问卷链接（https://www.wjx.cn/jq/9714648...）
作者：Alkin Tezuysal
Django是Python应用程序开发人员常用的框架。它包含的包可以简化授权和内容管理等任务。Django支持包括MySQL在内的许多数据库，这使得不需要修改应用程序代码就可以在Vitess上运行Django应用程序。让我们看看如何结合这两个开放源码框架的优点。
我们使用Vitess操作器构建这个示例。你可以在这篇博客文章中看到Vitess操作器实现的细节。
先决条件
- 本地Python环境（3.X）
- Kubernetes环境（minikube、GKE）
- 通过Vitess支持Django ORM
在本例中，我们将在GKE使用一个现有的Kubernetes集群。你也可以通过本地的minikube来完成此操作。
我们使用的Django示例是“天气应用程序”。我们首先使用提供的配置启动vitess操作器。
以下部分包括这些步骤：
- 创建Vitess操作器pod
- 构建Vitess集群组件（1x主tablet、1x复制tablet、3x etcd pod、1x vtgate、1x vtctld、1x vitessbackup）
- 创建“weatherapp”数据库模式和用户。
$ kubectl apply -f operator.yaml
customresourcedefinition.apiextensions.k8s.io/etcdlockservers.planetscale.com created
customresourcedefinition.apiextensions.k8s.io/vitessbackups.planetscale.com created
customresourcedefinition.apiextensions.k8s.io/vitessbackupstorages.planetscale.com created
customresourcedefinition.apiextensions.k8s.io/vitesscells.planetscale.com created
customresourcedefinition.apiextensions.k8s.io/vitessclusters.planetscale.com created
customresourcedefinition.apiextensions.k8s.io/vitesskeyspaces.planetscale.com created
customresourcedefinition.apiextensions.k8s.io/vitessshards.planetscale.com created
serviceaccount/vitess-operator created
role.rbac.authorization.k8s.io/vitess-operator created
rolebinding.rbac.authorization.k8s.io/vitess-operator created
priorityclass.scheduling.k8s.io/vitess created
priorityclass.scheduling.k8s.io/vitess-operator-control-plane created
deployment.apps/vitess-operator created
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
vitess-operator-7f9c9d58f6-q5zlf 1/1 Running 0 20s用一个名为“weatherapp”的示例数据库初始化这个集群，访问它的用户/密码将嵌入到配置文件中。我们基本上是在创建一个数据库，类似于Vitess中的密钥空间。
$ kubectl apply -f 101_initial_cluster.yaml.django
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
example-90089e05-vitessbackupstorage-subcontroller 1/1 Running 0 94s
example-etcd-faf13de3-1 1/1 Running 0 94s
example-etcd-faf13de3-2 1/1 Running 0 94s
example-etcd-faf13de3-3 1/1 Running 0 94s
example-vttablet-zone1-1542279354-edf1c7bf 2/3 Running 1 94s
example-vttablet-zone1-3763665199-476cbd65 2/3 Running 2 94s
example-weatherapp-x-x-vtbackup-init-75efaeeb 0/1 Completed 0 74s
example-zone1-vtctld-1d4dcad0-67bfd56b8b-4dr9s 1/1 Running 2 94s
example-zone1-vtgate-bc6cde92-59b88bc8d8-6wz86 1/1 Running 2 94s
vitess-operator-7f9c9d58f6-q5zlf 1/1 Running 0 4m30s如你所见，这将带来一个功能齐全的托管Vitess集群，其中包含一个未分片的密钥空间，其中包括一个“主”和一个“副本”。
步骤1 - 设置portforward
$ cat pf.sh ; ./pf.sh &
#!/bin/sh
kubectl port-forward --address localhost "$(kubectl get service --selector="planetscale.com/component=vtctld" -o name | head -n1)" 15000 15999 &
process_id1=$!
kubectl port-forward --address localhost "$(kubectl get service --selector="planetscale.com/component=vtgate,!planetscale.com/cell" -o name | head -n1)" 15306:3306 &
process_id2=$!
sleep 2
echo "You may point your browser to http://localhost:15000, use the following aliases as shortcuts:"
echo 'alias vtctlclient="vtctlclient -server=localhost:15999 -logtostderr"'
echo 'alias mysql="mysql -h 127.0.0.1 -P 15306 -u user"'
echo "Hit Ctrl-C to stop the port forwards"
wait $process_id1
wait $process_id2检查Tablets：
$ vtctlclient ListAllTablets
Handling connection for 15999
zone1-1542279354 weatherapp - replica 10.100.1.75:15000 10.100.1.75:3306 []
zone1-3763665199 weatherapp - master 10.100.3.57:15000 10.100.3.57:3306 [] 2020-10-16T09:06:59Z 步骤2 - 验证数据库
$ alias mysql="mysql -h 127.0.0.1 -P 15306 -u djangouser -p"
$ mysql
mysql: [Warning] Using a password on the command line interface can be insecure.
Handling connection for 15306
Welcome to the MySQL monitor. Commands end with ; or g.
Your MySQL connection id is 1
Server version: 5.7.9-Vitess MySQL Community Server (GPL)
Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or 'h' for help. Type 'c' to clear the current input statement.
mysql> show databases;
+------------+
| Databases |
+------------+
| weatherapp |
+------------+
1 row in set (0.16 sec)
步骤3 - 设置应用程序环境
现在我们已经设置了具有MySQL后端的Vitess集群，接下来可以构建Django应用程序了。我们将使用Django-admin命令构建一个Django项目。
$ mkdir my_weather_app
$ cd my_weather_app
$ python3 -m venv env
$ . env/bin/activate
(env) askdba:my_weather_app askdba$
$ pip install django
$ django-admin startproject weatherapp
$ cd weatherapp/
$ ls -la
total 8
drwxr-xr-x 4 askdba staff 128 Oct 16 12:19 .
drwxr-xr-x 4 askdba staff 128 Oct 16 12:18 ..
-rwxr-xr-x 1 askdba staff 666 Oct 16 12:18 manage.py
drwxr-xr-x 7 askdba staff 224 Oct 16 12:18 weatherapp
Edit configuration file and update following section.
$ vi weatherapp/settings.py [link to sample file]
import os
# Database
# https://docs.djangoproject.com/en/3.0/ref/settings/#databases
DATABASES = {
'default': {
'ENGINE': 'custom_db_backends.vitess',
'OPTIONS': {
'read_default_file': '/usr/local/mysql/my.cnf',
},
}
}
STATIC_ROOT = os.path.join(BASE_DIR, 'static')
...
# SECURITY WARNING: don't run with debug turned on in production!
DEBUG = True
ALLOWED_HOSTS = ['127.0.0.1']
# Application definition
...将customs_db_backends目录复制到项目目录。你可以将Vitess项目克隆到本地目录。
$ cp -r ~/vitess/support/django/custom_db_backends .
$ vi /usr/local/mysql/my.cnf [link to sample my.cnf]
[client]
database = weatherapp
user = djangouser
password = ********
port = 15306
host = 127.0.0.1
default-character-set = utf8mb4步骤4 - 安装MySQL客户端连接器
$ pip install mysqlclient
Collecting mysqlclient
Using cached mysqlclient-2.0.1.tar.gz (87 kB)
Using legacy 'setup.py install' for mysqlclient, since package 'wheel' is not installed.
Installing collected packages: mysqlclient
Running setup.py install for mysqlclient ... done
Successfully installed mysqlclient-2.0.1步骤5 - 在Vitess集群上构建Django框架
在这个阶段，我们已经准备好运行迁移来创建初始的Django元数据。
$ python manage.py migrate
Operations to perform:
Apply all migrations: admin, auth, contenttypes, sessions
Running migrations:
Applying contenttypes.0001_initial... OK
Applying auth.0001_initial... OK
Applying admin.0001_initial... OK
Applying admin.0002_logentry_remove_auto_add... OK
Applying admin.0003_logentry_add_action_flag_choices... OK
Applying contenttypes.0002_remove_content_type_name... OK
Applying auth.0002_alter_permission_name_max_length... OK
Applying auth.0003_alter_user_email_max_length... OK
Applying auth.0004_alter_user_username_opts... OK
Applying auth.0005_alter_user_last_login_null... OK
Applying auth.0006_require_contenttypes_0002... OK
Applying auth.0007_alter_validators_add_error_messages... OK
Applying auth.0008_alter_user_username_max_length... OK
Applying auth.0009_alter_user_last_name_max_length... OK
Applying auth.0010_alter_group_name_max_length... OK
Applying auth.0011_update_proxy_permissions... OK
Applying auth.0012_alter_user_first_name_max_length... OK
Applying sessions.0001_initial... OK步骤6 - 创建一个管理员用户
创建一个管理用户来访问Django管理界面。
$ python manage.py createsuperuser
Username (leave blank to use 'askdba'): askdba
Email address: [email protected]
Password:
Password (again):
The password is too similar to the email address.
This password is too short. It must contain at least 8 characters.
Bypass password validation and create user anyway? [y/N]: y
Superuser created successfully.
(env) askdba:weatherapp askdba$步骤7 - 启动Django守护进程
$ python manage.py runserver 127.0.0.1:8000
Watching for file changes with StatReloader
Performing system checks...
System check identified no issues (0 silenced).
October 16, 2020 - 09:37:02
Django version 3.1.2, using settings 'weatherapp.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CONTROL-C.步骤8 - 转到Django管理页面
将浏览器指向http://127.0.0.1:8000/admin
管理员登录界面
用户/角色管理屏幕
你可以通过这里继续构建应用程序。
总结
Vitess是一个非常强大的切分框架，它带有一个内置的控制平面，允许后端开发人员轻松地调整他们的应用程序。结合强大的应用程序框架（如Django），开发人员可以利用开源工具的强大功能，开箱即用地创建可伸缩的应用程序。
参考文献
How To Make a Django Blog App and Connect it to MySQL
Getting Started With Django: Build A Weather App
Django MySQL Notes
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