Plan 02 Summary: Force-Fetch Lock Contention Handling

What Was Built

When a user force-fetches a source that is already being fetched, the system now fails fast with a clear "Fetch already in progress" warning toast instead of retrying 5 times over 2.5 minutes. Scheduled fetches retain their existing retry behavior.

The solution works at two levels:

1. Pre-enqueue check: FetchRunner.enqueue detects fetch_status == "fetching" before even creating a job, returning :already_fetching immediately
2. Job-level fallback: If a force-fetch job does encounter a ConcurrencyError (race condition), it skips retries and resets the source status to idle

Tasks Completed

1. Task 1: ConcurrencyError handling in FetchFeedJob (verified existing - commit 47361b2)

   • rescue_from ConcurrencyError differentiates force vs scheduled fetches
   • Force: logs skip, resets status to idle, no retry
   • Scheduled: retries up to 5 times with 30s wait

2. Task 2: Pre-enqueue check in FetchRunner.enqueue (commit 6ada960)

   • Added early return of :already_fetching when force: true and source is fetching
   • Prevents duplicate job creation entirely

3. Task 3: SourceRetriesController warning toast (commit cfe7016)

   • Checks return value from FetchRunner.enqueue
   • Renders warning-level toast: "Fetch already in progress for this source..."

4. Task 4: Tests (commit 6731ac5)

   • force_fetch_lock_test.rb: 6 tests for FetchRunner pre-enqueue behavior
   • fetch_feed_job_test.rb: 3 new tests for force-fetch ConcurrencyError handling
   • source_retries_controller_test.rb: 1 new test for warning toast response

Files Modified

• lib/source_monitor/fetching/fetch_runner.rb - pre-enqueue check
• app/controllers/source_monitor/source_retries_controller.rb - warning toast handling
• app/jobs/source_monitor/fetch_feed_job.rb - (Task 1, pre-existing commit)

Files Created

• test/lib/source_monitor/fetching/force_fetch_lock_test.rb - integration tests

Files Modified (Tests)

• test/jobs/source_monitor/fetch_feed_job_test.rb - force-fetch ConcurrencyError tests
• test/controllers/source_monitor/source_retries_controller_test.rb - warning toast test

Commits

• 47361b2 feat(fetching): handle force-fetch ConcurrencyError without retries (pre-existing)
• 6ada960 feat(fetching): add pre-enqueue check for force-fetch lock contention
• cfe7016 feat(controller): show warning toast when force-fetch is already in progress
• 6731ac5 test(fetching): add tests for force-fetch lock contention handling

Deviations

None. All tasks completed as planned.

Validation

• bin/rubocop: 0 offenses on all modified files
• bin/rails test: 1257 runs, 3895 assertions, 0 failures, 0 errors, 0 skips