Knowledgebase

Introduction

Redis is an in-memory data store that offers a flexible data structure, high performance, and on-demand scalability. A Rcs Managed Database for Redis offers high availability, a high throughput, and low latency for mission-critical applications. This guide explains how to use a Rcs Managed Database for Redis in Python to create highly available applications.

Prerequisites

Before you begin:

• Deploy a Rcs Managed Database for Redis
• Deploy a Rcs Linux server to use as the development machine
• Using SSH, access the server as a non-root user

Set Up the Python Development Environment

To integrate a Rcs Managed Database for Redis to your Python application, install the Python redis module and set up a sample project directory to store the application files.

1. Upgrade the Python pip package manager

    $ pip install --upgrade pip

2. Install the Python redis driver to connect to the Redis database

    $ pip install redis

3. Create a new project directory.

    $ mkdir project

4. Navigate to the new project directory.

    $ cd project

Create the Redis Gateway Class

To use your Rcs Managed Database for Redis connection in your Python application files, create a central Python module that connects to the database. You can then reuse the module by declaring the database module using the import clause in your application. Follow the steps below to create the Redis connection module

1. Using a text editor such as Vim, create a new redis_gateway.py file

    $ nano redis_gateway.py

2. Add the following code to the file. Replace the vultr-prod-abcd.vultrdb.com, 16752, and example-password values with your correct Rcs Managed Database for Redis details

    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'
            )

   Save and close the file

   The above Python application code declares a RedisGateway class with an __init__(self) method. This method executes every time you create an instance of the RedisGateway class. Then, it connects to the Redis database using the self.r_client = redis.Redis(...) function.

   To import the Redis database module to other Python source code files, use the following declarations:

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

Implement Redis Strings

In Redis, a string is a sequence of bytes and it's the most used data type. You can use the string data type to store session IDs, user passwords, product information, and static HTML content. To create a key in a Redis server, use the set keyword. To retrieve a key value, use the get keyword. In this section, create a Python application to implement Redis strings as described below.

1. Create a new redis_strings.py file

    $ nano redis_strings.py

2. Add the following contents to the file

    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 redis_gateway module you created earlier, then:

   • 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

3. 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 example-password for the string key john_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 lpush and rpush commands. Create a new Python application to test the Redis Lists functionality as described below.

1. Create a new redis_lists.py file

    $ nano redis_lists.py

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

3. Run the redis_lists.py application file

    $ 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.

1. Create a new redis_hash.py file

    $ nano redis_hash.py

2. 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 r_hash variable represents the hash key in the Redis database.

   • The r_client.hset(r_hash, "company_name", "XYZ COMPANY") function sets a hash in the Redis server. This function is the same as:

       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

3. 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 zadd and zrange functions for adding and retrieving sorted sets values. Implement these functions in a Python application as described below.

1. Create a new redis_sorted_set.py file

    $ nano redis_sorted_set.py

2. 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

3. 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']

Conclusion

In this guide, you have implemented different data types using a Rcs Managed Database for Redis with Python. Based on your application use case, implement the relevant Redis data type to cache and store data in your database.

Next Steps

To integrate more solutions using your Rcs Managed Database for Redis, visit the following resources:

• Authenticate a Python Application with Rcs Managed Databases for PostgreSQL and Redis.
• How to Cache MySQL Data with Redis and Node.js.
• How to Manage PHP Session Data With Redis On Ubuntu 20.04.
• Create a Redis Leaderboard with Golang.