[Intermittent] Email preferences are not always saved

[mariaberlinger]

FxA Affected versions:

• 1.251.3

Prerequisites:

• User is on the “Manage your Email Preferences”

Steps to reproduce:

1. User checks some email sections;
2. User clicks on the Save button;
3. “Consider is done” messages is displayed;
4. User clicks on the “Back to email preferences” link;
5. User is now back on the “Manage your Email Preferences”;
6. Email preferences are properly saved;
7. Uncheck the emails checkboxes;
8. Click the Save button;
9. Click on the “Back to email preferences” link;
10. Observe the checkboxes on the “Manage your Email Preferences”;

Expected results:

• Email preferences are properly saved;

Actual results:

• Email preferences are not properly saved;

Notes:

• See the attached screen record;
  

[alexgibson]

Thanks for reporting, I can reproduce this.

[alexgibson]

I've done some local testing on this and the issue is certainly intermittent, however I was able to debug a bit:

• As far as i can tell, the issue doesn't seem to be in bedrock's front-end sending stale data. I can see the correct newsletters in the POST request each time after updating.
• When the bug occurs, I can see the incorrect newsletters being returned in the basket API call when the page loads after clicking "back to email-preferences". Setting {cache: 'no-store'} in the fetch request does not seem to make any difference. Neither does hard force-refreshing the browser.
• After a couple of minutes, refreshing the page again will suddenly return the updated data.

Given the above, might the issue be due to a delay somewhere when processing the initial preference change?

[stevejalim]

Yeah, the requests go in to a task queue, so the update won't always be immediate. In the past it's taken a few mins for things to work through the pipes.

Might be that we need to scale up the queue workers, but I also note that @robhudson is planning some work to replace the current task queue tooling with a different setup, so that might be a good time to revisit throughput