Nuxt•7d ago

Test SWR locally

reading the docs and i think swr is a good solution for me, but how can i confirm its working? i feel like my pages aren't loading as fast as i would expect. how/where do i check on the server if the pages have been rendered and stored is there a way to test this locally? with nuxt dev i don't see anything in the .nuxt/ folder

5 Replies

kapa.ai•7d ago

Hi @thejacer87. I'm kapa.ai, your friendly support bot. I will try to answer your question by searching through the knowledge base. :wave: ---------------------- To test Server-Side Rendering with SWR (stale-while-revalidate) caching locally, you'll need to understand how Nuxt handles this feature and how to verify it's working correctly. Testing SWR Locally When using nuxt dev, you won't see cached content in the .nuxt/ folder because the development server doesn't fully implement the caching behavior that would be present in production. The SWR caching happens at the Nitro server level, not in the .nuxt/ directory. Here's how you can test SWR locally: 1. Configure SWR in your application First, make sure you've properly configured SWR in your nuxt.config.ts:

export default defineNuxtConfig({
  routeRules: {
    '/products': { swr: true },
    '/products/**': { swr: 3600 }, // Cache for 1 hour
  }
})

export default defineNuxtConfig({
  routeRules: {
    '/products': { swr: true },
    '/products/**': { swr: 3600 }, // Cache for 1 hour
  }
})

2. Build for production and run locally To properly test SWR caching, you need to build your application for production:

npx nuxi build
node .output/server/index.mjs

npx nuxi build
node .output/server/index.mjs

This will create a production build and run it locally, allowing you to see the caching behavior. 3. Verify caching is working You can verify that SWR is working by: 1. Check response headers: The first request to a page with SWR enabled should include cache-related headers. 2. Monitor response times: Make an initial request to a page with SWR enabled, then make subsequent requests. The subsequent requests should be noticeably faster if caching is working properly. 3. Check server logs: When using the Nitro server, it will cache responses according to your SWR configuration. You might see logs indicating cache hits/misses. 4. Use browser developer tools You can use browser developer tools to: - Check the Network tab to see response times - Examine response headers for cache-related information Understanding SWR in Nuxt SWR in Nuxt works by adding cache headers to the server response and caching it on the server or reverse proxy for a configurable TTL (time to live). When the TTL expires, the cached response will be sent while the page regenerates in the background Hybrid Rendering. The Nitro server preset is able to cache the full response, which is why you need to run a production build to properly test this feature. If you're finding that pages aren't loading as fast as expected, it could be because: 1. The SWR configuration isn't properly set up 2. You're testing in development mode where caching isn't fully implemented 3. The initial cache is still being built (first requests will be slower) Remember that SWR is part of Nuxt's hybrid rendering capabilities, which allows different caching rules per route. Hope this helps you test and verify your SWR implementation! ---------------------- Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: ----------------------

kapa.ai•7d ago

<@291389486720352266> Kapa.ai is still learning and improving, please let me know how I did by reacting below.

thejacer87OP•7d ago

@kapa.ai i don't see anything in the response headers

kapa.ai•7d ago

Let me check the knowledge base for you again. One moment! :books: ---------------------- If you're not seeing any cache-related headers in your response when testing SWR, there could be several reasons for this. Let's troubleshoot the issue: Why Cache Headers Might Not Appear 1. Development Mode: If you're still using nuxt dev, SWR caching won't be fully implemented. Make sure you're testing with a production build as mentioned previously. 2. Cache Storage Configuration: By default, Nitro uses an in-memory cache. The headers might not be explicitly shown in the response even though caching is happening internally. 3. Route Configuration: Ensure your route rules are correctly configured for the specific routes you're testing. Verifying SWR is Working Since you don't see the headers, here are alternative ways to verify SWR is working: 1. Add Console Logs: You can modify your server handlers to log when a cache hit occurs:

// In a server route
export default defineCachedEventHandler((event) => {
  console.log('Handler called, checking cache...');
  // Your handler logic
  return { data: 'your data' };
}, {
  maxAge: 3600 // 1 hour
})

// In a server route
export default defineCachedEventHandler((event) => {
  console.log('Handler called, checking cache...');
  // Your handler logic
  return { data: 'your data' };
}, {
  maxAge: 3600 // 1 hour
})

2. Test Response Times: Make an initial request to a page with SWR enabled, then make subsequent requests. The subsequent requests should be faster if caching is working. 3. Use defineCachedEventHandler: For API routes, you can use this helper which provides more explicit caching behavior:

// server/api/data.js
export default defineCachedEventHandler(async (event) => {
  console.log('Cache miss - generating new data');
  // Simulate slow data fetch
  await new Promise(resolve => setTimeout(resolve, 2000));
  return { data: 'example', timestamp: Date.now() };
}, {
  maxAge: 60, // Cache for 60 seconds
  swr: true
})

// server/api/data.js
export default defineCachedEventHandler(async (event) => {
  console.log('Cache miss - generating new data');
  // Simulate slow data fetch
  await new Promise(resolve => setTimeout(resolve, 2000));
  return { data: 'example', timestamp: Date.now() };
}, {
  maxAge: 60, // Cache for 60 seconds
  swr: true
})

Then check if subsequent requests return faster and if the timestamp remains the same (indicating a cached response). Important Note About readBody with Cached Handlers Be aware that if you're using readBody or readValidatedBody within a cached handler, you might encounter issues. According to a GitHub issue:

When readBody is used within the defineCachedEventHandler, the received value will always be undefined. This is because cached event handler entry keys are based only on the request path, not the body or headers. Github Issue #31535

If you need to cache responses that depend on request body data, consider using separate handlers for different HTTP methods or using an internal cached function. Let me know if you need more specific guidance based on your implementation! ---------------------- Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: ----------------------

kapa.ai•7d ago

<@291389486720352266> Kapa.ai is still learning and improving, please let me know how I did by reacting below.

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