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149 lines
3.6 KiB
Markdown
149 lines
3.6 KiB
Markdown
# 示例: 将 k8s runtime 数据注入容器
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本教程将会介绍如何声明变量以及如何在容器中的命令使用变量。要注意的是，变量的查找和替换并不适用于任意字段，默认仅适用于容器的env，args和command。
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运行WordPress，以下是必须的：
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- WordPress 连接 MySQL 数据库
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- MySQL 服务可以被 WordPress 容器访问
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首先构建一个工作空间：
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<!-- @makeDemoHome @test -->
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```bash
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DEMO_HOME=$(mktemp -d)
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MYSQL_HOME=$DEMO_HOME/mysql
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mkdir -p $MYSQL_HOME
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WORDPRESS_HOME=$DEMO_HOME/wordpress
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mkdir -p $WORDPRESS_HOME
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```
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### 下载 resources
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下载 WordPress 的 resources 和 `kustomization.yaml` 。
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<!-- @downloadResources @test -->
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```bash
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CONTENT="https://raw.githubusercontent.com\
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/kubernetes-sigs/kustomize\
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/master/examples/wordpress/wordpress"
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curl -s -o "$WORDPRESS_HOME/#1.yaml" \
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"$CONTENT/{deployment,service,kustomization}.yaml"
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```
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下载 MySQL 的 resources 和 `kustomization.yaml` 。
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<!-- @downloadResources @test -->
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```bash
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CONTENT="https://raw.githubusercontent.com\
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/kubernetes-sigs/kustomize\
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/master/examples/wordpress/mysql"
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curl -s -o "$MYSQL_HOME/#1.yaml" \
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"$CONTENT/{deployment,service,secret,kustomization}.yaml"
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```
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### 创建 kustomization.yaml
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基于 `wordpress` 和 `mysql` 的两个 bases 创建一个新的 `kustomization.yaml` ：
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<!-- @createKustomization @test -->
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```bash
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cat <<EOF >$DEMO_HOME/kustomization.yaml
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resources:
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- wordpress
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- mysql
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namePrefix: demo-
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patchesStrategicMerge:
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- patch.yaml
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EOF
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```
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### 下载 WordPress 的 patchs
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在新的 kustomization 中应用 WordPress Deployment 的 patch ，该 patch 包含：
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- 添加初始容器来显示mysql的服务名称
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- 添加允许 wordpress 查找到 mysql 数据库的环境变量
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<!-- @downloadPatch @test -->
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```bash
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CONTENT="https://raw.githubusercontent.com\
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/kubernetes-sigs/kustomize\
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/master/examples/wordpress"
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curl -s -o "$DEMO_HOME/#1.yaml" \
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"$CONTENT/{patch}.yaml"
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```
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该 patch 内容如下：
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> ```yaml
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> apiVersion: apps/v1
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> kind: Deployment
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> metadata:
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> name: wordpress
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> spec:
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> template:
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> spec:
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> initContainers:
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> - name: init-command
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> image: debian
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> command:
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> - "echo $(WORDPRESS_SERVICE)"
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> - "echo $(MYSQL_SERVICE)"
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> containers:
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> - name: wordpress
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> env:
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> - name: WORDPRESS_DB_HOST
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> value: $(MYSQL_SERVICE)
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> - name: WORDPRESS_DB_PASSWORD
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> valueFrom:
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> secretKeyRef:
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> name: mysql-pass
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> key: password
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> ```
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初始化容器的命令需要依赖于k8s资源对象字段的信息，由占位符变量 $(WORDPRESS_SERVICE) 和 $(MYSQL_SERVICE) 表示。
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### 将变量绑定到k8s对象字段
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<!-- @addVarRef @test -->
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```bash
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cat <<EOF >>$DEMO_HOME/kustomization.yaml
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vars:
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- name: WORDPRESS_SERVICE
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objref:
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kind: Service
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name: wordpress
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apiVersion: v1
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fieldref:
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fieldpath: metadata.name
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- name: MYSQL_SERVICE
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objref:
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kind: Service
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name: mysql
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apiVersion: v1
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EOF
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```
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`WORDPRESS_SERVICE` 来自 `wordpress` 服务的 `metadata.name` 字段。如果不指定 `fieldref` ，则使用默认的 `metadata.name` 。因此 `MYSQL_SERVICE` 来自 `mysql` 服务的 `metadata.name` 字段。
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### 替换
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运行命令查看替换结果：
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<!-- @kustomizeBuild @test -->
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```bash
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kustomize build $DEMO_HOME
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```
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预期的输出为：
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> ```yaml
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> (truncated)
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> ...
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> initContainers:
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> - command:
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> - echo demo-wordpress
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> - echo demo-mysql
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> image: debian
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> name: init-command
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>
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> ```
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