2023年3月7日(火) 17:19 Yoav Weiss <yoavwe...@chromium.org>: > > > On Tue, Mar 7, 2023 at 1:03 AM 'Yoshisato Yanagisawa' via blink-dev < > blink-dev@chromium.org> wrote: > >> Contact emails >> >> yyanagis...@google.com >> >> Explainer >> >> >> https://github.com/yoshisatoyanagisawa/service-worker-skip-no-op-fetch-handler >> >> Specification >> >> https://github.com/w3c/ServiceWorker/pull/1672 >> >> Summary >> >> The feature makes the navigation of pages with no-op service worker fetch >> handlers fast by skipping them. >> >> Some sites have a no-op (no operation) fetch listener (e.g. onfetch = () >> => {}). Since having the fetch listener was one of the requirements to be >> a progressive web app (PWA), we assume they did that to make their site >> recognized as PWA. However, it only brings overheads to start a service >> worker and execute a no-op listener without bringing any feature benefits >> like caching or offline capabilities because the code does nothing. To >> make the navigation to such pages faster, we would like to omit the service >> worker start and the listener dispatch from the navigation critical path if >> a user agent identifies that all the service worker's fetch listeners are >> no-ops. >> >> From version 112, Chromium starts to show console warnings if all the >> service worker’s fetch listeners are no-ops, and encourages developers to >> remove the useless fetch listeners. Hopefully sites stop using the useless >> fetch listeners and we can deprecate the feature in the future. >> >> Blink component >> >> Blink>ServiceWorker >> <https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3EServiceWorker> >> >> TAG review >> >> https://github.com/w3ctag/design-reviews/issues/815 >> >> TAG review status >> >> Issues addressed >> >> Risks >> >> Interoperability and Compatibility >> >> We believe the change has very small compatibility risk. >> >> Updating the no-op fetch handler in a service worker is ignored, which >> was not allowed to ignore before. Upon our observation, this happens to a >> negligible amount ( >> https://chromestatus.com/metrics/feature/timeline/popularity/4453). >> > > It seems like we don't yet have data from this. > Can you explain this counter a bit more? Doesn't it also count cases where > an operational fetch handler is updated after initialization? > >
Sure. The counter has been added in https://chromium-review.googlesource.com/c/chromium/src/+/4190509, and cherry-picked in M111, which is now eary stable according to https://chromereleases.googleblog.com/. There is the counter to watch all event handler updates in service worker https://chromium-review.googlesource.com/c/chromium/src/+/4259225, and we can see some numbers. https://chromestatus.com/metrics/feature/timeline/popularity/4469 Therefore, it might be safe to say that the number of run-time fetch handler updates is too small and not observable. > > >> >> https://github.com/yoshisatoyanagisawa/service-worker-skip-no-op-fetch-handler/#approaches-to-deal-with-the-handler-updates-after-the-initialization >> >> Navigation Preload is ignored for the no-op fetch handler. The spec >> requires the same resource fetched twice for no-op fetch handler due to >> lack of respondWith, which could result in two different network requests >> in rare situation, but this behavior only happens when they are >> misconfigured (a page was set up to send a Navigation Preload request they >> do not use). >> >> >> https://github.com/yoshisatoyanagisawa/service-worker-skip-no-op-fetch-handler/#how-does-it-work-with-navigation-preload >> >> Gecko: No signal ( >> https://github.com/mozilla/standards-positions/issues/744) >> >> WebKit: No signal ( >> https://github.com/WebKit/standards-positions/issues/129) >> >> Web developers: No signals. When you search with the query "A2HS", you >> will find many sites recommending you to add a no-op fetch handler (e.g. >> addEventListener("fetch", ()=>{})). Thus, you can easily assume that >> people who want to make their site to be added to the home screen would >> just add the no-op fetch handler for that purpose. Therefore, having the >> no-op fetch handler is common among sites (upon our investigation on >> popular site fetch handler usage, 3-5% of them were affected). Such >> sites will benefit from shipping this performance improvement, but we do >> not have specific examples of sites supporting this Intent. (Probably, if >> they were aware of the problem, they would just remove the empty fetch >> handler.) >> >> Other signals: >> >> 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? >> >> There are no special risks for WebView-based applications. >> >> >> Debuggability >> >> If a service worker is affected, its "Fetch handler type" field in >> chrome://serviceworker-internals/ will be EMPTY_FETCH_HANDLER. From >> version 112, there will be a console warning saying "Fetch event handler is >> recognized as no-op. No-op fetch handler may bring overhead during >> navigation. Consider removing the handler if possible." if the service >> worker is affected. >> >> Will this feature be supported on all six Blink platforms (Windows, Mac, >> Linux, Chrome OS, 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> >> ? >> >> No. The specification proposal adds this as an optional behavior, so >> testing it with web platform tests is not very useful. (Note that no >> existing web platform tests needed to be updated to allow this behavior, >> since the observable changes are only visible in edge cases.) >> >> Flag name >> >> #skip-service-worker-fetch-handler >> >> Requires code in //chrome? >> >> False >> >> Tracking bug >> >> https://bugs.chromium.org/p/chromium/issues/detail?id=1347319 >> >> Estimated milestones >> >> DevTrial on desktop >> >> 111 >> >> DevTrial on Android >> >> 111 >> >> >> 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). >> >> https://github.com/w3c/ServiceWorker/pull/1672 is mostly finished, but >> still undergoing final review by the spec mentor. >> >> Link to entry on the Chrome Platform Status >> >> https://chromestatus.com/feature/5136946693668864 >> >> This intent message was generated by Chrome Platform Status >> <https://chromestatus.com/>, and modified by hand. >> >> >> -- >> 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 blink-dev+unsubscr...@chromium.org. >> To view this discussion on the web visit >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAPNB-6VZntByJg-K_GNFb4xENkOEsmR8GewsKNJFyWbqnsWAHw%40mail.gmail.com >> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAPNB-6VZntByJg-K_GNFb4xENkOEsmR8GewsKNJFyWbqnsWAHw%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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