245 lines
12 KiB
Markdown
245 lines
12 KiB
Markdown
---
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title: 容器生命周期回调
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content_type: concept
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weight: 40
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---
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<!--
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reviewers:
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- mikedanese
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- thockin
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title: Container Lifecycle Hooks
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content_type: concept
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weight: 40
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-->
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<!-- overview -->
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<!--
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This page describes how kubelet managed Containers can use the Container lifecycle hook framework
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to run code triggered by events during their management lifecycle.
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-->
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这个页面描述了 kubelet 管理的容器如何使用容器生命周期回调框架，
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藉由其管理生命周期中的事件触发，运行指定代码。
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<!-- body -->
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<!--
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## Overview
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Analogous to many programming language frameworks that have component lifecycle hooks, such as Angular,
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Kubernetes provides Containers with lifecycle hooks.
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The hooks enable Containers to be aware of events in their management lifecycle
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and run code implemented in a handler when the corresponding lifecycle hook is executed.
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-->
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## 概述
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类似于许多具有生命周期回调组件的编程语言框架，例如 Angular、Kubernetes 为容器提供了生命周期回调。
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回调使容器能够了解其管理生命周期中的事件，并在执行相应的生命周期回调时运行在处理程序中实现的代码。
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<!--
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## Container hooks
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There are two hooks that are exposed to Containers:
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-->
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## 容器回调 {#container-hooks}
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有两个回调暴露给容器：
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`PostStart`
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<!--
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This hook is executed immediately after a container is created.
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However, there is no guarantee that the hook will execute before the container ENTRYPOINT.
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No parameters are passed to the handler.
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-->
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这个回调在容器被创建之后立即被执行。
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但是，不能保证回调会在容器入口点（ENTRYPOINT）之前执行。
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没有参数传递给处理程序。
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`PreStop`
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<!--
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This hook is called immediately before a container is terminated due to an API request or management
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event such as a liveness/startup probe failure, preemption, resource contention and others. A call
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to the `PreStop` hook fails if the container is already in a terminated or completed state and the
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hook must complete before the TERM signal to stop the container can be sent. The Pod's termination
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grace period countdown begins before the `PreStop` hook is executed, so regardless of the outcome of
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the handler, the container will eventually terminate within the Pod's termination grace period. No
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parameters are passed to the handler.
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-->
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在容器因 API 请求或者管理事件（诸如存活态探针、启动探针失败、资源抢占、资源竞争等）
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而被终止之前，此回调会被调用。
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如果容器已经处于已终止或者已完成状态，则对 preStop 回调的调用将失败。
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在用来停止容器的 TERM 信号被发出之前，回调必须执行结束。
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Pod 的终止宽限周期在 `PreStop` 回调被执行之前即开始计数，
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所以无论回调函数的执行结果如何，容器最终都会在 Pod 的终止宽限期内被终止。
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没有参数会被传递给处理程序。
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<!--
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A more detailed description of the termination behavior can be found in
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[Termination of Pods](/docs/concepts/workloads/pods/pod-lifecycle/#pod-termination).
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-->
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有关终止行为的更详细描述，请参见
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[终止 Pod](/zh-cn/docs/concepts/workloads/pods/pod-lifecycle/#pod-termination)。
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<!--
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### Hook handler implementations
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Containers can access a hook by implementing and registering a handler for that hook.
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There are three types of hook handlers that can be implemented for Containers:
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-->
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### 回调处理程序的实现
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容器可以通过实现和注册该回调的处理程序来访问该回调。
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针对容器，有三种类型的回调处理程序可供实现：
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<!--
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* Exec - Executes a specific command, such as `pre-stop.sh`, inside the cgroups and namespaces of the Container.
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Resources consumed by the command are counted against the Container.
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* HTTP - Executes an HTTP request against a specific endpoint on the Container.
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* Sleep - Pauses the container for a specified duration.
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The "Sleep" action is available when the [feature gate](/docs/reference/command-line-tools-reference/feature-gates/)
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`PodLifecycleSleepAction` is enabled.
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-->
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* Exec - 在容器的 cgroups 和名字空间中执行特定的命令（例如 `pre-stop.sh`）。
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命令所消耗的资源计入容器的资源消耗。
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* HTTP - 对容器上的特定端点执行 HTTP 请求。
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* Sleep - 将容器暂停一段指定的时间。
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当[特性门控](/zh-cn/docs/reference/command-line-tools-reference/feature-gates/) `PodLifecycleSleepAction` 被启用时，
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“Sleep” 操作才可用。
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<!--
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### Hook handler execution
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When a Container lifecycle management hook is called,
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the Kubernetes management system executes the handler according to the hook action,
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`httpGet` , `tcpSocket` and `sleep` are executed by the kubelet process, and `exec` is executed in the container.
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-->
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### 回调处理程序执行
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当调用容器生命周期管理回调时，Kubernetes 管理系统根据回调动作执行其处理程序，
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`httpGet`、`tcpSocket` 和 `sleep` 由 kubelet 进程执行，而 `exec` 在容器中执行。
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<!--
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Hook handler calls are synchronous within the context of the Pod containing the Container.
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This means that for a `PostStart` hook,
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the Container ENTRYPOINT and hook fire asynchronously.
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However, if the hook takes too long to run or hangs,
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the Container cannot reach a `running` state.
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-->
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回调处理程序调用在包含容器的 Pod 上下文中是同步的。
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这意味着对于 `PostStart` 回调，容器入口点和回调异步触发。
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但是，如果回调运行或挂起的时间太长，则容器无法达到 `running` 状态。
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<!--
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`PreStop` hooks are not executed asynchronously from the signal
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to stop the Container; the hook must complete its execution before
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the TERM signal can be sent.
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If a `PreStop` hook hangs during execution,
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the Pod's phase will be `Terminating` and remain there until the Pod is
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killed after its `terminationGracePeriodSeconds` expires.
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This grace period applies to the total time it takes for both
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the `PreStop` hook to execute and for the Container to stop normally.
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If, for example, `terminationGracePeriodSeconds` is 60, and the hook
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takes 55 seconds to complete, and the Container takes 10 seconds to stop
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normally after receiving the signal, then the Container will be killed
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before it can stop normally, since `terminationGracePeriodSeconds` is
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less than the total time (55+10) it takes for these two things to happen.
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-->
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`PreStop` 回调并不会与停止容器的信号处理程序异步执行；回调必须在可以发送信号之前完成执行。
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如果 `PreStop` 回调在执行期间停滞不前，Pod 的阶段会变成 `Terminating`并且一直处于该状态，
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直到其 `terminationGracePeriodSeconds` 耗尽为止，这时 Pod 会被杀死。
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这一宽限期是针对 `PreStop` 回调的执行时间及容器正常停止时间的总和而言的。
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例如，如果 `terminationGracePeriodSeconds` 是 60，回调函数花了 55 秒钟完成执行，
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而容器在收到信号之后花了 10 秒钟来正常结束，那么容器会在其能够正常结束之前即被杀死，
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因为 `terminationGracePeriodSeconds` 的值小于后面两件事情所花费的总时间（55+10）。
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<!--
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If either a `PostStart` or `PreStop` hook fails,
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it kills the Container.
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-->
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如果 `PostStart` 或 `PreStop` 回调失败，它会杀死容器。
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<!--
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Users should make their hook handlers as lightweight as possible.
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There are cases, however, when long running commands make sense,
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such as when saving state prior to stopping a Container.
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-->
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用户应该使他们的回调处理程序尽可能的轻量级。
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但也需要考虑长时间运行的命令也很有用的情况，比如在停止容器之前保存状态。
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<!--
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### Hook delivery guarantees
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Hook delivery is intended to be *at least once*,
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which means that a hook may be called multiple times for any given event,
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such as for `PostStart` or `PreStop`.
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It is up to the hook implementation to handle this correctly.
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-->
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### 回调递送保证
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回调的递送应该是**至少一次**，这意味着对于任何给定的事件，
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例如 `PostStart` 或 `PreStop`，回调可以被调用多次。
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如何正确处理被多次调用的情况，是回调实现所要考虑的问题。
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<!--
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Generally, only single deliveries are made.
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If, for example, an HTTP hook receiver is down and is unable to take traffic,
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there is no attempt to resend.
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In some rare cases, however, double delivery may occur.
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For instance, if a kubelet restarts in the middle of sending a hook,
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the hook might be resent after the kubelet comes back up.
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-->
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通常情况下，只会进行单次递送。
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例如，如果 HTTP 回调接收器宕机，无法接收流量，则不会尝试重新发送。
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然而，偶尔也会发生重复递送的可能。
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例如，如果 kubelet 在发送回调的过程中重新启动，回调可能会在 kubelet 恢复后重新发送。
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<!--
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### Debugging Hook handlers
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The logs for a Hook handler are not exposed in Pod events.
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If a handler fails for some reason, it broadcasts an event.
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For `PostStart`, this is the `FailedPostStartHook` event,
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and for `PreStop`, this is the `FailedPreStopHook` event.
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To generate a failed `FailedPostStartHook` event yourself, modify the [lifecycle-events.yaml](https://raw.githubusercontent.com/kubernetes/website/main/content/en/examples/pods/lifecycle-events.yaml) file to change the postStart command to "badcommand" and apply it.
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Here is some example output of the resulting events you see from running `kubectl describe pod lifecycle-demo`:
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-->
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### 调试回调处理程序
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回调处理程序的日志不会在 Pod 事件中公开。
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如果处理程序由于某种原因失败，它将播放一个事件。
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对于 `PostStart`，这是 `FailedPostStartHook` 事件，对于 `PreStop`，这是 `FailedPreStopHook` 事件。
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要自己生成失败的 `FailedPostStartHook` 事件，请修改
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[lifecycle-events.yaml](https://raw.githubusercontent.com/kubernetes/website/main/content/en/examples/pods/lifecycle-events.yaml)
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文件将 postStart 命令更改为 “badcommand” 并应用它。
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以下是通过运行 `kubectl describe pod lifecycle-demo` 后你看到的一些结果事件的示例输出：
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```
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Events:
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Type Reason Age From Message
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---- ------ ---- ---- -------
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Normal Scheduled 7s default-scheduler Successfully assigned default/lifecycle-demo to ip-XXX-XXX-XX-XX.us-east-2...
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Normal Pulled 6s kubelet Successfully pulled image "nginx" in 229.604315ms
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Normal Pulling 4s (x2 over 6s) kubelet Pulling image "nginx"
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Normal Created 4s (x2 over 5s) kubelet Created container lifecycle-demo-container
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Normal Started 4s (x2 over 5s) kubelet Started container lifecycle-demo-container
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Warning FailedPostStartHook 4s (x2 over 5s) kubelet Exec lifecycle hook ([badcommand]) for Container "lifecycle-demo-container" in Pod "lifecycle-demo_default(30229739-9651-4e5a-9a32-a8f1688862db)" failed - error: command 'badcommand' exited with 126: , message: "OCI runtime exec failed: exec failed: container_linux.go:380: starting container process caused: exec: \"badcommand\": executable file not found in $PATH: unknown\r\n"
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Normal Killing 4s (x2 over 5s) kubelet FailedPostStartHook
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Normal Pulled 4s kubelet Successfully pulled image "nginx" in 215.66395ms
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Warning BackOff 2s (x2 over 3s) kubelet Back-off restarting failed container
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```
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## {{% heading "whatsnext" %}}
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<!--
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* Learn more about the [Container environment](/docs/concepts/containers/container-environment/).
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* Get hands-on experience
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[attaching handlers to Container lifecycle events](/docs/tasks/configure-pod-container/attach-handler-lifecycle-event/).
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-->
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* 进一步了解[容器环境](/zh-cn/docs/concepts/containers/container-environment/)。
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* 动手[为容器的生命周期事件设置处理函数](/zh-cn/docs/tasks/configure-pod-container/attach-handler-lifecycle-event/)。
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