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Merge pull request #23077 from tengqm/zh-rework-stateful
[zh] Rework stateful application tasks
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‎content/zh/docs/tasks/run-application/run-single-instance-stateful-application.md

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---
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title: 运行一个单实例有状态应用
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content_type: tutorial
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weight: 20
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---
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<!-- overview -->
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本文介绍在 Kubernetes 中使用 PersistentVolume 和 Deployment 如何运行一个单实例有状态应用. 该应用是 MySQL.
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<!--
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This page shows you how to run a single-instance stateful application
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in Kubernetes using a PersistentVolume and a Deployment. The
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application is MySQL.
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-->
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本文介绍在 Kubernetes 中如何使用 PersistentVolume 和 Deployment 运行一个单实例有状态应用。该应用是 MySQL.
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## {{% heading "objectives" %}}
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* 在环境中通过磁盘创建一个PersistentVolume.
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* 创建一个MySQL Deployment.
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* 在集群内以一个已知的 DNS 名将 MySQL 暴露给其他 pods.
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<!--
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* Create a PersistentVolume referencing a disk in your environment.
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* Create a MySQL Deployment.
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* Expose MySQL to other pods in the cluster at a known DNS name.
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-->
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* 在你的环境中创建一个引用磁盘的 PersistentVolume
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* 创建一个 MySQL Deployment.
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* 在集群内以一个已知的 DNS 名称将 MySQL 暴露给其他 Pod
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## {{% heading "prerequisites" %}}
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* {{< include "task-tutorial-prereqs.md" >}} {{< version-check >}}
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* {{< include "default-storage-class-prereqs.md" >}}
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<!-- lessoncontent -->
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## 部署MySQL
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注意: 在配置的 yaml 文件中定义密码的做法是不安全的. 具体安全解决方案请参考
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[Kubernetes Secrets](/docs/concepts/configuration/secret/).
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## 部署 MySQL {#deploy-mysql}
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<!--
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You can run a stateful application by creating a Kubernetes Deployment
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and connecting it to an existing PersistentVolume using a
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PersistentVolumeClaim. For example, this YAML file describes a
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Deployment that runs MySQL and references the PersistentVolumeClaim. The file
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defines a volume mount for /var/lib/mysql, and then creates a
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PersistentVolumeClaim that looks for a 20G volume. This claim is
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satisfied by any existing volume that meets the requirements,
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or by a dynamic provisioner.
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-->
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你可以通过创建一个 Kubernetes Deployment 并使用 PersistentVolumeClaim 将其连接到
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某已有的 PV 卷来运行一个有状态的应用。
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例如，这里的 YAML 描述的是一个运行 MySQL 的 Deployment，其中引用了 PVC 申领。
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文件为 /var/lib/mysql 定义了加载卷，并创建了一个 PVC 申领，寻找一个 20G 大小的卷。
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该申领可以通过现有的满足需求的卷来满足，也可以通过动态供应卷的机制来满足。
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<!--
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Note: The password is defined in the config yaml, and this is insecure. See
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[Kubernetes Secrets](/docs/concepts/configuration/secret/)
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for a secure solution.
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-->
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注意：在配置的 YAML 文件中定义密码的做法是不安全的。具体安全解决方案请参考
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[Kubernetes Secrets](/zh/docs/concepts/configuration/secret/).
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{{< codenew file="application/mysql/mysql-deployment.yaml" >}}
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{{< codenew file="application/mysql/mysql-pv.yaml" >}}
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1. 部署 YAML 文件中定义的 PV 和 PVC：
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kubectl apply -f https://k8s.io/examples/application/mysql/mysql-pv.yaml
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1. 部署 YAML 文件中定义的 Deployment：
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kubectl apply -f https://k8s.io/examples/application/mysql/mysql-deployment.yaml
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1. 展示 Deployment 相关信息:
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kubectl describe deployment mysql
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Name: mysql
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Namespace: default
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CreationTimestamp: Tue, 01 Nov 2016 11:18:45 -0700
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Labels: app=mysql
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Annotations: deployment.kubernetes.io/revision=1
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Selector: app=mysql
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Replicas: 1 desired | 1 updated | 1 total | 0 available | 1 unavailable
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StrategyType: Recreate
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MinReadySeconds: 0
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Pod Template:
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Labels: app=mysql
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Containers:
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mysql:
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Image: mysql:5.6
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Port: 3306/TCP
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Environment:
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MYSQL_ROOT_PASSWORD: password
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Mounts:
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/var/lib/mysql from mysql-persistent-storage (rw)
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Volumes:
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mysql-persistent-storage:
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Type: PersistentVolumeClaim (a reference to a PersistentVolumeClaim in the same namespace)
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ClaimName: mysql-pv-claim
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ReadOnly: false
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Conditions:
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Type Status Reason
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---- ------ ------
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Available False MinimumReplicasUnavailable
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Progressing True ReplicaSetUpdated
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OldReplicaSets: <none>
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NewReplicaSet: mysql-63082529 (1/1 replicas created)
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Events:
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FirstSeen LastSeen Count From SubobjectPath Type Reason Message
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--------- -------- ----- ---- ------------- -------- ------ -------
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33s 33s 1 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set mysql-63082529 to 1
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1. 列举出 Deployment 创建的 pods:
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kubectl get pods -l app=mysql
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NAME READY STATUS RESTARTS AGE
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mysql-63082529-2z3ki 1/1 Running 0 3m
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1. 查看 PersistentVolumeClaim:
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kubectl describe pvc mysql-pv-claim
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Name: mysql-pv-claim
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Namespace: default
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StorageClass:
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Status: Bound
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Volume: mysql-pv-volume
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Labels: <none>
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Annotations: pv.kubernetes.io/bind-completed=yes
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pv.kubernetes.io/bound-by-controller=yes
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Capacity: 20Gi
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Access Modes: RWO
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Events: <none>
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## 访问 MySQL 实例
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前面 YAML 文件中创建了一个允许集群内其他 pods 访问数据库的服务. 该服务中选项
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`clusterIP: None` 让服务 DNS 名称直接解析为 Pod 的 IP 地址. 当在一个服务下只有一个 pod
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并且不打算增加 pods 的数量这是最好的.
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1. <!--Deploy the PV and PVC of the YAML file-->
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部署 YAML 文件中定义的 PV 和 PVC：
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```shell
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kubectl apply -f https://k8s.io/examples/application/mysql/mysql-pv.yaml
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```
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1. <!-- Deploy the contents of the YAML file -->
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部署 YAML 文件中定义的 Deployment：
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```shell
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kubectl apply -f https://k8s.io/examples/application/mysql/mysql-deployment.yaml
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```
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1. <!-- Display information about the Deployment -->
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展示 Deployment 相关信息:
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```shell
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kubectl describe deployment mysql
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```
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```
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Name: mysql
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Namespace: default
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CreationTimestamp: Tue, 01 Nov 2016 11:18:45 -0700
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Labels: app=mysql
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Annotations: deployment.kubernetes.io/revision=1
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Selector: app=mysql
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Replicas: 1 desired | 1 updated | 1 total | 0 available | 1 unavailable
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StrategyType: Recreate
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MinReadySeconds: 0
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Pod Template:
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Labels: app=mysql
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Containers:
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mysql:
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Image: mysql:5.6
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Port: 3306/TCP
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Environment:
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MYSQL_ROOT_PASSWORD: password
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Mounts:
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/var/lib/mysql from mysql-persistent-storage (rw)
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Volumes:
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mysql-persistent-storage:
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Type: PersistentVolumeClaim (a reference to a PersistentVolumeClaim in the same namespace)
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ClaimName: mysql-pv-claim
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ReadOnly: false
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Conditions:
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Type Status Reason
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---- ------ ------
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Available False MinimumReplicasUnavailable
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Progressing True ReplicaSetUpdated
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OldReplicaSets: <none>
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NewReplicaSet: mysql-63082529 (1/1 replicas created)
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Events:
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FirstSeen LastSeen Count From SubobjectPath Type Reason Message
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--------- -------- ----- ---- ------------- -------- ------ -------
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33s 33s 1 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set mysql-63082529 to 1
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```
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1. <!-- List the pods created by the Deployment -->
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列举出 Deployment 创建的 pods:
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```shell
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kubectl get pods -l app=mysql
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```
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```
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NAME READY STATUS RESTARTS AGE
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mysql-63082529-2z3ki 1/1 Running 0 3m
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```
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1. <!-- Inspect the PersistentVolumeClaim -->
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查看 PersistentVolumeClaim：
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```shell
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kubectl describe pvc mysql-pv-claim
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```
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```
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Name: mysql-pv-claim
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Namespace: default
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StorageClass:
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Status: Bound
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Volume: mysql-pv-volume
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Labels: <none>
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Annotations: pv.kubernetes.io/bind-completed=yes
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pv.kubernetes.io/bound-by-controller=yes
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Capacity: 20Gi
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Access Modes: RWO
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Events: <none>
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```
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<!--
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## Accessing the MySQL instance
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The preceding YAML file creates a service that
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allows other Pods in the cluster to access the database. The Service option
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`clusterIP: None` lets the Service DNS name resolve directly to the
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Pod's IP address. This is optimal when you have only one Pod
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behind a Service and you don't intend to increase the number of Pods.
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Run a MySQL client to connect to the server:
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-->
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## 访问 MySQL 实例 {#accessing-the-mysql-instance}
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前面 YAML 文件中创建了一个允许集群内其他 Pod 访问的数据库服务。该服务中选项
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`clusterIP: None` 让服务 DNS 名称直接解析为 Pod 的 IP 地址。
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当在一个服务下只有一个 Pod 并且不打算增加 Pod 的数量这是最好的.
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运行 MySQL 客户端以连接到服务器:
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```
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kubectl run -it --rm --image=mysql:5.6 --restart=Never mysql-client -- mysql -h mysql -ppassword
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```
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此命令在集群内创建一个新的 Pod 并运行 MySQL 客户端,并通过 Service 将其连接到服务器.如果连接成功,你就知道有状态的 MySQL 数据库正处于运行状态.
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<!--
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This command creates a new Pod in the cluster running a MySQL client
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and connects it to the server through the Service. If it connects, you
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know your stateful MySQL database is up and running.
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-->
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此命令在集群内创建一个新的 Pod 并运行 MySQL 客户端，并通过 Service 连接到服务器。
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如果连接成功，你就知道有状态的 MySQL 数据库正处于运行状态。
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```
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Waiting for pod default/mysql-client-274442439-zyp6i to be running, status is Pending, pod ready: false
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mysql>
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```
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## 更新
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<!--
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## Updating
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The image or any other part of the Deployment can be updated as usual
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with the `kubectl apply` command. Here are some precautions that are
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specific to stateful apps:
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-->
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## 更新 {#updating}
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Deployment 中镜像或其他部分同往常一样可以通过 `kubectl apply` 命令更新. 以下是
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特定于有状态应用的一些注意事项:
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Deployment 中镜像或其他部分同往常一样可以通过 `kubectl apply` 命令更新。
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以下是特定于有状态应用的一些注意事项:
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* 不要弹性伸缩. 弹性伸缩仅适用于单实例应用. 下层的 PersistentVolume 仅只能挂载一个 pod. 对于集群级有状态应用, 请参考 StatefulSet 文档
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<!--
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* Don't scale the app. This setup is for single-instance apps
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only. The underlying PersistentVolume can only be mounted to one
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Pod. For clustered stateful apps, see the
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[StatefulSet documentation](/docs/concepts/workloads/controllers/statefulset/).
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* 在 Deployment 的 YAML 文件中使用 `strategy:` `type: Recreate` . 该选项指示 Kubernetes 不使用滚动升级. 滚动升级将无法工作, 由于一次不能运行多个 pod. 在更新配置文件
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创建一个新的 pod 前 `Recreate` 策略将先停止第一个 pod.
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## 删除 Deployment
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* Use `strategy:` `type: Recreate` in the Deployment configuration
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YAML file. This instructs Kubernetes to _not_ use rolling
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updates. Rolling updates will not work, as you cannot have more than
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one Pod running at a time. The `Recreate` strategy will stop the
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first pod before creating a new one with the updated configuration.
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-->
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* 不要对应用进行规模扩缩。这里的设置仅适用于单实例应用。下层的 PersistentVolume
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仅只能挂载到一个 Pod 上。对于集群级有状态应用，请参考
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[StatefulSet 文档](/zh/docs/concepts/workloads/controllers/statefulset/).
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* 在 Deployment 的 YAML 文件中使用 `strategy:` `type: Recreate`。
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该选项指示 Kubernetes _不_ 使用滚动升级。滚动升级无法工作，因为这里一次不能
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运行多个 Pod。在使用更新的配置文件创建新的 Pod 前，`Recreate` 策略将
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保证先停止第一个 Pod。
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<!--
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## Deleting a deployment
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Delete the deployed objects by name:
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-->
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## 删除 Deployment {#deleting-a-deployment}
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通过名称删除部署的对象:
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kubectl delete pv mysql-pv-volume
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```
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如果通过手动的方式分配 PersistentVolume, 那么也需要手动的删除它，以及释放下层资源.
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如果是用过动态分配 PersistentVolume 的方式，在删除 PersistentVolumeClaim 后 PersistentVolume 将被自动的删除. 一些存储服务(比如 EBS 和 PD)也会在 PersistentVolume 被删除时自动回收下层资源.
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<!--
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If you manually provisioned a PersistentVolume, you also need to manually
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delete it, as well as release the underlying resource.
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If you used a dynamic provisioner, it automatically deletes the
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PersistentVolume when it sees that you deleted the PersistentVolumeClaim.
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Some dynamic provisioners (such as those for EBS and PD) also release the
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underlying resource upon deleting the PersistentVolume.
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-->
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如果通过手动的方式供应 PersistentVolume, 那么也需要手动删除它以释放下层资源。
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如果是用动态供应方式创建的 PersistentVolume，在删除 PersistentVolumeClaim 后
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PersistentVolume 将被自动删除。
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一些存储服务（比如 EBS 和 PD）也会在 PersistentVolume 被删除时自动回收下层资源。
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## {{% heading "whatsnext" %}}
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<!--
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* Learn more about [Deployment objects](/docs/concepts/workloads/controllers/deployment/).
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* 了解更多 Deployment 对象请参考 [Deployment objects](/docs/concepts/workloads/controllers/deployment/).
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* 了解更多 Deployment 应用请参考 [Deploying applications](/docs/user-guide/deploying-applications/)
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* Learn more about [Deploying applications](/docs/tasks/run-application/run-stateless-application-deployment/)
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* kubectl run 文档请参考[kubectl run documentation](/docs/reference/generated/kubectl/kubectl-commands/#run)
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* [kubectl run documentation](/docs/reference/generated/kubectl/kubectl-commands/#run)
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* 卷和持久卷请参考 [Volumes](/docs/concepts/storage/volumes/) 和 [Persistent Volumes](/docs/concepts/storage/persistent-volumes/)
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* [Volumes](/docs/concepts/storage/volumes/) and [Persistent Volumes](/docs/concepts/storage/persistent-volumes/)
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-->
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* 欲进一步了解 Deployment 对象，请参考 [Deployment 对象](/zh/docs/concepts/workloads/controllers/deployment/)
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* 进一步了解[部署应用](/zh/docs/tasks/run-application/run-stateless-application-deployment/)
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* 参阅 [kubectl run 文档](/docs/reference/generated/kubectl/kubectl-commands/#run)
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* 参阅[卷](/zh/docs/concepts/storage/volumes/)和[持久卷](/zh/docs/concepts/storage/persistent-volumes/)
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