sync 2023-05-04-statefulset-autodelete.md
sync 2023-05-04-statefulset-autodelete.mdpull/41109/head
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---
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layout: blog
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title: 'Kubernetes 1.27: StatefulSet PVC 自动删除(beta)'
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date: 2023-05-04
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slug: kubernetes-1-27-statefulset-pvc-auto-deletion-beta
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---
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<!--
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layout: blog
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title: 'Kubernetes 1.27: StatefulSet PVC Auto-Deletion (beta)'
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date: 2023-05-04
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slug: kubernetes-1-27-statefulset-pvc-auto-deletion-beta
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-->
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<!--
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**Author:** Matthew Cary (Google)
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-->
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**作者**：Matthew Cary (Google)
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**译者**：顾欣 (ICBC)
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<!--
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Kubernetes v1.27 graduated to beta a new policy mechanism for
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[`StatefulSets`](/docs/concepts/workloads/controllers/statefulset/) that controls the lifetime of
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their [`PersistentVolumeClaims`](/docs/concepts/storage/persistent-volumes/) (PVCs). The new PVC
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retention policy lets users specify if the PVCs generated from the `StatefulSet` spec template should
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be automatically deleted or retrained when the `StatefulSet` is deleted or replicas in the `StatefulSet`
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are scaled down.
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-->
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Kubernetes v1.27 将一种新的策略机制升级到 Beta 阶段，这一策略用于控制
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[`StatefulSets`](/zh-cn/docs/concepts/workloads/controllers/statefulset/)
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的 [`PersistentVolumeClaims`](/zh-cn/docs/concepts/storage/persistent-volumes/)（PVCs）的生命周期。
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这种新的 PVC 保留策略允许用户指定当删除 `StatefulSet` 或者缩减 `StatefulSet` 中的副本时，
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是自动删除还是保留从 `StatefulSet` 规约模板生成的 PVC。
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<!--
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## What problem does this solve?
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A `StatefulSet` spec can include `Pod` and PVC templates. When a replica is first created, the
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Kubernetes control plane creates a PVC for that replica if one does not already exist. The behavior
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before the PVC retention policy was that the control plane never cleaned up the PVCs created for
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`StatefulSets` - this was left up to the cluster administrator, or to some add-on automation that
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you’d have to find, check suitability, and deploy. The common pattern for managing PVCs, either
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manually or through tools such as Helm, is that the PVCs are tracked by the tool that manages them,
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with explicit lifecycle. Workflows that use `StatefulSets` must determine on their own what PVCs are
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created by a `StatefulSet` and what their lifecycle should be.
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-->
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## 所解决的问题
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`StatefulSet` 规约可以包含 `Pod` 和 PVC 模板。
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当首次创建副本时，Kubernetes 控制平面会为该副本创建一个 PVC （如果不存在）。
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在 PVC 保留策略出现之前，控制平面不会清理为 `StatefulSets` 创建的 PVC，
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该任务通常由集群管理员负责，或者通过一些附加的自动化工具来处理。
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你需要寻找这些工具，并检查其适用性，然后进行部署。
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通常管理 PVC 的常见模式，无论是手动管理还是通过诸如 Helm 等工具进行管理，
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都是由负责管理它们的工具跟踪，具有明确的生命周期。
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使用 `StatefulSets` 的工作流必须自行确定由 `StatefulSet` 创建的 PVC，
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并确定其生命周期。
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<!--
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Before this new feature, when a StatefulSet-managed replica disappears, either because the
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`StatefulSet` is reducing its replica count, or because its `StatefulSet` is deleted, the PVC and its
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backing volume remains and must be manually deleted. While this behavior is appropriate when the
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data is critical, in many cases the persistent data in these PVCs is either temporary, or can be
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reconstructed from another source. In those cases, PVCs and their backing volumes remaining after
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their `StatefulSet` or replicas have been deleted are not necessary, incur cost, and require manual
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cleanup.
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-->
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在引入这个新特性之前，当一个由 StatefulSet 管理的副本消失时，
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无论是因为 `StatefulSet` 正在减少其副本数量，还是因为其 `StatefulSet` 被删除，
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PVC 及其支持卷仍然存在，必须手动删除。尽管在数据至关重要时这种行为是合适的，
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但在许多情况下，这些 PVC 中的持久数据要么是临时的，要么可以从其他来源重建。
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在这些情况下，删除 `StatefulSet` 或副本后仍保留 PVC 及其支持卷是不必要的，
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这会产生成本，并且需要手动清理。
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<!--
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## The new `StatefulSet` PVC retention policy
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The new `StatefulSet` PVC retention policy is used to control if and when PVCs created from a
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`StatefulSet`’s `volumeClaimTemplate` are deleted. There are two contexts when this may occur.
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-->
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## 新的 `StatefulSet` PVC 保留策略
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新的 `StatefulSet` PVC 保留策略用于控制是否以及何时删除从 `StatefulSet`
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的 `volumeClaimTemplate` 创建的 PVC。有两种情况可能需要就此作出决定。
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<!--
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The first context is when the `StatefulSet` resource is deleted (which implies that all replicas are
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also deleted). This is controlled by the `whenDeleted` policy. The second context, controlled by
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`whenScaled` is when the `StatefulSet` is scaled down, which removes some but not all of the replicas
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in a `StatefulSet`. In both cases the policy can either be `Retain`, where the corresponding PVCs are
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not touched, or `Delete`, which means that PVCs are deleted. The deletion is done with a normal
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[object deletion](/docs/concepts/architecture/garbage-collection/), so that, for example, all
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retention policies for the underlying PV are respected.
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This policy forms a matrix with four cases. I’ll walk through and give an example for each one.
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-->
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第一种是当删除 `StatefulSet` 资源时（意味着所有副本也会被删除）。
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这时的行为由 `whenDeleted` 策略控制。第二种场景由 `whenScaled` 控制，
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即当 `StatefulSet` 缩减规模时，它会移除一部分而不是全部副本。在这两种情况下，
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策略可以是 `Retain`，表示相应的 PVC 不受影响，或者是 `Delete`，表示 PVC 将被删除。
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删除操作是通过普通的[对象删除](/zh-cn/docs/concepts/architecture/garbage-collection/)完成的，
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这样可以确保对底层 PV 的所有保留策略都得到遵守。
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这个策略形成了一个矩阵，包括四种情况。接下来，我将逐一介绍每种情况并给出一个示例。
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<!--
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* **`whenDeleted` and `whenScaled` are both `Retain`.**
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This matches the existing behavior for `StatefulSets`, where no PVCs are deleted. This is also
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the default retention policy. It’s appropriate to use when data on `StatefulSet` volumes may be
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irreplaceable and should only be deleted manually.
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-->
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* **`whenDeleted` 和 `whenScaled` 都是 `Retain`。**
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这与现有的 `StatefulSets` 行为相匹配，所有 PVC 都不会被删除。这也是默认的保留策略。
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当 `StatefulSet` 卷上的数据可能是不可替代的，并且应该仅在手动情况下删除时，这种策略是适当的。
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<!--
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* **`whenDeleted` is `Delete` and `whenScaled` is `Retain`.**
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In this case, PVCs are deleted only when the entire `StatefulSet` is deleted. If the
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`StatefulSet` is scaled down, PVCs are not touched, meaning they are available to be reattached
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if a scale-up occurs with any data from the previous replica. This might be used for a temporary
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`StatefulSet`, such as in a CI instance or ETL pipeline, where the data on the `StatefulSet` is
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needed only during the lifetime of the `StatefulSet` lifetime, but while the task is running the
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data is not easily reconstructible. Any retained state is needed for any replicas that scale
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down and then up.
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-->
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* **`whenDeleted` 是 `Delete`，`whenScaled` 是 `Retain`。**
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在这种情况下，只有在整个 `StatefulSet` 被删除时，PVC 才会被删除。
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如果 `StatefulSet` 进行缩减操作，PVC 将不会受到影响，这意味着如果缩减后再进行扩展，
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并且使用了来自之前副本的任何数据，PVC 可以被重新关联。这种情况适用于临时的 `StatefulSet`，
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例如在 CI 实例或 ETL 流水线中，`StatefulSet` 上的数据只在其生命周期内需要，
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但在任务运行时，数据不容易重建。对于先被缩容后被扩容的副本而言，所有已保留的状态都是需要的。
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<!--
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* **`whenDeleted` and `whenScaled` are both `Delete`.**
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PVCs are deleted immediately when their replica is no longer needed. Note this does not include
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when a `Pod` is deleted and a new version rescheduled, for example when a node is drained and
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`Pods` need to migrate elsewhere. The PVC is deleted only when the replica is no longer needed
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as signified by a scale-down or `StatefulSet` deletion. This use case is for when data does not
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need to live beyond the life of its replica. Perhaps the data is easily reconstructable and the
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cost savings of deleting unused PVCs is more important than quick scale-up, or perhaps that when
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a new replica is created, any data from a previous replica is not usable and must be
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reconstructed anyway.
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-->
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* **`whenDeleted` 和 `whenScaled` 都是 `Delete`。**
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当副本不再需要时，PVC 会立即被删除。需要注意的是，
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这不包括当删除一个 Pod 并重新调度一个新版本时的情况，
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例如当一个节点被排空并且 Pods 需要迁移到其他地方时。只有在副本不再被需要时，
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即通过缩减规模或删除 `StatefulSet` 时，PVC 才会被删除。
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这种情况适用于数据不需要在其副本的生命周期之外存在的情况。也许数据很容易重建，
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删除未使用的 PVC 可以节省成本比快速扩展更重要，或者当创建一个新副本时，
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来自前一个副本的任何数据都无法使用，必须进行重建。
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<!--
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* **`whenDeleted` is `Retain` and `whenScaled` is `Delete`.**
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This is similar to the previous case, when there is little benefit to keeping PVCs for fast
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reuse during scale-up. An example of a situation where you might use this is an Elasticsearch
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cluster. Typically you would scale that workload up and down to match demand, whilst ensuring a
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minimum number of replicas (for example: 3). When scaling down, data is migrated away from
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removed replicas and there is no benefit to retaining those PVCs. However, it can be useful to
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bring the entire Elasticsearch cluster down temporarily for maintenance. If you need to take the
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Elasticsearch system offline, you can do this by temporarily deleting the `StatefulSet`, and
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then bringing the Elasticsearch cluster back by recreating the `StatefulSet`. The PVCs holding
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the Elasticsearch data will still exist and the new replicas will automatically use them.
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-->
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* **`whenDeleted` 是 `Retain`，`whenScaled` 是 `Delete`。**
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这与前面的情况类似，保留 PVC 以便在扩容时进行快速重用的好处微乎其微。
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一个使用这种策略的例子是 Elasticsearch 集群。通常，你会根据需求调整该工作负载的规模，
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同时确保有一定数量的副本（例如：3个）一直存在。在缩容时，数据会从被删除的副本迁移走，
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保留这些 PVC 没有好处。然而，如果需要临时关闭整个 Elasticsearch 集群进行维护，
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可以通过暂时删除 `StatefulSet` 然后重建 `StatefulSet` 来恢复 Elasticsearch 集群。
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持有 Elasticsearch 数据的 PVC 仍然存在，新的副本将自动使用它们。
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<!--
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Visit the
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[documentation](/docs/concepts/workloads/controllers/statefulset/#persistentvolumeclaim-policies) to
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see all the details.
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## What’s next?
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Try it out! The `StatefulSetAutoDeletePVC` feature gate is beta and enabled by default on
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cluster running Kubernetes 1.27. Create a `StatefulSet` using the new policy, test it out and tell
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us what you think!
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-->
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请访问[文档](/zh-cn/docs/concepts/workloads/controllers/statefulset/#persistentvolumeclaim-policies)
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以查看所有详细信息。
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## 下一步是什么？
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试一试吧！在 Kubernetes 1.27 的集群中，`StatefulSetAutoDeletePVC` 特性门控是 Beta 阶段，
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使用新的策略创建一个 `StatefulSet`，进行测试并告诉我们你的想法！
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<!--
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I'm very curious to see if this owner reference mechanism works well in practice. For example, I
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realized there is no mechanism in Kubernetes for knowing who set a reference, so it’s possible that
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the `StatefulSet` controller may fight with custom controllers that set their own
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references. Fortunately, maintaining the existing retention behavior does not involve any new owner
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references, so default behavior will be compatible.
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Please tag any issues you report with the label `sig/apps` and assign them to Matthew Cary
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([@mattcary](https://github.com/mattcary) at GitHub).
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Enjoy!
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-->
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我非常好奇这个所有者引用机制在实践中是否运行良好。例如，
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我意识到在 Kubernetes 中没有机制可以知道是谁设置了引用，
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因此 `StatefulSet` 控制器可能会与设置自己引用的自定义控制器产生冲突。
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幸运的是，保持现有的保留行为不涉及任何新的所有者引用，因此默认行为将是兼容的。
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请在你报告的任何 issue 上标记标签 sig/apps，
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并将它们指派给 Matthew Cary (@mattcary at GitHub)。
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祝您使用愉快！
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