fix: eliminate head-of-line blocking in RedisWorker.fetch_task() - #7975
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fix: eliminate head-of-line blocking in RedisWorker.fetch_task()#7975dkliban wants to merge 1 commit into
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When the task queue has thousands of tasks needing the same blocked resource, workers could not reach tasks for free resources further down the queue. The old algorithm doubled its query window and restarted from position 0 each time, re-scanning the same blocked tasks repeatedly. Track resources that acquire_locks() reports as blocked and exclude tasks needing those resources from subsequent DB queries using PostgreSQL's array overlap operator against the existing GIN index on reserved_resources_record. In the incident scenario (17,000+ tasks blocked on one repository), this reduces the search from ~11 doubling iterations fetching ~37,000 rows to 2 queries fetching ~40 rows. Closes: pulp#7900 Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
Fixes head-of-line blocking in RedisWorker.fetch_task() when thousands of
tasks need the same exclusive resource (#7900).
After acquire_locks reports a resource is blocked, tasks needing that resource
are excluded from subsequent DB queries using the GIN-indexed
reserved_resources_record overlap check. Both raw and shared: prefixed
variants are excluded so tasks needing either exclusive or shared access
to the blocked resource are skipped.
Changes
Testing
finds the free task in <= 5 acquire_locks calls (old algorithm needs ~8)
Benchmark results (from factory)
Fixes #7900
Co-Authored-By: Claude Opus 4.6 (1M context) noreply@anthropic.com