Nuxt•7mo ago

How to deal with chunks not found after deployment?

Hi there, I'm deploying my Nuxt project to Cloudflare Pages. Right now it's fully client-side rendered. I'm facing the following problem: Let's say a user opens my website, visits just the home page. Then I make a deployment and after I deployed the user wants to navigate to a sub page. This will throw an error, because the chunks the client thinks it needs to request, aren't there anymore. What's the best way to deal with that?

11 Replies

kapa.ai•7mo ago

Hi @Shufflepuff. I'm kapa.ai, your friendly support bot. I will try to answer your question by searching through the knowledge base. :wave: ---------------------- This is a common issue when deploying client-side rendered (CSR) Nuxt applications, especially on platforms like Cloudflare Pages. After a deployment, the old JavaScript chunk files referenced by users' browsers may no longer exist, leading to chunk loading errors when navigating to new pages. Why does this happen? - When you deploy a new version, the hashed filenames of your JS chunks change. - If a user loaded the site before the deployment, their browser cache (and/or the CDN) may still reference the old chunk URLs. - When they navigate to a new route, Nuxt tries to load a chunk that no longer exists, resulting in a 404 error. How to handle this in Nuxt: 1. Automatic Chunk Error Handling - Nuxt provides built-in support for handling chunk loading errors. By default, when a chunk fails to load during route navigation, Nuxt will perform a reload of the new route. This helps the app recover by reloading the page and fetching the latest assets. - You can control this behavior with the experimental.emitRouteChunkError option in your nuxt.config.ts:

     export default defineNuxtConfig({
       experimental: {
         emitRouteChunkError: 'automatic' // default
       }
     })

     export default defineNuxtConfig({
       experimental: {
         emitRouteChunkError: 'automatic' // default
       }
     })

- Setting it to 'automatic-immediate' will reload the current route immediately when a chunk fails to load, which can be useful for lazy-loaded components or when errors are not triggered by navigation. You can also set it to false (disable) or 'manual' (handle errors yourself) if you want custom behavior.
Nuxt config: emitRouteChunkError 2. Cache Control for Chunks - Ensure that your CDN (Cloudflare) and browser do not cache 404 responses for chunk files. If a 404 response is cached as immutable, users will keep getting the error until they clear their cache. - Set proper cache headers for your _nuxt assets. For example:

     export default defineNuxtConfig({
       routeRules: {
         '/_nuxt/**': {
           headers: {
             'Cache-Control': 'public, max-age=0, must-revalidate'
           }
         }
       }
     })

     export default defineNuxtConfig({
       routeRules: {
         '/_nuxt/**': {
           headers: {
             'Cache-Control': 'public, max-age=0, must-revalidate'
           }
         }
       }
     })

- This ensures that after a deployment, browsers and CDNs will always check for the latest version of the chunk files and not cache 404s.
See user solution for cache headers 3. Advanced: Serve Static Assets from Persistent Storage - For zero downtime and to avoid missing chunks, some teams upload their built assets to persistent storage (like S3 or Cloudflare R2) and serve them via a CDN. This ensures that all chunk files remain available even after a new deployment, so users with old HTML can still fetch the required JS files.
See discussion and example config Summary:
- Use Nuxt's built-in chunk error handling (emitRouteChunkError). - Set cache headers to prevent caching of 404s for chunk files. - Optionally, serve static assets from persistent storage for zero downtime. These steps should help you avoid or gracefully recover from chunk-not-found errors after deployment. ---------------------- Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: ----------------------

kapa.ai•7mo ago

<@128217979732230144> Kapa.ai is still learning and improving, please let me know how I did by reacting below.

ShufflepuffOP•7mo ago

@kapa.ai question about "Cache Control for Chunks": Will this basically disable all client-side caching?

kapa.ai•7mo ago

Let me check the knowledge base for you again. One moment! :books: ---------------------- Setting the following cache control header for your Nuxt chunk files:

export default defineNuxtConfig({
  routeRules: {
    '/_nuxt/**': {
      headers: {
        'Cache-Control': 'public, max-age=0, must-revalidate'
      }
    }
  }
})

export default defineNuxtConfig({
  routeRules: {
    '/_nuxt/**': {
      headers: {
        'Cache-Control': 'public, max-age=0, must-revalidate'
      }
    }
  }
})

will effectively disable persistent client-side caching for those files. This means that browsers and CDNs will always revalidate the files with the server before using a cached version, ensuring users get the latest assets after a deployment. However, it also means you lose the performance benefits of long-term caching for your JS chunks, as they will not be stored and reused between visits without a network check. This approach is often used to prevent issues with users receiving 404 errors for outdated chunks after a deployment, especially when using CDNs like Cloudflare. It is a trade-off between cache safety and performance. If you want to keep the benefits of caching while avoiding chunk-not-found errors, you may need a more advanced deployment strategy, such as serving assets from persistent storage as discussed in the referenced issues Github Issue: Failed to fetch dynamically imported module Github Issue: JS chunks return 404 after every deployment. ---------------------- Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: ----------------------

kapa.ai•7mo ago

<@128217979732230144> Kapa.ai is still learning and improving, please let me know how I did by reacting below.

ShufflepuffOP•7mo ago

@kapa.ai Ideally I'd be looking for a way so that Nuxt detects when it failed to load a remote chunk and if that's the case that it somehow updates the chunk mapping, if such a thing exists. Or at least emit an event so I can show a message to the user that the application has been updated and further navigation requires a reload.

kapa.ai•7mo ago

Let me check the knowledge base for you again. One moment! :books: ---------------------- Nuxt does not currently provide a built-in way to dynamically update the chunk mapping or hot-swap chunk manifests when a chunk fails to load after deployment. However, Nuxt does offer mechanisms to detect chunk loading errors and respond to them: - Event Emission:
When a chunk fails to load (for example, due to a new deployment invalidating old chunk URLs), Nuxt emits the app:chunkError hook. You can listen for this event and implement custom logic, such as showing a message to the user that a reload is required. This is configurable via the experimental.emitRouteChunkError option in your nuxt.config.ts:

  export default defineNuxtConfig({
    experimental: {
      emitRouteChunkError: 'manual' // or 'automatic', 'automatic-immediate', false
    }
  })

  export default defineNuxtConfig({
    experimental: {
      emitRouteChunkError: 'manual' // or 'automatic', 'automatic-immediate', false
    }
  })

- 'manual': You handle the chunk error yourself. - 'automatic': Nuxt reloads the route automatically on navigation. - 'automatic-immediate': Nuxt reloads the current route immediately when a chunk fails to load. - false: Disables automatic handling. See documentation - Custom Handling Example:
If you set emitRouteChunkError to 'manual', you can listen for the app:chunkError event and show a custom message:

  export default defineNuxtPlugin((nuxtApp) => {
    nuxtApp.hook('app:chunkError', (error) => {
      // Show a notification or modal to the user
      // e.g., "The application has been updated. Please reload."
    })
  })

  export default defineNuxtPlugin((nuxtApp) => {
    nuxtApp.hook('app:chunkError', (error) => {
      // Show a notification or modal to the user
      // e.g., "The application has been updated. Please reload."
    })
  })

- Limitations:
There is no built-in way in Nuxt to update the chunk mapping or manifest at runtime after a deployment. The recommended approach is to either reload the app or inform the user that a reload is required when a chunk error occurs Nuxt Error Handling Docs Nuxt Config: emitRouteChunkError. Summary:
- Nuxt emits an event (app:chunkError) when a chunk fails to load. - You can listen for this event and show a message to the user. - There is no built-in way to update the chunk mapping at runtime; a reload is the standard solution. ---------------------- Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: ----------------------

kapa.ai•7mo ago

<@128217979732230144> Kapa.ai is still learning and improving, please let me know how I did by reacting below.

ShufflepuffOP•7mo ago

Thanks @kapa.ai ! Very useful. So, if I'd go with the solution of using the app:chunkError hook, how can I actually test that locally? Is there a way for me to manually trigger such an error?

kapa.ai•7mo ago

Let me check the knowledge base for you again. One moment! :books: ---------------------- To test the app:chunkError hook locally in your Nuxt project, you need to simulate a scenario where a chunk fails to load. While the knowledge sources do not provide a step-by-step guide for manually triggering a chunk error, they do mention that chunk errors typically occur when a user tries to load a route or component whose associated chunk file is missing—often after a deployment that changes chunk hashes Nuxt Error Handling Docs. Here’s a practical approach based on the documented behavior: 1. Build and Serve Your App Locally: - Run nuxi build and then nuxi preview (or use your preferred static server). 2. Simulate a Missing Chunk: - After building, go to your .output/public/_nuxt/ (or dist/_nuxt/) directory. - Delete or rename one of the chunk files (e.g., a .js file with a hash in its name). - In your browser, navigate to a route or component that would require that chunk. 3. Observe the Error: - When the app tries to load the missing chunk, it should trigger a chunk loading error, which will emit the app:chunkError event if you have set up the hook. Note:
This approach is based on the documented chunk error handling mechanism in Nuxt, which states that errors can occur when JS chunks are missing due to deployment or network issues. The documentation also suggests that you can use the app:chunkError hook to handle such cases Nuxt Error Handling Docs Nuxt Config: emitRouteChunkError. If you need to automate this in tests, you may need to mock or intercept network requests for chunk files, but the knowledge sources do not provide explicit instructions for this. Summary:
- Build your app, delete a chunk file, and try to load a route/component that needs it. - This should trigger the app:chunkError event, allowing you to test your handler. If you need more advanced or automated testing, the knowledge sources do not provide further details. ---------------------- Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: ----------------------

kapa.ai•7mo ago

<@128217979732230144> Kapa.ai is still learning and improving, please let me know how I did by reacting below.

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How to deal with chunks not found after deployment?

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