New I/O for Ruby (nio4r): cross-platform asynchronous I/O primitives for scalable network clients and servers. Modeled after the Java NIO API, but simplified for ease-of-use.

nio4r provides an abstract, cross-platform stateful I/O selector API for Ruby. I/O selectors are the heart of "reactor"-based event loops, and monitor multiple I/O objects for various types of readiness, e.g. ready for reading or writing.

Projects using nio4r

-<a href='https://rubygems.org/gems/actioncable'>ActionCable</a>: Rails 5 WebSocket protocol, uses nio4r for a WebSocket server
-<a href='https://github.com/celluloid/celluloid-io'>Celluloid</a>: Actor-based concurrency framework, uses nio4r for async I/O
-<a href='https://github.com/socketry/async'>Async</a>: Asynchronous I/O framework for Ruby
-<a href='https://github.com/puma/puma'>Puma</a>: Ruby/Rack web server built for concurrency

Goals

- Expose high-level interfaces for stateful IO selectors
- Keep the API small to maximize both portability and performance across many
different OSes and Ruby VMs
- Provide inherently thread-safe facilities for working with IO objects

Supported platforms

- Ruby 2.5
- Ruby 2.6
- Ruby 2.7
- Ruby 3.0
-<a href='https://github.com/jruby/jruby'>JRuby</a>
-<a href='https://github.com/oracle/truffleruby'>TruffleRuby</a>

Supported backends

- **libev**: MRI C extension targeting multiple native IO selector APIs (e.g epoll, kqueue)
- **Java NIO**: JRuby extension which wraps the Java NIO subsystem
- **Pure Ruby**: `Kernel.select`-based backend that should work on any Ruby interpreter

Documentation

Please see the nio4r wiki for more detailed documentation and usage notes:

-<a href='https://github.com/socketry/nio4r/wiki/Getting-Started'>Getting Started</a>: Introduction to nio4r's components
-<a href='https://github.com/socketry/nio4r/wiki/Selectors'>Selectors</a>: monitor multiple `IO` objects for readiness events
-<a href='https://github.com/socketry/nio4r/wiki/Monitors'>Monitors</a>: control interests and inspect readiness for specific `IO` objects
-<a href='https://github.com/socketry/nio4r/wiki/Byte-Buffers'>Byte Buffers</a>: fixed-size native buffers for high-performance I/O

See also:

-<a href='http://www.rubydoc.info/gems/nio4r/frames'>YARD API documentation</a>

Non-goals

nio4r is not a full-featured event framework likeEventMachine](https://github.com/eventmachine/eventmachine) or [Cool.io. Instead, nio4r is the sort of thing you might write a library like that on top of. nio4r provides a minimal API such that individual Ruby implementers may choose to produce optimized versions for their platform, without having to maintain a large codebase.

Releases

Bump the version first:

bundle exec bake gem:release:version:patch

CRuby

rake clean
rake release

JRuby

You might need to delete Gemfile.lock before trying to bundle install.

# Ensure you have the correct JDK:
pacman -Syu jdk-openjdk
archlinux-java set java-19-openjdk

# Ensure you are using jruby:
chruby jruby
bundle update

# Build the package:
rake clean
rake compile
rake release