---
title: 为容器的生命周期事件设置处理函数
content_type: task
weight: 140
---
<!--
title: Attach Handlers to Container Lifecycle Events
content_type: task
weight: 140
-->

<!-- overview -->

<!--
This page shows how to attach handlers to Container lifecycle events. Kubernetes supports
the postStart and preStop events. Kubernetes sends the postStart event immediately
after a Container is started, and it sends the preStop event immediately before the
Container is terminated.A Container may specify one handler per event.
-->
这个页面将演示如何为容器的生命周期事件挂接处理函数。Kubernetes 支持 postStart 和 preStop 事件。
当一个容器启动后，Kubernetes 将立即发送 postStart 事件；在容器被终结之前，
Kubernetes 将发送一个 preStop 事件。容器可以为每个事件指定一个处理程序。

## {{% heading "prerequisites" %}}

{{< include "task-tutorial-prereqs.md" >}} {{< version-check >}}

<!-- steps -->

<!--
## Define postStart and preStop handlers

In this exercise, you create a Pod that has one Container. The Container has handlers
for the postStart and preStop events.
-->
## 定义 postStart 和 preStop 处理函数

在本练习中，你将创建一个包含一个容器的 Pod，该容器为 postStart 和 preStop 事件提供对应的处理函数。

<!--
Here is the configuration file for the Pod:
-->
下面是对应 Pod 的配置文件：

{{< codenew file="pods/lifecycle-events.yaml" >}}

<!--
In the configuration file, you can see that the postStart command writes a `message`
file to the Container's `/usr/share` directory. The preStop command shuts down
nginx gracefully. This is helpful if the Container is being terminated because of a failure.
-->
在上述配置文件中，你可以看到 postStart 命令在容器的 `/usr/share` 目录下写入文件 `message`。
命令 preStop 负责优雅地终止 nginx 服务。当因为失效而导致容器终止时，这一处理方式很有用。

<!--
Create the Pod:
-->
创建 Pod：

```shell
kubectl apply -f https://k8s.io/examples/pods/lifecycle-events.yaml
```

<!--
Verify that the Container in the Pod is running:
-->
验证 Pod 中的容器已经运行：

```shell
kubectl get pod lifecycle-demo
```

<!--
Get a shell into the Container running in your Pod:
-->
使用 shell 连接到你的 Pod 里的容器：

```
kubectl exec -it lifecycle-demo -- /bin/bash
```

<!--
In your shell, verify that the `postStart` handler created the `message` file:
-->
在 shell 中，验证 `postStart` 处理函数创建了 `message` 文件：

```
root@lifecycle-demo:/# cat /usr/share/message
```

<!--
The output shows the text written by the postStart handler:
-->
命令行输出的是 `postStart` 处理函数所写入的文本

```
Hello from the postStart handler
```

<!-- discussion -->

<!--
## Discussion

Kubernetes sends the postStart event immediately after the Container is created.
There is no guarantee, however, that the postStart handler is called before
the Container's entrypoint is called. The postStart handler runs asynchronously
relative to the Container's code, but Kubernetes' management of the container
blocks until the postStart handler completes. The Container's status is not
set to RUNNING until the postStart handler completes.
-->
## 讨论

Kubernetes 在容器创建后立即发送 postStart 事件。
然而，postStart 处理函数的调用不保证早于容器的入口点（entrypoint）
的执行。postStart 处理函数与容器的代码是异步执行的，但 Kubernetes
的容器管理逻辑会一直阻塞等待 postStart 处理函数执行完毕。
只有 postStart 处理函数执行完毕，容器的状态才会变成
RUNNING。

<!--
Kubernetes sends the preStop event immediately before the Container is terminated.
Kubernetes' management of the Container blocks until the preStop handler completes,
unless the Pod's grace period expires. For more details, see
[Termination of Pods](/docs/user-guide/pods/#termination-of-pods).
-->
Kubernetes 在容器结束前立即发送 preStop 事件。除非 Pod 宽限期限超时，Kubernetes 的容器管理逻辑
会一直阻塞等待 preStop 处理函数执行完毕。更多的相关细节，可以参阅
[Pods 的结束](/zh/docs/concepts/workloads/pods/pod-lifecycle/#pod-termination)。

<!--
Kubernetes only sends the preStop event when a Pod is *terminated*.
This means that the preStop hook is not invoked when the Pod is *completed*.
This limitation is tracked in [issue #55087](https://github.com/kubernetes/kubernetes/issues/55807).
-->
{{< note >}}
Kubernetes 只有在 Pod *结束（Terminated）* 的时候才会发送 preStop 事件，
这意味着在 Pod *完成（Completed）* 时
preStop 的事件处理逻辑不会被触发。这个限制在
[issue #55087](https://github.com/kubernetes/kubernetes/issues/55807) 中被追踪。
{{< /note >}}

## {{% heading "whatsnext" %}}

<!--
* Learn more about [Container lifecycle hooks](/docs/concepts/containers/container-lifecycle-hooks/).
* Learn more about the [lifecycle of a Pod](/docs/concepts/workloads/pods/pod-lifecycle/).
-->
* 进一步了解[容器生命周期回调](/zh/docs/concepts/containers/container-lifecycle-hooks/)。
* 进一步了解[Pod 的生命周期](/zh/docs/concepts/workloads/pods/pod-lifecycle/)。

<!--
### Reference

* [Lifecycle](/docs/reference/generated/kubernetes-api/{{< param "version" >}}/#lifecycle-v1-core)
* [Container](/docs/reference/generated/kubernetes-api/{{< param "version" >}}/#container-v1-core)
* See `terminationGracePeriodSeconds` in [PodSpec](/docs/reference/generated/kubernetes-api/{{< param "version" >}}/#podspec-v1-core)
-->
### 参考

* [Lifecycle](/docs/reference/generated/kubernetes-api/{{< param "version" >}}/#lifecycle-v1-core)
* [Container](/docs/reference/generated/kubernetes-api/{{< param "version" >}}/#container-v1-core)
* 参阅 [PodSpec](/docs/reference/generated/kubernetes-api/{{< param "version" >}}/#podspec-v1-core) 中关于`terminationGracePeriodSeconds` 的部分

