ZTE-SH-CN-run-application-run-single-instance-stateful-application-pr-2017-… (#5363)
* zte-run-application-run-single-instance-stateful-application-pr-2017-09-09 * ZTE-SH-CN-run-application-run-single-instance-stateful-application-pr-2017-09-12 * ZTE-SH-CN-run-application-run-single-instance-stateful-application-pr-2017-09-13 * ZTE-SH-CN-run-application-run-single-instance-stateful-application-pr-2017-09-14
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jianglingxia
Andrew Chen
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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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---
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{% capture 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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{% endcapture %}
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{% capture 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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{% endcapture %}
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{% capture prerequisites %}
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* {% include task-tutorial-prereqs.md %}
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* 为了数据持久性我们将在环境上通过磁盘创建一个持久卷. 环境支持的类型见这里[here](/docs/user-guide/persistent-volumes/#types-of-persistent-volumes). 本篇文档将介绍 `GCEPersistentDisk` . `GCEPersistentDisk`卷只能工作在Google Compute Engine平台上.
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{% endcapture %}
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{% capture lessoncontent %}
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## 在环境中设置一个磁盘
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你可以为有状态的应用使用任何类型的持久卷. 有关支持环境的磁盘列表，请参考持久卷类型[Types of Persistent Volumes](/docs/user-guide/persistent-volumes/#types-of-persistent-volumes). 对于Google Compute Engine, 请运行:
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```
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gcloud compute disks create --size=20GB mysql-disk
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```
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接下来创建一个指向刚创建的 `mysql-disk`磁盘的PersistentVolume. 下面是一个PersistentVolume的配置文件，它指向上面创建的Compute Engine磁盘:
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{% include code.html language="yaml" file="gce-volume.yaml" ghlink="/docs/tasks/run-application/gce-volume.yaml" %}
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注意`pdName: mysql-disk` 这行与Compute Engine环境中的磁盘名称相匹配. 有关为其
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他环境编写PersistentVolume配置文件的详细信息，请参见持久卷[Persistent Volumes](/docs/concepts/storage/persistent-volumes/).
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创建持久卷:
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```
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kubectl create -f https://k8s.io/docs/tasks/run-application/gce-volume.yaml
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```
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## 部署MySQL
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通过创建Kubernetes Deployment并使用PersistentVolumeClaim将其连接到现已存在的PersistentVolume上来运行一个有状态的应用. 例如, 下面这个YAML文件描述了一个运行MySQL
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并引用PersistentVolumeClaim的Deployment. 该文件定义了一个volume其挂载目录为/var/lib/mysql, 然后创建一个内存为20G的卷的PersistentVolumeClaim. 此申领可以通过任
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何符合需求的卷来满足, 在本例中满足上面创建的卷.
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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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{% include code.html language="yaml" file="mysql-deployment.yaml" ghlink="/docs/tasks/run-application/mysql-deployment.yaml" %}
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1. 部署YAML文件中定义的内容:
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kubectl create -f https://k8s.io/docs/tasks/run-application/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. 查看持久卷:
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kubectl describe pv mysql-pv
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Name: mysql-pv
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Labels: <none>
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Status: Bound
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Claim: default/mysql-pv-claim
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Reclaim Policy: Retain
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Access Modes: RWO
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Capacity: 20Gi
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Message:
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Source:
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Type: GCEPersistentDisk (a Persistent Disk resource in Google Compute Engine)
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PDName: mysql-disk
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FSType: ext4
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Partition: 0
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ReadOnly: false
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No events.
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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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Status: Bound
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Volume: mysql-pv
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Labels: <none>
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Capacity: 20Gi
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Access Modes: RWO
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No events.
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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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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 mysql-client -- mysql -h <pod-ip> -p <password>
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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,并通过服务将其连接到服务器.如果连接成功,你就知道有状态的MySQL database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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If you don't see a command prompt, try pressing enter.
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mysql>
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```
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## 更新
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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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* 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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[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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通过名称删除部署的对象:
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```
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kubectl delete deployment,svc mysql
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kubectl delete pvc mysql-pv-claim
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kubectl delete pv mysql-pv
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```
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如果使用Compute Engine磁盘，也可以使用如下命令:
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```
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gcloud compute disks delete mysql-disk
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```
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{% endcapture %}
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{% capture whatsnext %}
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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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* kubectl run文档请参考[kubectl run documentation](/docs/user-guide/kubectl/v1.6/#run)
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* 卷和持久卷请参考[Volumes](/docs/concepts/storage/volumes/) and [Persistent Volumes](/docs/concepts/storage/persistent-volumes/)
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{% endcapture %}
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{% include templates/tutorial.md %}
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