I am using the same fetch call in generateMetadata in layout and the page itself. It seems like it is not cached and server response took the full time to make the 2 fetch call?
#fetch cache
weak rock
autumn horizonBOT
Hi @weak rock. I'm kapa.ai, your friendly support bot. I will try to answer your question by searching through the knowledge base. :wave:
Next.js extends the native fetch Web API to allow each request on the server to set its own persistent caching semantics. This means that you can configure how a server-side fetch request will interact with the framework's persistent HTTP cache.
However, it's important to note that memoization only applies to the GET method in fetch requests and to the React Component tree. This means it applies to fetch requests in generateMetadata, generateStaticParams, Layouts, Pages, and other Server Components. It doesn't apply to fetch requests in Route Handlers as they are not a part of the React component tree.
Here's an example of how you can use fetch with caching options in your server components:
export default async function Page() {
// This request should be cached until manually invalidated.
// Similar to `getStaticProps`.
// `force-cache` is the default and can be omitted.
const staticData = await fetch(`<https://...`,> { cache: 'force-cache' })
// This request should be refetched on every request.
// Similar to `getServerSideProps`.
const dynamicData = await fetch(`<https://...`,> { cache: 'no-store' })
// This request should be cached with a lifetime of 10 seconds.
// Similar to `getStaticProps` with the `revalidate` option.
const revalidatedData = await fetch(`<https://...`,> {
next: { revalidate: 10 },
})
return <div>...</div>
}
(Source: Next.js Docs - Functions - fetch (https://nextjs.org/docs/app/api-reference/functions/fetch))
If you're still experiencing issues with caching, it might be due to a bug or a specific configuration in your project. There have been issues reported (https://github.com/vercel/next.js/issues/48833) on the Next.js GitHub repository about fetch requests not being cached as expected. It's recommended to check if you're using the latest version of Next.js, as some of these issues might have been resolved in more recent updates.
Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:
weak rock
@autumn horizon how do I verify that the fetch response is cached from server component?
autumn horizonBOT
Let me check the knowledge base for you. One moment! :books:
To verify if a fetch response is cached from a server component, you can use the cache option of fetch to configure the caching behavior. By default, data requests that use fetch are cached.
Here's an example of how you can use fetch with caching options in your server components:
export default async function Page() {
// This request should be cached until manually invalidated.
// `force-cache` is the default and can be omitted.
const staticData = await fetch(`<https://...`,> { cache: 'force-cache' })
// This request should be refetched on every request.
const dynamicData = await fetch(`<https://...`,> { cache: 'no-store' })
// This request should be cached with a lifetime of 10 seconds.
const revalidatedData = await fetch(`<https://...`,> {
next: { revalidate: 10 },
})
return <div>...</div>
}
(Source: Next.js Docs - Functions - fetch (https://nextjs.org/docs/app/api-reference/functions/fetch))
In this example, staticData should be cached until manually invalidated, dynamicData should be refetched on every request, and revalidatedData should be cached with a lifetime of 10 seconds.
If you want to verify whether your data requests are being cached or not, you can check the network tab in your browser's developer tools. If a request is being served from the cache, it will usually say so in the size column (it might say something like "(from memory cache)" or "(from disk cache)").
Please note that the actual behavior might depend on your specific configuration and the nature of your data requests. If you're still having issues, it might be a good idea to check the Next.js documentation (https://nextjs.org/docs/app/building-your-application/caching#data-cache) or ask for help on the Next.js GitHub repository (https://github.com/vercel/next.js).
Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:
weak rock
@autumn horizon Do components running on ssr:false, also counts towards serverless function duration?
autumn horizonBOT
Let me check the knowledge base for you. One moment! :books:
Serverless functions are used to handle HTTP requests in your Next.js application. When you set ssr: false in your Next.js page, it means that the page will be rendered on the client-side and not on the server-side. Therefore, it will not count towards the serverless function duration.
However, if your client-side rendered page is making API calls to serverless functions, those will count towards the serverless function duration. The duration of a serverless function is the time it takes for the function to process an HTTP request, from the moment the function starts running until it finishes processing the request.
In the context of Vercel, each serverless function is built separately in the build step and has its own cache, based on the runtime used. The number and size of serverless functions will affect your build time. At the end of each build step, successful builds will update the cache and failed builds will not modify the existing cache (source (https://vercel.com/docs/deployments/troubleshoot-a-build)).
For cost optimization, it's recommended to set maximum durations for your serverless functions and ensure that Server-Side Rendering (SSR) usage is not over the limits (source (https://vercel.com/docs/production-checklist)).
Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:
weak rock
@autumn horizon if ssr: false is used on this component, is the fetch in this component a client or serverless function?
async function Post() {
const posts = await fetch('https://www.api.com/get-posts`);
return posts.toString();
}
const Post = dynamic(() => import('./Post'), { ssr: false });
Let me check the knowledge base for you. One moment! :books:
In the code you provided, the fetch call is inside a component that is dynamically imported with ssr: false. This means that the component, and everything inside it including the fetch call, will be executed on the client-side, not on the server-side.
Here's the relevant code:
async function Post() {
const posts = await fetch('<https://www.api.com/get-posts'>);
return posts.toString();
}
const Post = dynamic(() => import('./Post'), { ssr: false });
In this case, the fetch call to '<https://www.api.com/get-posts'> will be made from the client's browser when the Post component is rendered. This fetch call is not a serverless function, it's a client-side data fetching operation.
Remember, when you set ssr: false for a component, it means that the component will be rendered on the client-side and not on the server-side. Therefore, any data fetching operations inside that component will also be executed on the client-side.
Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:
weak rock
@autumn horizon From what I see, the fetch call is not called from the client side, as I try to log the output of posts, it logs on the server and not on the browser.
autumn horizonBOT
Let me check the knowledge base for you. One moment! :books:
The behavior you're experiencing might be due to the fact that the fetch call is inside an async function that is not being invoked inside a React effect hook. In Next.js, data fetching should be done inside useEffect for client-side rendering or inside getStaticProps/getServerSideProps for server-side rendering.
Here's an example of how you can use fetch inside useEffect for client-side data fetching:
import React, { useState, useEffect } from 'react'
export default function Post() {
const [posts, setPosts] = useState(null)
useEffect(() => {
const fetchData = async () => {
const response = await fetch('<https://www.api.com/get-posts'>)
const data = await response.json()
setPosts(data)
}
fetchData().catch((e) => {
console.error('An error occurred while fetching the data: ', e)
})
}, [])
return <div>{posts ? `Posts: ${JSON.stringify(posts)}` : 'Loading...'}</div>
}
In this example, fetch is called inside useEffect, which runs after the component has been rendered to the DOM, ensuring that the data fetching operation is performed on the client-side.
If you're still seeing the fetch call being made on the server-side, it might be due to a specific configuration in your project or a misunderstanding of how Next.js handles data fetching. I would recommend checking the Next.js Data Fetching documentation (https://nextjs.org/docs/basic-features/data-fetching) for more information.
Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:
weak rock
@autumn horizon Does that mean that if a fetch call is inside an async function component, even with ssr: false, it will still be server rendered?
autumn horizonBOT
Let me check the knowledge base for you. One moment! :books: