website/content/zh-cn/docs/concepts/services-networking/topology-aware-routing.md

---
reviewers:
- robscott
title: 拓扑感知路由
content_type: concept
weight: 100
description: >-
  **拓扑感知路由**提供了一种机制帮助保持网络流量处于流量发起的区域内。
  在集群中 Pod 之间优先使用相同区域的流量有助于提高可靠性、性能（网络延迟和吞吐量）或降低成本。
---
<!--
reviewers:
- robscott
title: Topology Aware Routing
content_type: concept
weight: 100
description: >-
  _Topology Aware Routing_ provides a mechanism to help keep network traffic within the zone
  where it originated. Preferring same-zone traffic between Pods in your cluster can help
  with reliability, performance (network latency and throughput), or cost.
-->

<!-- overview -->

{{< feature-state for_k8s_version="v1.23" state="beta" >}}

{{< note >}}
<!--
Prior to Kubernetes 1.27, this feature was known as _Topology Aware Hints_.
-->
在 Kubernetes 1.27 之前，此特性称为**拓扑感知提示（Topology Aware Hint）**。
{{</ note >}}

<!--
_Topology Aware Routing_ adjusts routing behavior to prefer keeping traffic in
the zone it originated from. In some cases this can help reduce costs or improve
network performance.
-->
**拓扑感知路由（Toplogy Aware Routing）** 调整路由行为，以优先保持流量在其发起区域内。
在某些情况下，这有助于降低成本或提高网络性能。

<!-- body -->

<!--
## Motivation

Kubernetes clusters are increasingly deployed in multi-zone environments.
_Topology Aware Routing_ provides a mechanism to help keep traffic within the
zone it originated from. 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 {{< glossary_tooltip
term_id="kube-proxy" text="kube-proxy" >}} can then consume those hints, and use
them to influence how the traffic is routed (favoring topologically closer
endpoints).
-->
## 动机   {#motivation}

Kubernetes 集群越来越多地部署在多区域环境中。
**拓扑感知路由** 提供了一种机制帮助流量保留在其发起所在的区域内。
计算 {{<glossary_tooltip term_id="Service">}} 的端点时，
EndpointSlice 控制器考虑每个端点的物理拓扑（地区和区域），并填充提示字段以将其分配到区域。
诸如 {{<glossary_tooltip term_id="kube-proxy" text="kube-proxy">}}
等集群组件可以使用这些提示，影响流量的路由方式（优先考虑物理拓扑上更近的端点）。

<!--
## Enabling Topology Aware Routing
-->
## 启用拓扑感知路由   {#enabling-topology-aware-routing}

{{< note >}}
<!--
Prior to Kubernetes 1.27, this behavior was controlled using the
`service.kubernetes.io/topology-aware-hints` annotation.
-->
在 Kubernetes 1.27 之前，此行为是通过 `service.kubernetes.io/topology-aware-hints` 注解来控制的。
{{</ note >}}

<!--
You can enable Topology Aware Routing for a Service by setting the
`service.kubernetes.io/topology-mode` annotation to `Auto`. When there are
enough endpoints available in each zone, Topology Hints will be populated on
EndpointSlices to allocate individual endpoints to specific zones, resulting in
traffic being routed closer to where it originated from.
-->
你可以通过将 `service.kubernetes.io/topology-mode` 注解设置为 `Auto` 来启用 Service 的拓扑感知路由。
当每个区域中有足够的端点可用时，系统将为 EndpointSlices 填充拓扑提示，把每个端点分配给特定区域，
从而使流量被路由到更接近其来源的位置。

<!--
## When it works best

This feature works best when:
-->
## 何时效果最佳   {#when-it-works-best}

此特性在以下场景中的工作效果最佳：

<!--
### 1. Incoming traffic is evenly distributed

If a large proportion of traffic is originating from a single zone, that traffic
could overload the subset of endpoints that have been allocated to that zone.
This feature is not recommended when incoming traffic is expected to originate
from a single zone.
-->
### 1. 入站流量均匀分布   {#incoming-traffic-is-evently-distributed}

如果大部分流量源自同一个区域，则该流量可能会使分配到该区域的端点子集过载。
当预计入站流量源自同一区域时，不建议使用此特性。

<!--
### 2. The Service has 3 or more endpoints per zone {#three-or-more-endpoints-per-zone}

In a three zone cluster, this means 9 or more endpoints. If there are fewer than
3 endpoints per zone, there is a high (≈50%) probability that the EndpointSlice
controller will not be able to allocate endpoints evenly and instead will fall
back to the default cluster-wide routing approach.
-->
### 2. 服务在每个区域具有至少 3 个端点 {#three-or-more-endpoints-per-zone}

在一个三区域的集群中，这意味着有至少 9 个端点。如果每个区域的端点少于 3 个，
则 EndpointSlice 控制器很大概率（约 50％）无法平均分配端点，而是回退到默认的集群范围的路由方法。

<!--
## How It Works

The "Auto" heuristic attempts to proportionally allocate a number of endpoints
to each zone. Note that this heuristic works best for Services that have a
significant number of endpoints.
-->
## 工作原理 {#how-it-works}

“自动”启发式算法会尝试按比例分配一定数量的端点到每个区域。
请注意，这种启发方式对具有大量端点的 Service 效果最佳。

<!--
### EndpointSlice controller {#implementation-control-plane}

The EndpointSlice controller is responsible for setting hints on EndpointSlices
when this heuristic 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 allocate twice
as many endpoints to the zone with 2 CPU cores.
-->
### EndpointSlice 控制器 {#implementation-control-plane}

当启用此启发方式时，EndpointSlice 控制器负责在各个 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。
这个比例基于在该区域中运行的节点的[可分配](/zh-cn/docs/tasks/administer-cluster/reserve-compute-resources/#node-allocatable)
CPU 核心数。例如，如果一个区域有 2 个 CPU 核心，而另一个区域只有 1 个 CPU 核心，
那么控制器将给那个有 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，控制器在另一不同的区域中分配端点，以确保在多个区域之间更平均地分配端点。
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信息前，会应用一些保护措施规则。
如果规则无法顺利通过，kube-proxy 将无视区域限制，从集群中的任意位置选择端点。

<!--
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。
   如果控制器不能确保此“期望的过载”值低于每一个区域可接受的阈值，控制器将不添加提示信息。
   重要的是，这不是基于实时反馈。所以对于特定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 Node 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，
   进而 kube-proxy 也就不能根据区域来过滤端点。

<!--
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. **至少一个端点没有设置区域提示：** 当这种情况发生时，
   kube-proxy 会假设从拓扑感知提示到拓扑感知路由（或反方向）的迁移仍在进行中，
   在这种场合下过滤 Service 的端点是有风险的，所以 kube-proxy 回退到使用所有端点。

<!--
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
   back to using endpoints from all zones. This is most likely to happen as you add
   a new zone into your existing cluster.
-->
5. **提示中不存在某区域：** 如果 kube-proxy 无法找到提示中指向它当前所在的区域的端点，
   它将回退到使用来自所有区域的端点。当你向现有集群新增新的区域时，这种情况发生概率很高。

<!-- 
## Constraints
-->
## 限制 {#constraints}

<!--
* Topology Aware Hints are not used when `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 `internalTrafficPolicy` 值设置为 `Local` 时，
  系统将不使用拓扑感知提示信息。你可以在同一集群中的不同 Service 上使用这两个特性，
  但不能在同一个 Service 上这么做。

<!--
* 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 Service。
  相反，这项技术的假设是入站流量与各区域中节点的服务能力成比例关系。

<!--
* 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 控制器在计算各区域的比例时，会忽略未就绪的节点。
  在大部分节点未就绪的场景下，这样做会带来非预期的结果。

<!--
* The EndpointSlice controller ignores nodes with the
  `node-role.kubernetes.io/control-plane` or `node-role.kubernetes.io/master`
  label set. This could be problematic if workloads are also running on those
  nodes.
-->
* EndpointSlice 控制器忽略设置了 `node-role.kubernetes.io/control-plane` 或
  `node-role.kubernetes.io/master` 标签的节点。如果工作负载也在这些节点上运行，也可能会产生问题。

<!--
* The EndpointSlice controller does not take into account {{< glossary_tooltip
  text="tolerations" term_id="toleration" >}} when deploying or 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 控制器在分派或计算各区域的比例时，并不会考虑
  {{< glossary_tooltip text="容忍度" term_id="toleration" >}}。
  如果 Service 背后的各 Pod 被限制只能运行在集群节点的一个子集上，计算比例时不会考虑这点。

<!--
* 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.
-->
* 这项技术和自动扩缩容机制之间可能存在冲突。例如，如果大量流量来源于同一个区域，
  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 自动水平扩缩容" term_id="horizontal-pod-autoscaler" >}}
  要么不能处理这种场景，要么会在别的区域添加 Pod。

<!--
## Custom heuristics
-->
## 自定义启发方式   {#custom-heuristics}

<!--
Kubernetes is deployed in many different ways, there is no single heuristic for
allocating endpoints to zones will work for every use case. A key goal of this
feature is to enable custom heuristics to be developed if the built in heuristic
does not work for your use case. The first steps to enable custom heuristics
were included in the 1.27 release. This is a limited implementation that may not
yet cover some relevant and plausible situations.
-->
Kubernetes 的部署方式有很多种，没有一种按区域分配端点的启发式方法能够适用于所有场景。
此特性的一个关键目标是：如果内置的启发方式不能满足你的使用场景，则可以开发自定义的启发方式。
启用自定义启发方式的第一步包含在了 1.27 版本中。
这是一个限制性较强的实现，可能尚未涵盖一些重要的、可进一步探索的场景。

## {{% heading "whatsnext" %}}

<!--
* Follow the [Connecting Applications with Services](/docs/tutorials/services/connect-applications-service/) tutorial
* Learn about the
  [trafficDistribution](/docs/concepts/services-networking/service/#traffic-distribution)
  field, which is closely related to the `service.kubernetes.io/topology-mode`
  annotation and provides flexible options for traffic routing within
  Kubernetes.
-->
* 参阅[使用 Service 连接到应用](/zh-cn/docs/tutorials/services/connect-applications-service/)教程。
* 进一步了解 [trafficDistribution](/zh-cn/docs/concepts/services-networking/service/#traffic-distribution)字段，
  该字段与 `service.kubernetes.io/topology-mode` 注解密切相关，并为 Kubernetes 中的流量路由提供灵活的配置选项。