cache hit/miss logging

[random edge]

Hi @runic rock. I'm kapa.ai, your friendly support bot. I will try to answer your question by searching through the knowledge base. :wave:

---

Yes, there are ways to enable cache hit/miss logging in Next.js 14, similar to how the fetch API used to work. Here are a couple of approaches you can use:

1. Using the logging configuration in next.config.js:

Next.js 14 provides a logging configuration option that allows you to log data fetching using the fetch API. You can enable this by adding the following to your next.config.js file:

module.exports = {
  logging: {
    fetches: {
      fullUrl: true,
    },
  },
}

This configuration will log the full URL of fetch requests, which can help you identify cache hits and misses Next.js Docs: Logging (https://nextjs.org/docs/app/api-reference/next-config-js/logging).

2. Using Vercel's Runtime Logs:

If you're deploying your Next.js 14 application on Vercel, you can use their Runtime Logs feature to view cache behavior. The logs include a "Cache" field that shows values such as HIT, MISS, STALE, BYPASS, PRERENDER, or REVALIDATED Vercel Docs: Runtime Logs (https://vercel.com/docs/observability/runtime-logs#log-details).

Additionally, Vercel provides an x-vercel-cache response header that indicates whether the response was served from the edge cache. The possible values include MISS, HIT, STALE, and PRERENDER Vercel Docs: x-vercel-cache Header (https://vercel.com/docs/edge-network/headers/response-headers#x-vercel-cache).

Keep in mind that the exact behavior and availability of cache logging may depend on your specific setup and deployment environment. If you need more detailed or custom logging, you might need to implement a custom cache handler, as shown in some community discussions GitHub Issue: Custom Cache Handler (https://github.com/vercel/next.js/issues/58094).

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[runic rock]

What about the next.js 14 unstable cache api? @random edge

[random edge]

Let me check the knowledge base for you again. Give me one moment! :books:

---

Next.js 14 introduced the unstable_cache API, which provides a way to cache the results of expensive operations, such as database queries, and reuse them across multiple requests. Here's what you need to know about the unstable_cache API:

1. Usage:
   The unstable_cache function allows you to wrap an asynchronous operation and cache its result. Here's a basic example:

   import { unstable_cache } from 'next/cache';
   
   const getCachedUser = unstable_cache(
     async (id) => getUser(id),
     ['my-app-user']
   );
   
   export default async function Component({ userID }) {
     const user = await getCachedUser(userID);
     // ...
   }
   

   Next.js Docs: unstable_cache (https://nextjs.org/docs/app/api-reference/functions/unstable_cache)

2. Parameters:

   • fetchData: An asynchronous function that fetches the data you want to cache.
   • keyParts: An array that identifies the cached key.
   • options: An object to control cache behavior, including tags and revalidate.

3. Caching behavior:
   The caching behavior depends on whether the route segment is statically or dynamically rendered. For static segments, the output is cached and revalidated as part of the route segment. For dynamic segments, the output is not cached and is re-fetched on every request.

   Next.js Docs: Fetching data on the Server with third-party libraries (https://nextjs.org/docs/app/building-your-application/data-fetching/fetching-caching-and-revalidating#fetching-data-on-the-server-with-third-party-libraries)

4. Example with ORM or Database:
   You can use unstable_cache to cache database queries:

   import { unstable_cache } from 'next/cache'
   import { db, posts } from '@/lib/db'
   
   const getPosts = unstable_cache(
     async () => {
       return await db.select().from(posts)
     },
     ['posts'],
     { revalidate: 3600, tags: ['posts'] }
   )
   
   export default async function Page() {
     const allPosts = await getPosts()
     // ...
   }

Next.js Docs: Caching data with an ORM or Database (https://nextjs.org/docs/app/building-your-application/data-fetching/fetching#caching-data-with-an-orm-or-database)

5. Limitations:

   • Accessing dynamic data sources like headers or cookies inside a cache scope is not supported.
   • The API is marked as unstable, which means it may change in future versions.

   Next.js Docs: unstable_cache (https://nextjs.org/docs/app/api-reference/functions/unstable_cache)

Remember that while unstable_cache provides powerful caching capabilities, it's still an experimental feature. Be prepared for potential changes in future versions of Next.js.

Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:

@runic rock Kapa.ai is still learning and improving, please let me know how I did by reacting below.

[runic rock]

is there a way to enable cache hit/miss logging in next.js 14 similar to how the fetch api use to work? I am using the unstable cache api @random edge

[random edge]

Let me check the knowledge base for you again. Give me one moment! :books:

---

Unfortunately, I don't have enough specific information about cache hit/miss logging for the unstable_cache API in Next.js 14. The knowledge sources provided don't contain details about built-in logging capabilities for this particular API.

However, based on the available information, here are a few points to consider:

1. The unstable_cache API is still experimental, as indicated by its name and the warning in the documentation: "This API is unstable and may change in the future." Next.js Docs: unstable_cache (https://nextjs.org/docs/app/api-reference/functions/unstable_cache)

2. There are known issues with the unstable_cache API, as evidenced by open GitHub issues. For example, one issue mentions that the cache might be fetching twice during builds on Vercel GitHub Issue: unstable_cache fetches twice every build on Vercel (https://github.com/vercel/next.js/issues/61423)

3. Unlike the fetch API, which had built-in cache logging, there's no mention of similar functionality for unstable_cache in the provided documentation.

Given these points, if you need detailed cache hit/miss logging for unstable_cache, you might need to implement a custom solution. This could involve wrapping the unstable_cache function with your own logging logic or using external monitoring tools.

If you're deploying on Vercel, you might be able to use their Runtime Logs feature, which provides some cache-related information, although it's not clear if this works specifically with unstable_cache Vercel Docs: Runtime Logs (https://vercel.com/docs/observability/runtime-logs#cache).

For the most up-to-date and accurate information, I recommend checking the latest Next.js documentation or reaching out to the Next.js community forums or GitHub issues for guidance on logging with unstable_cache.

Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: