Long queue time on the initial index.html request during SW update with heavy precache

[taozhou-glean]

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Library Affected:
workbox-precaching

Browser & Platform:
all browsers

Issue or Feature Request Description:

notice long queue time on the initial index.html request when SW updates itself, especially when it requires a lot changes in precached assets, it seems the request on handling the index.html got blocked by all the other fetches happening on precache.

repro step is:

1. on a website that precache a lot files (hundreds of them)
2. clear the Cache but keep the service worker - you may also want to disable network cache
3. enable update on reload for SW
4. reload

our precache setting is very short:

precacheAndRoute(self.__WB_MANIFEST, { ignoreURLParametersMatching: [/.*/] })

tho the __WB_MANIFEST is quite a lot, like ~500 assets , and it does include the index.html itself, not sure if that's the issue that why index.html request itself got queued there - I would expect it will serve the old version with the old service worker before precache finished

[taozhou-glean]

tried to mark precache requests to low priority but still the highest request is waiting on low priority requests, seems wrong: