ENG-3925: Write execution log when stuck task reaper errors a privacy request

[eastandwestwind]

Ticket https://ethyca.atlassian.net/browse/ENG-3928

Description Of Changes

When a privacy request task dies at the worker level (OOM kill, crash, etc.), the request stays in in_processing until the stuck task reaper finds it. The reaper calls _cancel_interrupted_tasks_and_error_privacy_request which sets the status to error — but it never created an execution log. The error message (e.g., "stuck without a running task") was only written to server logs via logger.error(), invisible in the Admin UI.

This adds an add_error_execution_log() call so the reaper's error message is visible in the request's Activity tab, giving operators immediate visibility into why a request failed.

Code Changes

• src/fides/api/service/privacy_request/request_service.py — Added add_error_execution_log() call in _cancel_interrupted_tasks_and_error_privacy_request before error_processing(), with try/except to handle DB write failures gracefully
• tests/fides/task/test_requeue_interrupted_tasks.py — 5 new tests:
  • Creates error execution log with explicit error message
  • Creates execution log with default message when none provided
  • Handles execution log write failure gracefully (request still errored)
  • Handles error_processing failure gracefully (no raise)
  • Verifies Celery tasks are cancelled

Steps to Confirm

1. Simulate a stuck privacy request (kill the worker while a request is processing)
2. Wait for the stuck task reaper to run (~5 min default interval)
3. Check the request in Admin UI → Activity tab
4. Verify an error execution log entry appears with the reaper's message (e.g., "No task ID found... stuck without a running task")

Pre-Merge Checklist

• Issue requirements met
• All CI pipelines succeeded
• CHANGELOG.md updated
  • Add a db-migration This indicates that a change includes a database migration label
  • Add a high-risk This issue suggests changes that have a high-probability of breaking existing code label
  • Updates unreleased work already in Changelog, no new entry necessary
• UX feedback:
  • No UX review needed
• Followup issues:
  • No followup issues
• Database migrations:
  • No migrations
• Documentation:
  • No documentation updates required

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
fides-plus-nightly	Ready	Preview, Comment	May 21, 2026 2:22pm

1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
fides-privacy-center	Ignored		May 21, 2026 2:22pm

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.15%. Comparing base (38b3296) to head (082e804).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8253   +/-   ##
=======================================
  Coverage   85.15%   85.15%           
=======================================
  Files         670      670           
  Lines       43497    43501    +4     
  Branches     5093     5093           
=======================================
+ Hits        37039    37043    +4     
+ Misses       5351     5350    -1     
- Partials     1107     1108    +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.