Reactor, fiber scheduler and async in Ruby 3.0

[Jacob Carlborg]

In Ruby 3.0, support for reactor, fiber scheduler and async has been added.

async seems to be implemented in library code. The existing IO related 
methods in the core/standard library has been updated to be fiber 
scheduler aware. That basically means that if there is no fiber 
scheduler set, the IO operations will be blocking. If a fiber scheduler 
has been set, they will instead be non-blocking. A lot of existing code 
and gems will just work without having to be adopted for async.

Here's an example:

require 'async'
require 'net/http'
require 'uri'

Async do
   ["ruby", "rails", "async"].each do |topic|
     Async do
       Net::HTTP.get(URI "https://www.google.com/search?q=#{topic}")
     end
   end
end

IO#read and IO#write are two of the methods that have been made fiber 
scheduler aware. Net::HTTP#get uses these methods under the hood and 
therefore will be non-blocking inside the Async block. See [1] for more 
details.

BTW, Zig uses the same idea with the underlying IO functions that can 
adopt and become non-blocking.

https://www.ruby-lang.org/en/news/2020/12/25/ruby-3-0-0-released/

-- 
/Jacob Carlborg