Qiming Teng
73ed1da84a
Fixed some inaccuracies, removed texts that disappear from English version, resync revised contents.
418 lines
12 KiB
Markdown
418 lines
12 KiB
Markdown
---
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title: 自动扩缩集群 DNS 服务
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content_type: task
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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_type: task
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-->
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<!-- 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 服务的自动扩缩功能。
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## {{% heading "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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* 本指南假设你的节点使用 AMD64 或 Intel 64 CPU 架构
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* 确保已启用 [DNS 功能](/zh/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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<!-- 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 水平自动扩缩特性已经启用 {#determining-whether-dns-horizontal-autoscaling-is-already-enabled}
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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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```
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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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```
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如果在输出中看到 “dns-autoscaler”，说明 DNS 水平自动扩缩已经启用，可以跳到
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[调优自动扩缩参数](#tuning-autoscaling-parameters)。
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<!--
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## Getting the name of your DNS Deployment {#find-scaling-target}
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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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-->
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## 获取 DNS Deployment 的名称 {#find-scaling-target}
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列出集群内 kube-system 名字空间中的 DNS Deployment：
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```shell
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kubectl get deployment -l k8s-app=kube-dns --namespace=kube-system
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```
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输出类似如下这样：
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```
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NAME READY 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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```
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<!--
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If you don't see a Deployment for DNS services, you can also look for it by name:
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-->
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如果看不到 DNS 服务的 Deployment，你也可以通过名字来查找：
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```shell
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kubectl get deployment --namespace=kube-system
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```
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<!--
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and look for a deployment named `coredns` or `kube-dns`.
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-->
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并在输出中寻找名称为 `coredns` 或 `kube-dns` 的 Deployment。
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<!--
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Your scale target is:
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-->
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你的扩缩目标为：
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```
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Deployment/<your-deployment-name>
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```
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<!--
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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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-->
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其中 `<your-deployment-name>` 是 DNS Deployment 的名称。
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例如，如果你的 DNS Deployment 名称是 `coredns`，则你的扩展目标是 Deployment/coredns。
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<!--
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CoreDNS is the default DNS service for Kubernetes. CoreDNS sets the label
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`k8s-app=kube-dns` so that it can work in clusters that originally used
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kube-dns.
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-->
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{{< note >}}
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CoreDNS 是 Kubernetes 的默认 DNS 服务。CoreDNS 设置标签 `k8s-app=kube-dns`，
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以便能够在原来使用 `kube-dns` 的集群中工作。
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{{< /note >}}
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<!--
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## Enabling DNS horizontal autoscaling {#enablng-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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-->
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## 启用 DNS 水平自动扩缩 {#enablng-dns-horizontal-autoscaling}
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在本节，我们创建一个 Deployment。Deployment 中的 Pod 运行一个基于
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`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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<!--
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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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-->
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在文件中，将 `<SCALE_TARGET>` 替换成扩缩目标。
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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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<!--
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The output of a successful command is:
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-->
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一个成功的命令输出是：
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```
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deployment.apps/dns-autoscaler created
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```
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<!--
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DNS horizontal autoscaling is now enabled.
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-->
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DNS 水平自动扩缩在已经启用了。
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<!--
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## Tuning autoscaling parameters {#tuning-autoscaling-parameters}
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Verify that the dns-autoscaler {{< glossary_tooltip text="ConfigMap" term_id="configmap" >}} exists:
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-->
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## 调优自动扩缩参数 {#tuning-autoscaling-parameters}
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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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<!--
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The output is similar to this:
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-->
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输出类似于：
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```
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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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```
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<!--
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Modify the data in the ConfigMap:
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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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<!--
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Look for this line:
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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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<!--
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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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-->
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根据需要修改对应的字段。“min” 字段表明 DNS 后端的最小数量。
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实际后端的数量通过使用如下公式来计算：
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```
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replicas = max( ceil( cores * 1/coresPerReplica ) , ceil( nodes * 1/nodesPerReplica ) )
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```
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<!--
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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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注意 `coresPerReplica` 和 `nodesPerReplica` 的值都是整数。
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背后的思想是，当一个集群使用具有很多核心的节点时，由 `coresPerReplica` 来控制。
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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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其它的扩缩模式也是支持的，详情查看
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[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 水平自动扩缩
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有几个可供调优的 DNS 水平自动扩缩选项。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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-->
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### 选项 1：缩容 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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<!-- The output is: -->
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输出如下所示：
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```
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deployment.apps/dns-autoscaler scaled
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```
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<!--
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Verify that the replica count is zero:
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-->
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验证当前副本数为 0：
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```shell
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kubectl get rs --namespace=kube-system
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```
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<!--
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The output displays 0 in the DESIRED and CURRENT columns:
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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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```
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NAME DESIRED CURRENT READY AGE
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...
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dns-autoscaler-6b59789fc8 0 0 0 ...
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...
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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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-->
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### 选项 2：删除 dns-autoscaler Deployment
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如果 dns-autoscaler 为你所控制，也就说没有人会去重新创建它，可以选择此选项：
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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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输出内容如下所示：
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```
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deployment.apps "dns-autoscaler" deleted
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```
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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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-->
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### 选项 3：从主控节点删除 dns-autoscaler 清单文件
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如果 dns-autoscaler 在[插件管理器](https://git.k8s.io/kubernetes/cluster/addons/README.md)
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的控制之下，并且具有操作 master 节点的写权限，可以使用此选项。
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<!--
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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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-->
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登录到主控节点，删除对应的清单文件。
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dns-autoscaler 对应的路径一般为：
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```
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/etc/kubernetes/addons/dns-horizontal-autoscaler/dns-horizontal-autoscaler.yaml
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```
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<!--
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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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当清单文件被删除后，插件管理器将删除 dns-autoscaler Deployment。
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<!-- discussion -->
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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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-->
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## 理解 DNS 水平自动扩缩工作原理
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* cluster-proportional-autoscaler 应用独立于 DNS 服务部署。
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* autoscaler Pod 运行一个客户端，它通过轮询 Kubernetes API 服务器获取集群中节点和核心的数量。
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<!--
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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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-->
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* 系统会基于当前可调度的节点个数、核心数以及所给的扩缩参数，计算期望的副本数并应用到 DNS 后端。
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* 扩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，
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以与最近期望的扩缩参数保持一致。
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<!--
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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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* 扩缩参数是可以被修改的，而且不需要重建或重启 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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## {{% heading "whatsnext" %}}
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<!--
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* Read about [Guaranteed Scheduling For Critical Add-On Pods](/docs/tasks/administer-cluster/guaranteed-scheduling-critical-addon-pods/).
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* Learn more about the
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[implementation of cluster-proportional-autoscaler](https://github.com/kubernetes-incubator/cluster-proportional-autoscaler).
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-->
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* 阅读[为关键插件 Pod 提供的调度保障](/zh/docs/tasks/administer-cluster/guaranteed-scheduling-critical-addon-pods/)
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* 进一步了解 [cluster-proportional-autoscaler 实现](https://github.com/kubernetes-incubator/cluster-proportional-autoscaler)
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