116 lines
4.4 KiB
Markdown
116 lines
4.4 KiB
Markdown
---
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title: 定义相互依赖的环境变量
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content_type: task
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weight: 20
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---
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<!--
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title: Define Dependent Environment Variables
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-->
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<!-- overview -->
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<!--
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This page shows how to define dependent environment variables for a container
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in a Kubernetes Pod.
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-->
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本页展示了如何为 Kubernetes Pod 中的容器定义相互依赖的环境变量。
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## {{% heading "prerequisites" %}}
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{{< include "task-tutorial-prereqs.md" >}}
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<!-- steps -->
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<!--
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## Define an environment dependent variable for a container
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When you create a Pod, you can set dependent environment variables for the containers that run in the Pod. To set dependent environment variables, you can use $(VAR_NAME) in the `value` of `env` in the configuration file.
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In this exercise, you create a Pod that runs one container. The configuration
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file for the Pod defines an dependent environment variable with common usage defined. Here is the configuration manifest for the
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Pod:
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-->
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## 为容器定义相互依赖的环境变量 {#define-an-environment-dependent-variable-for-a-container}
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当创建一个 Pod 时，你可以为运行在 Pod 中的容器设置相互依赖的环境变量。
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设置相互依赖的环境变量，你就可以在配置清单文件的 `env` 的 `value` 中使用 $(VAR_NAME)。
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在本练习中，你会创建一个单容器的 Pod。
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此 Pod 的配置文件定义了一个已定义常用用法的相互依赖的环境变量。
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下面是 Pod 的配置清单：
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{{< codenew file="pods/inject/dependent-envars.yaml" >}}
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<!-- 1. Create a Pod based on that manifest: -->
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1. 依据清单创建 Pod：
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```shell
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kubectl apply -f https://k8s.io/examples/pods/inject/dependent-envars.yaml
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```
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```
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pod/dependent-envars-demo created
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```
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<!-- 2. List the running Pods: -->
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2. 列出运行的 Pod：
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```shell
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kubectl get pods dependent-envars-demo
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```
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```
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NAME READY STATUS RESTARTS AGE
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dependent-envars-demo 1/1 Running 0 9s
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```
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<!-- 3. Check the logs for the container running in your Pod: -->
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3. 检查 Pod 中运行容器的日志：
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```shell
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kubectl logs pod/dependent-envars-demo
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```
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```
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UNCHANGED_REFERENCE=$(PROTOCOL)://172.17.0.1:80
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SERVICE_ADDRESS=https://172.17.0.1:80
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ESCAPED_REFERENCE=$(PROTOCOL)://172.17.0.1:80
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```
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<!--
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As shown above, you have defined the correct dependency reference of `SERVICE_ADDRESS`, bad dependency reference of `UNCHANGED_REFERENCE` and skip dependent references of `ESCAPED_REFERENCE`.
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When an environment variable is already defined when being referenced,
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the reference can be correctly resolved, such as in the `SERVICE_ADDRESS` case.
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-->
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如上所示，你已经定义了 `SERVICE_ADDRESS` 的正确依赖引用，
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`UNCHANGED_REFERENCE` 的错误依赖引用，
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并跳过了 `ESCAPED_REFERENCE` 的依赖引用。
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如果环境变量被引用时已事先定义，则引用可以正确解析，
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比如 `SERVICE_ADDRESS` 的例子。
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<!--
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When the environment variable is undefined or only includes some variables, the undefined environment variable is treated as a normal string, such as `UNCHANGED_REFERENCE`. Note that incorrectly parsed environment variables, in general, will not block the container from starting.
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The `$(VAR_NAME)` syntax can be escaped with a double `$`, ie: `$$(VAR_NAME)`.
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Escaped references are never expanded, regardless of whether the referenced variable
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is defined or not. This can be seen from the `ESCAPED_REFERENCE` case above.
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-->
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当环境变量未定义或仅包含部分变量时，未定义的变量会被当做普通字符串对待，
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比如 `UNCHANGED_REFERENCE` 的例子。
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注意，解析不正确的环境变量通常不会阻止容器启动。
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`$(VAR_NAME)` 这样的语法可以用两个 `$` 转义，既：`$$(VAR_NAME)`。
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无论引用的变量是否定义，转义的引用永远不会展开。
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这一点可以从上面 `ESCAPED_REFERENCE` 的例子得到印证。
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## {{% heading "whatsnext" %}}
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<!--
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* Learn more about [environment variables](/docs/tasks/inject-data-application/environment-variable-expose-pod-information/).
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* See [EnvVarSource](/docs/reference/generated/kubernetes-api/{{< param "version" >}}/#envvarsource-v1-core).
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-->
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* 进一步了解[环境变量](/zh/docs/tasks/inject-data-application/environment-variable-expose-pod-information/).
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* 参阅 [EnvVarSource](/docs/reference/generated/kubernetes-api/{{< param "version" >}}/#envvarsource-v1-core).
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