Async is a composable asynchronous I/O framework for Ruby based on io-event.

"Lately I've been looking into async, as one of my projects – tus-ruby-server – would really benefit from non-blocking I/O. It's really beautifully designed." janko

Development Status



Please browse the source code index or refer to the guides below.

Getting Started

This guide shows how to add async to your project and run code asynchronously.

Asynchronous Tasks

This guide explains how asynchronous tasks work and how to use them.

Event Loop

This guide gives an overview of how the event loop is implemented.


This guide gives an overview of the compatibility of Async with Ruby and other frameworks.

Best Practices

This guide gives an overview of best practices for using Async.


This guide explains how to debug issues with programs that use Async.


We welcome contributions to this project.

  1. Fork it.
  2. Create your feature branch (git checkout -b my-new-feature).
  3. Commit your changes (git commit -am 'Add some feature').
  4. Push to the branch (git push origin my-new-feature).
  5. Create new Pull Request.

Developer Certificate of Origin

This project uses the Developer Certificate of Origin. All contributors to this project must agree to this document to have their contributions accepted.

Contributor Covenant

This project is governed by the Contributor Covenant. All contributors and participants agree to abide by its terms.

See Also