1932780 - Translations Performance Impacted By Mutation Observer Changes

Status: VERIFIED FIXED

(Firefox :: Translations, defect, P1)

Description

[Erik Nordin [:nordzilla]]

Attachment: before-and-after.webm

Description

Bug 1909632 (push log) introduced changes to the mutation observers for Translations, which fixed some long-standing bugs, but have introduced a new impact on performance for Translations.

The following steps to reproduce feel like an edge case of triggering multiple translations in a row with auto-translate enabled, however I have noticed the same impact (though less reliably reproducible) when translating only a single page.

I have particularly noticed this impact when testing out a zhen model and translating content on https://zh.wikipedia.org/wiki/Mozilla_Firefox.

---

Steps to reproduce

Note:

See attached video for example STR on Linux.

The attached video shows behavior on Linux where hovering the mouse over a hyperlink triggers a translation for that node after the translation has stalled. I have only been able to reproduce this exact behavior on Linux. The slowdown is noticeable on macOS, however mousing over a hyperlink seems to have no effect. I have not tried yet on Windows.

1. Open the browser to a translatable page, e.g. https://es.wikipedia.org/wiki/Mozilla_Firefox.
2. Enable auto-translate for the page language.
3. Click on new hyper links in rapid succession until the page translation is no longer quick.

Expected Behavior
The page translation is fast no matter how many links you click on.

Actual Behavior
The page translation stalls for much of the visible content after clicking on a few links in succession.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1909632

:gregtatum, since you are the author of the regressor, bug 1909632, could you take a look?

For more information, please visit BugBot documentation.

Comment 2

[Greg Tatum [:gregtatum]]

I think this has to do with the popovers on Wikipedia causing the mutation observer to run, and changing the timing of the translations queue. We don't do a good job of managing the queue for prioritization. I suspect that Bug 1820252 would help alleviate this. Wikipedia articles are big and take a long time to run. Before, they would go from top to bottom, but I wonder how the queue is getting shifted with the new behavior.

Comment 3

[Greg Tatum [:gregtatum]]

Attachment: Bug 1932780 - Make the translationsId unique across page loads; r?#translations-reviewers

This was causing an issue where performing an action using a
translationId would affect translations from another page load. This
race condition would be prevalent when using the auto translation
feature and navigating quickly between pages.

Comment 4

[Greg Tatum [:gregtatum]]

This is actually a correctness issue, not a perf issue. The mutations were re-translating incorrectly discarded translations request.

Comment 5

[Greg Tatum [:gregtatum]]

https://treeherder.mozilla.org/jobs?repo=try&group_state=expanded&revision=64decc65b9279376756039a39e2d80c619f9e270

Comment 6

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1909632

Comment 7

[Phabricator Automation]

Comment on attachment 9439418 [details]
Bug 1932780 - Make the translationsId unique across page loads; r?#translations-reviewers

Revision D229958 was moved to bug 1934997. Setting attachment 9439418 [details] to obsolete.

Comment 8

[Greg Tatum [:gregtatum]]

Attachment: Bug 1932780 - Correct mistaken use of discardTranslationQueue; r?#translations-reviewers

This was calling the wrong method and causing bad translation issues
when mutations were being canceled.

Comment 9

[Greg Tatum [:gregtatum]]

https://treeherder.mozilla.org/jobs?repo=try&revision=5e32e9310ba8908b0aadee1e70f5cffc3e541b0b

Comment 10

[Greg Tatum [:gregtatum]]

Attachment: Bug 1932780 - Correct the spelling of translationId in message passing; r?#translations-reviewers

Comment 11

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/fda9afeffafd
Correct mistaken use of discardTranslationQueue; r=translations-reviewers,nordzilla
https://hg.mozilla.org/integration/autoland/rev/f77db234d79b
Correct the spelling of translationId in message passing; r=translations-reviewers,nordzilla

Comment 12

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/fda9afeffafd
https://hg.mozilla.org/mozilla-central/rev/f77db234d79b

Comment 13

[BugBot [:suhaib / :marco/ :calixte]]

The patch landed in nightly and beta is affected.
:gregtatum, is this bug important enough to require an uplift?

• If yes, please nominate the patch for beta approval.
• If no, please set status-firefox134 to wontfix.

For more information, please visit BugBot documentation.

Comment 14

[Greg Tatum [:gregtatum]]

Attachment: Bug 1932780 - Correct mistaken use of discardTranslationQueue;

This was calling the wrong method and causing bad translation issues
when mutations were being canceled.

Original Revision: https://phabricator.services.mozilla.com/D231011

Comment 15

[Greg Tatum [:gregtatum]]

Attachment: Bug 1932780 - Correct the spelling of translationId in message passing;

Original Revision: https://phabricator.services.mozilla.com/D231092

Comment 16

[Phabricator Automation]

beta Uplift Approval Request

• User impact if declined: Full page translation will not fully translate a page when there is a mutation.
• Code covered by automated testing: yes
• Fix verified in Nightly: yes
• Needs manual QE test: yes
• Steps to reproduce for manual QE testing: See comment
• Risk associated with taking this patch: Low
• Explanation of risk level: It should be minimal, as it's fixing the call to an incorrect method. The specific fix isn't covered by a test for the behavior as it's hard to test, but the overall codebase for translations is well tested for this area.
• String changes made/needed: None
• Is Android affected?: yes

Comment 17

[Pulsebot]

https://hg.mozilla.org/releases/mozilla-beta/rev/93e5dea253a8
https://hg.mozilla.org/releases/mozilla-beta/rev/5519c2f050e7

Comment 18

[Ina Popescu, Desktop QA]

I've managed to reproduce this issue in Nightly 134.0a1 (2024-11-21) using the STR from Comment 0 on Ubuntu 22.04.
Marking this as Verified Fixed, as the issue is no longer reproducible in the latest Nightly 135.0a1 and Firefox 134.0b8 versions on Windows 11, macOS 13, and Ubuntu 22.04, where the page is translated without delay when clicking on various links.