[Segment Cache] Support <Link prefetch={true}> #74172
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This implements background revalidation of partial segment entries in
client Segment Cache.
Until this PR, entries were never replaced in the Segment Cache, they
were only evicted upon becoming stale, or if the LRU overflowed. But
there are cases where we'll want to replace an existing entry with a
new one; for example, if the current segment has more dynamic holes than
the new one.
Most commonly this happens when multiple fetching strategies are mixed
within the same app. For example: when a shared layout belongs to both
a PPR-enabled route and a non-PPR enabled route, the layout data might
be omitted when prefetching the non-PPR enabled route, if it's wrapped
in a loading boundary. But that shouldn't prevent it from being
included when prefetching the route that has PPR enabled.
(Another example is when a shared layout is prefetched both on viewport
entry and also via <Link prefetch={true}>. A viewport prefetch will
only include the static data, but prefetch={true} includes both the
static and the dynamic.
<Link prefetch={true}> is not yet implemented by the Segment Cache but
it will use a similar background revalidation strategy as the one
implemented in this PR.)
Stats from current PRDefault Build (Increase detected
|
| vercel/next.js canary | acdlite/next.js segment-cache-full-prefetch | Change | |
|---|---|---|---|
| buildDuration | 18.6s | 19.1s | |
| buildDurationCached | 15.1s | 13s | N/A |
| nodeModulesSize | 416 MB | 417 MB | |
| nextStartRea..uration (ms) | 475ms | 471ms | N/A |
Client Bundles (main, webpack) Overall increase ⚠️
| vercel/next.js canary | acdlite/next.js segment-cache-full-prefetch | Change | |
|---|---|---|---|
| 1187-HASH.js gzip | 52.4 kB | 53.2 kB | |
| 8276.HASH.js gzip | 169 B | 168 B | N/A |
| 8377-HASH.js gzip | 5.36 kB | 5.36 kB | N/A |
| bccd1874-HASH.js gzip | 52.8 kB | 53 kB | |
| framework-HASH.js gzip | 57.5 kB | 57.5 kB | N/A |
| main-app-HASH.js gzip | 232 B | 235 B | N/A |
| main-HASH.js gzip | 34.1 kB | 34.1 kB | N/A |
| webpack-HASH.js gzip | 1.71 kB | 1.71 kB | N/A |
| Overall change | 105 kB | 106 kB |
Legacy Client Bundles (polyfills)
| vercel/next.js canary | acdlite/next.js segment-cache-full-prefetch | Change | |
|---|---|---|---|
| polyfills-HASH.js gzip | 39.4 kB | 39.4 kB | ✓ |
| Overall change | 39.4 kB | 39.4 kB | ✓ |
Client Pages
| vercel/next.js canary | acdlite/next.js segment-cache-full-prefetch | Change | |
|---|---|---|---|
| _app-HASH.js gzip | 193 B | 193 B | ✓ |
| _error-HASH.js gzip | 193 B | 193 B | ✓ |
| amp-HASH.js gzip | 512 B | 510 B | N/A |
| css-HASH.js gzip | 343 B | 342 B | N/A |
| dynamic-HASH.js gzip | 1.84 kB | 1.84 kB | ✓ |
| edge-ssr-HASH.js gzip | 265 B | 265 B | ✓ |
| head-HASH.js gzip | 363 B | 362 B | N/A |
| hooks-HASH.js gzip | 393 B | 392 B | N/A |
| image-HASH.js gzip | 4.49 kB | 4.49 kB | N/A |
| index-HASH.js gzip | 268 B | 268 B | ✓ |
| link-HASH.js gzip | 2.35 kB | 2.34 kB | N/A |
| routerDirect..HASH.js gzip | 328 B | 328 B | ✓ |
| script-HASH.js gzip | 397 B | 397 B | ✓ |
| withRouter-HASH.js gzip | 323 B | 326 B | N/A |
| 1afbb74e6ecf..834.css gzip | 106 B | 106 B | ✓ |
| Overall change | 3.59 kB | 3.59 kB | ✓ |
Client Build Manifests
| vercel/next.js canary | acdlite/next.js segment-cache-full-prefetch | Change | |
|---|---|---|---|
| _buildManifest.js gzip | 749 B | 746 B | N/A |
| Overall change | 0 B | 0 B | ✓ |
Rendered Page Sizes
| vercel/next.js canary | acdlite/next.js segment-cache-full-prefetch | Change | |
|---|---|---|---|
| index.html gzip | 524 B | 523 B | N/A |
| link.html gzip | 539 B | 537 B | N/A |
| withRouter.html gzip | 520 B | 520 B | ✓ |
| Overall change | 520 B | 520 B | ✓ |
Edge SSR bundle Size Overall increase ⚠️
| vercel/next.js canary | acdlite/next.js segment-cache-full-prefetch | Change | |
|---|---|---|---|
| edge-ssr.js gzip | 128 kB | 129 kB | N/A |
| page.js gzip | 206 kB | 206 kB | |
| Overall change | 206 kB | 206 kB |
Middleware size
| vercel/next.js canary | acdlite/next.js segment-cache-full-prefetch | Change | |
|---|---|---|---|
| middleware-b..fest.js gzip | 671 B | 669 B | N/A |
| middleware-r..fest.js gzip | 155 B | 156 B | N/A |
| middleware.js gzip | 31.2 kB | 31.3 kB | N/A |
| edge-runtime..pack.js gzip | 844 B | 844 B | ✓ |
| Overall change | 844 B | 844 B | ✓ |
Next Runtimes Overall increase ⚠️
| vercel/next.js canary | acdlite/next.js segment-cache-full-prefetch | Change | |
|---|---|---|---|
| 274-experime...dev.js gzip | 322 B | 322 B | ✓ |
| 274.runtime.dev.js gzip | 314 B | 314 B | ✓ |
| app-page-exp...dev.js gzip | 359 kB | 357 kB | N/A |
| app-page-exp..prod.js gzip | 129 kB | 129 kB | |
| app-page-tur..prod.js gzip | 142 kB | 142 kB | |
| app-page-tur..prod.js gzip | 137 kB | 137 kB | N/A |
| app-page.run...dev.js gzip | 347 kB | 347 kB | N/A |
| app-page.run..prod.js gzip | 125 kB | 125 kB | |
| app-route-ex...dev.js gzip | 37.5 kB | 37.5 kB | N/A |
| app-route-ex..prod.js gzip | 25.5 kB | 25.5 kB | N/A |
| app-route-tu..prod.js gzip | 25.5 kB | 25.5 kB | N/A |
| app-route-tu..prod.js gzip | 25.4 kB | 25.3 kB | N/A |
| app-route.ru...dev.js gzip | 39.2 kB | 39.1 kB | N/A |
| app-route.ru..prod.js gzip | 25.4 kB | 25.3 kB | N/A |
| pages-api-tu..prod.js gzip | 9.69 kB | 9.69 kB | ✓ |
| pages-api.ru...dev.js gzip | 11.6 kB | 11.6 kB | ✓ |
| pages-api.ru..prod.js gzip | 9.68 kB | 9.68 kB | ✓ |
| pages-turbo...prod.js gzip | 21.7 kB | 21.7 kB | N/A |
| pages.runtim...dev.js gzip | 27.5 kB | 27.5 kB | N/A |
| pages.runtim..prod.js gzip | 21.7 kB | 21.7 kB | N/A |
| server.runti..prod.js gzip | 916 kB | 916 kB | N/A |
| Overall change | 427 kB | 429 kB |
build cache
| vercel/next.js canary | acdlite/next.js segment-cache-full-prefetch | Change | |
|---|---|---|---|
| 0.pack gzip | 2.08 MB | 2.08 MB | N/A |
| index.pack gzip | 75.3 kB | 74.2 kB | N/A |
| Overall change | 0 B | 0 B | ✓ |
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failed to diffThis implements support in the Segment Cache for "full" link prefetches,
typically initiated by passing `prefetch={true}` to a `<Link>`.
The goal of a full prefetch is to request all the data needed for a
navigation, both static and dynamic, so that once the navigation occurs,
the router does not need to fetch any additional data. So, a full
prefetch implicitly instructs the client cache to treat the response as
static, even the dynamic data.
The implementation is largely the same as what we do to support non-PPR
-enabled routes — a request tree is sent to the server describing
which segments are already cached and which ones need to be rendered.
While constructing the request tree, if all the segments are already
in the client cache, the request can be skipped entirely. The main
difference is that a full prefetch will only reuse a cached segment
entry if it does not contain any dynamic holes.
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Based on:
This implements support in the Segment Cache for "full" link prefetches, typically initiated by passing
prefetch={true}to a<Link>.The goal of a full prefetch is to request all the data needed for a navigation, both static and dynamic, so that once the navigation occurs, the router does not need to fetch any additional data. So, a full prefetch implicitly instructs the client cache to treat the response as static, even the dynamic data.
The implementation is largely the same as what we do to support non-PPR-enabled routes — a request tree is sent to the server describing which segments are already cached and which ones need to be rendered. While constructing the request tree, if all the segments are already in the client cache, the request can be skipped entirely. The main difference is that a full prefetch will only reuse a cached segment entry if it does not contain any dynamic holes.