189 lines
7.3 KiB
Markdown
189 lines
7.3 KiB
Markdown
---
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title: 从 Pod 中访问 Kubernetes API
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content_type: task
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weight: 120
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---
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<!--
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title: Accessing the Kubernetes API from a Pod
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content_type: task
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weight: 120
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-->
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<!-- overview -->
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<!--
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This guide demonstrates how to access the Kubernetes API from within a pod.
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-->
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本指南演示了如何从 Pod 中访问 Kubernetes API。
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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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## Accessing the API from within a Pod
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When accessing the API from within a Pod, locating and authenticating
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to the API server are slightly different to the external client case.
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-->
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### 从 Pod 中访问 API {#accessing-the-api-from-within-a-pod}
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从 Pod 内部访问 API 时，定位 API 服务器和向服务器认证身份的操作
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与外部客户端场景不同。
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<!--
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The easiest way to use the Kubernetes API from a Pod is to use
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one of the official [client libraries](/docs/reference/using-api/client-libraries/). These
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libraries can automatically discover the API server and authenticate.
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-->
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从 Pod 使用 Kubernetes API 的最简单的方法就是使用官方的
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[客户端库](/zh/docs/reference/using-api/client-libraries/)。
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这些库可以自动发现 API 服务器并进行身份验证。
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<!--
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### Using Official Client Libraries
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From within a Pod, the recommended ways to connect to the Kubernetes API are:
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- For a Go client, use the official [Go client library](https://github.com/kubernetes/client-go/).
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The `rest.InClusterConfig()` function handles API host discovery and authentication automatically.
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See [an example here](https://git.k8s.io/client-go/examples/in-cluster-client-configuration/main.go).
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- For a Python client, use the official [Python client library](https://github.com/kubernetes-client/python/).
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The `config.load_incluster_config()` function handles API host discovery and authentication automatically.
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See [an example here](https://github.com/kubernetes-client/python/blob/master/examples/in_cluster_config.py).
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- There are a number of other libraries available, please refer to the [Client Libraries](/docs/reference/using-api/client-libraries/) page.
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In each case, the service account credentials of the Pod are used to communicate
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securely with the API server.
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-->
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#### 使用官方客户端库 {#using-official-client-libraries}
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从一个 Pod 内部连接到 Kubernetes API 的推荐方式为：
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- 对于 Go 语言客户端，使用官方的 [Go 客户端库](https://github.com/kubernetes/client-go/)。
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函数 `rest.InClusterConfig()` 自动处理 API 主机发现和身份认证。
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参见[这里的一个例子](https://git.k8s.io/client-go/examples/in-cluster-client-configuration/main.go)。
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- 对于 Python 客户端，使用官方的 [Python 客户端库](https://github.com/kubernetes-client/python/)。
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函数 `config.load_incluster_config()` 自动处理 API 主机的发现和身份认证。
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参见[这里的一个例子](https://github.com/kubernetes-client/python/blob/master/examples/in_cluster_config.py)。
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- 还有一些其他可用的客户端库，请参阅[客户端库](/zh/docs/reference/using-api/client-libraries/)页面。
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在以上场景中，客户端库都使用 Pod 的服务账号凭据来与 API 服务器安全地通信。
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<!--
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### Directly accessing the REST API
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While running in a Pod, the Kubernetes apiserver is accessible via a Service named
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`kubernetes` in the `default` namespace. Therefore, Pods can use the
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`kubernetes.default.svc` hostname to query the API server. Official client libraries
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do this automatically.
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-->
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#### 直接访问 REST API {#directly-accessing-the-rest-api}
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在运行在 Pod 中时，可以通过 `default` 命名空间中的名为 `kubernetes` 的服务访问
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Kubernetes API 服务器。也就是说，Pod 可以使用 `kubernetes.default.svc` 主机名
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来查询 API 服务器。官方客户端库自动完成这个工作。
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<!--
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The recommended way to authenticate to the API server is with a
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[service account](/docs/tasks/configure-pod-container/configure-service-account/) credential. By default, a Pod
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is associated with a service account, and a credential (token) for that
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service account is placed into the filesystem tree of each container in that Pod,
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at `/var/run/secrets/kubernetes.io/serviceaccount/token`.
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-->
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向 API 服务器进行身份认证的推荐做法是使用
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[服务账号](/zh/docs/tasks/configure-pod-container/configure-service-account/)凭据。
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默认情况下，每个 Pod 与一个服务账号关联，该服务账户的凭证（令牌）放置在此 Pod 中
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每个容器的文件系统树中的 `/var/run/secrets/kubernetes.io/serviceaccount/token` 处。
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<!--
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If available, a certificate bundle is placed into the filesystem tree of each
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container at `/var/run/secrets/kubernetes.io/serviceaccount/ca.crt`, and should be
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used to verify the serving certificate of the API server.
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-->
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如果证书包可用，则凭证包被放入每个容器的文件系统树中的
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`/var/run/secrets/kubernetes.io/serviceaccount/ca.crt` 处，
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且将被用于验证 API 服务器的服务证书。
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<!--
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Finally, the default namespace to be used for namespaced API operations is placed in a file
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at `/var/run/secrets/kubernetes.io/serviceaccount/namespace` in each container.
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-->
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最后，用于命名空间域 API 操作的默认命名空间放置在每个容器中的
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`/var/run/secrets/kubernetes.io/serviceaccount/namespace` 文件中。
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<!--
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### Using kubectl proxy
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If you would like to query the API without an official client library, you can run `kubectl proxy`
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as the [command](/docs/tasks/inject-data-application/define-command-argument-container/)
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of a new sidecar container in the Pod. This way, `kubectl proxy` will authenticate
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to the API and expose it on the `localhost` interface of the Pod, so that other containers
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in the Pod can use it directly.
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-->
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#### 使用 kubectl proxy {#use-kubectl-proxy}
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如果你希望不使用官方客户端库就完成 API 查询，可以将 `kubectl proxy` 作为
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[command](/zh/docs/tasks/inject-data-application/define-command-argument-container/)
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在 Pod 中启动一个边车（Sidecar）容器。这样，`kubectl proxy` 自动完成对 API
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的身份认证，并将其暴露到 Pod 的 `localhost` 接口，从而 Pod 中的其他容器可以
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直接使用 API。
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<!--
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### Without using a proxy
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It is possible to avoid using the kubectl proxy by passing the authentication token
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directly to the API server. The internal certificate secures the connection.
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-->
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### 不使用代理 {#without-using-a-proxy}
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通过将认证令牌直接发送到 API 服务器，也可以避免运行 kubectl proxy 命令。
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内部的证书机制能够为链接提供保护。
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```shell
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# 指向内部 API 服务器的主机名
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APISERVER=https://kubernetes.default.svc
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# 服务账号令牌的路径
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SERVICEACCOUNT=/var/run/secrets/kubernetes.io/serviceaccount
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# 读取 Pod 的名字空间
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NAMESPACE=$(cat ${SERVICEACCOUNT}/namespace)
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# 读取服务账号的持有者令牌
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TOKEN=$(cat ${SERVICEACCOUNT}/token)
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# 引用内部证书机构（CA）
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CACERT=${SERVICEACCOUNT}/ca.crt
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# 使用令牌访问 API
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curl --cacert ${CACERT} --header "Authorization: Bearer ${TOKEN}" -X GET ${APISERVER}/api
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```
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<!--
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The output will be similar to this:
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-->
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输出类似于：
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```json
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{
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"kind": "APIVersions",
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"versions": [
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"v1"
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],
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"serverAddressByClientCIDRs": [
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{
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"clientCIDR": "0.0.0.0/0",
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"serverAddress": "10.0.1.149:443"
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}
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]
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}
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```
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