v3.6.1

This is the fifty-sixth 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. Please note that we did break binary compatibility with 3.6.0 RC1 (not with 3.5.x) in order to fix some things, so if you published anything against that release you will need to reconsider your life choices.

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

Bug Fixes

• Also interrupt pollers when shutting down the WSTP by @durban in #4340
• Make deprecated IO.onError package private by @CJSmith-0141 in #4343

Documentation

• Document PollingSystem#metrics by @antoniojimeneznieto in #4334

Behind the Scenes

• Update versions for 3.6.0 by @djspiewak in #4311
• Restore GraalVM Native Image test in CI by @armanbilge in #4315

New Contributors

• @CJSmith-0141 made their first contribution in #4343

Full Changelog: v3.6.0...v3.6.1

v3.6.0

This is the fifty-fifth 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. Please note that we did break binary compatibility with 3.6.0 RC1 (not with 3.5.x) in order to fix some things, so if you published anything against that release you will need to reconsider your life choices.

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 is already under development and we plan to release it in 3.7.0 as soon as possible.

What's Changed

This release contains the largest change to the Cats Effect internal work scheduler since the introduction of work stealing back in the run up to 3.0.0. In particular, we have finally completed implementation of the integrated runtime we first conceived of back in early 2022. Well, I say "we", but really @armanbilge deserves the absolute lion's share of the credit here. He did almost all of the work not only on the direct implementation in Cats Effect, but also the downstream functionality built on top of it in Fs2 and in Http4s… not only on the JVM but also in Scala Native and across multiple operating systems! It is hard to overstate how gargantuan of an effort this was, both in design and implementation.

As immense as the effort has been, the impact is even more dramatic. We've already observed scenarios in which the performance of microservices implemented on top of Http4s Ember on the JVM leveraging io_uring is improved by over 3.5x! That is to say, the performance is 3.5x higher than baseline using classical NIO2! (as measured by TechEmpower, suggesting performance more than 2x higher than pekko-http) Now, TechEmpower does have its limitations as a framework, but it does represent a useful standard candle for certain access patterns, and improving an already very fast trio of frameworks by this magnitude is not something that happens every day. Even more excitingly, this is just the tip of the iceberg! We ran these tests with very early, almost PoC code with a lot of performance-impacting caveats. The best is yet to come.

And if that wasn't enough, the biggest impacts are not on the JVM but actually on Scala Native. Without diving too far into the details, this type of syscall scheduling mechanism is exactly what is necessary on Scala Native to achieve any measure of performance from downstream services. It is actually remarkably similar to what the Go runtime does, though implemented in a more extensible way (e.g. Go does not, at present, have native support for io_uring, whereas Cats Effect can and has implemented this via a third-party library).

Going forward, Cats Effect will be maintaining support for the following polling systems:

• JVM
  • Selector
• Native
  • kqueue
  • epoll

Support for io_uring is already under heavy development, and we expect to incorporate this into Cats Effect at some future date, supporting both Native and JVM. The integrated runtime was specifically designed with io_uring's unique data patterns in mind and we have already been able to demonstrate that downstream layers of the ecosystem will be able to fully leverage its benefits. Additionally, we believe we can meaningfully improve JVM performance by implementing epoll and kqueue support for the JVM (and not just Native), the former for situations where io_uring is unavailable. This is mostly because Selector is actually very very slow, and while the performance of the Selector-based runtime is roughly on par with what we've been able to achieve on top of NIO2 (which has its own syscall management and is incompatible with the integrated runtime), we know we can do quite a bit better.

On top of the above, this release contains a large number of other enhancements covering a number of major scenarios. Most noticeably, thanks to @kamilkloch, explicitly importing cats.syntax.all._ is no longer required for most usage involving explicit IO! You will still need the syntax import for any use of parametric effects (commonly referred to as "tagless final" or F[_]), and unfortunately due to the way Scala's type inference works, it is also required for the very common traverse function, but nearly any and all other cases have had their implicit search tweaked to avoid this inconvenience. This in turn means that . completion now mostly Just Works™ when using IO (and when it doesn't, hunting for methods on the IO companion object definitely works).

An additional class of work went into substantially improving the internal instrumentation and metrics associated with the runtime. As previously, these are all exposed as JMX MBeans on the JVM, but we have additionally added public APIs which allow applications to self-instrument (rather than forcing external untyped instrumentation via JMX). These metrics have been organized to mirror the structure of the runtime itself and can all be found within the cats.effect.unsafe.metrics package.

If you're an end-user of Cats Effect (in other words, you run applications built on Cats Effect, rather than building libraries or frameworks), one way you can very much aid the future development of the library is to incorporate these metrics (likely via JMX) into your application observability and key metrics. This should allow you to start to build up an intuition for what metrics are significant indicators of good or bad or just plain normal behavior. This is exactly the type of information that is difficult for library authors to realistically determine, but if end-users learn this on our behalf, you can help educate us on the precise details of how the runtime behaves for your application in your production context, shaping the future optimization and tuning of the framework! (note: Cats Effect does not proactively send metrics anywhere from your application, it merely exposes them to your own monitoring infrastructure)

Enhancements

• Polling system by @armanbilge in #3332
• evalOnExecutor by @homycdev in #3691
• Native signal handling and safe IOApp cancelation by @armanbilge in #3695
• Add warnOnNonMainThreadDetected configuration to IOApp by @diogocanut in #3815
• Block in-place if running on a virtual thread by @armanbilge in #3870
• Add GenConcurrent#parSequenceN_ and GenConcurrent#parTraverseN_. by @kamilkloch in #3916
• Apply @static annotation internally by @armanbilge in #3934
• Added PriorityQueue{Sink,Source} extending Queue{Sink,Source} by @neomaclin in #3930
• Timer stealing without a concurrent data structure by @armanbilge in #3781
• Embed cats.syntax.all._ into IO. by @kamilkloch in #3532
• Quick and dirty unsafe queue API by @djspiewak in #3975
• Implement async dropping queue by @iRevive in #4143
• Refactor Ref#mapK to take Functor[G] constraint instead of Functor[F] by @armanbilge in #4115
• Add ownPoller by @armanbilge in #4133
• Use IO.unit in Async[IO].unit by @iRevive in #4162
• Add default constructor for MapRef by @yisraelU in #4139
• Add SystemProperties by @massimosiani in #3924
• Make timeout/timeoutTo always return the outcome of the effect by @biochimia in #4059
• IOLocal propagation for unsafe access by @armanbilge in #3636
• Make UUIDGen more performant by @diogocanut in #3647
• cats.mtl.Local[IO, E] from IOLocal[E] by @rossabaker in #3429
• Implement IORuntimeMetrics by @iRevive in #3317
• Use global counter as an MBean ID for WSTP by @iRevive in #4186
• Add a memoizedAcquire method to Resource by @satabin in #4105
• Add TimerHeapMetrics by @iRevive in #4187
• Add pack count metric for TimerHeap by @armanbilge in #4207
• Add WorkerThread-specific metrics by @armanbilge in #4206
• Introduce PollerMetrics by @armanbilge in #4209
• Add UUIDGen inductive materializers for monad transformers by @bio-aeon in http...

v3.6.0-RC2

This is the fifty-fourth release in the Cats Effect 3.x lineage. It is fully binary compatible with every 3.x release and expected to be fully source-compatible with the eventual 3.6.x lineage. However, we did break binary-compatibility with the previous candidate v3.6.0-RC1.

This release candidate is expected to be very stable, and our main rationale for releasing it as such rather than as a full 3.6.0 is to allow the ecosystem (and adventurous end users!) to try it out and find unforeseen problems prior to full release. If fixing those problems require breaking compatibility prior to 3.6.0 (while maintaining bincompat with 3.x) we will do so, but otherwise you should expect this release to roughly represent the exact API surface area we will ultimately release.

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 is already under development and we plan to release it in 3.7.0 as soon as possible.

What's Changed

Enhancements

• Add UUIDGen inductive materializers for monad transformers by @bio-aeon in #4220
• Add helpers to Selector poller by @armanbilge in #4226
• Setup UncaughtExceptionHandler for WorkerThread by @armanbilge in #4233
• Add message to requirements by @Jasper-M in #4259
• Poll on the 0th tick, check external queue on 32nd by @armanbilge in #4270

Bug Fixes

• Report non-fatal Runnable failures on MainThread EC by @armanbilge in #4223
• Always report timers/events when worker unparked by @armanbilge in #4227
• Introduce PollResult, PollingSystem#processReadyEvents by @armanbilge in #4230
• Shutdown the runtime only when unforked by @armanbilge in #4234
• Restore ArrayBlockingQueue for worker-to-blocking state transfer by @armanbilge in #4255
• Refactor WorkerThread runloop; avoid pathological starvation of pollers by @armanbilge in #4247
• Transfer tick state when replacing a blocked thread by @armanbilge in #4264
• WorkStealingPoolMetrics -> WorkStealingThreadPoolMetrics by @armanbilge in #4271
• Run finalizers in IO#unsafeRunTimed by @armanbilge in #4279
• Create UnsafeNonFatal for use in the fiber runtime by @kapunga in #4263

Documentation

• Fix small typo in docs by @serragnoli in #4257
• Document Poll by @arturaz in #4277

Behind the Scenes

• flake.lock: Update by @typelevel-steward in #4219
• Update sbt-typelevel to 0.7.5 in series/3.x by @typelevel-steward in #4218
• Delete .envrc by @armanbilge in #4224
• New year who dis by @djspiewak in #4231
• update .scalafmt.conf. enforce new wildcard syntax by @xuwei-k in #4236
• Switch to GHA Linux ARM runners by @armanbilge in #4253
• fix warnings in scalafix rule by @xuwei-k in #4244

New Contributors

• @bio-aeon made their first contribution in #4220
• @serragnoli made their first contribution in #4257

Full Changelog: v3.6.0-RC1...v3.6.0-RC2

v3.6.0-RC1

This is the fifty-third release in the Cats Effect 3.x lineage. It is fully binary compatible with every 3.x release and expected to be fully source-compatible with the eventual 3.6.x lineage.

This release candidate is expected to be very stable, and our main rationale for releasing it as such rather than as a full 3.6.0 is to allow the ecosystem (and adventurous end users!) to try it out and find unforeseen problems prior to full release. If fixing those problems require breaking compatibility prior to 3.6.0 (while maintaining bincompat with 3.x) we will do so, but otherwise you should expect this release to roughly represent the exact API surface area we will ultimately release.

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 is already under development and we plan to release it in 3.7.0 as soon as possible.

What's Changed

This release contains the largest change to the Cats Effect internal work scheduler since the introduction of work stealing back in the run up to 3.0.0. In particular, we have finally completed implementation of the integrated runtime we first conceived of back in early 2022. Well, I say "we", but really @armanbilge deserves the absolute lion's share of the credit here. He did almost all of the work not only on the direct implementation in Cats Effect, but also the downstream functionality built on top of it in Fs2 and in Http4s… not only on the JVM but also in Scala Native and across multiple operating systems! It is hard to overstate how gargantuan of an effort this was, both in design and implementation.

As immense as the effort has been, the impact is even more dramatic. We've already observed scenarios in which the performance of microservices implemented on top of Http4s Ember on the JVM leveraging io_uring is improved by over 3.5x! That is to say, the performance is 3.5x higher than baseline using classical NIO2! (as measured by TechEmpower, suggesting performance more than 2x higher than pekko-http) Now, TechEmpower does have its limitations as a framework, but it does represent a useful standard candle for certain access patterns, and improving an already very fast trio of frameworks by this magnitude is not something that happens every day. Even more excitingly, this is just the tip of the iceberg! We ran these tests with very early, almost PoC code with a lot of performance-impacting caveats. The best is yet to come.

And if that wasn't enough, the biggest impacts are not on the JVM but actually on Scala Native. Without diving too far into the details, this type of syscall scheduling mechanism is exactly what is necessary on Scala Native to achieve any measure of performance from downstream services. It is actually remarkably similar to what the Go runtime does, though implemented in a more extensible way (e.g. Go does not, at present, have native support for io_uring, whereas Cats Effect can and has implemented this via a third-party library).

Going forward, Cats Effect will be maintaining support for the following polling systems:

• JVM
  • Selector
• Native
  • kqueue
  • epoll

Support for io_uring is already under heavy development, and we expect to incorporate this into Cats Effect at some future date, supporting both Native and JVM. The integrated runtime was specifically designed with io_uring's unique data patterns in mind and we have already been able to demonstrate that downstream layers of the ecosystem will be able to fully leverage its benefits. Additionally, we believe we can meaningfully improve JVM performance by implementing epoll and kqueue support for the JVM (and not just Native), the former for situations where io_uring is unavailable. This is mostly because Selector is actually very very slow, and while the performance of the Selector-based runtime is roughly on par with what we've been able to achieve on top of NIO2 (which has its own syscall management and is incompatible with the integrated runtime), we know we can do quite a bit better.

On top of the above, this release contains a large number of other enhancements covering a number of major scenarios. Most noticeably, thanks to @kamilkloch, explicitly importing cats.syntax.all._ is no longer required for most usage involving explicit IO! You will still need the syntax import for any use of parametric effects (commonly referred to as "tagless final" or F[_]), and unfortunately due to the way Scala's type inference works, it is also required for the very common traverse function, but nearly any and all other cases have had their implicit search tweaked to avoid this inconvenience. This in turn means that . completion now mostly Just Works™ when using IO (and when it doesn't, hunting for methods on the IO companion object definitely works).

An additional class of work went into substantially improving the internal instrumentation and metrics associated with the runtime. As previously, these are all exposed as JMX MBeans on the JVM, but we have additionally added public APIs which allow applications to self-instrument (rather than forcing external untyped instrumentation via JMX). These metrics have been organized to mirror the structure of the runtime itself and can all be found within the cats.effect.unsafe.metrics package.

If you're an end-user of Cats Effect (in other words, you run applications built on Cats Effect, rather than building libraries or frameworks), one way you can very much aid the future development of the library is to incorporate these metrics (likely via JMX) into your application observability and key metrics. This should allow you to start to build up an intuition for what metrics are significant indicators of good or bad or just plain normal behavior. This is exactly the type of information that is difficult for library authors to realistically determine, but if end-users learn this on our behalf, you can help educate us on the precise details of how the runtime behaves for your application in your production context, shaping the future optimization and tuning of the framework! (note: Cats Effect does not proactively send metrics anywhere from your application, it merely exposes them to your own monitoring infrastructure)

Enhancements

• Polling system by @armanbilge in #3332
• evalOnExecutor by @homycdev in #3691
• Native signal handling and safe IOApp cancelation by @armanbilge in #3695
• Add warnOnNonMainThreadDetected configuration to IOApp by @diogocanut in #3815
• Block in-place if running on a virtual thread by @armanbilge in #3870
• Add GenConcurrent#parSequenceN_ and GenConcurrent#parTraverseN_. by @kamilkloch in #3916
• Apply @static annotation internally by @armanbilge in #3934
• Added PriorityQueue{Sink,Source} extending Queue{Sink,Source} by @neomaclin in #3930
• Timer stealing without a concurrent data structure by @armanbilge in #3781
• Embed cats.syntax.all._ into IO. by @kamilkloch in #3532
• Quick and dirty unsafe queue API by @djspiewak in #3975
• Implement async dropping queue by @iRevive in #4143
• Refactor Ref#mapK to take Functor[G] constraint instead of Functor[F] by @armanbilge in #4115
• Add ownPoller by @armanbilge in #4133
• Use IO.unit in Async[IO].unit by @iRevive in #4162
• Add default constructor for MapRef by @yisraelU in #4139
• Add SystemProperties by @massimosiani in #3924
• Make timeout/timeoutTo always return the outcome of the effect by @biochimia in #4059
• IOLocal propagation for unsafe access by @armanbilge in #3636
• Make UUIDGen more performant by @diogocanut in #3647
• cats.mtl.Local[IO, E] from IOLocal[E] by @rossabaker in #3429
• Implement IORuntimeMetrics by @iRevive in #3317
• Use global counter as an MBean ID for WSTP by @iRevive in #4186
• Add a memoizedAcquire method to Resource by @satabin in #4105
• Add TimerHeapMetrics by @iRevive in #4187
• Add pack count metric for TimerHeap by @armanbilge in https://github.com/typelevel...

v3.5.7

This is the fifty-second release in the Cats Effect 3.x lineage. It is fully binary compatible with every 3.x release and fully source-compatible with every 3.5.x release.

Warning

The 3.5.x series contains some changes that may be semantically breaking with respect to earlier 3.x releases. If you're using fs2, http4s, or other libraries from the ecosystem, make sure you've upgraded to versions of these libraries that are compatible with this release (for fs2, that's 3.7.0+, for http4s it's 0.23.19+)!

Additionally, if you're using methods like fromFuture, make sure you're aware of the major changes to async, described in these release notes.

What's Changed

Enhancements

• Propagate Java thread interruption in Dispatcher#unsafeRunSync by @kamilkloch in #4167

Behind the Scenes

• Update versions for 3.5.6 by @samspills in #4175

Full Changelog: v3.5.6...v3.5.7

v3.5.6

This is the fifty-first release in the Cats Effect 3.x lineage. It is fully binary compatible with every 3.x release and fully source-compatible with every 3.5.x release.

Warning

The 3.5.x series contains some changes that may be semantically breaking with respect to earlier 3.x releases. If you're using fs2, http4s, or other libraries from the ecosystem, make sure you've upgraded to versions of these libraries that are compatible with this release (for fs2, that's 3.7.0+, for http4s it's 0.23.19+)!

Additionally, if you're using methods like fromFuture, make sure you're aware of the major changes to async, described in these release notes.

What's Changed

Enhancements

• Only remove error callback if we've added it by @durban in #4168

Bug Fixes

• Fix size updates in Dequeue state machine by @armanbilge, @reardonj in #4171

Documentation

• Fix joinWithNever docs by @lenguyenthanh in #4160

Behind the Scenes

• Update versions for 3.5.5 by @armanbilge in #4154

Full Changelog: v3.5.5...v3.5.6

v3.5.5

This is the fiftieth release in the Cats Effect 3.x lineage. It is fully binary compatible with every 3.x release and fully source-compatible with every 3.5.x release.

Warning

The 3.5.x series contains some changes that may be semantically breaking with respect to earlier 3.x releases. If you're using fs2, http4s, or other libraries from the ecosystem, make sure you've upgraded to versions of these libraries that are compatible with this release (for fs2, that's 3.7.0+, for http4s it's 0.23.19+)!

Additionally, if you're using methods like fromFuture, make sure you're aware of the major changes to async, described in these release notes.

What's Changed

Enhancements

• Dispatcher: avoid spinning by @durban in #4052
• Relax access semantics in MapRef implementations by @armanbilge in #4116
• optimize IO.whenA by @Jasper-M in #4135

Bug Fixes

• Fix #4066: shut down executors when IORuntime.global shuts down by @durban in #4067
• Use IOApp#reportFailure instead of printStackTrace() for blocking EC by @fredfp in #4044
• Fix cancelable to guarantee cancelation by @armanbilge in #4118

Documentation

• Update versions for 3.5.4 by @djspiewak in #4032
• Improve contributor documentation by @durban in #4038
• Expand the example of using Random[F] in the doc for 3.5.x by @sshark in #4041
• Document usage of -Wnonunit-statement by @froth in #4054
• link to MapRef docs in site sidebar by @samspills in #4122
• Add lifecycle diagrams to Supervisor web docs by @samspills in #4127

Behind the Scenes

• Fix CI step to post release to Discord by @armanbilge in #4031
• Create 8-core Cirrus CI job by @armanbilge in #4036
• Try to address DispatcherSpec timeout in CI by @durban in #4057
• Pin CI to macOS 12 by @armanbilge in #4078
• Remove GraalVM from CI matrix by @mzuehlke in #4153

New Contributors

• @sshark made their first contribution in #4041
• @fredfp made their first contribution in #4044

Full Changelog: v3.5.4...v3.5.5

v3.5.4

This is the forty-ninth release in the Cats Effect 3.x lineage. It is fully binary compatible with every 3.x release and fully source-compatible with every 3.5.x release.

Warning

The 3.5.x series contains some changes that may be semantically breaking with respect to earlier 3.x releases. If you're using fs2, http4s, or other libraries from the ecosystem, make sure you've upgraded to versions of these libraries that are compatible with this release (for fs2, that's 3.7.0+, for http4s it's 0.23.19+)!

Additionally, if you're using methods like fromFuture, make sure you're aware of the major changes to async, described in these release notes.

What's Changed

The most significant change in this release involves the complete greenfield rewrite of Dispatcher. While Dispatcher is, in practice, one of the most-used components of Cats Effect apart from IO itself, it is also one of the oldest and most "accreted" parts of the codebase. The original variant of Dispatcher had far fewer features and was thrown together relatively quickly during the 3.0 milestone process, and every change and enhancement to its functionality has been layered on top of that foundation.

In this release, we started with an empty editor buffer and rebuilt the whole thing, taking the opportunity to correct a number of corner cases in semantics while significantly beefing up the test suite. We're very confident that the results are much more stable and reliable than the previous iteration, and we're excited to get it into everyone's hands!

Enhancements

• IORuntimeConfig: reject invalid auto-yield and cancelation check thresholds by @durban in #3987
• Rewrote Dispatcher by @djspiewak in #3923

Bug Fixes

• Fix a few Supervisor bugs by @durban in #3972
• Clear the CallbackStack more aggressively by @samspills in #3973
• Fix issue #3998 by @durban in #4001
• Fix issue #4002 by @durban in #4003
• Introduce WeakList and use in FiberMonitor by @armanbilge in #3964

Documentation

• Fix typos in Async scaladoc by @durban in #3995
• Removes language:postfixOps from tutorial as it is not used. by @froth in #4025

Behind the Scenes

• Update versions for 3.5.3 by @armanbilge in #3957
• Fix Discord post step in release job by @armanbilge in #3956
• Refine steps about post-release scripts by @armanbilge in #3961
• Attempt to cancel the running test in case of a timeout by @durban in #3969
• Add explanatory comment to Mutex implementation by @durban in #3968
• Updated copyright year by @djspiewak in #3976
• Try to fix issue #3979 by @durban in #3983
• Fixed WeakList headers by @djspiewak in #4027

New Contributors

• @froth made their first contribution in #4025

Full Changelog: v3.5.3...v3.5.4

v3.5.3

This is the forty-eighth release in the Cats Effect 3.x lineage. It is fully binary compatible with every 3.x release and fully source-compatible with every 3.5.x release.

Warning

The 3.5.x series contains some changes that may be semantically breaking with respect to earlier 3.x releases. If you're using fs2, http4s, or other libraries from the ecosystem, make sure you've upgraded to versions of these libraries that are compatible with this release (for fs2, that's 3.7.0+, for http4s it's 0.23.19+)!

Additionally, if you're using methods like fromFuture, make sure you're aware of the major changes to async, described in these release notes.

What's Changed

Enhancements

• Optimize Dispatcher#unsafeRunAndForget by @kamilkloch in #3878
• Execute IO.blocking on WSTP without BlockContext indirection by @armanbilge in #3903
• Reset auto-cede counter after blocking by @armanbilge in #3938
• Remove unneeded notifyParked when worker transitions to blocking by @armanbilge in #3937
• Implement Fiber#join via asyncCheckAttempt by @armanbilge, @samspills in #3942

Bug Fixes

• Fix cancelation leak in fromFuture, fromFutureCancelable by @TimWSpence in #3892
• Fix #3898 for Dispatcher.parallel by @durban in #3900
• Immediately surface fatal errors in IO.raiseError by @scott-thomson239 in #3811
• Fix off-by-1 in CallbackStack#pack by @armanbilge in #3936
• Prevent Hotswap#get from acquiring a lock when there is no Resource present by @josgarmar28 in #3922
• Refactor CallbackStack based on new "pack locking" strategy by @armanbilge, @samspills, @mernst-github in #3943

Documentation

• Fix starvation demo app in tuning guide by @armanbilge in #3881
• Try to fix race condition in Hotswap example by @armanbilge in #3885
• Add note to starvation docs re: cpus in k8s by @Daenyth in #3750
• Add The Case For Effect Systems talk by @lenguyenthanh in #3905

Behind the Scenes

• Update versions for 3.5.2 by @armanbilge in #3857
• Release script improvements by @armanbilge in #3859
• Post release to Discord in CI by @armanbilge in #3855
• Tweak release notes config by @armanbilge, @samspills in #3951
• Decrease concurrency/replicas in CallbackStackSpec by @armanbilge, @samspills in #3952
• Update release.yml by @samspills in #3953
• Document release process by @armanbilge, @samspills in #3954

New Contributors

• @scott-thomson239 made their first contribution in #3811
• @josgarmar28 made their first contribution in #3922

Full Changelog: v3.5.2...v3.5.3

v3.5.2

This is the forty-seventh release in the Cats Effect 3.x lineage. It is fully binary compatible with every 3.x release and fully source-compatible with every 3.5.x release.

⚠️ Important note

The 3.5.x series contains some changes that may be semantically breaking with respect to earlier 3.x releases. If you're using fs2, http4s, or other libraries from the ecosystem, make sure you've upgraded to versions of these libraries that are compatible with this release (for fs2, that's 3.7.0+, for http4s it's 0.23.19+)!

Additionally, if you're using methods like fromFuture, make sure you're aware of the major changes to async, described in these release notes.

What's Changed

Features

• Optimize liveTraces() on JS by @armanbilge in #3724
• Elide thunk allocation when using sleepInternal by @armanbilge in #3775
• Remove Thunk.asFunction0 utility by @armanbilge in #3788
• Print warning when we detect a non-main-thread main by @Daenyth in #3774
• Optimize Dispatcher#{unsafeRunAsync,unsafeRunAndForget} by @kamilkloch in #3822

Bug Fixes

• Fix Hotswap#get being blocked by Hotswap#swap by @forkedcancel in #3800
• Acquire exclusive lock before finalizing Hotswap by @armanbilge in #3841

Behind the Scenes

• Fix major branch PR in release script by @armanbilge in #3713
• Added script for automatically posting release to discord by @djspiewak in #3711
• Add release notes config by @armanbilge in #3710
• Remove unused code by @durban in #3729
• Allow that the renamed blocker thread is terminated by @aeons in #3728
• Dispatcher: test cleanup by @samspills in #3749
• update CI to use graalvm@17 by @samspills in #3773
• Cirrus CI cutbacks ... by @armanbilge in #3796
• Drop macOS jobs from Cirrus by @armanbilge in #3831
• Enough is Enough by @djspiewak in #3833
• Run Cirrus only for labeled PRs or tags by @armanbilge in #3842
• Updated versions script to look for ** pattern by @djspiewak in #3843
• Try quoting labels in release notes config by @armanbilge in #3847
• Add catch-all category for unlabeled PRs by @armanbilge in #3854

Documentation

• Update versions for 3.5.1 by @armanbilge in #3718
• Fix typo by @durban in #3738
• update Deferred#complete type by @ag91 in #3740
• fix typo in tutorial by @vgrigoriu in #3760
• Explain "uhandled error" in reportFailure scaladoc by @kamilkloch in #3769
• Improve MapRef docs by @BalmungSan in #3829

New Contributors

• @ag91 made their first contribution in #3740
• @vgrigoriu made their first contribution in #3760
• @forkedcancel made their first contribution in #3800

Full Changelog: v3.5.1...v3.5.2