v2.12.1

Bug Fixes

• [BasicEngine] Never fetch jobs that have reached max attempts

  This adds a safeguard to the fetch_jobs function to prevent ever hitting the attempt <= max_attempts check constraint. Hitting the constraint causes the query to fail, which crashes the producer and starts an infinite loop of crashes. The previous commit should prevent this situation from occurring at the "staging" level, but to be absolutely safe this change prevents it at the
  "fetching" level too.

  There is a very minor performance hit from this change because the query can no longer run as an index only scan. For systems with a modest number of available jobs the performance impact is indistinguishable.

• [Plugins] Prevent unexpectedly modifying jobs selected by subqueries

  Most applications don't run at a serializable isolation level. That allows subqueries to run within a transaction without having the conditions rechecked—only predicates on UPDATE or DELETE are re-checked, not on subqueries. That allows a race condition where rows may be updated without another evaluation.

• [Repo] Set query_opts in Repo.transaction options to prevent logging begin and commit events in development loggers.

• [BasicEngine] Remove the ORDER BY clause from unique queries

  The previous ORDER BY id DESC significantly hurts unique query performance when there are a lot of potential jobs to check. The ordering was originally added to make test cases predictable and isn't important for the actual behavior of the unique check.