Cats Effect Files

This is the sixtieth release in the Cats Effect 3.x lineage. It is fully binary compatible with every 3.x release and fully source-compatible with the 3.6.x lineage. Barring critical security vulnerabilities, this will be our last release in the 3.6.x lineage, which also means this will be our last release targeting Scala Native 0.4.x.

[!WARNING] Please note that Cats Effect 3.6.x is targeting Scala Native 0.4.x, which means it does not at present support native multithreading. This was a very intentional choice meant to give us an opportunity to break binary compatibility only on Scala Native if necessary when upgrading to Scala Native 0.5 and as we discover the impacts of the integrated runtime on the downstream ecosystem. It also reduces risk since Native multithreading in the runtime is a significant lift and we want to make sure we isolate that change from the already significant changes in 3.6.0. This functionality has already merged into the development branch and we plan to release it in 3.7.0 as soon as possible.

What's Changed

The most significant change in this release is a fix for a resource leak arising from timeouts on Resources. This was commonly experienced in applications built on top of Http4s and could have a number of negative consequences. An additional significant change is a full rewrite of parTraverseN and parTraverseN_, eliminating a class of pathological performance degradation when a traversal errors or is canceled. We have more work to do on this function, but that will be released in the 3.7.x line.

Enhancements

• Implement PollerMetrics for EpollSystem by @antoniojimeneznieto in https://github.com/typelevel/cats-effect/pull/4335
• Implement PollerMetrics for KqueueSystem by @antoniojimeneznieto in https://github.com/typelevel/cats-effect/pull/4336
• Rewrote parTraverseN and parTraverseN_ for better performance by @djspiewak in https://github.com/typelevel/cats-effect/pull/4451

Bug Fixes

• Fix memory leak in Supervisor internal state by @durban in https://github.com/typelevel/cats-effect/pull/4500
• Fix scaladoc links in IOApp by @durban in https://github.com/typelevel/cats-effect/pull/4562
• Fix issue [#4489] by @durban in https://github.com/typelevel/cats-effect/pull/4625

Documentation

• Update weaver with typelevel org by @lenguyenthanh in https://github.com/typelevel/cats-effect/pull/4476
• Add FAQ on imports by @mtomko in https://github.com/typelevel/cats-effect/pull/4534

Behind the Scenes

• Switch to windows-2022 runner tag by @samspills in https://github.com/typelevel/cats-effect/pull/4470
• Actually run JVM IOApp tests in CI by @armanbilge in https://github.com/typelevel/cats-effect/pull/4518

Full Changelog: https://github.com/typelevel/cats-effect/compare/v3.6.3...v3.6.4