armanbilge / fs2-io_uring   0.2.0

Apache License 2.0 GitHub

they see me ringin'

Scala versions: 3.x 2.13
Scala Native versions: 0.4


A library implementing FS2 I/O APIs for Scala Native via the io_uring Linux kernel system call interface. The provided implementations are drop-in replacements that can be used to power http4s Ember, Skunk, and Rediculous.

At its heart fs2-io_uring is an I/O-integrated runtime for Cats Effect. The library is unique in how close to the bare-metal it is and thus how deeply it integrates with kernel I/O APIs. The implementation is literally Cats Effect sharing memory with and talking directly to the kernel: no JDK, no JNI, no overhead. Nearly all system calls are asynchronous, cancelable, and efficiently submitted in batches via the io_uring API. Even cancelation is async and fully-backpressured.


libraryDependencies += "com.armanbilge" %%% "fs2-io_uring" % "0.2.0"

You must also install liburing. For performance, I strongly recommend using static linking, for example:

nativeConfig ~= { c =>
  c.withCompileOptions(c.compileOptions :+ "-I/home/linuxbrew/.linuxbrew/include")
    .withLinkingOptions(c.linkingOptions :+ "/home/linuxbrew/.linuxbrew/lib/liburing.a")

To use fs2-io_uring in an application, you should replace IOApp with UringApp. For tests, you should override the runtime:

override def munitIORuntime =

Finally, you can import from to get an implicit io_uring-backed Network into scope. You may also directly construct instances of:

  • UringNetwork
  • UringSocketGroup
  • UringUnixSockets

Future releases will add support for datagram sockets and file I/O.

Versioning and compatibility

Because this library implements FS2 sealed interfaces, but is released and versioned independently, it is not covered by FS2's usual guarantee of backwards-binary-compatibility. Specifically, updating your FS2 version may cause fs2-io_uring to break.

Therefore, you should not add it as a dependency in libraries. Instead, make sure to expose the Network and UnixSockets constraints of your library, so that users can substitute the fs2-io_uring implementations of these APIs in their applications.