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? > > 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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