Under some circumstances (possibly related to opening Chrome DevTools),
requests are made with `cache: 'only-if-cached'` and `mode: 'no-cors'`.
These request will eventually fail, because `only-if-cached` is only
allowed to be used with `mode: 'same-origin'`.
This is likely a bug in Chrome DevTools.
This commit avoids errors related to such requests by not handling them.
Fixes#22362
PR Close#22883
Previously, when trying to fetch `ngsw.json` (e.g. during
`checkForUpdate()`) while either the client or the server were offline,
the ServiceWorker would enter a degrade mode, where only existing
clients would be served. This essentially meant that the ServiceWorker
didn't work offline.
This commit fixes it by differentiating offline errors and not entering
degraded mode. The ServiceWorker will remain in the current mode until
connectivity to the server is restored.
Fixes#21636
PR Close#22883
When the SW fetches URLs listed in a manifest with hashes, it checks
the content hash against the manifest to make sure it has the correct
version of the URL. In the event of a mismatch, the SW is supposed to
consider the manifest invalid, and avoid using it. There are 3 cases
to consider by which this can happen.
Case 1: during the initial SW installation, a manifest is activated
without waiting for every URL to be fully loaded. In the background,
every prefetch URL listed by the manifest is requested and cached.
One such prefetch request could fail the hash test, and cause the
manifest to be treated as invalid. In such a case, the SW should
enter a state of EXISTING_CLIENTS_ONLY, as the latest manifest is
invalid.
This case works today.
Case 2: during the initial SW installation, as in Case 1, a manifest
is activated without waiting for each URL to fully load. However,
it's possible that the application could request a URL with a bad
hash before background initialization tries to load that URL. This
happens if, for example, the application has a broken index.html.
In this case, the SW should enter a state of EXISTING_CLIENTS_ONLY,
and serve the request from the network instead.
What happens today is that the internal error escapes the SW and
is returned as a rejected Promise to respondWith(), causing a
browser-level error that the site cannot be loaded, breaking the
site.
This change allows the SW to detect the error and enter the correct
state, falling back on the network if needed.
Case 3: during checkForUpdate(), the SW will try to fully cache the
new update before making it the latest version. Failure here is
complicated - if the page fails to load due to transient network
conditions (timeouts, 500s, etc), then it makes sense to continue
serving the existing cached version, and attempt to activate the
update on the next cycle.
If the page fails due to non-transient conditions though (400 error,
hash mismatch, etc), then the SW should consider the updated
manifest invalid, and enter a state of EXISTING_CLIENTS_ONLY.
Currently, all errors are treated as transient.
This change causes the SW to treat all errors during updates as
non-transient, which can cause the SW to unnecessarily enter a
safe mode. A future change can allow the SW to remain in normal mode
if the error is provably transient.
PR Close#21288
Currently the Service Worker checks for updates only on SW startup,
an event which happens frequently but also nondeterministically. This
makes it hard for developers to observe the update process or reason
about how updates will be delivered to users. This problem is
exacerbated by the DevTools behavior of keeping the SW alive
indefinitely while opened, effectively preventing the page from
updating at all.
This change causes the SW to additionally check for updates on
navigation requests (app page reloads). This creates deterministic
update behavior, and is much easier for developers to reason about.
It does leave the old update-on-SW-startup behavior in place, as
removing that would be a breaking change.
Fixes#20877
Not every application is served from the domain root. The Service
Worker made a bad assumption that it would be, and so requested
/ngsw.json from the domain root.
This change corrects this assumption, and requests ngsw.json without
the leading slash. This causes the request to be interpreted
relative to the SW origin, which will be the application root.
This commit fixes several issues discovered through use in real apps.
* The sha1() function operated on text content, causing issues for binary-format files.
A sha1Binary() function which operates on unparsed data now avoids any encoding issues.
* The characters '?' and '+' were not escaped in Glob-to-regex conversion previously, but
are now.
* URLs from the browser contain the full origin, but were checked against the table of
hashes from the manifest which only has the path for URLs from the same origin. Now the
origin is checked and URLs are relativized to the domain root before comparison if
appropriate.
* ngsw: prefix was missing from data groups, is now added.
* Occasionally servers will return a redirected response for an asset, and caching it could
cause errors for navigation requests. The SW now handles this by detecting such responses
and following the redirect manually, to avoid caching a redirected response.
* The request for known assets is now created from scratch from the URL before fetching from
the network, in order to sanitize it and avoid carrying any special modes or headers that
might result in opaque responses.
* Debugging log for troubleshooting.
* Avoid creating errors by returning 504 responses on error.
* Fix bug where idle queue doesn't run in some circumstances.
* Add tests for the above.
This service worker is a conceptual derivative of the existing @angular/service-worker maintained at github.com/angular/mobile-toolkit, but has been rewritten to support use across a much wider variety of applications.
Entrypoints include:
@angular/service-worker: a library for use within Angular client apps to communicate with the service worker.
@angular/service-worker/gen: a library for generating ngsw.json files from glob-based SW config files.
@angular/service-worker/ngsw-worker.js: the bundled service worker script itself.
@angular/service-worker/ngsw-cli.js: a CLI tool for generating ngsw.json files from glob-based SW config files.
George Kalpakas
Alex Eagle
Alex Rickabaugh
Misko Hevery