如何在 Python 中使用 Vultr 托管数据库进行缓存

baishitou 06-29 0

介绍

Redis® 是一种内存数据存储，提供灵活的数据结构、高性能和按需可扩展性。Vultr Managed Database for Caching 为任务关键型应用程序提供高可用性、高吞吐量和低延迟。本指南介绍如何在 Python 中使用 Vultr Managed Database for Caching 创建高可用性应用程序。

先决条件

准备工作：

购买用于缓存的 Vultr 托管数据库
购买 Vultr Linux 服务器以用作开发计算机
使用 SSH 以非 root 用户身份访问服务器

设置 Python 开发环境

要将 Vultr Managed Database for Caching 集成到 Python 应用程序，请安装 Python 模块并设置示例项目目录来存储应用程序文件。redis

升级 Python 包管理器。pip
```
 $ pip install --upgrade pip
```
安装 Python 驱动程序以连接到 Redis® 数据库。redis
```
 $ pip install redis
```
创建一个新目录。project
```
 $ mkdir project
```
导航到新目录。project
```
 $ cd project
```

创建 Redis® 网关类

要在 Python 应用程序文件中使用 Vultr Managed Database for Caching 连接，请创建一个连接到数据库的中央 Python 模块。然后，可以通过在应用程序中使用子句声明数据库模块来重用该模块。按照以下步骤创建 Redis® 连接模块import

使用 Vim 等文本编辑器创建一个新文件redis_gateway.py
```
 $ nano redis_gateway.py
```
将以下代码添加到文件中。将、和值替换为正确的 Vultr Managed Database for Caching 详细信息vultr-prod-abcd.vultrdb.com16752example-password
```
 import redis

 class RedisGateway:

     def __init__(self):

         r_host = 'vultr-prod-abcd.vultrdb.com'
         r_port = 16752
         r_pass = 'example-password'

         self.r_client = redis.Redis(
             host     = r_host, 
             port     = r_port, 
             password = r_pass, 
             ssl      = 'true'
         )
```
保存并关闭文件

上面的 Python 应用程序代码使用方法声明一个类。每次创建类的实例时，都会执行此方法。然后，它使用该函数连接到 Redis® 数据库。RedisGateway__init__(self)RedisGatewayself.r_client = redis.Redis(...)

要将 Redis® 数据库模块导入到其他 Python 源代码文件，请使用以下声明：
```
 import redis_gateway 

 r_gateway = redis_gateway.RedisGateway() 
 r_client  = r_gateway.r_client
```

实现 Redis® 字符串

在 Redis® 中，字符串是字节序列，是最常用的数据类型。您可以使用字符串数据类型来存储会话 ID、用户密码、产品信息和静态 HTML 内容。要在 Redis® 服务器中创建密钥，请使用关键字。若要检索键值，请使用关键字。在本节中，创建一个 Python 应用程序来实现 Redis® 字符串，如下所述。setget

创建新文件redis_strings.py
```
 $ nano redis_strings.py
```
将以下内容添加到文件中
```
 import redis_gateway 

 r_gateway = redis_gateway.RedisGateway() 
 r_client  = r_gateway.r_client

 r_key   = "john_doe"
 r_value = "example-password"

 r_client.set(r_key, r_value)   

 print("...\r\n You've successfully set the Redis key.\r\n")

 if r_client.exists(r_key): 

     r_value = r_client.get(r_key).decode("utf-8")

     print("The value for the " + r_key + " key is " + r_value + "\r\n ...")
```
Save and close the file.

The above application file imports the module you created earlier, then:redis_gateway
- r_key: Defines the name of the string key you're setting in the Redis® database
- r_value: Defines the Redis® key value
- r_client.set(r_key, r_value): Sets the key in the Redis® database
- if r_client.exists(r_key): Verifies whether the key exists in the Redis® database server before retrieving it to avoid run time errors
- r_client.get(r_key).decode("utf-8"): Retrieves the key from the Redis® database
Run the Redis® strings application file
```
 $ python3 redis_strings.py
```
Output:
```
 ...
  You've successfully set the Redis key.

 The value for the john_doe key is example-password
  ...
```
As displayed in the above output, Python correctly connects to the Redis® database and sets the value for the string key .example-passwordjohn_doe

Implement Redis® Lists

A Redis® list is an ordered collection of strings used to implement queueing mechanisms. Redis® allows you to add elements to the head or tail of a list using the and commands. Create a new Python application to test the Redis® Lists functionality as described below.lpushrpush

Create a new fileredis_lists.py
```
 $ nano redis_lists.py
```

Add the following contents to the file

 import redis_gateway
 import json

 r_gateway = redis_gateway.RedisGateway() 
 r_client  = r_gateway.r_client

 r_list   = "sample_customer_job_list"

 sample_job_1 = {
     "firstName": "JOHN",
     "lastName": "DOE",
     "email": "john_doe@example.com"
 }

 sample_job_2 = {
     "firstName": "MARY",
     "lastName": "SMITH",
     "email": "mary_smith@example.com"
 }

 r_list_value_1  = json.dumps(sample_job_1)
 r_list_value_2  = json.dumps(sample_job_2)

 r_client.lpush(r_list, r_list_value_1, r_list_value_2) 

 print("...\r\n You've successfully added a customer registration jobs to the Redis list.\r\n...")

 while(r_client.llen(r_list) != 0):

     print("The values for the " + r_list + "\r\n...")

     print(r_client.lpop(r_list).decode("utf-8") + "\r\n...")

Save and close the file.

Below is what the above application code does:

The variable represents the key of your sample Redis® list.r_list
sample_job_1 = {...} and are sample list values.sample_job_1 = {...}
The function inserts the two sample jobs into the Redis® listr_client.lpush(r_list, r_list_value_1, r_list_value_2)
The loop queries the Redis® server and iterates through the variable to print the list valueswhile(r_client.llen(r_list) != 0):r_list

Run the application fileredis_lists.py

 $ python3 redis_lists.py

Output:

 ...
  You've successfully added a customer registration jobs to the Redis list.
 ...
 The values for the sample_customer_job_list
 ...
 {"firstName": "MARY", "lastName": "SMITH", "email": "mary_smith@example.com"}
 ...
 The values for the sample_customer_job_list
 ...
 {"firstName": "JOHN", "lastName": "DOE", "email": "john_doe@example.com"}
 ...

Implement Redis® Hashes

Redis® hashes are record types that map keys to value pairs. Implement Redis® hashes in the form of company data in a Python application as described below.

Create a new fileredis_hash.py
```
 $ nano redis_hash.py
```

Add the following contents to the file

 import redis_gateway
 import json

 r_gateway = redis_gateway.RedisGateway() 
 r_client  = r_gateway.r_client

 r_hash = "company_profile"

 r_client.hset(r_hash, "company_name", "XYZ COMPANY")
 r_client.hset(r_hash, "add_line_1", "123 SAMPLE STREET")
 r_client.hset(r_hash, "add_line_2", "APT BUILDING")
 r_client.hset(r_hash, "county", "3RD COUNTY")
 r_client.hset(r_hash, "city", "SUN CITY")
 r_client.hset(r_hash, "zip", "123456")

 print("...\r\nYou've successfully set a company profile.\r\n...")

 print("Company profile information \r\n" )

 print(json.dumps(str(r_client.hgetall(r_hash)))) 

 print("Company Name : " + r_client.hget(r_hash, "company_name").decode("utf-8"))

Save and close the file.

In the above application:

The variable represents the hash key in the Redis® database.r_hash
The function sets a hash in the Redis server. This function is the same as:r_client.hset(r_hash, "company_name", "XYZ COMPANY")
```
  company_profile['company_name'] =  "XYZ COMPANY"
```
r_client.hgetall(r_hash): Retrieves all key-value pairs for a given hash
r_client.hget(r_hash, "company_name"): Retrieves the value of a given key in the hash

Run the application

 $ python3 redis_hash.py

Output:

 ...
 You've successfully set a company profile.
 ...
 Company profile information

 "{b'company_name': b'XYZ COMPANY', b'add_line_1': b'123 SAMPLE STREET', b'add_line_2': b'APT BUILDING', b'county': b'3RD COUNTY', b'city': b'SUN CITY', b'zip': b'123456'}"
 Company Name : XYZ COMPANY

Implement Redis® Sorted Sets

Sorted sets represent a collection of strings arranged by an associated score. An element can only appear once in a sorted set. Redis® offers the and functions for adding and retrieving sorted sets values. Implement these functions in a Python application as described below.zaddzrange

Create a new fileredis_sorted_set.py
```
 $ nano redis_sorted_set.py
```

Add the following contents to the file

 import redis_gateway
 import json

 r_gateway = redis_gateway.RedisGateway() 
 r_client  = r_gateway.r_client

 r_sorted_set = "database_ratings"

 database_scores = {
     'MySQL': 1, 
     'PostgreSQl': 2,
     'SQLite': 3,
     'MongoDB': 4 
 }

 r_client.zadd(r_sorted_set, database_scores)

 print("...\r\nYou've successfully entered four database ratings.\r\n...")

 print("Database rating information: \r\n")

 print(r_client.zrange(r_sorted_set, 0, 3))

Save and close the file.

In the above application:

r_sorted_set: Declares a key for the sorted set
database_scores = {...}: Contains four elements with a matching score
r_client.zadd(r_sorted_set, database_scores): Adds the set elements to the Redis® server
r_client.zrange(r_sorted_set, 0, 3): Returns all sorted set values from the database

Run the application

 $ python3 redis_sorted_set.py

Output:

 ...
 You've successfully entered four database ratings.
 ...
 Database rating information:

 [b'MySQL', b'PostgreSQl', b'SQLite', b'MongoDB']

结语

在本指南中，您已使用 Vultr Managed Database for Caching with Python 实现了不同的数据类型。根据您的应用程序用例，实现相关的 Redis® 数据类型以在数据库中缓存和存储数据。