typelevel / typelevel/cats-effect
`parTraverseN` fairness
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- Dominant language
- Scala
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Description
The documentation of parTraverseN explicitly mentions fairness:
Note that the semantics of this operation aim to maximise fairness: when a spot to execute becomes available, every task has a chance to claim it, and not only the next
ntasks inta
But, based on some testing, later tasks in ta have a very very small chance of overtaking earlier ones. I suspect this is very task- and processor dependent, but (based on the wording) it seems to me that whoever wrote the docs felt that this is an important feature of parTraverseN, so it might be worth looking into...
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with the parTraverseN fairness documentation in kernel/shared/src/main/scala/cats/effect/kernel/GenConcurrent.scala at the linked lines, then locate the corresponding parTraverseN implementation and reproduce the reported behavior under different task and processor conditions. Determine whether the observed scheduling contradicts the documented fairness semantics; done means a confirmed behavior and an agreed implementation or documentation change.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- scala
- Domain
- backend
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 35/100