Part 48: Harnessing Incremental Static Regeneration and Fallback Options in Next.js

[Pages] Data Fetching

[Pages] Data Fetching

When building dynamic websites with Next.js, leveraging Incremental Static Regeneration (ISR) is a powerful way to ensure that pages are updated with fresh data from your backend without the need for full rebuilds. However, it's important to apply this concept consistently across different pages, such as the HomePage and individual ProductPage, to ensure a seamless user experience. Today, we'll explore how ISR works in tandem with the fallback option in getStaticPaths, especially when adding new products to your site.

The Challenge of New Products

Imagine you have a website where the HomePage showcases a list of products. If you update a product in your Content Management System (CMS), ISR ensures that the HomePage reflects these changes after revalidation. However, what happens when you add a new product?

Let's say we duplicate an existing product in the CMS, creating a new entry like "Aloe Vera - Large." The HomePage will eventually display this new product after the ISR process completes. But clicking on this new product might lead you to a dreaded 404 error. Why?

This happens because the new product wasn't included in the list generated by getStaticPaths during build time. As a result, Next.js doesn't have a pre-generated page for it, leading to the 404 error.

Understanding getStaticPaths and fallback

getStaticPaths is a Next.js function used to specify which dynamic routes should be pre-rendered at build time. It returns an array of paths and a fallback value. The fallback option tells Next.js what to do when a requested page isn't pre-rendered.

Fallback Options

• false: If a page isn't pre-rendered, Next.js returns a 404 error. This was our initial setup, which caused the 404 issue.

• true: Next.js serves a fallback version of the page while it fetches the data and generates the page in the background.

• 'blocking': The server waits for the page to be generated before sending it to the client, blocking the request until the new page is ready.

For our scenario, setting fallback to 'blocking' is ideal. It ensures that when a new product is accessed, the server generates the page on the fly, blocking the request until the page is ready to be served.

Implementing fallback: 'blocking'

Here's how you can implement this in your ProductPage:

// pages/products/[id].js

export async function getStaticPaths() {
  const products = await fetchProductsFromCMS(); // Fetch products from your CMS

  return {
    paths: products.map((product) => ({
      params: { id: product.id.toString() },
    })),
    fallback: 'blocking',
  };
}

Explanation

• Paths: We generate paths for all products available at build time.

• Fallback: By setting 'blocking', we ensure that any new product added after the initial build will have its page generated on-demand.

Testing the Setup

1. Rebuild the App: After changing the fallback setting, rebuild your app to apply the changes.

2. Add a New Product: Duplicate an existing product in your CMS and modify its details.

3. Check the HomePage: The new product should appear after a refresh.

4. Access the New Product: Click on the new product. With fallback: 'blocking', the page will be generated and displayed without a 404 error.

Conclusion

By using ISR in conjunction with the fallback option in getStaticPaths, we can efficiently handle dynamic content updates and new entries in our Next.js applications. This approach not only ensures that your website remains current but also provides a smooth user experience by preventing 404 errors on newly added items. Implementing fallback: 'blocking' is a simple yet powerful way to enhance the flexibility and responsiveness of your Next.js projects.