectl logs var-test very charm

五. ConfigMap修改

apiVersion: v1 kind: ConfigMap metadata: name: configmap-demo namespace: default data: index.html: | Hello Everyone

apiVersion: v1 kind: ReplicationController metadata: name: configmap-demo2 spec: template: metadata: labels: app: configmap-demo2 spec: containers: - name: configmap-demo2 image: test-registry:5000/nginx ports: - containerPort: 80 volumeMounts: - name: config-volume mountPath: /usr/share/nginx/html/ volumes: - name: config-volume configMap: name: configmap-demo

[root@master change]# curl http://172.25.2.2:80 Hello Everyone

修改

apiVersion: v1 kind: ConfigMap metadata: name: configmap-demo namespace: default data: index.html: | Hello World!

[root@master change]# kubectl replace -f k8s-configmap.yaml [root@master change]# curl http://172.25.2.2:80 Hello World!

修改configmap会有延时，要过一段时间容器的配置才会发生变化。

参考：
https://kubernetes.io/docs/user-guide/configmap/
http://www.javashuo.com/article/p-moxembsm-mp.html
https://github.com/thrawn01/configmap-microservice-demo