Compatibility

Async is compatible with a wide range of different Ruby versions.

Stable V1

The stable-v1 branch of async is compatible with Ruby 2.5+ & TruffleRuby, and partially compatible with JRuby.

Because it was designed with the interfaces available in Ruby 2.x, the following limitations apply:

class Async::Task implements context switching using Fiber.yield and Fiber.resume. This means that module Async may not be compatible with code which uses fibers for flow control, e.g. Enumerator.
class Async::Reactor is unable to intercept blocking operations with native interfaces. You need to use the wrappers provided by Async::IO.
DNS resolution is blocking.

The main branch of async is compatible with Ruby 3.0.2+, and partially compatible with TruffleRuby. JRuby is currently incompatble.

class Async::Task uses Fiber#transfer for scheduling so it is compatible with all other usage of Fiber.
class Async::Reactor implements the Fiber scheduler interface and is compatible with a wide range of non-blocking operations, including DNS, Process.wait, etc.
External C libraries that use blocking operations may still block.
Ruby <= 3.0.2 has some bugs in its non-blocking thread primitives. These should be fixed in 3.0.3+.