1542410 - Loading about:telemetry's Raw JSON data will hang Fenix, even after restarting the app

Status: RESOLVED INVALID

(GeckoView :: General, defect, P1)

Description

[Chris Peterson [:cpeterson]]

STR:

1. In Fenix, load about:telemetry.
2. Click the "Raw JSON" link.
3. Before the JSON finishes loading, press the Android Back button.

EXPECTED RESULT:
In Fennec and Focus+GV, the JSON data is loaded in the browser or you are given the open to open in a JSON Viewer app.

ACTUAL RESULT:
Fenix hangs while trying to load the JSON data.

If I kill the Fenix process and launch it again, Fenix will still hang. Perhaps the Fenix home screen is trying to show the JSON data in the list of recent sessions? I had to uninstall and reinstall Fenix to make it stop hanging.

Comment 1

[David Bolter [:davidb] (NeedInfo me for attention)]

I don't see a "Raw JSON" link.. did that get removed?

Comment 2

[Chris Peterson [:cpeterson]]

(In reply to David Bolter [:davidb] (NeedInfo me for attention) from comment #1)

I don't see a "Raw JSON" link.. did that get removed?

I still see "Raw JSON" at the bottom of the left column. It's a small text link beneath "Keyed Scalars".

I just reproduced the perma-hang (on my Moto G5) and now must uninstall/reinstall Fenix.

Comment 3

[Bobby Holley (:bholley)]

I reproduced this on a pixel 2. A few observations:

• You don't need to uninstall/reinstall Fenix to get unstuck, you can just clear the application data.
• This worked fine on the relatively-recent Fenix build I had installed, but I got the hang after upgrading. So this is a recent regression.
• It's not actually a hang, just a very long period of jank. It recovers (and displays the JSON as text) in about 2.5 minutes.
• I took a profile: https://perfht.ml/2XlrsdH . The Gecko threads in the parent and content processes seem idle and responsive.
• The hang doesn't actually require visiting the page, just putting the extremely-long data URI in the URL bar is sufficient. As such, I'm pretty sure the bug involves some exponential URL text processing in Fenix.

Comment 4

[Chris Peterson [:cpeterson]]

James says this is a Fenix issue. They shouldn't break long URLs.

I filed a Fenix issue: https://github.com/mozilla-mobile/fenix/issues/1824