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@orion-js/dogs@4.6.2 can now choose between two MongoDB indexes when claiming jobs. Each startWorkers() instance measures both alternatives against its own configured job names and keeps the faster hint in memory. This matters because the best acquisition plan depends on the scheduler’s workload. An application that accepts a small subset of job names can benefit from leading the index with jobName, while a server that accepts most jobs may scan less work when the index starts with priority.

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The two acquisition indexes

Dogs declares both indexes on orionjs.jobs_dogs_records:
The first remains the initial hint. The second is the alternative evaluated by the scheduler. The real atomic findOneAndUpdate claim always receives the hint currently selected by that startWorkers() instance.

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Measure the real claim shape

The comparison runs once at startup in the background and then every 30 minutes. It uses the same eligibility filter and sort as the real claim, including every job configured for the scheduler:
Each probe runs three explains per hint, alternating their order to reduce ordering bias. Queries run on the primary with maxTimeMS: 1000, and Dogs compares the median executionTimeMillis reported by MongoDB. The first successful probe applies its winner immediately. Later probes require the alternative to win twice consecutively before changing the active hint. Ties, failures, and timeouts keep the current hint and reset the pending win streak.

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Operational behavior

The feature requires no configuration and stores no state outside the running process. Different servers can therefore select different hints for the same collection when their configured jobs or data distributions differ. Dogs logs the initial selection and later changes at info, retained hints at debug, and probe failures at warn. A scheduler with zero configured jobs does not run probes. Calling stop() cancels the next scheduled probe and waits for an explain already in flight. Once that explain returns, Dogs discards the rest of the incomplete comparison.

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Upgrade notes

  • There are no public API or job-document changes.
  • Allow Orion’s normal collection index setup to create both declared indexes before starting work.
  • Each scheduler adds six lightweight explain queries at startup and every 30 minutes.
  • Both indexes remain present so the scheduler can adapt again when the workload changes.
See the Jobs guide for worker configuration and shutdown behavior.