an example of thundering horde and mitigation steps with react

thundering_horde.md

A thundering herd problem in React, where multiple components simultaneously fetch the same data, can be a major issue. To mitigate this, especially when using useEffect with a large, complex dependency array, you should avoid fetching data directly in components that are re-rendered frequently. A better approach is to centralize your data fetching logic.

1. Data Fetching Outside of Components

The best way to prevent the thundering herd problem is to move your fetching logic out of the component tree entirely. This ensures that the data is fetched only once, regardless of how many times the components that depend on it re-render.

• Custom Hooks: Create a custom hook that fetches and manages the data state. This hook can have its own internal state to prevent multiple fetches.
• Centralized State Management: Use a state management library like Redux, Zustand, or a similar pattern with React Context to manage the global state of your application. The fetch request is initiated from an action creator or a central store, and the data is then made available to all components.

2. Debouncing and Throttling

While not a complete solution, you can use debouncing or throttling to limit the number of times a fetch request is made. This is particularly useful for user-driven events, such as a search input.

• Debouncing: Debouncing waits until a certain amount of time has passed since the last event before calling the function. This is helpful for things like search bars, where you don't want to make an API call for every keystroke.

• Throttling: Throttling ensures that a function is called only once within a specified period, regardless of how many times the event is triggered. This is useful for events like window resizing or scrolling.

3. Caching and SWR (Stale-While-Revalidate)

One of the most effective solutions is to implement caching at the client level. . Libraries like React Query and SWR (Stale-While-Revalidate) are built specifically for this purpose.

SWR: This strategy first returns the data from the cache (stale), then sends a fetch request to revalidate the data, and finally updates the UI with the fresh data.

React Query: It provides powerful tools for caching, data synchronization, and managing the state of asynchronous data. It significantly reduces the number of duplicate requests, handles retries, and can even prefetch data to make the user experience feel instant.

How to Implement Centralized Fetching with a Custom Hook

Here is an example of a simple custom hook to centralize fetching and avoid redundant requests. JavaScript

import { useState, useEffect } from 'react';

const API_URL = 'https://api.example.com/data';

// A cache object to store fetched data
const cache = {};

export const useFetch = (key) => {
  const [data, setData] = useState(cache[key] || null);
  const [isLoading, setIsLoading] = useState(!cache[key]);

  useEffect(() => {
    if (!cache[key]) {
      const fetchData = async () => {
        try {
          const response = await fetch(API_URL);
          const result = await response.json();
          cache[key] = result;
          setData(result);
        } catch (error) {
          console.error('Fetch failed:', error);
        } finally {
          setIsLoading(false);
        }
      };
      fetchData();
    }
  }, [key]);

  return { data, isLoading };
};

This hook checks a local cache before making a network request. If the data is in the cache, it's returned immediately. Otherwise, a single fetch request is made, and the result is stored for future use.