zh-trans:/docs/tasks/administer-cluster/dns-horizontal-autoscaling.md (#16035)
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---
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title: 集群 DNS 服务自动伸缩
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content_template: templates/task
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---
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<!--
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---
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title: Autoscale the DNS Service in a Cluster
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content_template: templates/task
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---
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-->
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{{% capture overview %}}
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<!--
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This page shows how to enable and configure autoscaling of the DNS service in a
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Kubernetes cluster.
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-->
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本页展示了如何在集群中启用和配置 DNS 服务的自动伸缩功能。
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{{% /capture %}}
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{{% capture prerequisites %}}
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* {{< include "task-tutorial-prereqs.md" >}} {{< version-check >}}
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<!--
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* This guide assumes your nodes use the AMD64 or Intel 64 CPU architecture
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* Make sure the [DNS feature](/docs/concepts/services-networking/dns-pod-service/) itself is enabled.
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* Kubernetes version 1.4.0 or later is recommended.
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-->
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* 本指南假设您的节点使用 AMD64 或 Intel 64 CPU 架构
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* 确保已启用 [DNS 功能](/docs/concepts/services-networking/dns-pod-service/)本身。
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* 建议使用 Kubernetes 1.4.0 或更高版本。
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{{% /capture %}}
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{{% capture steps %}}
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<!--
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## Determining whether DNS horizontal autoscaling is already enabled
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List the {{< glossary_tooltip text="Deployments" term_id="deployment" >}}
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in your cluster in the kube-system namespace:
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```shell
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kubectl get deployment --namespace=kube-system
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```
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The output is similar to this:
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NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
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...
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dns-autoscaler 1 1 1 1 ...
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...
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If you see "dns-autoscaler" in the output, DNS horizontal autoscaling is
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already enabled, and you can skip to
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[Tuning autoscaling parameters](#tuning-autoscaling-parameters).
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-->
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## 确定是否 DNS 水平 水平自动伸缩特性已经启用
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在 kube-system 命名空间中列出集群中的 {{< glossary_tooltip text="Deployments" term_id="deployment" >}} ：
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```shell
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kubectl get deployment --namespace=kube-system
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```
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输出类似如下这样：
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NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
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...
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dns-autoscaler 1 1 1 1 ...
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...
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如果在输出中看到 “dns-autoscaler”，说明 DNS 水平自动伸缩已经启用，可以跳到 [调优自动伸缩参数](#tuning-autoscaling-parameters)。
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<!--
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## Getting the name of your DNS Deployment or ReplicationController
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List the Deployments in your cluster in the kube-system namespace:
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```shell
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kubectl get deployment --namespace=kube-system
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```
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The output is similar to this:
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NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
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...
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coredns 2 2 2 2 ...
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...
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In Kubernetes versions earlier than 1.12, the DNS Deployment was called "kube-dns".
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In Kubernetes versions earlier than 1.5 DNS was implemented using a
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ReplicationController instead of a Deployment. So if you don't see kube-dns,
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or a similar name, in the preceding output, list the ReplicationControllers in
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your cluster in the kube-system namespace:
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```shell
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kubectl get rc --namespace=kube-system
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```
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The output is similar to this:
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NAME DESIRED CURRENT READY AGE
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...
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kube-dns-v20 1 1 1 ...
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...
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-->
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## 获取 DNS Deployment 或 ReplicationController 的名称
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列出集群内 kube-system namespace 中的 Deployment：
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```shell
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kubectl get deployment --namespace=kube-system
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```
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输出类似如下这样：
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NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
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...
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coredns 2 2 2 2 ...
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...
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在早于 1.12 的 Kubernetes 版本中，DNS 部署称为 “kube-dns”。
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Kubernetes 1.5 或之前版本，DNS 通过使用 ReplicationController 来实现，而不是 Deployment。 所以看不到 kube-dns 或者类似的名称，在之前的输出中，列出了集群内 kube-system namespace 中的 ReplicationController：
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```shell
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kubectl get rc --namespace=kube-system
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```
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输出类似如下这样：
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NAME DESIRED CURRENT READY AGE
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...
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kube-dns-v20 1 1 1 ...
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...
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<!--
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## Determining your scale target
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If you have a DNS Deployment, your scale target is:
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Deployment/<your-deployment-name>
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where `<your-deployment-name>` is the name of your DNS Deployment. For example, if
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your DNS Deployment name is coredns, your scale target is Deployment/coredns.
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If you have a DNS ReplicationController, your scale target is:
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ReplicationController/<your-rc-name>
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where `<your-rc-name>` is the name of your DNS ReplicationController. For example,
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if your DNS ReplicationController name is kube-dns-v20, your scale target is
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ReplicationController/kube-dns-v20.
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-->
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## 确定伸缩目标
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如果有一个 DNS Deployment，伸缩目标是：
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Deployment/<your-deployment-name>
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其中 `<your-deployment-name>` 是 DNS 部署的名称。例如，如果您的 DNS 部署名称是 coredns，则您的扩展目标是 Deployment/coredns。
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如果有一个 DNS ReplicationController，那么伸缩目标为：
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ReplicationController/<your-rc-name>
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这里 `<your-rc-name>` 是 DNS ReplicationController 的名称。 例如，DNS ReplicationController 的名称是 kube-dns-v20，则伸缩目标为 ReplicationController/kube-dns-v20。
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<!--
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## Enabling DNS horizontal autoscaling
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In this section, you create a Deployment. The Pods in the Deployment run a
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container based on the `cluster-proportional-autoscaler-amd64` image.
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Create a file named `dns-horizontal-autoscaler.yaml` with this content:
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{{< codenew file="admin/dns/dns-horizontal-autoscaler.yaml" >}}
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In the file, replace `<SCALE_TARGET>` with your scale target.
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Go to the directory that contains your configuration file, and enter this
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command to create the Deployment:
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```shell
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kubectl apply -f dns-horizontal-autoscaler.yaml
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```
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The output of a successful command is:
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deployment.apps/kube-dns-autoscaler created
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DNS horizontal autoscaling is now enabled.
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-->
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## 启用 DNS 水平自动伸缩
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在本段，我们创建一个 Deployment。Deployment 中的 Pod 运行一个基于 `cluster-proportional-autoscaler-amd64` 镜像的容器。
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创建文件 `dns-horizontal-autoscaler.yaml`，内容如下所示：
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{{< codenew file="admin/dns/dns-horizontal-autoscaler.yaml" >}}
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在文件中，将 `<SCALE_TARGET>` 替换成 scale 目标。
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进入到包含配置文件的目录中，输入如下命令创建 Deployment：
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```shell
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kubectl apply -f dns-horizontal-autoscaler.yaml
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```
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一个成功的命令输出是：
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deployment.apps/kube-dns-autoscaler created
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DNS 水平自动伸缩在已经启用了。
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<!--
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## Tuning autoscaling parameters
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Verify that the dns-autoscaler {{< glossary_tooltip text="ConfigMap" term_id="configmap" >}} exists:
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```shell
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kubectl get configmap --namespace=kube-system
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```
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The output is similar to this:
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NAME DATA AGE
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...
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dns-autoscaler 1 ...
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...
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Modify the data in the ConfigMap:
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```shell
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kubectl edit configmap dns-autoscaler --namespace=kube-system
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```
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Look for this line:
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```yaml
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linear: '{"coresPerReplica":256,"min":1,"nodesPerReplica":16}'
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```
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Modify the fields according to your needs. The "min" field indicates the
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minimal number of DNS backends. The actual number of backends number is
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calculated using this equation:
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replicas = max( ceil( cores * 1/coresPerReplica ) , ceil( nodes * 1/nodesPerReplica ) )
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Note that the values of both `coresPerReplica` and `nodesPerReplica` are
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integers.
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The idea is that when a cluster is using nodes that have many cores,
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`coresPerReplica` dominates. When a cluster is using nodes that have fewer
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cores, `nodesPerReplica` dominates.
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There are other supported scaling patterns. For details, see
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[cluster-proportional-autoscaler](https://github.com/kubernetes-incubator/cluster-proportional-autoscaler).
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-->
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## 调优自动伸缩参数
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验证 dns-autoscaler {{< glossary_tooltip text="ConfigMap" term_id="configmap" >}} 是否存在：
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```shell
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kubectl get configmap --namespace=kube-system
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```
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输出类似如下所示：
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NAME DATA AGE
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...
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dns-autoscaler 1 ...
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...
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修改该 ConfigMap 中的数据：
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```shell
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kubectl edit configmap dns-autoscaler --namespace=kube-system
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```
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找到如下这行内容：
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```yaml
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linear: '{"coresPerReplica":256,"min":1,"nodesPerReplica":16}'
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```
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根据需要修改对应的字段。“min” 字段说明 DNS 后端的最小数量。实际后端的数量，通过使用如下公式来计算：
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replicas = max( ceil( cores * 1/coresPerReplica ) , ceil( nodes * 1/nodesPerReplica ) )
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注意 `coresPerReplica` 和 `nodesPerReplica` 的值都是整数。
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想法是，当一个集群使用具有很多核心的节点时，由 `coresPerReplica` 来控制。 当一个集群使用具有较少核心的节点时，由 `nodesPerReplica` 来控制。
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其它的伸缩模式也是支持的，详情查看 [cluster-proportional-autoscaler](https://github.com/kubernetes-incubator/cluster-proportional-autoscaler)。
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<!--
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## Disable DNS horizontal autoscaling
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There are a few options for tuning DNS horizontal autoscaling. Which option to
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use depends on different conditions.
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-->
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## 禁用 DNS 水平自动伸缩
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有几个 DNS 水平自动伸缩的选项。具体使用哪个选项因环境而异。
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<!--
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### Option 1: Scale down the dns-autoscaler deployment to 0 replicas
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This option works for all situations. Enter this command:
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```shell
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kubectl scale deployment --replicas=0 dns-autoscaler --namespace=kube-system
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```
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The output is:
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deployment.extensions/dns-autoscaler scaled
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Verify that the replica count is zero:
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```shell
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kubectl get deployment --namespace=kube-system
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```
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The output displays 0 in the DESIRED and CURRENT columns:
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NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
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...
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dns-autoscaler 0 0 0 0 ...
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...
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-->
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### 选项 1：调小 dns-autoscaler deployment 至 0 个副本
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该选项适用于所有场景。运行如下命令：
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```shell
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kubectl scale deployment --replicas=0 dns-autoscaler --namespace=kube-system
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```
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输出如下所示：
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deployment.extensions/dns-autoscaler scaled
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验证当前副本数为 0：
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```shell
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kubectl get deployment --namespace=kube-system
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```
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输出内容中，在 DESIRED 和 CURRENT 列显示为 0：
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NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
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...
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dns-autoscaler 0 0 0 0 ...
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...
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<!--
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### Option 2: Delete the dns-autoscaler deployment
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This option works if dns-autoscaler is under your own control, which means
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no one will re-create it:
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```shell
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kubectl delete deployment dns-autoscaler --namespace=kube-system
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```
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The output is:
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deployment.extensions "dns-autoscaler" deleted
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-->
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### 选项 2：删除 dns-autoscaler Deployment
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如果 dns-autoscaler 为您所控制，该选项可以正常工作，也就说没有人会去重新创建它：
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```shell
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kubectl delete deployment dns-autoscaler --namespace=kube-system
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```
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输出内容如下所示：
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deployment.extensions "dns-autoscaler" deleted
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<!--
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### Option 3: Delete the dns-autoscaler manifest file from the master node
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This option works if dns-autoscaler is under control of the (deprecated)
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[Addon Manager](https://git.k8s.io/kubernetes/cluster/addons/README.md),
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and you have write access to the master node.
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Sign in to the master node and delete the corresponding manifest file.
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The common path for this dns-autoscaler is:
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/etc/kubernetes/addons/dns-horizontal-autoscaler/dns-horizontal-autoscaler.yaml
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After the manifest file is deleted, the Addon Manager will delete the
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dns-autoscaler Deployment.
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-->
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### 选项 3：从 master 节点删除 dns-autoscaler manifest 文件
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如果 dns-autoscaler 在[插件管理器](https://git.k8s.io/kubernetes/cluster/addons/README.md)的控制之下，该选项可以工作，并且具有操作 master 节点的写权限。
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登录到 master 节点，删除对应的 manifest 文件。
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dns-autoscaler 的路径一般为：
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/etc/kubernetes/addons/dns-horizontal-autoscaler/dns-horizontal-autoscaler.yaml
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当 manifest 文件删除后，插件管理器将删除 dns-autoscaler Deployment。
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||||
{{% /capture %}}
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||||
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||||
{{% capture discussion %}}
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||||
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||||
<!--
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## Understanding how DNS horizontal autoscaling works
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* The cluster-proportional-autoscaler application is deployed separately from
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the DNS service.
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* An autoscaler Pod runs a client that polls the Kubernetes API server for the
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number of nodes and cores in the cluster.
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* A desired replica count is calculated and applied to the DNS backends based on
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the current schedulable nodes and cores and the given scaling parameters.
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* The scaling parameters and data points are provided via a ConfigMap to the
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autoscaler, and it refreshes its parameters table every poll interval to be up
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to date with the latest desired scaling parameters.
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* Changes to the scaling parameters are allowed without rebuilding or restarting
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the autoscaler Pod.
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* The autoscaler provides a controller interface to support two control
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patterns: *linear* and *ladder*.
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-->
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## 理解 DNS 水平自动伸缩工作原理
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* cluster-proportional-autoscaler 应用独立于 DNS service 部署。
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* autoscaler Pod 运行一个客户端，它通过轮询 Kubernetes API server 获取集群中节点和核心的数量。
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* 一个期望的副本数会被计算，并根据当前可调度的节点、核心数、给定伸缩参数，被应用到 DNS 后端。
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* 伸缩参数和数据点会基于一个 ConfigMap 来提供给 autoscaler，它会在每次轮询时刷新它的参数表，以与最近期望的伸缩参数保持一致。
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* 允许对伸缩参数进行修改，而不需要重建或重启 autoscaler Pod。
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* autoscaler 提供了一个控制器接口来支持两种控制模式：*linear* 和 *ladder*。
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<!--
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## Future enhancements
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Control patterns, in addition to linear and ladder, that consider custom metrics
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are under consideration as a future development.
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Scaling of DNS backends based on DNS-specific metrics is under consideration as
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a future development. The current implementation, which uses the number of nodes
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and cores in cluster, is limited.
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Support for custom metrics, similar to that provided by
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[Horizontal Pod Autoscaling](/docs/tasks/run-application/horizontal-pod-autoscale/),
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is under consideration as a future development.
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||||
-->
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## 未来功能增强
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|
||||
控制模式，除了 linear 和 ladder，正在考虑未来将开发自定义 metric。
|
||||
|
||||
基于 DNS 特定 metric 的 DNS 后端的伸缩，考虑未来会开发。当前实现是使用集群中节点和核心的数量是受限制的。
|
||||
|
||||
支持自定义 metric，类似于 [Horizontal Pod 自动伸缩](/docs/tasks/run-application/horizontal-pod-autoscale/) 所提供的，考虑未来进行开发。
|
||||
|
||||
{{% /capture %}}
|
||||
|
||||
{{% capture whatsnext %}}
|
||||
<!--
|
||||
* Learn more about the
|
||||
[implementation of cluster-proportional-autoscaler](https://github.com/kubernetes-incubator/cluster-proportional-autoscaler).
|
||||
-->
|
||||
* 了解更多关于 [cluster-proportional-autoscaler 实现](https://github.com/kubernetes-incubator/cluster-proportional-autoscaler)的相关信息。
|
||||
{{% /capture %}}
|
||||
Reference in New Issue
Block a user