What is Throttling, when why and how to use it?

Throttling is a technique used to limit the rate or frequency at which a client can access a particular service or API. It involves controlling the number of requests a client can make over a specific period of time to prevent overloading the server or network and ensure a stable and reliable user experience.

There are various reasons why throttling might be necessary. Some of the most common include:

1. To prevent DDoS attacks: By limiting the number of requests that can be made from a particular IP address, it can help protect against distributed denial of service (DDoS) attacks.
2. To manage server load: Limiting the rate of incoming requests can help manage server load and ensure that resources are allocated effectively.
3. To protect user data: Throttling can be used to prevent brute force attacks, where a hacker attempts to gain unauthorized access by repeatedly submitting login requests.
4. To ensure fair usage: Throttling can ensure that all users have fair access to a service or API by preventing a small number of clients from consuming an excessive amount of resources.

There are several ways to implement throttling, including:

1. Client-side throttling: This involves implementing throttling on the client side, typically by setting a delay between requests. This can be useful for low-level operations or when you have control over the client application.
2. Server-side throttling: This involves implementing throttling on the server side, typically using middleware or API management tools. This can be more effective for larger scale operations or when you have less control over the client application.
3. Network throttling: This involves controlling the rate of data transfer across a network, typically by limiting the bandwidth available to a particular client.

To use throttling in DRF, you need to configure the throttling classes and rates in your Django settings file. For example, you might set the following configuration to limit anonymous clients to 100 requests per day and authenticated clients to 1000 requests per day:

REST_FRAMEWORK = {
    'DEFAULT_THROTTLE_CLASSES': [
        'rest_framework.throttling.AnonRateThrottle',
        'rest_framework.throttling.UserRateThrottle',
    ],
    'DEFAULT_THROTTLE_RATES': {
        'anon': '100/day',
        'user': '1000/day',
    }
}

You can also create your own custom throttling classes by subclassing BaseThrottle and implementing the allow_request and wait methods. This allows you to implement more complex throttling rules, such as rate limiting based on the type or frequency of requests.

In summary, throttling in DRF is a powerful way to control access to your API and prevent overloading the server. By setting throttling limits, you can ensure fair usage for all clients and improve the performance and reliability of your API.