1685124 - Intermittent browser/modules/test/browser/browser_ProcessHangNotifications.js | A promise chain failed to handle a rejection: can't access property "isAppProvided", engine is null - stack: _updateURLBarPlaceholder@chrome://browser/content/browser.js:4138:

Status: RESOLVED FIXED

(Firefox :: Search, defect, P2)

Description

[Treeherder Bug Filer]

Filed by: rmaries [at] mozilla.com
Parsed log: https://treeherder.mozilla.org/logviewer?job_id=325859565&repo=autoland
Full log: https://firefox-ci-tc.services.mozilla.com/api/queue/v1/task/ScpTx_6MR7Srn8HyCLmRyA/runs/0/artifacts/public/logs/live_backing.log

---

[task 2021-01-05T16:36:29.163Z] 16:36:29     INFO - TEST-START | browser/modules/test/browser/browser_ProcessHangNotifications.js
[task 2021-01-05T16:36:30.406Z] 16:36:30     INFO - TEST-PASS | browser/modules/test/browser/browser_ProcessHangNotifications.js | With no open windows, should have terminated script for script hang. - 
[task 2021-01-05T16:36:30.406Z] 16:36:30     INFO - TEST-PASS | browser/modules/test/browser/browser_ProcessHangNotifications.js | With no open windows, should have terminated global for add-on hang. - 
[task 2021-01-05T16:36:30.406Z] 16:36:30     INFO - Buffered messages finished
[task 2021-01-05T16:36:30.406Z] 16:36:30     INFO - TEST-UNEXPECTED-FAIL | browser/modules/test/browser/browser_ProcessHangNotifications.js | A promise chain failed to handle a rejection: can't access property "isAppProvided", engine is null - stack: _updateURLBarPlaceholder@chrome://browser/content/browser.js:4138:9
[task 2021-01-05T16:36:30.406Z] 16:36:30     INFO - _updateURLBarPlaceholderFromDefaultEngine@chrome://browser/content/browser.js:4114:10
[task 2021-01-05T16:36:30.406Z] 16:36:30     INFO - Rejection date: Tue Jan 05 2021 16:36:29 GMT+0000 (Greenwich Mean Time) - false == true - JS frame :: resource://testing-common/PromiseTestUtils.jsm :: assertNoUncaughtRejections :: line 282
[task 2021-01-05T16:36:30.406Z] 16:36:30     INFO - Stack trace:
[task 2021-01-05T16:36:30.406Z] 16:36:30     INFO - resource://testing-common/PromiseTestUtils.jsm:assertNoUncaughtRejections:282
[task 2021-01-05T16:36:30.406Z] 16:36:30     INFO - chrome://mochikit/content/browser-test.js:Tester_execTest/<:1100
[task 2021-01-05T16:36:30.406Z] 16:36:30     INFO - Leaving test bound terminateNoWindows
[task 2021-01-05T16:36:30.406Z] 16:36:30     INFO - Entering test bound terminateClosedWindow
[task 2021-01-05T16:36:30.409Z] 16:36:30     INFO - GECKO(1988) | [Parent 1988: Main Thread]: I/DocShellAndDOMWindowLeak ++DOCSHELL 0x1313a4400 == 14 [pid = 1988] [id = 62]
[task 2021-01-05T16:36:30.409Z] 16:36:30     INFO - GECKO(1988) | [Parent 1988: Main Thread]: I/DocShellAndDOMWindowLeak ++DOMWINDOW == 27 (0x15cafc900) [pid = 1988] [serial = 127] [outer = 0x0]
[task 2021-01-05T16:36:30.409Z] 16:36:30     INFO - GECKO(1988) | [Parent 1988: Main Thread]: I/DocShellAndDOMWindowLeak ++DOMWINDOW == 28 (0x1317be400) [pid = 1988] [serial = 128] [outer = 0x15cafc900]
[task 2021-01-05T16:36:30.409Z] 16:36:30     INFO - GECKO(1988) | [Parent 1988, Main Thread] WARNING: NS_ENSURE_TRUE(uri) failed: file /builds/worker/checkouts/gecko/caps/BasePrincipal.cpp:1327
[task 2021-01-05T16:36:30.409Z] 16:36:30     INFO - Console message: [JavaScript Error: "URL constructor: null is not a valid URL." {file: "resource:///modules/ProcessHangMonitor.jsm" line: 403}]
[task 2021-01-05T16:36:30.409Z] 16:36:30     INFO - _recordTelemetryForReport@resource:///modules/ProcessHangMonitor.jsm:403:21
[task 2021-01-05T16:36:30.409Z] 16:36:30     INFO - stopHang@resource:///modules/ProcessHangMonitor.jsm:163:14
[task 2021-01-05T16:36:30.409Z] 16:36:30     INFO - stopAllHangs@resource:///modules/ProcessHangMonitor.jsm:343:12
[task 2021-01-05T16:36:30.409Z] 16:36:30     INFO - updateWindows@resource:///modules/ProcessHangMonitor.jsm:478:12
[task 2021-01-05T16:36:30.409Z] 16:36:30     INFO - reportHang@resource:///modules/ProcessHangMonitor.jsm:702:10
[task 2021-01-05T16:36:30.409Z] 16:36:30     INFO - observe@resource:///modules/ProcessHangMonitor.jsm:258:14
[task 2021-01-05T16:36:30.409Z] 16:36:30     INFO - terminateNoWindows/<@chrome://mochitests/content/browser/browser/modules/test/browser/browser_ProcessHangNotifications.js:435:18
[task 2021-01-05T16:36:30.409Z] 16:36:30     INFO - terminateNoWindows@chrome://mochitests/content/browser/browser/modules/test/browser/browser_ProcessHangNotifications.js:434:42```

Comment 1

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

Coincidence or not - bug 1680672 disabled the earlier executed browser_PermissionUI.js on debug platforms and the failures for this bug are all on debug.

Comment 2

[Mark Banner (:standard8)]

Looks like browser_PartnerLinkAttribution.js might be having an unexpected side-effect. I'll see if I can track something down.

Comment 3

[Mark Banner (:standard8)]

The order of events in the test are:

1. Load an engines list specific to the test.
2. Run tests
3. Set the default engine back to the default for the engines list defined in the test.
4. Run cleanup which involves reloading the main engines list.

The problem came from step 2 triggering a delayed save of the search settings (normal practice). During reloading the engines list, we were then loading the settings again - it would attempt to save any pending changes, but because we are inside _reloadEngines the save would be skipped.

As the save was skipped, it would still have one of the test engines as default, which then was set as default engine, only for it to be removed - so the default engine is defined but the engine is not in the engine list.

The _updateURLBarPlaceholderFromDefaultEngine and _updateURLBarPlaceholder code operates on the default engine, and then the name of that engine. So it would get an engine in _updateURLBarPlaceholderFromDefaultEngine, but then null when it tried to get it from the list via getEngineByName. Hence the failure in the test.

This would be helped slightly (and possibly hidden) if we had bug 1575649 which would clear the default engine when it was removed.

However, I think the fix for this bug needs to be that we ensure the settings are saved prior to the main body of _reloadEngines. In theory there's potential for a small dataloss there, but it would have to happen that the user triggers a change of search engine settings within a second prior to us reloading the engines - which generally only happens in this fashion on startup. A remotely triggered configuration update waits for the user to be idle for 5 minutes before it triggers the reload.

Comment 4

[Mark Banner (:standard8)]

Try pushes: https://treeherder.mozilla.org/jobs?repo=try&revision=62b4b2f5b349f92977c4ba82ad2eaf45174176d9
https://treeherder.mozilla.org/jobs?repo=try&revision=d94d5daf99a13b265883404654462de2eab00500

Comment 5

[Mark Banner (:standard8)]

Attachment: Bug 1685124 - Ensure search engine settings are saved before reloading engines. r?daleharvey!

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/c9a390a20847
Ensure search engine settings are saved before reloading engines. r=daleharvey

Comment 10

[Intermittent Failures Robot]

47 failures in 2956 pushes (0.016 failures/push) were associated with this bug in the last 7 days.

This is the #12 most frequent failure this week.

** This failure happened more than 30 times this week! Resolving this bug is a high priority. **

** Try to resolve this bug as soon as possible. If unresolved for 2 weeks, the affected test(s) may be disabled. **

Repository breakdown:

• autoland: 30
• mozilla-central: 16
• mozilla-beta: 1

Platform breakdown:

• windows10-64: 5
• macosx1014-64-qr: 22
• linux1804-64: 10
• windows10-64-qr: 9
• linux1804-64-tsan: 1

For more details, see:
https://treeherder.mozilla.org/intermittent-failures/bugdetails?bug=1685124&startday=2021-01-04&endday=2021-01-10&tree=all

Comment 11

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/c9a390a20847

Comment 13

[Intermittent Failures Robot]

1 failures in 3966 pushes (0.0 failures/push) were associated with this bug in the last 7 days.

Repository breakdown:

• mozilla-release: 1

Platform and build breakdown:

• linux1804-64: 1
  • debug: 1

For more details, see:
https://treeherder.mozilla.org/intermittent-failures/bugdetails?bug=1685124&startday=2021-02-01&endday=2021-02-07&tree=all