440 lines
16 KiB
Markdown
440 lines
16 KiB
Markdown
---
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title: "示例：使用 StatefulSet 部署 Cassandra"
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content_type: tutorial
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weight: 30
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---
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<!--
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title: "Example: Deploying Cassandra with a StatefulSet"
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reviewers:
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- ahmetb
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content_type: tutorial
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weight: 30
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-->
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<!-- overview -->
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<!--
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This tutorial shows you how to run [Apache Cassandra](https://cassandra.apache.org/) on Kubernetes.
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Cassandra, a database, needs persistent storage to provide data durability (application _state_).
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In this example, a custom Cassandra seed provider lets the database discover new Cassandra instances as they join the Cassandra cluster.
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-->
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本教程描述拉如何在 Kubernetes 上运行 [Apache Cassandra](https://cassandra.apache.org/)。
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数据库 Cassandra 需要永久性存储提供数据持久性（应用 _状态_）。
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在此示例中，自定义 Cassandra seed provider 使数据库在加入 Cassandra 集群时发现新的 Cassandra 实例。
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<!--
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*StatefulSets* make it easier to deploy stateful applications into your Kubernetes cluster.
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For more information on the features used in this tutorial, see
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[StatefulSet](/docs/concepts/workloads/controllers/statefulset/).
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-->
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使用 *StatefulSets* 可以更轻松地将有状态的应用程序部署到你的 Kubernetes 集群中。
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有关本教程中使用的功能的更多信息，
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参阅 [StatefulSet](/zh/docs/concepts/workloads/controllers/statefulset/)。
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<!--
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Cassandra and Kubernetes both use the term _node_ to mean a member of a cluster. In this
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tutorial, the Pods that belong to the StatefulSet are Cassandra nodes and are members
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of the Cassandra cluster (called a _ring_). When those Pods run in your Kubernetes cluster,
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the Kubernetes control plane schedules those Pods onto Kubernetes
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{{< glossary_tooltip text="Nodes" term_id="node" >}}.
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-->
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{{< note >}}
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Cassandra 和 Kubernetes 都使用术语 _node_ 来表示集群的成员。
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在本教程中，属于 StatefulSet 的 Pod 是 Cassandra 节点，并且是 Cassandra 集群的成员（称为 _ring_）。
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当这些 Pod 在你的 Kubernetes 集群中运行时，Kubernetes 控制平面会将这些 Pod 调度到 Kubernetes 的
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{{< glossary_tooltip text="节点" term_id="node" >}}上。
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<!--
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When a Cassandra node starts, it uses a _seed list_ to bootstrap discovery of other
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nodes in the ring.
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This tutorial deploys a custom Cassandra seed provider that lets the database discover
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new Cassandra Pods as they appear inside your Kubernetes cluster.
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-->
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当 Cassandra 节点启动时，使用 _seed列表_ 来引导发现 ring 中其他节点。
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本教程部署了一个自定义的 Cassandra seed provider，使数据库可以发现新的 Cassandra Pod 出现在 Kubernetes 集群中。
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{{< /note >}}
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## {{% heading "objectives" %}}
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<!--
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* Create and validate a Cassandra headless {{< glossary_tooltip text="Service" term_id="service" >}}.
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* Use a {{< glossary_tooltip term_id="StatefulSet" >}} to create a Cassandra ring.
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* Validate the StatefulSet.
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* Modify the StatefulSet.
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* Delete the StatefulSet and its {{< glossary_tooltip text="Pods" term_id="pod" >}}.
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-->
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* 创建并验证 Cassandra 无头（headless）{{< glossary_tooltip text="Service" term_id="service" >}}..
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* 使用 {{< glossary_tooltip term_id="StatefulSet" >}} 创建一个 Cassandra ring。
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* 验证 StatefulSet。
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* 修改 StatefulSet。
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* 删除 StatefulSet 及其 {{< glossary_tooltip text="Pod" term_id="pod" >}}.
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## {{% heading "prerequisites" %}}
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{{< include "task-tutorial-prereqs.md" >}}
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<!--
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To complete this tutorial, you should already have a basic familiarity with
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{{< glossary_tooltip text="Pods" term_id="pod" >}},
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{{< glossary_tooltip text="Services" term_id="service" >}}, and
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{{< glossary_tooltip text="StatefulSets" term_id="StatefulSet" >}}.
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-->
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要完成本教程，你应该已经熟悉 {{< glossary_tooltip text="Pod" term_id="pod" >}}，
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{{< glossary_tooltip text="Service" term_id="service" >}}和 {{< glossary_tooltip text="StatefulSet" term_id="StatefulSet" >}}。
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<!--
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### Additional Minikube setup instructions
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{{< caution >}}
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[Minikube](https://minikube.sigs.k8s.io/docs/) defaults to 1024MiB of memory and 1 CPU.
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Running Minikube with the default resource configuration results in insufficient resource
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errors during this tutorial. To avoid these errors, start Minikube with the following settings:
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-->
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### 额外的 Minikube 设置说明
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{{< caution >}}
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[Minikube](https://minikube.sigs.k8s.io/docs/)默认为 1024MiB 内存和 1 个 CPU。
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在本教程中，使用默认资源配置运行 Minikube 会导致资源不足的错误。为避免这些错误，请使用以下设置启动 Minikube：
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```shell
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minikube start --memory 5120 --cpus=4
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```
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{{< /caution >}}
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<!-- lessoncontent -->
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<!--
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## Creating a headless Service for Cassandra {#creating-a-cassandra-headless-service}
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In Kubernetes, a {{< glossary_tooltip text="Service" term_id="service" >}} describes a set of
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{{< glossary_tooltip text="Pods" term_id="pod" >}} that perform the same task.
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The following Service is used for DNS lookups between Cassandra Pods and clients within your cluster:
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Create a Service to track all Cassandra StatefulSet members from the `cassandra-service.yaml` file:
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-->
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## 为 Cassandra 创建无头（headless） Services {#creating-a-cassandra-headless-service}
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在 Kubernetes 中，一个 {{< glossary_tooltip text="Service" term_id="service" >}}
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描述了一组执行相同任务的 {{< glossary_tooltip text="Pod" term_id="pod" >}}。
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以下 Service 用于在 Cassandra Pod 和集群中的客户端之间进行 DNS 查找：
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{{< codenew file="application/cassandra/cassandra-service.yaml" >}}
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创建一个 Service 来跟踪 `cassandra-service.yaml` 文件中的所有 Cassandra StatefulSet：
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```shell
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kubectl apply -f https://k8s.io/examples/application/cassandra/cassandra-service.yaml
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```
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<!--
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### Validating (optional) {#validating}
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Get the Cassandra Service.
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-->
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### 验证(可选) {#validating}
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获取 Cassandra Service。
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```shell
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kubectl get svc cassandra
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```
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<!--
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The response is
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-->
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响应是：
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```
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NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
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cassandra ClusterIP None <none> 9042/TCP 45s
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```
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<!--
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If you don't see a Service named `cassandra`, that means creation failed. Read
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[Debug Services](/docs/tasks/debug-application-cluster/debug-service/)
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for help troubleshooting common issues.
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-->
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如果没有看到名为 `cassandra` 的服务，则表示创建失败。
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请阅读[Debug Services](/zh/docs/tasks/debug-application-cluster/debug-service/)，以解决常见问题。
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<!--
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## Using a StatefulSet to create a Cassandra ring
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The StatefulSet manifest, included below, creates a Cassandra ring that consists of three Pods.
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{{< note >}}
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This example uses the default provisioner for Minikube.
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Please update the following StatefulSet for the cloud you are working with.
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{{< /note >}}
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-->
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## 使用 StatefulSet 创建 Cassandra Ring
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下面包含的 StatefulSet 清单创建了一个由三个 Pod 组成的 Cassandra ring。
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{{< note >}}
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本示例使用 Minikube 的默认配置程序。
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请为正在使用的云更新以下 StatefulSet。
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{{< /note >}}
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{{< codenew file="application/cassandra/cassandra-statefulset.yaml" >}}
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<!--
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Create the Cassandra StatefulSet from the `cassandra-statefulset.yaml` file:
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-->
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使用 `cassandra-statefulset.yaml` 文件创建 Cassandra StatefulSet ：
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```shell
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# 如果你能未经修改地 apply cassandra-statefulset.yaml，请使用此命令
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kubectl apply -f https://k8s.io/examples/application/cassandra/cassandra-statefulset.yaml
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```
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<!--
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If you need to modify `cassandra-statefulset.yaml` to suit your cluster, download
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https://k8s.io/examples/application/cassandra/cassandra-statefulset.yaml and then apply
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that manifest, from the folder you saved the modified version into:
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-->
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如果你为了适合你的集群需要修改 `cassandra-statefulset.yaml`，
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下载 https://k8s.io/examples/application/cassandra/cassandra-statefulset.yaml，
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然后 apply 修改后的清单。
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```shell
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# 如果使用本地的 cassandra-statefulset.yaml ，请使用此命令
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kubectl apply -f cassandra-statefulset.yaml
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```
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<!--
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## Validating the Cassandra StatefulSet
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1. Get the Cassandra StatefulSet:
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-->
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## 验证 Cassandra StatefulSet
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1.获取 Cassandra StatefulSet:
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```shell
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kubectl get statefulset cassandra
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```
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<!--
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The response should be similar to:
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-->
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响应应该与此类似：
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```
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NAME DESIRED CURRENT AGE
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cassandra 3 0 13s
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```
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<!--
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The `StatefulSet` resource deploys Pods sequentially.
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1. Get the Pods to see the ordered creation status:
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-->
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`StatefulSet` 资源会按顺序部署 Pod。
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2.获取 Pod 查看已排序的创建状态：
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```shell
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kubectl get pods -l="app=cassandra"
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```
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<!--
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The response should be similar to:
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-->
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响应应该与此类似：
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```shell
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NAME READY STATUS RESTARTS AGE
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cassandra-0 1/1 Running 0 1m
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cassandra-1 0/1 ContainerCreating 0 8s
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```
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<!--
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It can take several minutes for all three Pods to deploy. Once they are deployed, the same command
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returns output similar to:
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-->
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这三个 Pod 要花几分钟的时间才能部署。部署之后，相同的命令将返回类似于以下的输出：
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```
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NAME READY STATUS RESTARTS AGE
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cassandra-0 1/1 Running 0 10m
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cassandra-1 1/1 Running 0 9m
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cassandra-2 1/1 Running 0 8m
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```
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<!--
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3. Run the Cassandra [nodetool](https://cwiki.apache.org/confluence/display/CASSANDRA2/NodeTool) inside the first Pod, to
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display the status of the ring.
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-->
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3.运行第一个 Pod 中的 Cassandra [nodetool](https://cwiki.apache.org/confluence/display/CASSANDRA2/NodeTool)，以显示 ring 的状态。
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```shell
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kubectl exec -it cassandra-0 -- nodetool status
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```
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<!--
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The response should be similar to:
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-->
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响应应该与此类似：
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```
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Datacenter: DC1-K8Demo
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======================
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Status=Up/Down
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|/ State=Normal/Leaving/Joining/Moving
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-- Address Load Tokens Owns (effective) Host ID Rack
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UN 172.17.0.5 83.57 KiB 32 74.0% e2dd09e6-d9d3-477e-96c5-45094c08db0f Rack1-K8Demo
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UN 172.17.0.4 101.04 KiB 32 58.8% f89d6835-3a42-4419-92b3-0e62cae1479c Rack1-K8Demo
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UN 172.17.0.6 84.74 KiB 32 67.1% a6a1e8c2-3dc5-4417-b1a0-26507af2aaad Rack1-K8Demo
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```
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<!--
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## Modifying the Cassandra StatefulSet
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Use `kubectl edit` to modify the size of a Cassandra StatefulSet.
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1. Run the following command:
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-->
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## 修改 Cassandra StatefulSet
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使用 `kubectl edit` 修改 Cassandra StatefulSet 的大小。
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1.运行以下命令：
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```shell
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kubectl edit statefulset cassandra
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```
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<!--
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This command opens an editor in your terminal. The line you need to change is the `replicas` field.
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The following sample is an excerpt of the StatefulSet file:
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-->
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此命令你的终端中打开一个编辑器。需要更改的是 `replicas` 字段。下面是 StatefulSet 文件的片段示例：
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```yaml
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# Please edit the object below. Lines beginning with a '#' will be ignored,
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# and an empty file will abort the edit. If an error occurs while saving this file will be
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# reopened with the relevant failures.
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#
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apiVersion: apps/v1
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kind: StatefulSet
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metadata:
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creationTimestamp: 2016-08-13T18:40:58Z
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generation: 1
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labels:
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app: cassandra
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name: cassandra
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namespace: default
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resourceVersion: "323"
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uid: 7a219483-6185-11e6-a910-42010a8a0fc0
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spec:
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replicas: 3
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```
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<!--
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1. Change the number of replicas to 4, and then save the manifest.
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The StatefulSet now scales to run with 4 Pods.
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1. Get the Cassandra StatefulSet to verify your change:
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-->
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2.将副本数 (replicas) 更改为 4，然后保存清单。
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StatefulSet 现在可以扩展到运行 4 个 Pod。
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3.获取 Cassandra StatefulSet 验证更改：
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```shell
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kubectl get statefulset cassandra
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```
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<!--
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The response should be similar to:
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-->
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响应应该与此类似：
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```
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NAME DESIRED CURRENT AGE
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cassandra 4 4 36m
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```
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## {{% heading "cleanup" %}}
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<!--
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Deleting or scaling a StatefulSet down does not delete the volumes associated with the StatefulSet.
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This setting is for your safety because your data is more valuable than automatically purging all related StatefulSet resources.
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{{< warning >}}
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Depending on the storage class and reclaim policy, deleting the *PersistentVolumeClaims* may cause the associated volumes
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to also be deleted. Never assume you'll be able to access data if its volume claims are deleted.
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{{< /warning >}}
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1. Run the following commands (chained together into a single command) to delete everything in the Cassandra StatefulSet:
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-->
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删除或缩小 StatefulSet 不会删除与 StatefulSet 关联的卷。
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这个设置是出于安全考虑，因为你的数据比自动清除所有相关的 StatefulSet 资源更有价值。
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{{< warning >}}
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根据存储类和回收策略，删除 *PersistentVolumeClaims* 可能导致关联的卷也被删除。
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千万不要认为其容量声明被删除，你就能访问数据。
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{{< /warning >}}
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1.运行以下命令（连在一起成为一个单独的命令）删除 Cassandra StatefulSet 中的所有内容：
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```shell
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grace=$(kubectl get pod cassandra-0 -o=jsonpath='{.spec.terminationGracePeriodSeconds}') \
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&& kubectl delete statefulset -l app=cassandra \
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&& echo "Sleeping ${grace} seconds" 1>&2 \
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&& sleep $grace \
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&& kubectl delete persistentvolumeclaim -l app=cassandra
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```
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<!--
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1. Run the following command to delete the Service you set up for Cassandra:
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-->
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2.运行以下命令，删除你为 Cassandra 设置的 Service：
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```shell
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kubectl delete service -l app=cassandra
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```
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<!--
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## Cassandra container environment variables
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The Pods in this tutorial use the [`gcr.io/google-samples/cassandra:v13`](https://github.com/kubernetes/examples/blob/master/cassandra/image/Dockerfile)
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image from Google's [container registry](https://cloud.google.com/container-registry/docs/).
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The Docker image above is based on [debian-base](https://github.com/kubernetes/kubernetes/tree/master/build/debian-base)
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and includes OpenJDK 8.
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This image includes a standard Cassandra installation from the Apache Debian repo.
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By using environment variables you can change values that are inserted into `cassandra.yaml`.
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-->
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## Cassandra 容器环境变量
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本教程中的 Pod 使用来自 Google [container registry](https://cloud.google.com/container-registry/docs/)
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的 [`gcr.io/google-samples/cassandra:v13`](https://github.com/kubernetes/examples/blob/master/cassandra/image/Dockerfile) 镜像。
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上面的 Docker 镜像基于 [debian-base](https://github.com/kubernetes/kubernetes/tree/master/build/debian-base)，并且包含 OpenJDK 8。
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该映像包括来自 Apache Debian 存储库的标准 Cassandra 安装。
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通过使用环境变量，您可以更改插入到 `cassandra.yaml` 中的值。
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| Environment variable | Default value |
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| ------------------------ |:---------------: |
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| `CASSANDRA_CLUSTER_NAME` | `'Test Cluster'` |
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| `CASSANDRA_NUM_TOKENS` | `32` |
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| `CASSANDRA_RPC_ADDRESS` | `0.0.0.0` |
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## {{% heading "whatsnext" %}}
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<!--
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* Learn how to [Scale a StatefulSet](/docs/tasks/run-application/scale-stateful-set/).
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* Learn more about the [*KubernetesSeedProvider*](https://github.com/kubernetes/examples/blob/master/cassandra/java/src/main/java/io/k8s/cassandra/KubernetesSeedProvider.java)
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* See more custom [Seed Provider Configurations](https://git.k8s.io/examples/cassandra/java/README.md)
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-->
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* 了解如何[扩缩 StatefulSet](/docs/tasks/run-application/scale-stateful-set/)。
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* 了解有关 [*KubernetesSeedProvider*](https://github.com/kubernetes/examples/blob/master/cassandra/java/src/main/java/io/k8s/cassandra/KubernetesSeedProvider.java) 的更多信息
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* 查看更多自定义 [Seed Provider Configurations](https://git.k8s.io/examples/cassandra/java/README.md)
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