In modern web development, it is common to interact with external APIs to fetch data for our applications. However, it is important to handle these requests in a controlled manner to prevent abuse or excessive usage. Two techniques commonly used to control the rate of API requests are rate limiting and throttling.

Rate limiting sets a maximum number of requests that can be made within a certain time frame, while throttling imposes a delay between consecutive requests. In this blog post, we will explore how to implement rate limiting and throttling in a Redux Toolkit application.

Rate Limiting

To implement rate limiting in Redux Toolkit, we will use a middleware called redux-thunk. This middleware allows us to write asynchronous actions, which is necessary to control the rate of API requests. Let’s assume we have an action creator to fetch data from an API:

import { createAsyncThunk } from '@reduxjs/toolkit';
import axios from 'axios';

export const fetchUserData = createAsyncThunk('user/fetchUserData', async () => {
  const response = await axios.get('/api/userData');
  return response.data;
});

To add rate limiting to this action, we can use a library like p-limit to restrict the number of concurrent requests. Install p-limit using npm or yarn:

npm install p-limit

Then, create a rate limiting middleware:

import pLimit from 'p-limit';

const limit = pLimit(5); // Allow 5 concurrent requests

const rateLimiterMiddleware = ({ dispatch }) => (next) => async (action) => {
  if (action.type === 'user/fetchUserData') {
    return limit(() => next(action));
  }

  return next(action);
};

In this example, we limit the number of concurrent requests for the fetchUserData action to 5. If there are already 5 requests in progress, the middleware will queue subsequent requests until a slot becomes available.

Finally, apply the rate limiting middleware to your store configuration:

import { configureStore, getDefaultMiddleware } from '@reduxjs/toolkit';

const store = configureStore({
  middleware: [...getDefaultMiddleware(), rateLimiterMiddleware]
});

Now, when multiple fetchUserData actions are dispatched simultaneously, the middleware will ensure that no more than 5 requests are sent at a time.

Throttling

To implement throttling in Redux Toolkit, we can again utilize the redux-thunk middleware and modify our action creator. Instead of limiting the number of requests, we will introduce a delay between consecutive requests.

import { createAsyncThunk } from '@reduxjs/toolkit';
import axios from 'axios';

export const fetchUserData = createAsyncThunk('user/fetchUserData', async () => {
  await new Promise((resolve) => setTimeout(resolve, 1000)); // Introduce a 1 second delay
  const response = await axios.get('/api/userData');
  return response.data;
});

By introducing a setTimeout with a specified delay, we can control the rate at which the requests are made. In this example, we have introduced a 1-second delay.

Remember to apply the redux-thunk middleware to your store configuration as mentioned earlier.

Conclusion

Rate limiting and throttling are important techniques to control the rate of API requests in Redux Toolkit applications. By using the redux-thunk middleware, we can easily implement these techniques and ensure that our applications interact with external APIs in a controlled manner.