New module src/core/dependent_queue.rs provides job queue operations
against the pending_dependent_fetches table. Designed for second-pass
fetches that depend on primary entity ingestion (resource events,
MR close references, MR file diffs).
Queue operations:
- enqueue_job: Idempotent INSERT OR IGNORE keyed on the UNIQUE
(project_id, entity_type, entity_iid, job_type) constraint.
Returns bool indicating whether the row was actually inserted.
- claim_jobs: Two-phase claim — SELECT available jobs (unlocked,
past retry window) then UPDATE locked_at in batch. Orders by
enqueued_at ASC for FIFO processing within a job type.
- complete_job: DELETE the row on successful processing.
- fail_job: Increments attempts, calculates exponential backoff
(30s * 2^(attempts-1), capped at 480s), sets next_retry_at,
clears locked_at, and records the error message. Reads current
attempts via query with unwrap_or(0) fallback for robustness.
- reclaim_stale_locks: Clears locked_at on jobs locked longer than
a configurable threshold, recovering from worker crashes.
- count_pending_jobs: GROUP BY job_type aggregation for progress
reporting and stats display.
Registers both events_db and dependent_queue in src/core/mod.rs.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
