Reporting page doesn't show any reports. User doesn't get report completed notifications

[LeeDr]

Kibana version: 7.10.0-snapshot (same problem on 8.0.0-snapshot)

Elasticsearch version: 7.10.0-snapshot

Server OS version: Ubuntu 16.04

Browser version: Chrome

Browser OS version: Windows 10

Original install method (e.g. download page, yum, from source, etc.): tar.gz default dist

Describe the bug: An automated test that uses watcher to email a dashboard PDF passed on the 7.x snapshot build from Aug 13th but failed on today's build (Aug 17th).

When I manually generate a dashboard PDF (using eCommerce sample data) I get the notification that the report was queued but I don't get a notification that it completed. I can see kibana logs that indicate the report was completed successfully.

Possibly related to this recent PR #74453

Steps to reproduce:

1. Install the default dist of Kibana tar.gz package DON'T configure security on Elasticsearch or Kibana
2. Load eCommerce sample data
3. go to the eCommerce dashboard and generate the PDF (doesn't matter if you optimize for printing or if you do the PNG instead).
4. tail -k the kibana log and grep for report so you can see when Job execution completed successfully while watching for the notification dialog in Kibana. (I don't see one)
5. check the reporting page in Kibana. It shows "No reports have been created"

Expected behavior: User should get notification. Reports should appear in Reporting page.

Screenshots (if relevant):

Errors in browser console (if relevant): No errors in Kibana browser console.

Provide logs and/or server output (if relevant): I'll update logs soon. Same problem on master branch.

Any additional context:

[elasticmachine]

Pinging @elastic/kibana-reporting-services (Team:Reporting Services)

[LeeDr]

Here's a log file (grep report in kibana.stdout) from 7.9.0 where the log looks like the PDF report finished successfully but no notification in the UI and no reports shown on reporting page;

reporting.txt

[tsullivan]

NOTE: #74453 isn't going to be part of the 7.9.0 release, but still exists in the 7.9 branch

[tsullivan]

I am not able to reproduce this, either with security enabled or disabled. I am thinking something is happening in the environment, or between the browser and server.

Update: I wasn't able to repro in the 7.9 branch, when assuming it would be evident there. But the bug description clearly says 7.10. I was able to reproduce this issue in the current 7.x branch.

[tsullivan]

I've dug in an think I have the root cause. A PR snuck in a change that switched the username for the "security disabled" scenario from false to null. With security disabled, the jobs query as it is can never find the jobs that belong to false because that user indexed them as null.

Going to roll back the change, this would be a headache of a breaking change.

[tsullivan]

The bug arose in this PR: #74915