Explore how to prevent duplicate data fetching requests in React applications using Suspense and resource deduplication techniques for improved performance and efficiency.
React Suspense has revolutionized how we handle asynchronous data fetching in React applications. By allowing components to "suspend" rendering until their data is available, it provides a cleaner and more declarative approach compared to traditional loading state management. However, a common challenge arises when multiple components attempt to fetch the same resource concurrently, leading to duplicate requests and potential performance bottlenecks. This article explores the problem of duplicate requests in React Suspense and provides practical solutions using resource deduplication techniques.
Understanding the Problem: The Duplicate Request Scenario
Imagine a scenario where multiple components on a page need to display the same user profile data. Without proper management, each component might initiate its own request to fetch the user profile, resulting in redundant network calls. This wastes bandwidth, increases server load, and ultimately degrades the user experience.
Here's a simplified code example to illustrate the issue:
import React, { Suspense } from 'react';
const fetchUser = (userId) => {
console.log(`Fetching user with ID: ${userId}`); // Simulate network request
return new Promise(resolve => {
setTimeout(() => {
resolve({ id: userId, name: `User ${userId}`, email: `user${userId}@example.com` });
}, 1000); // Simulate network latency
});
};
const UserResource = (userId) => {
let promise = null;
let status = 'pending'; // pending, success, error
let result;
const suspender = fetchUser(userId).then(
(r) => {
status = 'success';
result = r;
},
(e) => {
status = 'error';
result = e;
}
);
return {
read() {
if (status === 'pending') {
throw suspender;
} else if (status === 'error') {
throw result;
}
return result;
},
};
};
const UserProfile = ({ userId }) => {
const user = UserResource(userId).read();
return (
In this example, both UserProfile and UserDetails components attempt to fetch the same user data using UserResource. If you run this code, you'll see that Fetching user with ID: 1 is logged twice, indicating two separate requests.
Resource Deduplication Techniques
To prevent duplicate requests, we can implement resource deduplication. This involves ensuring that only one request is made for a specific resource, and the result is shared among all components that need it. Several techniques can be used to achieve this.
1. Caching the Promise
The most straightforward approach is to cache the promise returned by the data fetching function. This ensures that if the same resource is requested again while the original request is still in flight, the existing promise is returned instead of creating a new one.
Here's how you can modify the UserResource to implement promise caching:
import React, { Suspense } from 'react';
const fetchUser = (userId) => {
console.log(`Fetching user with ID: ${userId}`); // Simulate network request
return new Promise(resolve => {
setTimeout(() => {
resolve({ id: userId, name: `User ${userId}`, email: `user${userId}@example.com` });
}, 1000); // Simulate network latency
});
};
const cache = {}; // Simple cache
const UserResource = (userId) => {
if (!cache[userId]) {
let promise = null;
let status = 'pending'; // pending, success, error
let result;
const suspender = fetchUser(userId).then(
(r) => {
status = 'success';
result = r;
},
(e) => {
status = 'error';
result = e;
}
);
cache[userId] = {
read() {
if (status === 'pending') {
throw suspender;
} else if (status === 'error') {
throw result;
}
return result;
},
};
}
return cache[userId];
};
const UserProfile = ({ userId }) => {
const user = UserResource(userId).read();
return (
Now, the UserResource checks if a resource already exists in the cache. If it does, the cached resource is returned. Otherwise, a new request is initiated, and the resulting promise is stored in the cache. This ensures that only one request is made for each unique userId.
2. Using a Dedicated Caching Library (e.g., `lru-cache`)
For more complex caching scenarios, consider using a dedicated caching library like lru-cache or similar. These libraries provide features like cache eviction based on Least Recently Used (LRU) or other policies, which can be crucial for managing memory usage, especially when dealing with a large number of resources.
First, install the library:
npm install lru-cache
Then, integrate it into your UserResource:
import React, { Suspense } from 'react';
import LRUCache from 'lru-cache';
const fetchUser = (userId) => {
console.log(`Fetching user with ID: ${userId}`); // Simulate network request
return new Promise(resolve => {
setTimeout(() => {
resolve({ id: userId, name: `User ${userId}`, email: `user${userId}@example.com` });
}, 1000); // Simulate network latency
});
};
const cache = new LRUCache({
max: 100, // Maximum number of items in the cache
ttl: 60000, // Time-to-live in milliseconds (1 minute)
});
const UserResource = (userId) => {
if (!cache.has(userId)) {
let promise = null;
let status = 'pending'; // pending, success, error
let result;
const suspender = fetchUser(userId).then(
(r) => {
status = 'success';
result = r;
cache.set(userId, {
read() {
return result;
},
});
},
(e) => {
status = 'error';
result = e;
cache.set(userId, {
read() {
throw result;
},
});
}
);
cache.set(userId, {
read() {
if (status === 'pending') {
throw suspender;
} else if (status === 'error') {
throw result;
}
return result;
}
});
}
return cache.get(userId);
};
const UserProfile = ({ userId }) => {
const user = UserResource(userId).read();
return (
This approach provides more control over the cache's size and expiration policy.
3. Request Coalescing with Libraries like `axios-extensions`
Libraries like axios-extensions offer more advanced features such as request coalescing. Request coalescing combines multiple identical requests into a single request, further optimizing network usage. This is particularly useful in scenarios where requests are initiated very close to each other in time.
First, install the library:
npm install axios axios-extensions
Then, configure Axios with the cache adapter provided by axios-extensions.
Example using `axios-extensions` and creating a resource:
import React, { Suspense } from 'react';
import axios from 'axios';
import { cacheAdapterEnhancer, throttleAdapterEnhancer } from 'axios-extensions';
const instance = axios.create({
baseURL: 'https://api.example.com', // Replace with your API endpoint
adapter: cacheAdapterEnhancer(axios.defaults.adapter, { enabledByDefault: true }),
});
const fetchUser = async (userId) => {
console.log(`Fetching user with ID: ${userId}`); // Simulate network request
const response = await instance.get(`/users/${userId}`);
return response.data;
};
const UserResource = (userId) => {
let promise = null;
let status = 'pending'; // pending, success, error
let result;
const suspender = fetchUser(userId).then(
(r) => {
status = 'success';
result = r;
},
(e) => {
status = 'error';
result = e;
}
);
return {
read() {
if (status === 'pending') {
throw suspender;
} else if (status === 'error') {
throw result;
}
return result;
},
};
};
const UserProfile = ({ userId }) => {
const user = UserResource(userId).read();
return (
This configures Axios to use a cache adapter, automatically caching responses based on the request configuration. The cacheAdapterEnhancer function provides options for configuring the cache, such as setting a maximum cache size or expiration time. throttleAdapterEnhancer can also be used to limit the number of requests made to the server within a certain time period, further optimizing performance.
Best Practices for Resource Deduplication
Centralize Resource Management: Create dedicated modules or services for managing resources. This promotes code reuse and makes it easier to implement deduplication strategies.
Use Unique Keys: Ensure that your caching keys are unique and accurately represent the resource being fetched. This is crucial for avoiding cache collisions.
Consider Cache Invalidation: Implement a mechanism for invalidating the cache when data changes. This ensures that your components always display the most up-to-date information. Common techniques include using webhooks or manually invalidating the cache when updates occur.
Monitor Cache Performance: Track cache hit rates and response times to identify potential performance bottlenecks. Adjust your caching strategy as needed to optimize performance.
Implement Error Handling: Ensure that your caching logic includes robust error handling. This prevents errors from propagating to your components and provides a better user experience. Consider strategies for retrying failed requests or displaying fallback content.
Use AbortController: If a component unmounts before the data is fetched, use `AbortController` to cancel the request to prevent unnecessary work and potential memory leaks.
Global Considerations for Data Fetching and Deduplication
When designing data fetching strategies for a global audience, several factors come into play:
Content Delivery Networks (CDNs): Utilize CDNs to distribute your static assets and API responses across geographically diverse locations. This reduces latency for users accessing your application from different parts of the world.
Localized Data: Implement strategies for serving localized data based on the user's location or language preferences. This may involve using different API endpoints or applying transformations to the data on the server or client-side. For instance, a European e-commerce site might show prices in Euros, while the same site viewed from the United States might show prices in US Dollars.
Time Zones: Be mindful of time zones when displaying dates and times. Use appropriate formatting and conversion libraries to ensure that times are displayed correctly for each user.
Currency Conversion: When dealing with financial data, use a reliable currency conversion API to display prices in the user's local currency. Consider providing options for users to switch between different currencies.
Accessibility: Ensure that your data fetching strategies are accessible to users with disabilities. This includes providing appropriate ARIA attributes for loading indicators and error messages.
Data Privacy: Comply with data privacy regulations such as GDPR and CCPA when collecting and processing user data. Implement appropriate security measures to protect user information.
For example, a travel booking website targeting a global audience might use a CDN to serve flight and hotel availability data from servers located in different regions. The website would also use a currency conversion API to display prices in the user's local currency and provide options for filtering search results based on language preferences.
Conclusion
Resource deduplication is an essential optimization technique for React applications using Suspense. By preventing duplicate data fetching requests, you can significantly improve performance, reduce server load, and enhance the user experience. Whether you choose to implement a simple promise cache or leverage more advanced libraries like lru-cache or axios-extensions, the key is to understand the underlying principles and choose the solution that best fits your specific needs. Remember to consider global factors like CDNs, localization, and accessibility when designing your data fetching strategies for a diverse audience. By implementing these best practices, you can build faster, more efficient, and more user-friendly React applications.