431 lines
19 KiB
Markdown
431 lines
19 KiB
Markdown
---
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title: 为应用程序设置干扰预算（Disruption Budget）
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content_type: task
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weight: 110
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---
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<!--
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title: Specifying a Disruption Budget for your Application
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content_type: task
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weight: 110
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-->
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<!-- overview -->
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{{< feature-state for_k8s_version="v1.5" state="beta" >}}
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<!--
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This page shows how to limit the number of concurrent disruptions
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that your application experiences, allowing for higher availability
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while permitting the cluster administrator to manage the clusters
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nodes.
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-->
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本文展示如何限制应用程序的并发干扰数量，在允许集群管理员管理集群节点的同时保证高可用。
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## {{% heading "prerequisites" %}}
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<!--
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* You are the owner of an application running on a Kubernetes cluster that requires
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high availability.
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* You should know how to deploy [Replicated Stateless Applications](/docs/tasks/run-application/run-stateless-application-deployment/)
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and/or [Replicated Stateful Applications](/docs/tasks/run-application/run-replicated-stateful-application/).
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* You should have read about [Pod Disruptions](/docs/concepts/workloads/pods/disruptions/).
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* You should confirm with your cluster owner or service provider that they respect
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Pod Disruption Budgets.
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-->
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* 你是 Kubernetes 集群中某应用的所有者，该应用有高可用要求。
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* 你应了解如何部署[无状态应用](/zh/docs/tasks/run-application/run-stateless-application-deployment/)
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和/或[有状态应用](/zh/docs/tasks/run-application/run-replicated-stateful-application/)。
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* 你应当已经阅读过关于 [Pod 干扰](/zh/docs/concepts/workloads/pods/disruptions/) 的文档。
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* 用户应当与集群所有者或服务提供者确认其遵从 Pod 干扰预算（Pod Disruption Budgets）的规则。
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<!-- steps -->
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<!--
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## Protecting an Application with a PodDisruptionBudget
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1. Identify what application you want to protect with a PodDisruptionBudget (PDB).
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1. Think about how your application reacts to disruptions.
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1. Create a PDB definition as a YAML file.
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1. Create the PDB object from the YAML file.
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-->
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## 用 PodDisruptionBudget 来保护应用
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1. 确定想要使用 PodDisruptionBudget (PDB) 来保护的应用。
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1. 考虑应用对干扰的反应。
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1. 以 YAML 文件形式定义 PDB 。
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1. 通过 YAML 文件创建 PDB 对象。
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<!-- discussion -->
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<!--
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## Identify an Application to Protect
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The most common use case when you want to protect an application
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specified by one of the built-in Kubernetes controllers:
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-->
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## 确定要保护的应用
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用户想要保护通过内置的 Kubernetes 控制器指定的应用，这是最常见的使用场景：
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- Deployment
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- ReplicationController
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- ReplicaSet
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- StatefulSet
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<!--
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In this case, make a note of the controller's `.spec.selector`; the same
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selector goes into the PDBs `.spec.selector`.
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-->
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在这种情况下，在控制器的 `.spec.selector` 字段中做记录，并在 PDB 的
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`.spec.selector` 字段中加入同样的选择算符。
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<!--
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From version 1.15 PDBs support custom controllers where the [scale subresource](/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definitions/#scale-subresource) is enabled.
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-->
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从 1.15 版本开始，PDB 支持启用
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[scale 子资源](/zh/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definitions/#scale-subresource)
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的自定义控制器。
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<!--
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You can also use PDBs with pods which are not controlled by one of the above
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controllers, or arbitrary groups of pods, but there are some restrictions,
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described in [Arbitrary Controllers and Selectors](#arbitrary-controllers-and-selectors).
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-->
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用户也可以用 PDB 来保护不受上述控制器控制的 Pod，或任意的 Pod 集合，但是正如
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[任意控制器和选择算符](#arbitrary-controllers-and-selectors)中描述的，这里存在一些限制。
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<!--
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## Think about how your application reacts to disruptions
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Decide how many instances can be down at the same time for a short period
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due to a voluntary disruption.
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-->
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## 考虑应用对干扰的反应
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确定在自发干扰时，多少实例可以在短时间内同时关闭。
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<!--
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- Stateless frontends:
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- Concern: don't reduce serving capacity by more than 10%.
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- Solution: use PDB with minAvailable 90% for example.
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- Single-instance Stateful Application:
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- Concern: do not terminate this application without talking to me.
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- Possible Solution 1: Do not use a PDB and tolerate occasional downtime.
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- Possible Solution 2: Set PDB with maxUnavailable=0. Have an understanding
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(outside of Kubernetes) that the cluster operator needs to consult you before
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termination. When the cluster operator contacts you, prepare for downtime,
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and then delete the PDB to indicate readiness for disruption. Recreate afterwards.
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- Multiple-instance Stateful application such as Consul, ZooKeeper, or etcd:
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- Concern: Do not reduce number of instances below quorum, otherwise writes fail.
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- Possible Solution 1: set maxUnavailable to 1 (works with varying scale of application).
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- Possible Solution 2: set minAvailable to quorum-size (e.g. 3 when scale is 5). (Allows more disruptions at once).
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- Restartable Batch Job:
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- Concern: Job needs to complete in case of voluntary disruption.
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- Possible solution: Do not create a PDB. The Job controller will create a replacement pod.
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-->
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- 无状态的前端：
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- 关注：不能降低服务能力 10% 以上。
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- 解决方案：例如，使用 PDB，指定其 minAvailable 值为 90%。
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- 单实例有状态应用：
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- 关注：不要在不通知的情况下终止该应用。
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- 可能的解决方案 1：不使用 PDB，并忍受偶尔的停机。
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- 可能的解决方案 2：设置 maxUnavailable=0 的 PDB。
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意为（Kubernetes 范畴之外的）集群操作人员需要在终止应用前与用户协商，
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协商后准备停机，然后删除 PDB 表示准备接受干扰，后续再重新创建。
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- 多实例有状态应用，如 Consul、ZooKeeper 或 etcd：
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- 关注：不要将实例数量减少至低于仲裁规模，否则将出现写入失败。
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- 可能的解决方案 1：设置 maxUnavailable 值为 1 (适用于不同规模的应用)。
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- 可能的解决方案 2：设置 minAvailable 值为仲裁规模（例如规模为 5 时设置为 3）。
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(允许同时出现更多的干扰)。
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- 可重新启动的批处理任务：
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- 关注：自发干扰的情况下，需要确保任务完成。
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- 可能的解决方案：不创建 PDB。 任务控制器会创建一个替换 Pod。
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<!--
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### Rounding logic when specifying percentages
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Values for `minAvailable` or `maxUnavailable` can be expressed as integers or as a percentage.
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-->
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### 指定百分比时的舍入逻辑
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`minAvailable` 或 `maxUnavailable` 的值可以表示为整数或百分比。
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<!--
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- When you specify an integer, it represents a number of Pods. For instance, if you set `minAvailable` to 10, then 10
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Pods must always be available, even during a disruption.
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- When you specify a percentage by setting the value to a string representation of a percentage (eg. `"50%"`), it represents a percentage of
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total Pods. For instance, if you set `minUnavailable` to `"50%"`, then only 50% of the Pods can be unavailable during a
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disruption.
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-->
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- 指定整数值时，它表示 Pod 个数。例如，如果将 minAvailable 设置为 10，
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那么即使在干扰期间，也必须始终有 10 个Pod可用。
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- 通过将值设置为百分比的字符串表示形式（例如 “50％”）来指定百分比时，它表示占总 Pod 数的百分比。
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例如，如果将 "minUnavailable" 设置为 “50％”，则干扰期间只允许 50％ 的 Pod 不可用。
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<!--
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When you specify the value as a percentage, it may not map to an exact number
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of Pods. For example, if you have 7 Pods and you set `minAvailable` to
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`"50%"`, it's not immediately obvious whether that means 3 Pods or 4 Pods must
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be available. Kubernetes rounds up to the nearest integer, so in this case, 4
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Pods must be available. You can examine the
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[code](https://github.com/kubernetes/kubernetes/blob/23be9587a0f8677eb8091464098881df939c44a9/pkg/controller/disruption/disruption.go#L539)
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that controls this behavior.
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-->
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如果将值指定为百分比，则可能无法映射到确切数量的 Pod。例如，如果你有 7 个 Pod，
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并且你将 `minAvailable` 设置为 `"50％"`，具体是 3 个 Pod 或 4 个 Pod 必须可用
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并非显而易见。
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Kubernetes 采用向上取整到最接近的整数的办法，因此在这种情况下，必须有 4 个 Pod。
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你可以检查控制此行为的
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[代码](https://github.com/kubernetes/kubernetes/blob/23be9587a0f8677eb8091464098881df939c44a9/pkg/controller/disruption/disruption.go#L539)。
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<!--
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## Specifying a PodDisruptionBudget
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A `PodDisruptionBudget` has three fields:
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-->
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## 指定 PodDisruptionBudget
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一个 `PodDisruptionBudget` 有 3 个字段：
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<!--
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* A label selector `.spec.selector` to specify the set of
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pods to which it applies. This field is required.
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* `.spec.minAvailable` which is a description of the number of pods from that
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set that must still be available after the eviction, even in the absence
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of the evicted pod. `minAvailable` can be either an absolute number or a percentage.
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* `.spec.maxUnavailable` (available in Kubernetes 1.7 and higher) which is a description
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of the number of pods from that set that can be unavailable after the eviction.
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It can be either an absolute number or a percentage.
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-->
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* 标签选择算符 `.spec.selector` 用于指定其所作用的 Pod 集合，该字段为必需字段。
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* `.spec.minAvailable` 表示驱逐后仍须保证可用的 Pod 数量。即使因此影响到 Pod 驱逐
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（即该条件在和 Pod 驱逐发生冲突时优先保证）。
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`minAvailable` 值可以是绝对值，也可以是百分比。
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* `.spec.maxUnavailable` （Kubernetes 1.7 及更高的版本中可用）表示驱逐后允许不可用的
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Pod 的最大数量。其值可以是绝对值或是百分比。
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<!--
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For versions 1.8 and earlier: When creating a `PodDisruptionBudget`
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object using the `kubectl` command line tool, the `minAvailable` field has a
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default value of 1 if neither `minAvailable` nor `maxUnavailable` is specified.
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-->
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{{< note >}}
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对于1.8及更早的版本：当你用 `kubectl` 命令行工具创建 `PodDisruptionBudget` 对象时，
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如果既未指定 `minAvailable` 也未指定 `maxUnavailable`，
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则 `minAvailable` 字段有一个默认值 1。
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{{< /note >}}
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<!--
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You can specify only one of `maxUnavailable` and `minAvailable` in a single `PodDisruptionBudget`.
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`maxUnavailable` can only be used to control the eviction of pods
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that have an associated controller managing them. In the examples below, "desired replicas"
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is the `scale` of the controller managing the pods being selected by the
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`PodDisruptionBudget`.
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-->
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用户在同一个 `PodDisruptionBudget` 中只能够指定 `maxUnavailable` 和 `minAvailable` 中的一个。
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`maxUnavailable` 只能够用于控制存在相应控制器的 Pod 的驱逐（即不受控制器控制的 Pod 不在
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`maxUnavailable` 控制范围内）。在下面的示例中，
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“所需副本” 指的是相应控制器的 `scale`，控制器对 `PodDisruptionBudget` 所选择的 Pod 进行管理。
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<!--
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Example 1: With a `minAvailable` of 5, evictions are allowed as long as they leave behind
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5 or more healthy pods among those selected by the PodDisruptionBudget's `selector`.
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-->
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示例 1：设置 `minAvailable` 值为 5 的情况下，驱逐时需保证 PodDisruptionBudget 的 `selector`
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选中的 Pod 中 5 个或 5 个以上处于健康状态。
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<!--
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Example 2: With a `minAvailable` of 30%, evictions are allowed as long as at least 30%
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of the number of desired replicas are healthy.
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-->
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示例 2：设置 `minAvailable` 值为 30% 的情况下，驱逐时需保证 Pod 所需副本的至少 30% 处于健康状态。
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<!--
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Example 3: With a `maxUnavailable` of 5, evictions are allowed as long as there are at most 5
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unhealthy replicas among the total number of desired replicas.
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-->
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示例 3：设置 `maxUnavailable` 值为 5 的情况下，驱逐时需保证所需副本中最多 5 个处于不可用状态。
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<!--
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Example 4: With a `maxUnavailable` of 30%, evictions are allowed as long as no more than 30%
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of the desired replicas are unhealthy.
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-->
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示例 4：设置 `maxUnavailable` 值为 30% 的情况下，驱逐时需保证所需副本中最多 30% 处于不可用状态。
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<!--
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In typical usage, a single budget would be used for a collection of pods managed by
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a controller—for example, the pods in a single ReplicaSet or StatefulSet.
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-->
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在典型用法中，干扰预算会被用于一个控制器管理的一组 Pod 中 —— 例如：一个 ReplicaSet 或 StatefulSet
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中的 Pod。
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<!--
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A disruption budget does not truly guarantee that the specified
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number/percentage of pods will always be up. For example, a node that hosts a
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pod from the collection may fail when the collection is at the minimum size
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specified in the budget, thus bringing the number of available pods from the
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collection below the specified size. The budget can only protect against
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voluntary evictions, not all causes of unavailability.
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-->
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{{< note >}}
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干扰预算并不能真正保证指定数量/百分比的 Pod 一直处于运行状态。例如： 当 Pod 集合的
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规模处于预算指定的最小值时，承载集合中某个 Pod 的节点发生了故障，这样就导致集合中可用 Pod 的
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数量低于预算指定值。预算只能够针对自发的驱逐提供保护，而不能针对所有 Pod 不可用的诱因。
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{{< /note >}}
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<!--
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A `maxUnavailable` of 0% (or 0) or a `minAvailable` of 100% (or equal to the
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number of replicas) may block node drains entirely. This is permitted as per the
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semantics of `PodDisruptionBudget`.
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-->
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设置 `maxUnavailable` 值为 0%（或 0）或设置 `minAvailable` 值为 100%（或等于副本数）
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可能会阻塞节点，导致资源耗尽。按照 `PodDisruptionBudget` 的语义，这是允许的。
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<!--
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You can find examples of pod disruption budgets defined below. They match pods with the label
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`app: zookeeper`.
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-->
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用户可以在下面看到 pod 干扰预算定义的示例，它们与带有 `app: zookeeper` 标签的 pod 相匹配：
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<!--
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Example PDB Using minAvailable:
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-->
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使用 minAvailable 的PDB 示例：
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{{< codenew file="policy/zookeeper-pod-disruption-budget-minavailable.yaml" >}}
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<!--
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Example PDB Using maxUnavailable (Kubernetes 1.7 or higher):
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-->
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使用 maxUnavailable 的 PDB 示例（Kubernetes 1.7 或更高的版本）：
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{{< codenew file="policy/zookeeper-pod-disruption-budget-maxunavailable.yaml" >}}
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<!--
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For example, if the above `zk-pdb` object selects the pods of a StatefulSet of size 3, both
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specifications have the exact same meaning. The use of `maxUnavailable` is recommended as it
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automatically responds to changes in the number of replicas of the corresponding controller.
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-->
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例如，如果上述 `zk-pdb` 选择的是一个规格为 3 的 StatefulSet 对应的 Pod，
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那么上面两种规范的含义完全相同。
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推荐使用 `maxUnavailable` ，因为它自动响应控制器副本数量的变化。
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<!--
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## Create the PDB object
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You can create the PDB object with a command like `kubectl apply -f mypdb.yaml`.
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-->
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## 创建 PDB 对象
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你可以通过类似 `kubectl apply -f mypdb.yaml` 的命令来创建 PDB。
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<!--
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You cannot update PDB objects. They must be deleted and re-created.
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-->
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PDB 对象无法更新，必须删除后重新创建。
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<!--
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## Check the status of the PDB
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Use kubectl to check that your PDB is created.
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-->
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## 检查 PDB 的状态
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使用 kubectl 来确认 PDB 被创建。
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<!--
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Assuming you don't actually have pods matching `app: zookeeper` in your namespace,
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then you'll see something like this:
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-->
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假设用户的名字空间下没有匹配 `app: zookeeper` 的 Pod，用户会看到类似下面的信息：
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```shell
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kubectl get poddisruptionbudgets
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```
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```
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NAME MIN AVAILABLE MAX UNAVAILABLE ALLOWED DISRUPTIONS AGE
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zk-pdb 2 N/A 0 7s
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```
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<!--
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If there are matching pods (say, 3), then you would see something like this:
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-->
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假设有匹配的 Pod (比如说 3 个), 那么用户会看到类似下面的信息：
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```shell
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kubectl get poddisruptionbudgets
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```
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```
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NAME MIN AVAILABLE MAX UNAVAILABLE ALLOWED DISRUPTIONS AGE
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zk-pdb 2 N/A 1 7s
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```
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<!--
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The non-zero value for `ALLOWED-DISRUPTIONS` means that the disruption controller has seen the pods,
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counted the matching pods, and updated the status of the PDB.
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You can get more information about the status of a PDB with this command:
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-->
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`ALLOWED-DISRUPTIONS` 值非 0 意味着干扰控制器已经感知到相应的 Pod，对匹配的 Pod 进行统计，
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并更新了 PDB 的状态。
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用户可以通过以下命令获取更多 PDB 状态相关信息：
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```shell
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kubectl get poddisruptionbudgets zk-pdb -o yaml
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```
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```yaml
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||
apiVersion: policy/v1beta1
|
||
kind: PodDisruptionBudget
|
||
metadata:
|
||
anntation: {}
|
||
creationTimestamp: "2020-03-04T04:22:56Z"
|
||
generation: 1
|
||
name: zk-pdb
|
||
…
|
||
status:
|
||
currentHealthy: 3
|
||
desiredHealthy: 2
|
||
disruptionsAllowed: 1
|
||
expectedPods: 3
|
||
observedGeneration: 1
|
||
```
|
||
|
||
<!--
|
||
## Arbitrary Controllers and Selectors
|
||
|
||
You can skip this section if you only use PDBs with the built-in
|
||
application controllers (Deployment, ReplicationController, ReplicaSet, and StatefulSet),
|
||
with the PDB selector matching the controller's selector.
|
||
-->
|
||
## 任意控制器和选择算符 {#arbitrary-controllers-and-selectors}
|
||
|
||
如果你只使用与内置的应用控制器（Deployment、ReplicationController、ReplicaSet 和 StatefulSet）
|
||
对应的 PDB，也就是 PDB 的选择算符与 控制器的选择算符相匹配，那么可以跳过这一节。
|
||
|
||
<!--
|
||
You can use a PDB with pods controlled by another type of controller, by an
|
||
"operator", or bare pods, but with these restrictions:
|
||
-->
|
||
你可以使用这样的 PDB：它对应的 Pod 可能由其他类型的控制器控制，可能由 "operator" 控制，
|
||
也可能为“裸的（不受控制器控制）” Pod，但该类 PDB 存在以下限制：
|
||
|
||
<!--
|
||
- only `.spec.minAvailable` can be used, not `.spec.maxUnavailable`.
|
||
- only an integer value can be used with `.spec.minAvailable`, not a percentage.
|
||
-->
|
||
- 只能够使用 `.spec.minAvailable` ，而不能够使用 `.spec.maxUnavailable。`
|
||
- 只能够使用整数作为 `.spec.minAvailable` 的值，而不能使用百分比。
|
||
|
||
<!--
|
||
You can use a selector which selects a subset or superset of the pods belonging to a built-in
|
||
controller. However, when there are multiple PDBs in a namespace, you must be careful not
|
||
to create PDBs whose selectors overlap.
|
||
-->
|
||
你可以令选择算符选择一个内置控制器所控制 Pod 的子集或父集。
|
||
然而，当名字空间下存在多个 PDB 时，用户必须小心，保证 PDB 的选择算符之间不重叠。
|
||
|