[zh] translate concepts/Topology Aware Hints

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+---
+title: 拓扑感知提示
+content_type: concept
+weight: 45
+---
+<!-- 
+---
+reviewers:
+- robscott
+title: Topology Aware Hints
+content_type: concept
+weight: 45
+---
+-->
+
+<!-- overview -->
+
+{{< feature-state for_k8s_version="v1.21" state="alpha" >}}
+
+<!-- 
+_Topology Aware Hints_ enable topology aware routing by including suggestions
+for how clients should consume endpoints. This approach adds metadata to enable
+consumers of EndpointSlice and / or and Endpoints objects, so that traffic to
+those network endpoints can be routed closer to where it originated.
+
+For example, you can route traffic within a locality to reduce
+costs, or to improve network performance.
+-->
+_拓扑感知提示_ 包含客户怎么使用服务端点的建议，从而实现了拓扑感知的路由功能。
+这种方法添加了元数据，以启用 EndpointSlice 和/或 Endpoints 对象的调用者，
+这样，访问这些网络端点的请求流量就可以在它的发起点附近就近路由。
+
+例如，你可以在一个地域内路由流量，以降低通信成本，或提高网络性能。
+
+<!-- body -->
+
+<!-- 
+## Motivation
+-->
+## 动机 {#motivation}
+
+<!-- 
+Kubernetes clusters are increasingly deployed in multi-zone environments.
+_Topology Aware Hints_ provides a mechanism to help keep traffic within the zone
+it originated from. This concept is commonly referred to as "Topology Aware
+Routing". When calculating the endpoints for a {{< glossary_tooltip term_id="Service" >}},
+the EndpointSlice controller considers the topology (region and zone) of each endpoint
+and populates the hints field to allocate it to a zone.
+Cluster components such as the {{< glossary_tooltip term_id="kube-proxy" text="kube-proxy" >}}
+can then consume those hints, and use them to influence how traffic to is routed
+(favoring topologically closer endpoints).
+-->
+Kubernetes 集群越来越多的部署到多区域环境中。
+_拓扑感知提示_ 提供了一种把流量限制在它的发起区域之内的机制。
+这个概念一般被称之为 “拓扑感知路由”。
+在计算 {{< glossary_tooltip term_id="Service" >}} 的端点时，
+EndpointSlice 控制器会评估每一个端点的拓扑（地域和区域），填充提示字段，并将其分配到某个区域。
+集群组件，例如{{< glossary_tooltip term_id="kube-proxy" text="kube-proxy" >}}
+就可以使用这些提示信息，并用他们来影响流量的路由（倾向于拓扑上相邻的端点）。
+
+<!-- 
+## Using Topology Aware Hints
+-->
+## 使用拓扑感知提示 {#using-topology-aware-hints}
+
+<!-- 
+If you have [enabled](/docs/tasks/administer-cluster/enabling-topology-aware-hints) the
+overall feature, you can activate Topology Aware Hints for a Service by setting the
+`service.kubernetes.io/topology-aware-hints` annotation to `auto`. This tells
+the EndpointSlice controller to set topology hints if it is deemed safe.
+Importantly, this does not guarantee that hints will always be set.
+-->
+如果你已经[启用](/zh/docs/tasks/administer-cluster/enabling-topology-aware-hints)了整个特性，
+就可以通过把注解 `service.kubernetes.io/topology-aware-hints` 的值设置为 `auto`，
+来激活服务的拓扑感知提示功能。
+这告诉 EndpointSlice 控制器在它认为安全的时候来设置拓扑提示。
+重要的是，这并不能保证总会设置提示（hints）。
+
+<!-- 
+## How it works {#implementation}
+-->
+## 工作原理 {#implementation}
+
+<!-- 
+The functionality enabling this feature is split into two components: The
+EndpointSlice controller and the kube-proxy. This section provides a high level overview
+of how each component implements this feature.
+-->
+此特性启用的功能分为两个组件：EndpointSlice 控制器和 kube-proxy。
+本节概述每个组件如何实现此特性。
+
+<!-- 
+### EndpointSlice controller {#implementation-control-plane}
+-->
+### EndpointSlice 控制器 {#implementation-control-plane}
+
+<!-- 
+The EndpointSlice controller is responsible for setting hints on EndpointSlices
+when this feature is enabled. The controller allocates a proportional amount of
+endpoints to each zone. This proportion is based on the
+[allocatable](/docs/tasks/administer-cluster/reserve-compute-resources/#node-allocatable)
+CPU cores for nodes running in that zone. For example, if one zone had 2 CPU
+cores and another zone only had 1 CPU core, the controller would allocated twice
+as many endpoints to the zone with 2 CPU cores.
+-->
+此特性开启后，EndpointSlice 控制器负责在 EndpointSlice 上设置提示信息。
+控制器按比例给每个区域分配一定比例数量的端点。
+这个比例来源于此区域中运行节点的
+[可分配](/zh/docs/tasks/administer-cluster/reserve-compute-resources/#node-allocatable)
+CPU 核心数。
+例如，如果一个区域拥有 2 CPU 核心，而另一个区域只有 1 CPU 核心，
+那控制器将给那个有 2 CPU 的区域分配两倍数量的端点。
+
+<!-- 
+The following example shows what an EndpointSlice looks like when hints have
+been populated:
+-->
+以下示例展示了提供提示信息后 EndpointSlice 的样子：
+
+```yaml
+apiVersion: discovery.k8s.io/v1
+kind: EndpointSlice
+metadata:
+  name: example-hints
+  labels:
+    kubernetes.io/service-name: example-svc
+addressType: IPv4
+ports:
+  - name: http
+    protocol: TCP
+    port: 80
+endpoints:
+  - addresses:
+      - "10.1.2.3"
+    conditions:
+      ready: true
+    hostname: pod-1
+    zone: zone-a
+    hints:
+      forZones:
+        - name: "zone-a"
+```
+
+### kube-proxy {#implementation-kube-proxy}
+
+<!-- 
+The kube-proxy component filters the endpoints it routes to based on the hints set by
+the EndpointSlice controller. In most cases, this means that the kube-proxy is able
+to route traffic to endpoints in the same zone. Sometimes the controller allocates endpoints
+from a different zone to ensure more even distribution of endpoints between zones.
+This would result in some traffic being routed to other zones.
+-->
+kube-proxy 组件依据 EndpointSlice 控制器设置的提示，过滤由它负责路由的端点。
+在大多数场合，这意味着 kube-proxy 可以把流量路由到同一个区域的端点。
+有时，控制器从某个不同的区域分配端点，以确保在多个区域之间更平均的分配端点。
+这会导致部分流量被路由到其他区域。
+
+<!-- 
+## Safeguards
+-->
+## 保护措施 {#safeguards}
+
+<!-- 
+The Kubernetes control plane and the kube-proxy on each node apply some
+safeguard rules before using Topology Aware Hints. If these don't check out,
+the kube-proxy selects endpoints from anywhere in your cluster, regardless of the
+zone.
+-->
+Kubernetes 控制平面和每个节点上的 kube-proxy，在使用拓扑感知提示功能前，会应用一些保护措施规则。
+如果没有检出，kube-proxy 将无视区域限制，从集群中的任意节点上选择端点。
+
+<!-- 
+1. **Insufficient number of endpoints:** If there are less endpoints than zones
+   in a cluster, the controller will not assign any hints.
+-->
+1. **端点数量不足：** 如果一个集群中，端点数量少于区域数量，控制器不创建任何提示。
+
+<!-- 
+2. **Impossible to achieve balanced allocation:** In some cases, it will be
+   impossible to achieve a balanced allocation of endpoints among zones. For
+   example, if zone-a is twice as large as zone-b, but there are only 2
+   endpoints, an endpoint allocated to zone-a may receive twice as much traffic
+   as zone-b. The controller does not assign hints if it can't get this "expected
+   overload" value below an acceptable threshold for each zone. Importantly this
+   is not based on real-time feedback. It is still possible for individual
+   endpoints to become overloaded.
+-->
+2. **不可能实现均衡分配：** 在一些场合中，不可能实现端点在区域中的平衡分配。
+   例如，假设 zone-a 比 zone-b 大两倍，但只有 2 个端点，
+   那分配到 zone-a 的端点可能收到比 zone-b多两倍的流量。
+   如果控制器不能确定此“期望的过载”值低于每一个区域可接受的阈值，控制器将不指派提示信息。
+   重要的是，这不是基于实时反馈。所以对于单独的端点仍有可能超载。
+
+<!-- 
+3. **One or more Nodes has insufficient information:** If any node does not have
+   a `topology.kubernetes.io/zone` label or is not reporting a value for
+   allocatable CPU, the control plane does not set any topology-aware endpoint
+   hints and so kube-proxy does not filter endpoints by zone.
+-->
+3. **一个或多个节点信息不足：** 如果任一节点没有设置标签 `topology.kubernetes.io/zone`，
+   或没有上报可分配的 CPU 数据，控制平面将不会设置任何拓扑感知提示，
+   继而 kube-proxy 也就不能通过区域过滤端点。
+
+<!-- 
+4. **One or more endpoints does not have a zone hint:** When this happens,
+   the kube-proxy assumes that a transition from or to Topology Aware Hints is
+   underway. Filtering endpoints for a Service in this state would be dangerous
+   so the kube-proxy falls back to using all endpoints.
+-->
+4. **一个或多个端点没有设置区域提示：** 当这类事情发生时，
+   kube-proxy 会假设这是正在执行一个从/到拓扑感知提示的转移。
+   在这种场合下过滤Service 的端点是有风险的，所以 kube-proxy 回撤为使用所有的端点。
+
+<!-- 
+5. **A zone is not represented in hints:** If the kube-proxy is unable to find
+   at least one endpoint with a hint targeting the zone it is running in, it falls
+   to using endpoints from all zones. This is most likely to happen as you add
+   a new zone into your existing cluster.
+-->
+5. **不在提示中的区域：** 如果 kube-proxy 不能根据一个指示在它所在的区域中发现一个端点，
+   它回撤为使用所有节点的端点。当你的集群新增一个新的区域时，这种情况发生概率很高。
+
+<!-- 
+## Constraints
+-->
+## 限制 {#constraints}
+
+<!-- 
+* Topology Aware Hints are not used when either `externalTrafficPolicy` or
+  `internalTrafficPolicy` is set to `Local` on a Service. It is possible to use
+  both features in the same cluster on different Services, just not on the same
+  Service.
+-->
+* 当 Service 的 `externalTrafficPolicy` 或 `internalTrafficPolicy` 设置值为 `Local` 时，
+  拓扑感知提示功能不可用。
+  你可以在一个集群的不同服务中使用这两个特性，但不能在同一个服务中这么做。
+
+<!-- 
+* This approach will not work well for Services that have a large proportion of
+  traffic originating from a subset of zones. Instead this assumes that incoming
+  traffic will be roughly proportional to the capacity of the Nodes in each
+  zone.
+-->
+* 这种方法不适用于大部分流量来自于一部分区域的服务。
+  相反的，这里假设入站流量将根据每个区域中节点的服务能力按比例的分配。
+
+<!-- 
+* The EndpointSlice controller ignores unready nodes as it calculates the
+  proportions of each zone. This could have unintended consequences if a large
+  portion of nodes are unready.
+-->
+* EndpointSlice 控制器在计算每一个区域的容量比例时，会忽略未就绪的节点。
+  在大量节点未就绪的场景下，这样做会带来非预期的结果。
+
+<!-- 
+* The EndpointSlice controller does not take into account {{< glossary_tooltip
+  text="tolerations" term_id="toleration" >}} when deploying calculating the
+  proportions of each zone. If the Pods backing a Service are limited to a
+  subset of Nodes in the cluster, this will not be taken into account.
+-->
+* EndpointSlice 控制器在计算每一个区域的部署比例时，并不会考虑
+  {{< glossary_tooltip text="容忍度" term_id="toleration" >}}。
+  如果服务后台的 Pod 被限制只能运行在集群节点的一个子集上，这些信息并不会被使用。
+
+<!-- 
+* This may not work well with autoscaling. For example, if a lot of traffic is
+  originating from a single zone, only the endpoints allocated to that zone will
+  be handling that traffic. That could result in {{< glossary_tooltip
+  text="Horizontal Pod Autoscaler" term_id="horizontal-pod-autoscaler" >}}
+  either not picking up on this event, or newly added pods starting in a
+  different zone.
+-->
+* 这种方法和自动扩展机制之间不能很好的协同工作。例如，如果大量流量来源于一个区域，
+  那只有分配到该区域的端点才可用来处理流量。这会导致
+  {{< glossary_tooltip text="Pod 自动水平扩展" term_id="horizontal-pod-autoscaler" >}}
+  要么不能拾取此事件，要么新增 Pod 被启动到其他区域。
+
+## {{% heading "whatsnext" %}}
+
+<!-- 
+* Read about [enabling Topology Aware Hints](/docs/tasks/administer-cluster/enabling-topology-aware-hints/)
+* Read [Connecting Applications with Services](/docs/concepts/services-networking/connect-applications-service/)
+-->
+* 参阅[启用拓扑感知提示](/zh/docs/tasks/administer-cluster/enabling-topology-aware-hints/)
+* 参阅[通过服务连通应用](/zh/docs/concepts/services-networking/connect-applications-service/)