228 lines
7.6 KiB
Markdown
228 lines
7.6 KiB
Markdown
---
|
||
title: 运行一个单实例有状态应用
|
||
content_template: templates/tutorial
|
||
---
|
||
|
||
{{% capture overview %}}
|
||
|
||
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.
|
||
|
||
{{% /capture %}}
|
||
|
||
|
||
{{% capture objectives %}}
|
||
|
||
* 在环境中通过磁盘创建一个PersistentVolume.
|
||
* 创建一个MySQL Deployment.
|
||
* 在集群内以一个已知的DNS名将MySQL暴露给其他pods.
|
||
|
||
{{% /capture %}}
|
||
|
||
|
||
{{% capture prerequisites %}}
|
||
|
||
* {{< include "task-tutorial-prereqs.md" >}} {{< version-check >}}
|
||
|
||
* 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.
|
||
|
||
{{% /capture %}}
|
||
|
||
|
||
{{% capture lessoncontent %}}
|
||
|
||
## 在环境中设置一个磁盘
|
||
|
||
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:
|
||
|
||
```
|
||
gcloud compute disks create --size=20GB mysql-disk
|
||
```
|
||
|
||
|
||
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:
|
||
|
||
{{< code file="gce-volume.yaml" >}}
|
||
|
||
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
|
||
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/).
|
||
|
||
|
||
创建持久卷:
|
||
|
||
```
|
||
kubectl create -f https://k8s.io/docs/tasks/run-application/gce-volume.yaml
|
||
```
|
||
|
||
|
||
|
||
## 部署MySQL
|
||
|
||
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
|
||
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
|
||
何符合需求的卷来满足, 在本例中满足上面创建的卷.
|
||
|
||
|
||
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
|
||
[Kubernetes Secrets](/docs/concepts/configuration/secret/).
|
||
|
||
{{< code file="mysql-deployment.yaml" >}}
|
||
|
||
|
||
1. 部署YAML文件中定义的内容:
|
||
|
||
kubectl create -f https://k8s.io/docs/tasks/run-application/mysql-deployment.yaml
|
||
|
||
|
||
1. 展示Deployment相关信息:
|
||
|
||
kubectl describe deployment mysql
|
||
|
||
Name: mysql
|
||
Namespace: default
|
||
CreationTimestamp: Tue, 01 Nov 2016 11:18:45 -0700
|
||
Labels: app=mysql
|
||
Annotations: deployment.kubernetes.io/revision=1
|
||
Selector: app=mysql
|
||
Replicas: 1 desired | 1 updated | 1 total | 0 available | 1 unavailable
|
||
StrategyType: Recreate
|
||
MinReadySeconds: 0
|
||
Pod Template:
|
||
Labels: app=mysql
|
||
Containers:
|
||
mysql:
|
||
Image: mysql:5.6
|
||
Port: 3306/TCP
|
||
Environment:
|
||
MYSQL_ROOT_PASSWORD: password
|
||
Mounts:
|
||
/var/lib/mysql from mysql-persistent-storage (rw)
|
||
Volumes:
|
||
mysql-persistent-storage:
|
||
Type: PersistentVolumeClaim (a reference to a PersistentVolumeClaim in the same namespace)
|
||
ClaimName: mysql-pv-claim
|
||
ReadOnly: false
|
||
Conditions:
|
||
Type Status Reason
|
||
---- ------ ------
|
||
Available False MinimumReplicasUnavailable
|
||
Progressing True ReplicaSetUpdated
|
||
OldReplicaSets: <none>
|
||
NewReplicaSet: mysql-63082529 (1/1 replicas created)
|
||
Events:
|
||
FirstSeen LastSeen Count From SubobjectPath Type Reason Message
|
||
--------- -------- ----- ---- ------------- -------- ------ -------
|
||
33s 33s 1 {deployment-controller } Normal ScalingReplicaSet Scaled up replica set mysql-63082529 to 1
|
||
|
||
|
||
1. 列举出Deployment创建的pods:
|
||
|
||
kubectl get pods -l app=mysql
|
||
|
||
NAME READY STATUS RESTARTS AGE
|
||
mysql-63082529-2z3ki 1/1 Running 0 3m
|
||
|
||
|
||
1. 查看持久卷:
|
||
|
||
kubectl describe pv mysql-pv
|
||
|
||
Name: mysql-pv
|
||
Labels: <none>
|
||
Status: Bound
|
||
Claim: default/mysql-pv-claim
|
||
Reclaim Policy: Retain
|
||
Access Modes: RWO
|
||
Capacity: 20Gi
|
||
Message:
|
||
Source:
|
||
Type: GCEPersistentDisk (a Persistent Disk resource in Google Compute Engine)
|
||
PDName: mysql-disk
|
||
FSType: ext4
|
||
Partition: 0
|
||
ReadOnly: false
|
||
No events.
|
||
|
||
|
||
1. 查看PersistentVolumeClaim:
|
||
|
||
kubectl describe pvc mysql-pv-claim
|
||
|
||
Name: mysql-pv-claim
|
||
Namespace: default
|
||
Status: Bound
|
||
Volume: mysql-pv
|
||
Labels: <none>
|
||
Capacity: 20Gi
|
||
Access Modes: RWO
|
||
No events.
|
||
|
||
|
||
## 访问MySQL实例
|
||
|
||
|
||
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
|
||
`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
|
||
并且不打算增加pods的数量这是最好的.
|
||
|
||
|
||
运行MySQL客户端以连接到服务器:
|
||
|
||
```
|
||
kubectl run -it --rm --image=mysql:5.6 mysql-client -- mysql -h <pod-ip> -p <password>
|
||
```
|
||
|
||
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.
|
||
|
||
```
|
||
Waiting for pod default/mysql-client-274442439-zyp6i to be running, status is Pending, pod ready: false
|
||
If you don't see a command prompt, try pressing enter.
|
||
|
||
mysql>
|
||
```
|
||
|
||
## 更新
|
||
|
||
|
||
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
|
||
特定于有状态应用的一些注意事项:
|
||
|
||
* 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
|
||
[StatefulSet documentation](/docs/concepts/workloads/controllers/statefulset/).
|
||
* 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
|
||
创建一个新的pod前 `Recreate`策略将先停止第一个pod.
|
||
|
||
|
||
## 删除deployment
|
||
|
||
|
||
通过名称删除部署的对象:
|
||
|
||
```
|
||
kubectl delete deployment,svc mysql
|
||
kubectl delete pvc mysql-pv-claim
|
||
kubectl delete pv mysql-pv
|
||
```
|
||
|
||
如果使用Compute Engine磁盘，也可以使用如下命令:
|
||
|
||
```
|
||
gcloud compute disks delete mysql-disk
|
||
```
|
||
|
||
{{% /capture %}}
|
||
|
||
|
||
{{% capture whatsnext %}}
|
||
|
||
* 了解更多Deployment对象请参考 [Deployment objects](/docs/concepts/workloads/controllers/deployment/).
|
||
|
||
* 了解更多Deployment应用请参考 [Deploying applications](/docs/user-guide/deploying-applications/)
|
||
|
||
* kubectl run文档请参考[kubectl run documentation](/docs/user-guide/kubectl/v1.6/#run)
|
||
|
||
* 卷和持久卷请参考[Volumes](/docs/concepts/storage/volumes/) and [Persistent Volumes](/docs/concepts/storage/persistent-volumes/)
|
||
|
||
{{% /capture %}}
|
||
|
||
|