1594836 - Service Worker sources are sometimes missing

Status: RESOLVED FIXED

(DevTools :: Debugger, defect, P2)

Description

[:Harald Kirschner :digitarald]

What were you doing?

1. Open Debugger on platform-status.mozilla.org/ (See offline-worker.js in Sources pane and in Threads)
2. Set a breakpoint in offline-worker.js after self.addEventListener('fetch' …
3. Reload

Alternatively, I had a case where the sources didn't show when the Debugger opened but when appeared on reload.

What happened?

offline-worker.js is gone, no pausing.

What should have happened?

Workers stays there so it can actually be paused upon.

Comment 1

[Jan Honza Odvarko [:Honza] (always need-info? me)]

Attachment: image.png

I don't see offline-worker.js. How can I repro this bug?

Honza

Comment 2

[Brian Hackett [Laid off!]]

The devtools.debugger.features.windowless-service-workers preference needs to be set as well I think.

Comment 3

[Jan Honza Odvarko [:Honza] (always need-info? me)]

I have the pref set and I still don't see anything

Btw. I can see it in Chrome
Honza

Comment 4

[Brian Hackett [Laid off!]]

The problem here is related to how the debugger behaves when reloading. When reloading, the debugger detaches from all threads it has attached to. After the reload it attempts to reattach to any threads it can find, but this doesn't actually do anything because detaching from a target's thread seems to leave that thread in a more or less permanently detached state.

I think the right fix here is to just not detach from threads when reloading or navigating. I don't think that detaching from the thread really does that much other than mess up future attach attempts, as the worker's target is left alone. Additionally, the debugger needs to move away from managing attaching/detaching to targets (this is the framework's responsibility), and this is a step in that direction.

It's curious that this bug manifests consistently despite us having a test that we can reload when there is a service worker and things will work.

Comment 5

[Brian Hackett [Laid off!]]

Attachment: Bug 1594836 - Don't detach from threads in the debugger when navigating, r=jlast.

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/32ee3bf157f4
Don't detach from threads in the debugger when navigating, r=jlast.

Comment 7

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/32ee3bf157f4

Comment 8

[Cristian Fogel [:cfogel]]

Confirmed issue with :72.0a1 (2019-11-07) on Windows 10.
Fix verified with 74.0a1 (2020-02-09) - Windows 10 (for now).

However, in trying to verify the fix with RC build - 73.0 I am unable to see the offline-worker.js either.
Any extra pref needed for the Release builds?

Comment 9

[Cristian Fogel [:cfogel]]

Considering Brian's note, anyone else I could get in touch with to confirm the previous comment?