[zh] sync leases.md
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---
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title: 租约
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content_type: concept
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weight: 30
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---
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<!--
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title: Leases
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content_type: concept
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weight: 30
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-->
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<!-- overview -->
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<!--
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Distrbuted systems often have a need for "leases", which provides a mechanism to lock shared resources and coordinate activity between nodes.
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In Kubernetes, the "lease" concept is represented by `Lease` objects in the `coordination.k8s.io` API group, which are used for system-critical
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capabilities like node heart beats and component-level leader election.
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-->
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分布式系统通常需要“租约”，它提供了一种机制来锁定共享资源并协调节点之间的活动。
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在 Kubernetes 中，“租约”概念表示为 `coordination.k8s.io` API 组中的 `Lease` 对象，
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常用于类似节点心跳和组件级领导者选举等系统核心能力。
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<!-- body -->
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<!--
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## Node Heart Beats
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Kubernetes uses the Lease API to communicate kubelet node heart beats to the Kubernetes API server.
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For every `Node` , there is a `Lease` object with a matching name in the `kube-node-lease`
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namespace. Under the hood, every kubelet heart beat is an UPDATE request to this `Lease` object, updating
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the `spec.renewTime` field for the Lease. The Kubernetes control plane uses the time stamp of this field
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to determine the availability of this `Node`.
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See [Node Lease objects](/docs/concepts/architecture/nodes/#heartbeats) for more details.
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-->
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## 节点心跳 {#node-heart-beats}
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Kubernetes 使用 Lease API 将 kubelet 节点心跳传递到 Kubernetes API 服务器。
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对于每个 `Node`，在 `kube-node-lease` 名字空间中都有一个具有匹配名称的 `Lease` 对象。
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在此基础上，每个 kubelet 心跳都是对该 `Lease` 对象的 UPDATE 请求，更新该 Lease 的 `spec.renewTime` 字段。
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Kubernetes 控制平面使用此字段的时间戳来确定此 `Node` 的可用性。
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更多细节请参阅 [Node Lease 对象](/zh-cn/docs/concepts/architecture/nodes/#heartbeats)。
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<!--
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## Leader Election
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Leases are also used in Kubernetes to ensure only one instance of a component is running at any given time.
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This is used by control plane components like `kube-controller-manager` and `kube-scheduler` in
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HA configurations, where only one instance of the component should be actively running while the other
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instances are on stand-by.
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-->
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## 领导者选举 {#leader-election}
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租约在 Kubernetes 中还用于确保在任何给定时间某个组件只有一个实例在运行。
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这在高可用配置中由 `kube-controller-manager` 和 `kube-scheduler` 等控制平面组件进行使用，
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这些组件只应有一个实例激活运行，而其他实例待机。
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<!--
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## API Server Identity
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-->
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## API 服务器身份 {#api-server-identity}
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{{< feature-state for_k8s_version="v1.26" state="beta" >}}
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<!--
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Starting in Kubernetes v1.26, each `kube-apiserver` uses the Lease API to publish its identity to the
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rest of the system. While not particularly useful on its own, this provides a mechanism for clients to
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discover how many instances of `kube-apiserver` are operating the Kubernetes control plane.
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Existence of kube-apiserver leases enables future capabilities that may require coordination between
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each kube-apiserver.
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You can inspect Leases owned by each kube-apiserver by checking for lease objects in the `kube-system` namespace
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with the name `kube-apiserver-<sha256-hash>`. Alternatively you can use the label selector `k8s.io/component=kube-apiserver`:
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-->
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从 Kubernetes v1.26 开始，每个 `kube-apiserver` 都使用 Lease API 将其身份发布到系统中的其他位置。
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虽然它本身并不是特别有用，但为客户端提供了一种机制来发现有多少个 `kube-apiserver` 实例正在操作
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Kubernetes 控制平面。kube-apiserver 租约的存在使得未来可以在各个 kube-apiserver 之间协调新的能力。
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你可以检查 `kube-system` 名字空间中名为 `kube-apiserver-<sha256-hash>` 的 Lease 对象来查看每个
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kube-apiserver 拥有的租约。你还可以使用标签选择算符 `k8s.io/component=kube-apiserver`：
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```shell
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$ kubectl -n kube-system get lease -l k8s.io/component=kube-apiserver
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NAME HOLDER AGE
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kube-apiserver-c4vwjftbvpc5os2vvzle4qg27a kube-apiserver-c4vwjftbvpc5os2vvzle4qg27a_9cbf54e5-1136-44bd-8f9a-1dcd15c346b4 5m33s
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kube-apiserver-dz2dqprdpsgnm756t5rnov7yka kube-apiserver-dz2dqprdpsgnm756t5rnov7yka_84f2a85d-37c1-4b14-b6b9-603e62e4896f 4m23s
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kube-apiserver-fyloo45sdenffw2ugwaz3likua kube-apiserver-fyloo45sdenffw2ugwaz3likua_c5ffa286-8a9a-45d4-91e7-61118ed58d2e 4m43s
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```
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<!--
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The SHA256 hash used in the lease name is based on the OS hostname as seen by kube-apiserver. Each kube-apiserver should be
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configured to use a hostname that is unique within the cluster. New instances of kube-apiserver that use the same hostname
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will take over existing Leases using a new holder identity, as opposed to instantiating new lease objects. You can check the
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hostname used by kube-apisever by checking the value of the `kubernetes.io/hostname` label:
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-->
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租约名称中使用的 SHA256 哈希基于 kube-apiserver 所看到的操作系统主机名生成。
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每个 kube-apiserver 都应该被配置为使用集群中唯一的主机名。
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使用相同主机名的 kube-apiserver 新实例将使用新的持有者身份接管现有租约，而不是实例化新的 Lease 对象。
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你可以通过检查 `kubernetes.io/hostname` 标签的值来查看 kube-apisever 所使用的主机名：
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```shell
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kubectl -n kube-system get lease kube-apiserver-c4vwjftbvpc5os2vvzle4qg27a -o yaml
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```
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```yaml
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apiVersion: coordination.k8s.io/v1
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kind: Lease
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metadata:
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creationTimestamp: "2022-11-30T15:37:15Z"
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labels:
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k8s.io/component: kube-apiserver
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kubernetes.io/hostname: kind-control-plane
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name: kube-apiserver-c4vwjftbvpc5os2vvzle4qg27a
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namespace: kube-system
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resourceVersion: "18171"
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uid: d6c68901-4ec5-4385-b1ef-2d783738da6c
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spec:
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holderIdentity: kube-apiserver-c4vwjftbvpc5os2vvzle4qg27a_9cbf54e5-1136-44bd-8f9a-1dcd15c346b4
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leaseDurationSeconds: 3600
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renewTime: "2022-11-30T18:04:27.912073Z"
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```
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<!--
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Expired leases from kube-apiservers that no longer exist are garbage collected by new kube-apiservers after 1 hour.
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-->
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kube-apiserver 中不再存续的已到期租约将在到期 1 小时后被新的 kube-apiservers 作为垃圾收集。
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