>From the explainer, expects_no_vary_search helps because when we're prefetching but have not yet received headers, we don't know if that request would match what the user is now navigating to. Do you have a sense of how often the failure cases happen? (ie we waited for that navigation request to finish but we shouldn't have, or vice versa). Also what is the cost of this failure? It seems like this is a good addition but it seems like a very fine-grained control for cases that may not be problematic or costly.
On Thu, Jun 6, 2024 at 12:45 PM Chris Harrelson <[email protected]> wrote: > LGTM2 > > On Wed, Jun 5, 2024 at 9:58 PM Mike Taylor <[email protected]> wrote: > >> LGTM1 >> On 6/5/24 11:21 PM, Liviu Tinta wrote: >> >> Contact emails >> >> [email protected], [email protected], [email protected] >> >> Explainer >> >> >> https://github.com/WICG/nav-speculation/blob/main/triggers.md#no-vary-search-hint >> >> Specification >> >> https://wicg.github.io/nav-speculation/prerendering.html >> >> Summary >> >> Adds a hint to speculation rules that informs the navigation prerender >> cache that the URL to be prerendered expects to receive the same >> No-Vary-Search header in the response. >> >> The hint is useful because prerenders that depend on No-Vary-Search to >> match to navigations do not benefit the user if the navigation happens >> before prerender headers return from the server. Using the hint, the web >> browser will expect, but verify, that the No-Vary-Search hint matches with >> the No-Vary-Search header. If the No-Vary-Search hint does not match the >> No-Vary-Search header received then the web browser will send a new request. >> >> We would like to ship "No-Vary-Search Hint for Prerender Speculation >> Rules" together with "No-Vary-Search support for prerender >> <https://chromestatus.com/feature/5099218903760896>". >> >> Blink component >> >> Internals>Preload>Prerender >> <https://bugs.chromium.org/p/chromium/issues/list?q=component:Internals%3EPreload%3EPrerender> >> >> TAG review >> >> Not applicable. The TAG has already given a negative opinion on the >> overall complexity of speculation rules ( >> https://github.com/w3ctag/design-reviews/issues/721 ), so we anticipate >> it would not be a good use of their time to review additions to the syntax. >> The addition itself is small and any architectural questions about it would >> be covered under the general closed speculation rules review. >> >> TAG review status >> >> Not applicable >> >> Risks >> >> Interoperability and Compatibility >> >> None >> >> >> Gecko: No signal ( >> https://github.com/mozilla/standards-positions/issues/620#issuecomment-1608195274 >> ) >> >> WebKit: No signal ( >> https://github.com/WebKit/standards-positions/issues/54#issuecomment-1608197504 >> ) >> >> Web developers: Below is the text from the I2S of the No-Vary-Search on >> navigational prefetch, and we believe the same applies to Prerendering. >> Google Search has been experimenting with No-Vary-Search header / >> Speculation Rules "expects_no_vary_search". This functionality helps Google >> Search to match prefetched content to the next user navigation. Developers >> can use parameters in the prefetched URL that are not needed when >> navigating to the actual link (e.g. the source of the link click). The >> server can customize behavior using these parameters without causing a >> cache miss in the browser. "expects_no_vary_search" addition to Speculation >> Rules allows the browser to completely handle the case where the user >> navigates to a URL that is currently prefetched by waiting for the ongoing >> prefetch instead of directly requesting the page from the server. Google >> Search conducted experiments prefetching Search results pages from the >> search box and other links that lead to another Search results page. There >> was significant latency improvement for navigating to Search result pages >> prefetched using No-Vary-Search header and "expects_no_vary_search". >> >> Other signals: No-Vary-Search header has been discussed, together with >> No-Vary-Search Hint for Prefetch Speculation Rules at Web Perf WG meeting >> at TPAC 2023. >> https://docs.google.com/presentation/u/1/d/1GK92nCORW5vKd7LgGtTsgy35eqTV7P71l05pHsni8ok/edit#slide=id.g240fd6541f7_0_31 >> >> Ergonomics >> >> (Text taken from Prefetch NVS I2S) >> >> No-Vary-Search will be used in tandem with Speculation Rules ( >> https://wicg.github.io/nav-speculation/speculation-rules.html). The >> default usage of No-Vary-Search will not make it hard for Chrome to >> maintain good performance. >> >> >> Security >> >> See: >> https://github.com/WICG/nav-speculation/blob/main/no-vary-search-security-privacy-questionnaire.md >> >> >> WebView application risks >> >> Does this intent deprecate or change behavior of existing APIs, such that >> it has potentially high risk for Android WebView-based applications? >> >> We are closely working with Android WebView team, and the broader >> prerender feature is gated through new AwSettings API (currently >> @RequiresOptIn) so there's zero risk that it will break existing WebView >> apps. >> >> >> >> >> Debuggability >> >> None >> >> >> Will this feature be supported on all six Blink platforms (Windows, Mac, >> Linux, ChromeOS, Android, and Android WebView)? >> >> Yes >> >> Is this feature fully tested by web-platform-tests >> <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md> >> ? >> >> Yes >> >> >> https://wpt.fyi/results/speculation-rules/prerender?label=experimental&label=master&aligned >> >> (The test files starting with no-vary-search) >> >> >> Flag name on chrome://flags >> >> None >> >> Finch feature name >> >> Prerender2NoVarySearch >> >> Requires code in //chrome? >> >> False >> >> Estimated milestones >> >> Shipping on desktop >> >> 127 >> >> Shipping on Android >> >> 127 >> >> Shipping on WebView >> >> 127 >> >> >> >> Anticipated spec changes >> >> Open questions about a feature may be a source of future web compat or >> interop issues. Please list open issues (e.g. links to known github issues >> in the project for the feature specification) whose resolution may >> introduce web compat/interop risk (e.g., changing to naming or structure of >> the API in a non-backward-compatible way). >> >> None >> >> Link to entry on the Chrome Platform Status >> >> https://chromestatus.com/feature/5190922953555968?gate=5148879099265024 >> >> Links to previous Intent discussions >> >> Intent to prototype: >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CA%2B7y87rgssbBecLSY5fz03ATcAAjgy%3DjY322w_2roQdsehP4Dg%40mail.gmail.com >> >> This intent message was generated by Chrome Platform Status >> <https://chromestatus.com/>. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "blink-dev" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAHaAqYJphk8wg8yLr-VFe2QJDZ4N%3D8Z%2BBAs9VL5scY-brTmRTg%40mail.gmail.com >> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAHaAqYJphk8wg8yLr-VFe2QJDZ4N%3D8Z%2BBAs9VL5scY-brTmRTg%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> >> -- >> You received this message because you are subscribed to the Google Groups >> "blink-dev" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/457ce01c-56ea-42a9-b9ef-1d84216ccd90%40chromium.org >> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/457ce01c-56ea-42a9-b9ef-1d84216ccd90%40chromium.org?utm_medium=email&utm_source=footer> >> . >> > -- > You received this message because you are subscribed to the Google Groups > "blink-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAOMQ%2Bw9p78D28sGy7zBHQk1cij7PwDs7EE8GnDZ62hpudydOtg%40mail.gmail.com > <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAOMQ%2Bw9p78D28sGy7zBHQk1cij7PwDs7EE8GnDZ62hpudydOtg%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "blink-dev" group. 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