372 lines
10 KiB
Markdown
372 lines
10 KiB
Markdown
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## 前言
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其实ConfigMap功能在Kubernetes1.2版本的时候就有了，许多应用程序会从配置文件、命令行参数或环境变量中读取配置信息。这些配置信息需要与docker image解耦，你总不能每修改一个配置就重做一个image吧？ConfigMap API给我们提供了向容器中注入配置信息的机制，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。
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## ConfigMap概览
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**ConfigMap API**资源用来保存**key-value pair**配置数据，这个数据可以在**pods**里使用，或者被用来为像**controller**一样的系统组件存储配置数据。虽然ConfigMap跟[Secrets](https://kubernetes.io/docs/user-guide/secrets/)类似，但是ConfigMap更方便的处理不含敏感信息的字符串。 注意：ConfigMaps不是属性配置文件的替代品。ConfigMaps只是作为多个properties文件的引用。你可以把它理解为Linux系统中的`/etc`目录，专门用来存储配置文件的目录。下面举个例子，使用ConfigMap配置来创建Kuberntes Volumes，ConfigMap中的每个data项都会成为一个新文件。
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```yaml
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kind: ConfigMap
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apiVersion: v1
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metadata:
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creationTimestamp: 2016-02-18T19:14:38Z
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name: example-config
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namespace: default
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data:
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example.property.1: hello
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example.property.2: world
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example.property.file: |-
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property.1=value-1
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property.2=value-2
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property.3=value-3
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```
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`data`一栏包括了配置数据，ConfigMap可以被用来保存单个属性，也可以用来保存一个配置文件。 配置数据可以通过很多种方式在Pods里被使用。ConfigMaps可以被用来：
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1. 设置环境变量的值
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2. 在容器里设置命令行参数
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3. 在数据卷里面创建config文件
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用户和系统组件两者都可以在ConfigMap里面存储配置数据。
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其实不用看下面的文章，直接从`kubectl create configmap -h`的帮助信息中就可以对ConfigMap究竟如何创建略知一二了。
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```
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Examples:
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# Create a new configmap named my-config based on folder bar
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kubectl create configmap my-config --from-file=path/to/bar
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# Create a new configmap named my-config with specified keys instead of file basenames on disk
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kubectl create configmap my-config --from-file=key1=/path/to/bar/file1.txt --from-file=key2=/path/to/bar/file2.txt
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# Create a new configmap named my-config with key1=config1 and key2=config2
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kubectl create configmap my-config --from-literal=key1=config1 --from-literal=key2=config2
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```
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## 创建ConfigMaps
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可以使用该命令，用给定值、文件或目录来创建ConfigMap。
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```
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kubectl create configmap
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```
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### 使用目录创建
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比如我们已经有个了包含一些配置文件，其中包含了我们想要设置的ConfigMap的值：
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```bash
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$ ls docs/user-guide/configmap/kubectl/
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game.properties
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ui.properties
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$ cat docs/user-guide/configmap/kubectl/game.properties
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enemies=aliens
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lives=3
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enemies.cheat=true
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enemies.cheat.level=noGoodRotten
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secret.code.passphrase=UUDDLRLRBABAS
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secret.code.allowed=true
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secret.code.lives=30
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$ cat docs/user-guide/configmap/kubectl/ui.properties
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color.good=purple
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color.bad=yellow
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allow.textmode=true
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how.nice.to.look=fairlyNice
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```
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使用下面的命令可以创建一个包含目录中所有文件的ConfigMap。
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```bash
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$ kubectl create configmap game-config --from-file=docs/user-guide/configmap/kubectl
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```
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`—from-file`指定在目录下的所有文件都会被用在ConfigMap里面创建一个键值对，键的名字就是文件名，值就是文件的内容。
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让我们来看一下这个命令创建的ConfigMap：
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```Yaml
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$ kubectl describe configmaps game-config
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Name: game-config
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Namespace: default
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Labels: <none>
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Annotations: <none>
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Data
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====
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game.properties: 158 bytes
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ui.properties: 83 bytes
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```
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我们可以看到那两个key是从kubectl指定的目录中的文件名。这些key的内容可能会很大，所以在kubectl describe的输出中，只能够看到键的名字和他们的大小。 如果想要看到键的值的话，可以使用`kubectl get`：
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```bash
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$ kubectl get configmaps game-config -o yaml
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```
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我们以`yaml`格式输出配置。
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```yaml
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apiVersion: v1
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data:
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game.properties: |
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enemies=aliens
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lives=3
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enemies.cheat=true
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enemies.cheat.level=noGoodRotten
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secret.code.passphrase=UUDDLRLRBABAS
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secret.code.allowed=true
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secret.code.lives=30
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ui.properties: |
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color.good=purple
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color.bad=yellow
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allow.textmode=true
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how.nice.to.look=fairlyNice
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kind: ConfigMap
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metadata:
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creationTimestamp: 2016-02-18T18:34:05Z
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name: game-config
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namespace: default
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resourceVersion: "407"
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selfLink: /api/v1/namespaces/default/configmaps/game-config
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uid: 30944725-d66e-11e5-8cd0-68f728db1985
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```
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### 使用文件创建
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刚才**使用目录创建**的时候我们`—from-file`指定的是一个目录，只要指定为一个文件就可以从单个文件中创建ConfigMap。
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```bash
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$ kubectl create configmap game-config-2 --from-file=docs/user-guide/configmap/kubectl/game.properties
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$ kubectl get configmaps game-config-2 -o yaml
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```
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```Yaml
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apiVersion: v1
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data:
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game-special-key: |
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enemies=aliens
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lives=3
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enemies.cheat=true
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enemies.cheat.level=noGoodRotten
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secret.code.passphrase=UUDDLRLRBABAS
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secret.code.allowed=true
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secret.code.lives=30
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kind: ConfigMap
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metadata:
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creationTimestamp: 2016-02-18T18:54:22Z
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name: game-config-3
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namespace: default
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resourceVersion: "530"
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selfLink: /api/v1/namespaces/default/configmaps/game-config-3
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uid: 05f8da22-d671-11e5-8cd0-68f728db1985
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```
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`—from-file`这个参数可以使用多次，你可以使用两次分别指定上个实例中的那两个配置文件，效果就跟指定整个目录是一样的。
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### 使用Literal值创建
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使用文字值创建，利用`—from-literal`参数传递配置信息，该参数可以使用多次，格式如下；
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```bash
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$ kubectl create configmap special-config --from-literal=special.how=very --from-literal=special.type=charm
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$ kubectl get configmaps special-config -o yaml
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```
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```yaml
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apiVersion: v1
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data:
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special.how: very
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special.type: charm
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kind: ConfigMap
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metadata:
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creationTimestamp: 2016-02-18T19:14:38Z
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name: special-config
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namespace: default
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resourceVersion: "651"
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selfLink: /api/v1/namespaces/default/configmaps/special-config
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uid: dadce046-d673-11e5-8cd0-68f728db1985
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```
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## Pod中使用ConfigMap
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**使用ConfigMap来替代环境变量**
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ConfigMap可以被用来填入环境变量。看下下面的ConfigMap。
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```Yaml
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apiVersion: v1
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kind: ConfigMap
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metadata:
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name: special-config
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namespace: default
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data:
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special.how: very
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special.type: charm
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```
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```yaml
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apiVersion: v1
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kind: ConfigMap
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metadata:
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name: env-config
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namespace: default
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data:
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log_level: INFO
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```
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我们可以在Pod中这样使用ConfigMap：
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```Yaml
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apiVersion: v1
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kind: Pod
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metadata:
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name: dapi-test-pod
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spec:
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containers:
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- name: test-container
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image: gcr.io/google_containers/busybox
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command: [ "/bin/sh", "-c", "env" ]
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env:
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- name: SPECIAL_LEVEL_KEY
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valueFrom:
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configMapKeyRef:
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name: special-config
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key: special.how
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- name: SPECIAL_TYPE_KEY
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valueFrom:
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configMapKeyRef:
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name: special-config
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key: special.type
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envFrom:
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- configMapRef:
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name: env-config
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restartPolicy: Never
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```
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这个Pod运行后会输出如下几行：
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```
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SPECIAL_LEVEL_KEY=very
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SPECIAL_TYPE_KEY=charm
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log_level=INFO
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```
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**用ConfigMap设置命令行参数**
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ConfigMap也可以被使用来设置容器中的命令或者参数值。它使用的是Kubernetes的$(VAR_NAME)替换语法。我们看下下面这个ConfigMap。
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```Yaml
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apiVersion: v1
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kind: ConfigMap
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metadata:
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name: special-config
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namespace: default
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data:
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special.how: very
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special.type: charm
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```
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为了将ConfigMap中的值注入到命令行的参数里面，我们还要像前面那个例子一样使用环境变量替换语法`${VAR_NAME)`。（其实这个东西就是给Docker容器设置环境变量，以前我创建镜像的时候经常这么玩，通过docker run的时候指定-e参数修改镜像里的环境变量，然后docker的CMD命令再利用该$(VAR_NAME)通过sed来来修改配置文件或者作为命令行启动参数。）
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```Yaml
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apiVersion: v1
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kind: Pod
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metadata:
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name: dapi-test-pod
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spec:
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containers:
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- name: test-container
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image: gcr.io/google_containers/busybox
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command: [ "/bin/sh", "-c", "echo $(SPECIAL_LEVEL_KEY) $(SPECIAL_TYPE_KEY)" ]
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env:
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- name: SPECIAL_LEVEL_KEY
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valueFrom:
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configMapKeyRef:
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name: special-config
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key: special.how
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- name: SPECIAL_TYPE_KEY
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valueFrom:
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configMapKeyRef:
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name: special-config
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key: special.type
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restartPolicy: Never
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```
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运行这个Pod后会输出：
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```
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very charm
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```
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**通过数据卷插件使用ConfigMap**
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ConfigMap也可以在数据卷里面被使用。还是这个ConfigMap。
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```Yaml
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apiVersion: v1
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kind: ConfigMap
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metadata:
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name: special-config
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namespace: default
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data:
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special.how: very
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special.type: charm
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```
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在数据卷里面使用这个ConfigMap，有不同的选项。最基本的就是将文件填入数据卷，在这个文件中，键就是文件名，键值就是文件内容：
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```Yaml
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apiVersion: v1
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kind: Pod
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metadata:
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name: dapi-test-pod
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spec:
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containers:
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- name: test-container
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image: gcr.io/google_containers/busybox
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command: [ "/bin/sh", "-c", "cat /etc/config/special.how" ]
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volumeMounts:
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- name: config-volume
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mountPath: /etc/config
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volumes:
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- name: config-volume
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configMap:
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name: special-config
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restartPolicy: Never
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```
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运行这个Pod的输出是`very`。
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我们也可以在ConfigMap值被映射的数据卷里控制路径。
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|
|||
|
|
```Yaml
|
|||
|
|
apiVersion: v1
|
|||
|
|
kind: Pod
|
|||
|
|
metadata:
|
|||
|
|
name: dapi-test-pod
|
|||
|
|
spec:
|
|||
|
|
containers:
|
|||
|
|
- name: test-container
|
|||
|
|
image: gcr.io/google_containers/busybox
|
|||
|
|
command: [ "/bin/sh","-c","cat /etc/config/path/to/special-key" ]
|
|||
|
|
volumeMounts:
|
|||
|
|
- name: config-volume
|
|||
|
|
mountPath: /etc/config
|
|||
|
|
volumes:
|
|||
|
|
- name: config-volume
|
|||
|
|
configMap:
|
|||
|
|
name: special-config
|
|||
|
|
items:
|
|||
|
|
- key: special.how
|
|||
|
|
path: path/to/special-key
|
|||
|
|
restartPolicy: Never
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
运行这个Pod后的结果是`very`。
|